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The Ultimate BC Science 10 Review Guide

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Madison MMM

on 27 December 2013

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Transcript of The Ultimate BC Science 10 Review Guide

The Ultimate BC Science 10 Review Guide

Sustaining Earth's Ecosystems
Chemical Reactions and Radioactivity
Energy Transfer in Natural Systems
Chapter 1
Biomes and ecosystems are divisions of the biosphere.
every environment has biotic and abiotic components
biotic components are the living organisms inside an environment
biotic components interact with each other and their environment
abiotic components are the non-living parts of an environment
scientists study the biosphere by breaking it down into smaller divisions
the larges of these divisions is a biome, which includes large regions that have similar biotic and abiotic components.
Section Introduction
Introducing Biomes of the World
Factors That Influence the Characteristics and Distribution of Biomes
Adaptions and Biomes
Temperature and Precipitation
Ocean Currents
Symbiotic Relationships
Parts of an Ecosystem
Abiotic Interactions in Ecosystems
Biotic Interactions in Ecosystems and Populations
Biodiversity in Ecosystems
Chapter 2
Energy flow and nutrient cycles support life in ecosystems
Energy Flow in Ecosystems
Nutrient Cycles in Ecosystems
Effects of Bioaccumulation on Ecosystems
Section Introduction
How Energy Flows and Energy Loss
Food Chains and Food Webs
Food Pyramids
The Cycling of Nutrients in the Biosphere
The Effect of Human Activities of Nutrient Cycles
The Carbon, Nitrogen, and Phosphorus Cycles
The Carbon Cycle
Human Activities and the Carbon Cycle
The Nitrogen Cycle
Human Activities and the Nitrogen Cycle
The Phosphorus Cycle
Human Activities and the Phosphorus Cycle
How Changes in Nutrient Cycles Affect Biodiversity
How Carbon is Stored
How Carbon is Cycled Through Ecosystems
Cellular Respiration
Other Ways Carbon is Cycled Through Ecosystems
How Nitrogen is Stored
How Nitrogen is Cycled Through Ecosystems
Nitrogen Fixation
Nitrification and Uptake
How Nitrogen is returned to the atmosphere
How Nitrogen is Removed from Ecosystems
How Phosphorus is Stored
How Phosphorus is Cycled through Ecosystems
How Pollutants Climb the Food Chain
PBCs and the Orcas
Persistent Organic Pollutants
Heavy Metals
Reducing the Effects of Chemical Pollution
Chapter 3
Ecosystems continually change over time.
How Changes Occur Naturally in Ecosystems
How Humans Influence Ecosystems
How Introduced Species Affect Ecosystems
How Organisms Adapt to Change
How Ecosystems Change Over Time
How Natural Events Affect Ecosystems
Primary Succession
Mature Communities
Secondary Succession
Insect Infestations
Understanding Sustainability
The Effects of Land and Resource Use
Habitat Loss
The Effects of Deforestation
The Effects of Agriculture
The Effects of Resource Exploitation
Resource Management and Traditional Ecological Knowledge
The Effect of Overexploitation on Food Webs
Section Introduction
The Impact of Introduced Invasive Species
Disease and Parasites
Habitat Alteration
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Atomic theory explains the formation of compounds.
Compounds are classified in different ways.
Chemical reactions occur in predictable ways.
The atomic theory explains radioactivity.
Atomic Theory and Bonding
Names and Formulas of Compounds
Chemical Equations
Section Introduction
Atomic Theory
The Nucleus
Organization of the Periodic Table
The Periodic Table and Ion Formation
Bohr Diagrams
Patterns of Electron Arrangement in Periods
Patterns of Electron Arrangement in Groups
Forming Compounds
Lewis Diagrams
Ionic Bonding
Covalent Bonding
Lewis Diagrams of Ions
Lewis Diagrams of Compounds
Lewis Diagrams of Covalent Molecules
Lewis Diagrams of Diatomic Molecules
The Chemical Name of an Ionic Compound
The Chemical Formula of an Ionic Compound
Naming Ionic Compounds
Writing the Formulas of Ionic Compounds
Compounds Containing a Multivalent Metal
Formulas of Compounds Containing a Multivalent Metal
Naming Compounds that Contain a Multivalent Metal
Polyatomic Ions
Naming Binary Covalent Compounds
Comparing Ionic and Covalent Compounds
Section Introduction
Conservation of Mass in Chemical Change
The Law of Conservation of Mass
Writing and Balancing Chemical Equations
Counting Atoms to Balance an Equation
Hints for Writing Word Equations
Strategies for Balancing Equations
Acids and Bases
Organic Compounds
Section Introduction
pH Values of Common Substances
Using the pH Scale
pH Indicators
Other pH Indicators
Names of Acids
Production of Ions
Properties of Acids and Bases
Section Introduction
Acid-Base Neutralization
Metal Oxides and Non-Metal Oxides
Acids and Metals
Acids and Carbonates
Section Introduction
Recognizing Organic Compounds
Types of Chemical Reactions
Factors Affecting the Rate of Chemical Reactions
Classifying Chemical Reactions
Synthesis (Combination) Reactions
Decomposition Reactions
Single Replacement Reactions
Double Replacement Reactions
Neutralization (Acid-Base) Reactions
Combustion Reactions
Summary of Chemical Reaction Types
Section Introduction
Surface Area
Presence of a Catalyst
Catalytic Converters
Atomic Theory, Isotopes, and Radioactive Decay
Nuclear Reactions
Nuclear Fission
A Review of Chemical Reactions
Nuclear Reactions
Section Introduction
Searching for Invisible Rays
Isotopes and Mass Number
Number of Protons and Neutrons
Representing Isotopes
Radioactive Decay
Three Types of Radiation
Alpha Radiation
Beta Radiation
Gamma Radiation
Radiation and Radioactive Decay Summaries
Nuclear Equations for Radioactive Decay
Carbon Dating
The Rate of Radioactive Decay
Using a Decay Curve
Common Isotope Pairs
Using Data from a Potassium-40 Clock
Comparing Chemical Reactions With Nuclear Reactions
Nuclear Equations for Induced Nuclear Reactions
Subatomic Particle Symbols
Rules for Writing Nuclear Equations
Nuclear Fission of Uranium-235
Chain Reactions
CANDU Reactors
Hazardous Wastes
Nuclear Fusion
Fusion Nuclear Equation
Chapter 8
Average velocity is the rate of change is position.
Chapter 9
Acceleration is the rate of change in velocity.
The Language of Motion
Average Velocity
Direction Makes a Difference
Representing Vectors
Time and Time Interval
Calculating Time Interval
Displacement and Distance
Watch for Signs
Graphing Uniform Motion
Uniform Motion
Using a Best-Fit Line
Positive Slope
Zero Slope
Negative Slope
Speed and Velocity
Same Speed, Different Velocities
Calculating the Slope of a Position-Time Graph
Average Velocity
Position-Time Graphs and Average Velocity
Converting Between m/s and km/h
Calculating Average Velocity
Calculating Displacement
Calculating Time
Describing Acceleration
Calculating Acceleration
Positive and Negative Changes in Velocity
Positive Changes in Velocity
Negative Changes in Velocity
Constant Velocity
Non-Uniform Motion
Comparing Acceleration
Positive and Negative Acceleration
Positive Acceleration
Negative Acceleration
Velocity-Time Graphs
Velocity and Best-Fit Line
Acceleration and Best-Fit Line
Determining Motion from a Velocity-Time Graph
Calculating Acceleration
Calculating Change in Velocity and Time
Gravity and Acceleration
Gravity and Air Resistance
Acceleration Due to Gravity
Calculating Motion Due to Gravity
Chapter 10
Chapter 11
Chapter 12
The kinetic molecular theory explains the transfer of thermal energy.
Climate change occurs through natural processes and human activities.
Thermal energy transfer drives plate tectonics.
Temperature, Thermal Energy, and Heat
Energy Transfer in the Atmosphere
Section Introduction
Temperature Scales
Thermal Energy
Heat Transfer
Section Introduction
The Origin of Earth's Atmosphere
The Layers of the Atmosphere
The Troposphere
The Stratosphere
The Upper Atmosphere
Radiation and Conduction in the Atmosphere
The Radiation Budget
What is Weather?
Atmospheric Pressure
Measuring Atmospheric Pressure
Altitude Affects Atmospheric Pressure
Temperature Affects Atmospheric Pressure
Humidity Affects Atmospheric Pressure
Movement of Air Masses
High Pressure Systems
Low Pressure Systems
Prevailing Winds
Local Winds
The Coriolis Effect
Global Wind
Jet Streams
Extreme Weather
Tropical Cyclones
Natural Causes of Climate Change
Human Activity and Climate Change
Describing Climate
Looking Forward by Studying the Past
The Composition of Earth's Atmosphere
Earth's Tilt, Rotation, and Orbit Around the Sun
The Water Cycle
Ocean Currents
El Nino and La Nina
The Carbon Cycle
Catastrophic Events
Global Warming
The Enhanced Greenhouse Effect
Carbon Dioxide
Nitrous Oxide
Albedo and Climate
The Role of Science in Understanding Climate Change
The Role of International Cooperation in Dealing with Climate Change
Global Impacts of Climate Change
Impacts of Climate Change on Canada
Impacts of Climate Change on British Columbia
Uncertainty and Decision
An Action Plan for the Global Community
Canada's Response to Climate Change
Evidence for Continental Drift
Features of Plate Tectonics
Section Introduction
The Jigsaw Puzzle Fit
Matching Geological Structures and Rocks
Matching Fossils
Climatic Evidence for Continental Drift
How Can Continents Move?
A Possible Mechanism
Evidence from Ocean Rock and Sediments
Evidence from Paleomagnetism
Sea Floor Spreading: An Explanation
Section Introduction
Tectonic Plates
A Cross-Section of Earth
Plate Motion
Push and Pull
Plate Interactions
Divergent Plate Boundaries
Convergent Plate Boundaries
Oceanic-Continental Plate Convergence
Oceanic-Oceanic Plate Convergence
Continental-Continental Plate Convergence
Transform Plate Boundaries
Describing Earthquakes
Seismic Waves
Measuring Earthquakes
Composite Volcanoes
Shield Volcanoes
Rift Eruptions
aquatic biomes are water-based biomes
terrestrial biomes are land-based biomes
different scientists classify different biomes in different ways
biomes can be classified according to precipitation, temperature, plant life, animal life, and/or many other abiotic and biotic factors
similar biomes can be located at very different parts of the world
similar biomes are in the same category because they have similar characteristics
for example, most tropical rainforests have a high annual precipitation, and lush plant growth
temperature and precipitation are two of the most important abiotic factors that influence the distribution of world biomes
certain animals and plants can only survive in certain weather conditions
for example, the slugs that you can find in rainforests could not survive in a desert, they need a certain amount of rain to survive
temperature and precipitation are not the only factors that influence what biome the area will be classified as
latitude is the distance measured in degrees north or south from the equator
latitude can influence temperature and precipitation
at the equator, the sun's rays are the strongest due to the low angle of incidence, therefore the annual average temperatures get higher the closer to the equator you go
locations on the equator also receive 12 hours or daylight every day of the year and experience little change in temperature throughout the seasons
the farther away from the equator you get, the lower the average annual temperature is
since the equatorial area gets the most intense sun rays, the moist air will be heated and rise, and then fall back down as rain
therefore areas near the equator get more precipitation.
elevation is the height of a land mass above sea level
elevation also has an effect on temperature
temperature changes occur because the atmosphere becomes thinner at higher elevations, and a thinner atmosphere retains less heat, so higher elevation generally means lower temperatures
elevation also has an effect on precipitation patterns
on the windward side of a mountain, clouds rise and cool, then release precipitation
on a leeward side of a mountain, which is sheltered from the wind, the air warms again, which allows it to absorb water, creating a dry area
since elevation influence both precipitation and temperature, different biomes can be found at different elevations
ocean currents affect temperature and precipitation, therefore influencing the type of biome
rainforests in British Columbia are influenced by ocean currents, which make them warmer and wetter than other temperate biomes
temperature and precipitation are to important factors that determine climate
climate is the average pattern of weather conditions that occur in a region for over 30 years
a climatograph is a graph of climate data for a specific region, generated from data obtained over 30 years
climatographs usually include average monthly temperature and an average of the total monthly precipitation
you can use climatographs to compare the conditions of different regions
Structural Adaptations
Physiological Adaptations
Behavioral Adaptations
certain types of animals and plants are characteristic of certain biomes because they are better adapted for survival in the conditions of these locations
adaptations are characteristics that enable organisms to better survive and reproduce
the three types of adaptations are structural, physiological, and behaviorial
a structural adaptation is a physical feature of an organism's body having a specific function that contributes to the survival of the organism
for example, pine trees are cone-shaped and therefore shed snow easily, so their branches don't break from the weight of the snow
the arctic fox's coat changes color so it can camouflage itself
a physiological adaptation is a physical or chemical event that occurs within the body of an organism that enables survival
for example, wolves can maintain a constant body temperature even in cold weather
cacti don't need as much water for photosynthesis as other plants, which enables them to survive in dry conditions
a behavioral adaptation is what an organism does to survive in the conditions of its environment
these adaptations can include how the organism feeds, mates, cares for its young, migrates, hibernates, or burrows to escape predators
for example, burrowing owls line their nests with grass to keep it cool during the day, and put cow dung at the entrance to hide the scent of the owls from predators
an ecosystem has abiotic components such as oxygen, water, nutrients, light, and soil that interact with biotic components such as plants, animals, and micro-organisms
biomes contain may type of ecosystems, which can cover many hectacres of land or be very small, such as a rotting log or a tide pool
within ecosystems are habitats, which are the places where certain organisms live
a habitat is basically where an organism lives or nests
the abiotic factors in an ecosystem such as water, oxygen, light, and soil are just as important as the biotic factors.
plants and animals cannot survive without oxygen
without an adequate amount of oxygen in the water, fish will 'gulp for air'
the cells of most living things contain between 50 and 90 percent water
without water, no organism would survive, and you could survive longer without any food that without any water
water also carries nutrients from one place to another in an ecosystem
nutrients such as nitrogen and phosphorus are chemicals that are required for plant and animal growth
light is required for photosynthesis, the process in which plants convert solar energy into sugar
more light equals more plant life
soil is also very important to terrestrial ecosystems, it provides nutrients for plants and supports many species of small organisms
1m squared may have as many as 1000 species of invertebrates in it
soil holds water and nutrients in place for small organisms and bacteria to use
bacteria break down pollutants, and other organisms store carbon by eating animal remains
a species is a group of closely related organisms that can reproduce with one another
a population refers to all the members or a particular species within an ecosystem
all the different populations in an ecosystem form a community, which is all the populations of a the different species that interact
these biotic interactions are sometimes ordered in ecological hierarchy of organism, population, community, and ecosystem
within an ecosystem, organisms interact constantly within their species and with other organisms
commensalism, mutualism, and parasitism are examples of symbiosis or symbiotic relationships
symbiosis refers to the interaction between members of two different species that live together in close association
commensalism is a symbiotic relationship in which one species benefits and the other species is neither helped nor harmed
often the host species provides shelter or transportation for the other
for example, barnacles attach to whales and are transported to new locations in the ocean.
the whales are not harmed or helped, but the barnacles are helped
mutualism is a symbiotic relationship in which both organisms benefit
in some mutualistic relationships, one species is unable to survive without the other
for example, bees go from flower to flower gathering pollen. the flower benefits because its pollen is being spread around, creating new flowers, and the bee benefits because now it has food
lichen is the most famous example of mutualism
every lichen has an alga and a fungus that live together.
the alga produces sugars and oxygen for the fungus through photosynthesis, and the fungus provides carbon dioxide, water, minerals, and protection from dehydration
Parasitism is a symbiotic relationship in which one species benefits and the other is harmed
parasites are often smaller and much more numerous than their hosts
worms are a good example of a parasite.
the worm gains nutrients from the animal, and the animal often becomes sick
organisms have special roles in the ecosystems in which they live
the term niche is used to describe these roles
an organism's niche includes the way in which the organism contributes to and fits into its environment
all the interactions required for a species to survive, grow, and reproduce are part of an organism's niche
competition is a harmful interaction between two or more organisms that can occur when organisms compete for the same resource in the same location at the same time
the health of an organism and its ability to grow and reproduce is reduced if the organism expends energy competing
some organisms are successful competitors
some animals will even compete against those of their own species
predation is the term used to describe predator-prey interactions in which one organism (the predator) eats all or part of another organism (the prey)
this is an example of parasitism, and it moves energy through an ecosystem
predatory animals have adaptations that make them successful predators, such as long teeth
prey animals also have adaptations that keep them from being eaten, such as camouflage
the size or a prey population can be affected by the number of predators
predator-prey relationships are extremely complex
biodiversity is often an indicator of good health in an organism
as humans leave a footprint in the ecosystem, maintaining biodiversity becomes more difficult
to understand how much organic mass is produced in different parts of the biosphere, scientists estimate biomass
biomass refers to the total mass of living plants, animals, fungi, and bacteria in a given area
biomass can also refer to the mass of particular types of organic matter such as trees, plant crops, manures, and other organic materials
estimates of biomass are usually expressed in grams or kilograms per square meter
each organism interacts with its ecosystem in two ways:
the organism obtains food energy from the ecosystem
the organism contributes energy to the ecosystem
this way, energy flows from the ecosystem to an organism and from one organism to another
this is called energy flow, and humans are a part of it
plants are called producers because they produce food in the form of carbohydrates during photosynthesis
carbohydrates stored in plants become an energy source for other life forms.
an insect such as a bee that feeds on a plant such as a sunflower is called a consumer
consumers may also become energy sources if they are eaten by another consumer
after an organism dies, they break down in a process know as decomposition
the action of living organisms such as bacteria to break down dead organic matter is called biodegradation
organisms that biodegrade such as bacteria and fungi are called decomposers
decomposers change wastes and dead organisms into usable nutrients for other organisms to use
scientists use different models to help them understand how energy flows through or is lost in an ecosystem
these models are food chains, food webs, and food pyramids
these models reflect the feeding relationships of organisms within ecosystems
food chains are models that show the flow of energy from plant to animal and from animal to animal
each step in a food chain is called a trophic level, the levels show the feeding and niche relationships among organism
since plants and phytoplankton such as algae are the producers, they are at the first trophic level and are referred to as primary producers
primary consumers such as grasshoppers are in the second trophic level and gain energy by eating primary producers
secondary consumers such as frogs and crabs are in the third trophic level and gain energy by eating primary consumers
tertiary consumers such as hawks and sea otters are in the fourth trophic level and gain energy by eating secondary consumers
First Trophic Level
Primary Consumers
Examples: grasshopper, krill
Secondary Consumers
Third Trophic Level
Tertiary Consumers
Examples: hawk, sea otter, bear
dertrivores are consumers that obtain their energy and nutrients by eating the bodies of small dead animals, dead plant matter, and animal wastes
in terrestrial ecosystems, dertrivores include small insects, earthworms, bacteria, and fungi
dertrivores feed at every trophic level and make up their own important food chains, in fact, food chains based on dead plant and animal matter outnumber food chains based on living plants and animals
dertrivores such as worms and beetles are an important energy source for consumers such as birds
herbivores are primary consumers that eat plants
carnivores are secondary consumers that eat primary consumers
carnivores also eat other secondary consumers and are often at the tertiary level of the food chain
carnivores at the tertiary level are often referred to as to consumers, top carnivores, or top predators
many animals are part of more than one food chain and eat more that one kind of food in order to meet energy requirements
for example, squirrels are primary consumers when they eat seeds or fruit, but when they eat insects they are secondary or tertiary consumers
consumers that eat both plants and animals are called omnivores
interconnected food chains form a food web
food webs are models of the feeding relationships within an ecosystems
Primary Producers
Examples: sunflowers, grass, trees
Second Trophic Level
Examples: frog, crab
Fourth Trophic Level
when an insect eats leaves, energy is transferred from the plant to the insect, and when a bird eats the insect, the energy is then transferred to the bird
not all the energy that organisms obtain by eating is stored, lots is used to repair tissue, move, and digest food
between 80 and 90 percent of food energy is lost to the ecosystem as heat, and very little is used for growth or to increase biomass
a food pyramid is a model that shows the loss of energy from one trophic level to another
food pyramids are often referred to as ecological pyramids, and their are many kinds: that of biomass, numbers, and energy.
the amount of life that an ecosystem can support is determined by the amount of energy captured by producers
little vegetation means few organisms
because of the 90 percent decrease in energy from one level to the next, there are fewer organisms in the higher trophic levels
nutrients are chemicals that are required for plant and animal growth and other life processes
nutrients are accumulated for short or long periods of time in earth's atmosphere, oceans, and land masses
these accumulations of nutrients are called stores
biotic processes such as decomposition and aboitic processes such as river run-off cause nutrients to flow in and out of stores, and these flow of nutrients are called the nutrient cycles
the nutrients cycles are nearly in balance because without human interference, amount of nutrients flowing out of the stores would be nearly the same as the amount flowing into the stores
Human activity such as land clearing, agriculture, urban expansion, and mining can affect a nutrient cycle by increasing the amounts of nutrients in the cycle than natural processes can move them back to the stores
over time, as a result of these activities increased amounts of nutrients can have significant effects on the environment
there are five chemical elements (or nutrients) that limit the amount and types of life possible in an ecosystem: carbon, hydrogen, oxygen, nitrogen, and phosphorus
carbon, hydrogen, oxygen, and nitrogen atoms are cycled between living organisms and the atmosphere
phosphorus atoms enter the environment from sedimentary rock
carbon, hydrogen, and oxygen make up molecules such as DNA, carbohydrates, and proteins
nitrogen is found in proteins and DNA
the health of an organism depends on the balance of these five nutrients
all living things contain billions of carbon atoms in their cells

it is an essential component in the chemical reactions that sustain life, such as cellular respiration
short-term stores of carbon are found in vegetation on land, in plants in oceans, in land-based and marine animals, and in decaying organic matter in soil
carbon is also found in the atmosphere as carbon dioxide gas and is stored, in its dissolved form, in the top layers of the ocean
long-term stores of carbon are found in coal deposits and in oil and gas deposits, which formed millions of years ago
coal, oil, and natural gas are fossil fuels that are formed from dead plants and animals
the larges long-term stores of carbon are found in marine sediments and sedimentary rock
sedimentation is the process that contributes to the formation of sedimentary rock
during sedimentation, soil particles and decaying and dead organic matter accumulate in layers on the ground or at the bottom of oceans and/or lakes
these layers are turned into rock by slow geological processes that take palce over long periods of time
some marine sediments and sedimentary rock form from the shells of marine organisms such as coral and clams, which contain carbonate, a combination of carbon and oxygen that is dissolved in ocean water
these shell accumulate on the ocean floor when the organisms die and form carbonate-rich deposits, which, in time, will turn to limestone, a sedimentary rock
a variety of natural processes move carbon through ecosystems
these processes include photosynthesis, respiration, decomposition, ocean processes, and events such as volcanic eruptions and large-scale forest fires
photosynthesis is a chemical reaction that converts solar energy into chemical energy, and is an important process in which carbon and oxygen are cycled through ecosystems
during photosynthesis, carbon, in the form of carbon dioxide in the atmosphere, enters through the leaves of plants and reacts with water in the presence of sunlight to produce energy-rich sugars (carbohydrates) and oxygen
photosynthesis provide usable energy to plants, and by eating plants, consumers can gain the plant's energy
cellular respiration is the process in which both plants and animals release carbon dioxide back into the atmosphere by converting carbohydrates and oxygen into carbon dioxide and water
during cellular respiration, energy is released within the cells of organisms and made available for growth, repair, and reproduction
carbon dioxide gas is released as a waste product
decomposition refers to the breaking down of dead organic matter

decomposers such as bacteria and fungi convert organic molecules such as cellulose (a type of carbohydrate found in plants) back into carbon dioxide, which is released into the atmosphere
processes that occur in oceans and as a result of geologic or natural events are also part of the carbon cycle
for example, the process of ocean mixing moves carbon throughout the world's oceans and pumps more carbon into the oceans that is released back into the atmosphere
in this process, carbon dioxide dissolved in the cold ocean waters found at high latitudes
the cold water sinks and moves slowly in deep ocean currents toward the tropics
in the warm tropics, the water rises as it warms, mixing with water at intermediate levels and at the surface
some carbon dioxide is released to the tropical atmosphere as ocean currents carry the warmed water back toward polar areas
occasionally, some carbon dioxide is released from volcanoes following the subduction and melting of sedimentary rock in tectonic plates
some carbon dioxide is also slowly released from decomposing trees and rapidly released through forest fires
human activities such as industry and motorized transportation have changed the natural carbon cycle
since the industrial revolution, the amount of carbon gas has increased by over 30 percent
human activities that involve burning fossil fuels have greatly increased the amount of carbon in the atmosphere
carbon dioxide is a greenhouse gas, and can contribute to global climate change
nitrogen is an important component of DNA and proteins, which are essential for life processes inside a cell
nitrogen is important for muscle function and growth
the largest store of nitrogen is in the atmosphere, where it exists as a gas
other major sources of nitrogen include oceans and organic matter in soil
in terrestrial ecosystems, living things, lakes, and marches also store nitrogen but in smaller amounts
although 78 percent of earth's atmosphere is nitrogen, most organisms cannot use it in this form
therefore, much of the nitrogen cycle involves processes that make nitrogen available to plants and eventually animals
three of these processes are nitrogen fixation, nitrification, and uptake
nitrogen fixation is the process in which nitrogen gas is converted into compounds that contain nitrate or ammonium
both of these compounds are usable by plants
nitrogen fixation occurs in three ways: in the atmosphere, in the soil, and in water bodies
atmospheric nitrogen fixation occurs when nitrogen gas is converted into nitrate and other nitrogen-containing compounds by lightning
lightning is an electrical discharge of static electricity in the atmosphere
it provides the energy needed for nitrogen to react with oxygen to form these compounds
nitrate and other nitrogen-containing compounds enter terrestrial and aquatic biomes in rain
only a small amount of nitrogen-containing compounds are fixed in the atmosphere are a result of this process
nitrogen fixation is soil occurs when nitrogen gas is converted into ammonium by bacteria during the decomposition process
certain types of bacteria, called nitrogen-fixing bacteria play a significant role in nitrogen fixation
for example, Rhizobium is a species of nitrogen-fixing bacteria that lives in the roots of beans and other plants
the plants supply the bacteria with sugars, and the bacteria supply the host plants with ammonium
certain species of cyanobacteria in aquatic ecosystems also fix nitrogen into ammonium
the cyanobacteria make ammonium available to plants in the surface waters of oceans, wetlands, and lakes
since not all plants live in association with nitrogen-fixing bacteria, they must obtain it in another form
in a process called nitrification, ammonium is converted into nitrate
nitrification takes place in two stages and involves certain soil bacteria known as nitrifying bacteria
in the first stage of nitrification, certain species of nitrifying bacteria convert ammonium into nitrite, and in the second stage the bacteria turns the nitrite into nitrate
once nitrates are made available by nitrifying bacteria, nitrates can enter plant roots and be incorporated into plant proteins
the uptake of nitrates is important not only for plants but also for other organisms
when herbivores and omnivores eat plants, they incorporate nitrogen into the proteins in their tissues
other types of decomposer bacteria and fungi are able to take the nitrogen trapped in the proteins and DNA of dead organisms and convert it back into ammonium
nitrogen is returned to the atmosphere in a process called nitrification, which involves certain bacteria known as denitrifying bacteria
in a series of chemical reactions, denitrifying bacteria convert nitrate back into nitrogen gas, which is returned to the atmosphere

excess nitrate and ammonium that are not taken up by plants mix with rainwater and are washed from the soil into ground water and streams
this unused nitrogen may settle to ocean, lake, or river bottoms in sediments and eventually the sediments will form rock and the nitrogen will not be available
only after centuries of weathering will the nitrogen be released back into the water
human activities have doubled the available nitrogen in the biosphere in the past 50 years
millions of tonnes are added every hear through fossil fuel combustion in power plants, and motorized transportation
clearing forests and grasslands by burning also releases trapped nitrogen into the atmosphere
chemical fertilizers contain nitrogen-containing compounds, so when they are applied, extra nitrogen is leeched into the soil
extra nitrogen can also cause eutrophication, which is when there is excess plant production and decay
this can cause algae blooms, depriving other plants from light and oxygen, and also can produce neurotoxins
phosphorus is essential for a variety of life processes
helps strengthen bones, in plants it helps with root and seed development
very important in cells
unlike carbon, oxygen, and nitrogen, phosphorus is not stored in the atmosphere as a gas
instead, it is trapped in phosphate that makes up phosphate rock and the sediments of ocean floors
weathering releases phosphate into the soil
weathering is the process of breaking down rock into smaller fragments
chemical weathering and physical weathering are two types involved in the phosphorus cycle
in chemical weathering, a chemical reaction causes phosphate rocks to break down and release phosphate into soil
acid precipitation and the chemicals released by lichens can cause chemical weathering
in physical weathering, processes such as wind, rain, and freezing release particles of rock and phosphate into the soil
on land, plants quickly take up phosphate through their roots and animals obtain phosphate by eating the plants
the action of decomposition breaks down the phosphate and enters the soil to be available for plants again
water plants take up some dissolved phosphate for aquatic ecosystems
most phosphate run-off settles on lake and ocean bottom and will not enter the biotic community unless the sediment is disturbed
the sediment will turn to rock, and the phosphate will remain trapped for millions of years
when the phosphate is eventually exposed, the cycle will start again
geological uplift refers to the process of mountain building in which earth's crust folds, and deeply buried rock layers rise and are exposed
phosphate rock is mined to make commercial fertilizes and detergents such as those used in dishwashers
on some islands, guano, bird droppings, have been collected for phosphate
fertilizers, detergent, and other phosphate-containing products leech into waterways, adding to the phosphate in the atmosphere
too much phosphorus can cause some organisms death
human activities can also reduce phosphorus supplies
the clearing of forests by the slash and burn method releases the phosphates contained in tree is the form of ash, which eventually settles on ocean bottom where it is unavailable
changes in carbon, nitrogen, and phosphorus cycles can affect the health and variety of organisms that live in an ecosystem
decreased or increases amounts of any of theses nutrients can have very negative effects
Human activities can make natural disturbances such as forest fires much worse
rapid changes threaten the lives of many organisms
one of the biggest changes has been the introduction into the environment of synthetic (human-made) chemicals
synthetic and organic chemicals build up in the environment when decomposers cannot break them down through biodegradation
bioaccumulation is the build up of these chemicals in living organisms
a chemical will accumulate if it is taken up and stored faster that it can be broken down
chemicals can enter organisms through respiration, skin contact, or food intake
high accumulation can be very harmful
some chemicals are temporarily stored in fat tissue then released when the fat is burned
chemicals can affect all systems of an organism, and if they come into contact with a keystone species, all organisms in the ecosystem will be affected
keystone species are species that can greatly affect the population numbers and health of an ecosystem
biomagnification is the process in which chemicals accumulate and become more concentrated at each level
chemicals bioaccumulate and become biomagnified when pollutants ate stored in plant tissue in plants and fat tissue in animals
chemicals remain trapped in plants and animals until they are eaten and the tissues and fats are broken down for energy
even small concentrations of chemicals in producers and consumers can build up to cause problems at higher concentrations
for example, even if there is only a little pollution in some water, it will pass onto small fish, a big fish will eat lots of small fish, and a whale will eat lots of big fish, so by the time the pollutant gets to the whale it is in a high concentration
PCBs (polychlorinated biphenyls) are synthetic chemicals that were widely used from the 30's to the 70's in plastics and many other products
in 1977 they were banned in North America; they can be harmful to environment and humans, and they bioaccumulate, biomagnify, and have along half-life
half-life is the time it takes for the amount of a substance to decrease by half
PBC's stay in organisms a long time, might cause cancer in humans, and are especially harmful in aquatic ecosystems
orca whales have been heavily affected by PBCs, and they will continue to be until 2030
orcas retain high PBC levels, especially the calves
biomagnification is responsible for the high concentration of PBCs in orcas
PBCs belong to a class of compounds called persistent organic pollutants, or POPs
POPs are carbon containing compounds that remain in water and soil for many years
many POPs enter the environment through insecticide sprays
DDT (dichloro-diphenyl trichloroethane) is a well known POP that was introduced to control mosquitoes
it is now banned in many countries because it biomagnifies and has a long half-life
DDT stays in soil for a long time and bioaccumulates in the fatty tissue of animals and in plants
becomes magnified throughout the food chain
chemical accumulation is measured in parts per million (ppm)
one ppm means one particle of a given substance mixed with 999 999 other particles, which is equivalent to one drop of dye mixed with 150 L of water
DDT is considered toxic or harmful at levels of 5 ppm
can cause many disorders in animals
Heavy metals are metallic elements with a high density that are toxic to organisms at low concentrations
within the biosphere they do not degrade and cannot be destroyed
heavy metals such as copper, selenium, and zinc are essential to human health in very small quantities
heavy metals can be found in water and air and bioaccumulate and biomagnify
three most polluting heavy metals are lead, cadium, and mercury
lead is naturally present in all soils, generally in the range of 15 ppm to 40 ppm
these levels have increased due to human activity
in the past lead was used in paint, plastic, and other products
today lead in products has been reduced
other uses of lead, such as electronics still contribute to lead in the environment
lead is extremely toxic, dangerous at 0.0012 ppm, and not considered safe at any level
lead particles can be ingested, absorbed through skin, or inhaled
much harm may result in bot humans and other animals
cadmium is found in earth's crust and is released through weathering, volcanoes, and forest fires
released also in the manufacture of plastic and other products
when present in soil it can be extremely dangerous, as it gos through the food chain
highly toxic to animals, associated with high death rates and low reproduction rates
for humans, the most serious cause of cadmium poisoning is smoking tobacco, and tobacco plants easily absorb the metal
non-smokers can ingest the metal from some seafood and mushrooms
half life in bone tissue us 30 years
can cause damage to nervous system, immune system, and DNA
mercury is released through natural sources such as rock weathering but the release rate has doubled since the burning of fossil fuels and mining
coal burning accounts for more that 40 percent of mercury released into the atmosphere
mercury returns to the earth in rainfall and dust
organisms circulate mercury through the food chain, and some bacteria changes mercury into methylmercury, a highly toxic compound that can cause serious problems in humans and animals

living organisms must change as the conditions of their environment change
the process that makes change possible in living things is called natural selection, in which members of a species having certain characteristics that give them an advantage over other species will be in better condition to mate
these individuals then may pass favorable characteristics on to their offspring
adaptive radiation is the change from a common ancestor into a number of different species that radiate out to inhabit different niches
each species of a certain animal is suited for a certain niche
for example, there are 13 species of finches that inhabit the Galapagos islands, some have big beaks for cracking open hard seeds, some have small beaks for small seeds
ecosystems are continually changing, and the types of species that live in an ecosystem change and the abiotic factors change
ecological succession is the term used to refer to changed that take place over time in the types of organisms that live in an area
there are two types of ecological succession: primary succession and secondary succession
primary succession occurs in an area where there is no soil, such as on bare rock
natural events such as retreating glaciers can scrape existing rock bare, or new rock can form after a volcano
wind and rain carry the spores of lichen to these rocks
the weathering caused by lichens and by processes such as wind and rain begin the formation of soil
as dead lichens decay, they also add organic matter to the soil
in time, the soil slowly accumulates, a process that may take hundreds of years in some places
species such as lichen are called pioneer species because they are the first to survive and reproduce in an area
each stage in primary succession is gradual and introduced different populations that compete for nutrients, sunlight, and soil
as each generation of plants die, they contribute to the soil
eventually seeds of trees that have been carried by wind or bird will germinate
although species and conditions vary, primary succession occurs in much the same way almost everywhere
the process of primary succession leads to the development of a mature community, sometimes called a climax community
boreal forests, tropcial rainforests, and grasslands are examples of climax communities
climates change over time, so therefore so do the abiotic and biotic factors of a mature community
mature communities still constantly change
After a forest fire, not much is left except ash and the burnt trees, but the forest will not remain lifeless for long, as seeds and micro-organisms blow in
this process is called secondary succession, which is like primary succession, but there was soil in the area before
secondary succession occurs much faster, and often depends on the recovery of existing plants
large disturbances such as forest fires have an impact on mature communities and result in secondary succession
other large disturbances such as flooding, drought, tsunamis, and insect infestations can also greatly affect mature communities
flooding occurs in coastal areas, rivers, and lakes, when the volume of water exceeds the ability of the water body to contain it
flooding can be part of a normal cycle or the result of heavy rainfall, run-off, or a tsunami
flooding can result in soil erosion and soil pollution if toxins are present in water
flooding can also spread disease among humans if sewage water or toxins enter drinking water supplies
climate change may be causing an increase in flooding in some parts of the world, such as Africa, where heavier annual rains are occuring
tsunami is the term used to describe a huge, rapidly moving wave
they are usually caused by large earthquakes or underwater volcanoes
on land, the force of the wave carries away or destroys plants and animals, disrupting food webs and habitats
the large volume of salt water can change the composition of soil
as a result, plants that cannot survive in a salty environment are unable to grow
drought is a recurring event in many parts of the world, and usually occurs when there is a below-average amount of precipitation in an area over a period of many months or years
most often, an ecosystem will recover from drought once the precipitation pattern is re-established
the effects of prolonged drought can lead to many deaths in organisms
droughts may have been made worse by climate change
insects play a major role in the natural succession of a forest
young, healthy trees are able to protect themselves from pine beetles by producing resin
pine beetles, in large numbers, can even kill young trees
weather conditions that would usually limit the number of pine beetles are no longer occurring due to climate change
sustainability refers to the ability of an ecosystem to sustain ecological processes
these processes are important to biological diversity
sustainability can also refer to using the resources of an ecosystem to meet our needs today without reducing the function and health of that ecosystem
land use refers to the ways we use the land around us for urban development, agriculture, industry, and mining
most of the products we use come from resources found in the environment
resource use refers to the ways we obtain and use these materials
the economy of BC relied on resources from the environment
as human population grows, so too have trade and industry
habitat loss refers to the destruction of habitats, which usually results from human activities, and causes the ecosystem to be unable to support some organisms
habitat fragmentation is the division of habitats into smaller, isolated fragments, sometimes caused by road building
this can cause lower rates of growth, survival, and reproduction
many farms in Brazil have been developed on land that was once lush rainforest
deforestation is the practice in which forests are logged or cleared for human use and never replanted
it continues at an alarming rate, and can be extremely harmful to ecosystems and organisms living in them
soil degradation can occur when water and wind erosion removes topsoil from bare land
topsoil is the upper layer of soil in which most plants grow
deforestation causes erosion because few plants are still there to hold the soil in place
when planting fields are left bare in the winter, erosion can reduce the amount of topsoil for plant production
soil compaction occurs when soil particles are squeezed together and the air spaces between the particles are reduced, which reduces the movement of air, water, and soil organisms, all of which are essential for soil health
when this happens increased run-off can occur
aeration, in which small plugs of soil are mechanically removed, is one method that reduces run-off by improving the movement of air and water through soil
resource use is also referred to as resource exploitation
we depend on resource exploitation to build our homes, eat, and provide energy to cities but it can cause habitat loss and the death of many organisms
contamination is the introduction of chemicals, toxins, wastes, or micro-organisms into the environment in concentrations that are harmful to living things
mine reclamation is the process in which land around a mine is restored after the mine has been closed
mine reclamation sometimes involves the use of plants to prevent run-off
overexploitation is the use or extraction of a resource until it is depleted, and can cause extinction
extinction is the dying out of a species
over exploitation of a species not only affects their numbers, it also results in a loss of genetic diversity
this means that populations are less resistant to disease and less able to adapt
overexploitaion affects many interactions in food webs, and sometimes the effects take decades to appear
kelp, sperm whales, and sea otters are all species that, when their number went down, affected the rest of their community
traditional ecological knowledge is the First Nation's people's knowledge of the environment
it is the knowledge of how the food chains and cycles work
native species are plants and animals that naturally inhabit an area
introduced species or foreign species are species that did not exist in a region previously, and were transported there intentionally or accidentally by people
invasive species are organisms that can take over the habitat of native species or invade their bodies
the introduction of invasive species is a major cause of global biodiversity loss
invasive species often have high reproduction rates, are aggressive competitors, and lack natural predators, making it hard to get rid of them
such species can affect native species through competition, predation, disease, parasitism, and habitat alteration
introduced invasive species compete against native species for resources such as food and habitat
while the original community has adapted to sharing resources, invasive species disturb the balance
introduced predators have more impact on a prey population than native predators, as prey may not have adaptations to escape or fight them
there are many times a greater number of invasive species, so the prey have a strong disadvantage
an invasion of parasites or disease-causing viruses and bacteria can weaken the immune responses or an ecosystem's native plants and animals, including humans
the weakening provides opportunities for less dominant species to out compete others, altering the food webs and ecosystems.
introduced invasive species can make natural habitat unsuitable for native species by changing its structure or composition
they may change light levels, decrease oxygen in water, change soil chemistry, or increase soil erosion
they can upset the balance of nutrient cycling, pollination, and energy flow
distance, time and speed have magnitude but not direction
magnitude refers to the size of a measurement or the amount you are counting
quantities that describe magnitude but do not include direction are called scalar quantities or scalars ie: 4 km/h
quantities that describe magnitude and also direction are called vectors ie: 4 km/h [W]
when a direction is written in a vector description, it is usually abbreviated and put in square brackets
for example: if your car's position is 10 km east of your home, you would write the position as 10 km [E]
speedometers measure how fast something is moving
odometers measure how far something has moved (the distance it has traveled)
distance (d) is a scalar quantity that describes the length of a path between two points or locations
the SI unit for distance is meters, m
position (d) is a vector quantity that describes a specific point relative to a reference point
position describes an object's location as see by an observer
for example, suppose after driving from home to the store you drive back home. your odometer will say you drove a distance of 20 km, put your position is 0m, since you are back in your original position
time (t) is when an event occurs
the difference between initial time (when the event begins) and final time (when the event ends) is called the time interval
the symbol for change in time or time interval is ∆t. ∆ is the Greek letter delta, often used to represent change
both time and time interval are scalar qauntities
the SI unit for time and time interval is seconds, s
to calculate time interval, subtract the initial time from the final time
for example, if at 2s you walk past a bench and at 7s you walk past a sign, the time interval to travel from the bench to the sign would be 5s, because:
∆t = final time - initial time
= 7s - 2s
= 5s
when you know the direction, you can describe the displacement
displacement describes the straight line distance and direction from one point to another
displacement is how much an object's position has changed; if the object ends up where it started, then the displacement is 0
displacement equals the final position minus the initial position

∆d = final d - initial d
= 7m [E] - 2m [E]
= 5m [E]
when we use vectors that are opposite in direction, it is convenient to designate these directions as either negative or positive
positive: +, up, right, north, east
negative: -, down, left, south, west
for example:
5m down, south, left, or west would become -5m
∆d = 5m [S] - 9m [N]
∆d = -5m - (+9m)
∆d = -4m, or 4m [S]
objects in uniform motion travel equal displacements in equal time intervals
because of air resistance, you can only achieve true uniform motion with no air (so no friction)
a motion diagram shows an object's position at given times, with a picture and benchmarks
by looking at a motion diagram you can make a position-time graph, which is a graph where the x-axis is time and the y-axis is position
a best-fit line is a smooth curve or straight line the most closely fits the general shape outlined by the points
if the motion is uniform, the line will pass through all the points
the slope of a position-time graph is the velocity
the slope of a graph refers to whether a line is horizontal or goes up or down to an angle
a slope may be positive, zero, or negative
a positive slope slants up to the right
a positive slope indicates that the object's position from the origin is increasing with respect to time
if the slope of the line is horizontal, it has a zero slope and the object is at rest
an object at rest is an example of uniform motion since the displacement during any time is constant
if the slope is negative, it slants down to the right
this means that the object is moving away or in a negative direction
speed (v) is the distance an object travels during a given time interval divided by the time interval
speed is a scalar quantity 5 km/h
velocity is speed with a direction, it is the displacement of an object during a time interval divided by the time interval
velocity is a vector quantity 5 km/h [W]
the SI unit for speed and velocity is m/s or km/h
objects traveling at the same speed can have different velocities if they are going in different directions
velocities change when magnitude or direction or both change
the slope of a position-time graph is the object's velocity
slope = ∆d/∆t (velocity = ∆d/∆t)
the steeper the slope, the faster the velocity
the slope of a position-time graph is the object's average velocity
average velocity is the rate of change in position for a time interval
it is like average speed but with a direction
a position-time graph can contain positive, zero, and negative slopes
if we designate moving away from the origin as positive, then a positive slope represents the average velocity of the object moving away from the origin
a horizontal line (zero slope) represents the object not moving
a negative slope represents the average velocity of the object moving back towards the origin
to convert from m/s to km/h:
15m/s to km/h
= 15 x 3600 / 1000
= 54 km/h
to convert km/h to m/s:
45 km/h to m/s
= 45 / 3600 x 1000
= 12.5 m/s
you can calculate the slope of a line by rise/run
rise/run = ∆y/∆x
on a position-time graph, slope = ∆d/∆t
velocity (average) = ∆d/∆t
Example: given ∆d = +75.0m, ∆t = 8.2s
average v = ∆d/∆t
= 75.0m/8.2s
= 9.146 m/s
= 9.1 m/s [forward]
displacement can be found using the same formula
given: v-av = 3.5 m/s [W], ∆t = 12s
∆d = (v-av)(∆t)
= 3.5 m/s x 12s
= 42 m
= 42 m [W]
you can calculate time using the same formula
given: v-av = 12 m/s [S], ∆d = 600 m [S]
∆t = ∆d/v-av
= 600m / 12 m/s
= 50s
a change in velocity (∆v) occurs when the speed of an object changes, the direction of an object changes, or both
changes in velocity can be classed as positive or negative
to find a change in velocity, subtract the initial velocity (v-i) from the final velocity(v-f)
∆v = v-f – v-i
a positive change in velocity would be if your velocity increased.
Example: you are riding your bike at 6 m/s, but then you speed up to 9 m/s
your change in velocity would be positive because your speed increased
you can calculate it:
∆v = v-f –v-i
= +9 m/s - (+6 m/s)
= +3 m/s
remember that + is forward
a negative change in velocity would be if you slowed down your speed
Example: you are riding your bike at 9 m/s and you slow down to 2 m/s, since you slowed down, your change in velocity is negative
calculate it:
∆v = v-f – v-i
= +2 m/s - (+9 m/s)
= -7 m/s
remember - is backwards
if you don's slow down or speed up, you have a constant velocity, and your initial and final velocities would be equal
therefore the change in velocity would be zero
any object traveling with uniform motion in a straight line would have zero change in velocity
uniform motion is motion that stays the same, not slowing down or speeding up
on a position-time graph, uniform motion would be a straight line
if there is any change in velocity, the motion is not uniform
acceleration is the rate of change in velocity
velocity is a vector, so it has two parts: the speed and the direction of the object
acceleration is also a vector because you must include how the objects speed changed and also how the object's direction changed
when comparing two objects, the object with the greater acceleration changes its velocity in a shorter time interval or has a greater change in velocity during the same time interval
it is like two cars: an old one will accelerate faster, therefor its velocity will reach a higher speed more quickly
whenever the velocity of an object changes, its motion is not uniform, and we say the object is accelerating
acceleration occurs when the speed of an object changes, or its direction of motion changes, or both
an object that is slowing down is also changing velocity, and is therefore accelerating
in straight-line motion, acceleration can be either positive or negative
suppose the forward motion of the car is represented by positive (+)
when the car's speed is decreasing, the car has negative acceleration
acceleration is the rate of change in velocity, therefore the direction of the acceleration is the same direction as the change in velocity
if an object's acceleration is the is in the same direction as its velocity, the object's speed increased and the object has a positive acceleration
negative acceleration is when the direction of acceleration is opposite the direction of the velocity, and is sometimes called deceleration
if you are driving on a straight road at 40 km/h, your velocity is constant and you have uniform motion
if you speed up to 60 km/h you are accelerating and your acceleration is positive
suppose the forward motion of the car is represented as positive
when the car's speed is increasing, the car has a positive acceleration
positive and negative acceleration are also dependent upon the direction of an object's motion
suppose a car driving forward increases its velocity from 2m/s to 6m/s
if forward motion is positive, then the car has a positive acceleration (positive change in velocity + positive direction = positive acceleration)
because the change in velocity is positive, which represents forward, the acceleration must also be positive
suppose a different car was increasing speed going backwards
negative direction + positive change in velocity = positive acceleration
because the change in velocity is negative, which represents backwards, the acceleration must also be backwards or negative
you can use a velocity-time graph to represent the motion of an object, whose velocity is changing
a velocity-time graph provides information about the object's velocity and acceleration
on a velocity-time graph the slope is the object's average acceleration
the unit for acceleration is m/s squared
even though the line is straight the motion is not uniform because the speed is increasing
unless the line is horizontal, meaning there is zero acceleration so the motion is uniform
when the best-fit line on a velocity-time graph passes through all of the data points, the object's velocity is changing as a constant rate and the motion is described as constant acceleration
however, since not all of the actual velocities may be directly on the best-fit line, the slope of a velocity time graph is the average acceleration
you can determine the acceleration of an object without drawing a velocity-time graph
the slope (acceleration) of a velocity-time graph is calculated as rise/run or a = ∆v/∆t
example - given: v-i = 2.5, v-f = 1.5, ∆t = 0.20s

a = ∆v/∆t
= -1.5 m/s – 2.5 m/s / 0.20s
= -4.0 m/s / 0.20s
= -20 m/s/s
= -20 m/s squared
you can use the same equation to calculate change in velocity and change in time
∆t = ∆v/a
∆v = a∆t
when an object falls near earth's surface, it is attracted downward by the force of gravity, which is an attractive force that acts between two or more masses
if you threw a ball into the air, on the way up, the ball's velocity is decreasing
up is positive, so the ball's change in velocity while rising in the air is negative
while the ball falls down, the velocity would be increasing but the direction is negative so the acceleration would still b negative
if you dropped a piece of paper and a baseball from the same height, the ball would hit the ground first, but not because of weight, but because of air resistance
since the piece of paper has more air resistance, it will hit the ground after the ball
if you crumpled up the piece of paper so it was the same shape as the ball, they would fall at the same speed
air resistance is a friction-like force that opposes the motion of objects that move through the air
in a vacuum (a place where there is no air) there is not air resistance and so therefore all objects will fall at the same velocity
acceleration due to gravity (g) is the acceleration of objects if there were no air resistance, and is about g = 9.8 m/s squared, downward
if you dropped a hammer and a feather on the moon from the same height, they would fall at the same velocity
with some objects on earth the air resistance is so small that we can assume there is none and assume the acceleration is 9.8 m/s/s
knowing this, you can calculate the average velocity, given: a = 9.8 m/s/s, ∆t = 1.5s

∆v = a x ∆t
= -9.8 x 1.5
= -15 m/s
an element is a pure substance that cannot be chemically broken down into simpler substances
a compounds is a pure substance that is composed to two or more atoms combined in a specific way
an atom is the smallest particle of any element that retains the properties of the element
if you lined up 50 million atoms it would be about 1cm long
chemical changes are changes in the ways that atoms and molecules in a substance are arranged and interconnected
subatomic particles are the particles that make up an atom
protons are subatomic particles that exist in the nucleus and have a positive electric charge of 1+
neutrons are subatomic particles that exist in the nucleus and have no electric charge
electrons are subatomic particles that have a negative electric charge of 1- and exist outside the nucleus
protons and neutrons are held tightly together at the center of the atom in a tiny region called the nucleus
electrons exist in the region around the nucleus in regular patterns called shells or energy levels
most of the volume of an atom is in the region occupied by electrons
atoms are uncharged or neutral because every atom has the same number of electrons and protons, so the charges balance out
the nucleus is at the center of the atom and is extremely tiny and dense
the simplest nucleus is that of the hydrogen atom, with only one proton
extra neutrons help make the nucleus more stable
the electric charge on the nucleus is always positive, since the protons have a positive charge and the neutrons don't have any charge
the nuclear charge is the term given to the electric charge of the nucleus, and is found simply by counting the number of protons
the nuclear charge is the same as the atomic number
many facts about the elements are recorded in the periodic table of the elements
each element is listed according to its atomic number, from left to right across each row and then row by row from top to bottom
each row is also called a period and each column is called a group or family
metals are on the left side and in the middle, while non-metals are in the upper right corner
the metalloids form a staircase toward the right side
elements in the same group or family have similar chemical properties
the alkali metals (group 1 besides hydrogen) - very reactive metals
the alkaline earth metals (group 2) - somewhat reactive metals
the halogens (group 17) - very reactive non-metals
the noble gases (group 18) - very unreactive gaseous non-metals
the block of elements from group 3-12 are collectively called the transition metals, and they include familiar elements such as nickel, copper, and gold
when atoms gain or lose electrons, they become electrically charged particles called ions
metal atoms, for example, lose electrons to from positively charged ions called cations
some metals can form ions in more than one way, (they are multivalent) and some can't
many non-metals also form ions by gaining electrons to form negative ions called anions
the periodic table represents patterns related to the arrangement of electrons in atoms
these patterns help to explain how elements behave during a chemical change
each shell in the electron region can hold up to a certain number of electrons but not more
1st shell:2, 2nd shell: 8, third shell: 8
a Bohr diagram is a diagram that shows how many electrons are in each shell surrounding the nucleus
the period number of an element equals the number of occupied shells of its atoms: sodium has 1 occupied shell, radium has 2, etc.
you can fit 2 electrons in shell 1, and 8 in shell 2 and 3
a stable octet refers to a complete set of 8 electrons in shell 2 or 3
elements in group 18 have stable octets in their atoms
the outermost shell that contains electron is called the valence shell
the electrons in the valence shell are called valence electrons
valence electrons are involved in chemical bonding
an atom's group number is also the number of valence electrons it has: lithium has 1 valence electron, calcium has 2, boron has 3, nitrogen has 5, etc.
this rule doesn't apply to groups 3-12
electrons in completed shells are arranged in pairs
when two atoms move close together, their valence electrons interact, and a chemical bond forms between the atoms if the new arrangement is stable
the stability of a atom, ion, or compound depends on the energy, lower energy is more stable
the lowest energy is achieved when the atoms in the compound have the same arrangement of valence electrons as the arrangement for the noble gas to which they are nearest in the periodic table
when an atom forms a compound, it may acquire a valence shell like that of its closest noble gas in one of three ways:
atoms of metals may lose electrons to other atoms, forming cations
atom of non-metals may gain electrons from other atoms, forming anions
compounds are of two basic types, ionic and covalent
an ionic compound usually contains a positive ion (usually a metal) and a negative ion (usually a non-metal)
in ionic bonding, one or more electrons transfers from each atom of the metal to each atom of the non-metal
for example: sodium has 11 electrons, and chlorine has 17. sodium gives an electron to chlorine, so now sodium has 10 (and a stable octet and full valence shell) and chlorine has 18 (also a stable octet and full valence shell)
now both atoms are in their most stable form and they are attached to make the compound NaCl
the atoms of many non-metals share electrons with other non-metal atoms
in covalent bonding, atoms overlap slightly, and one unpaired electron from each atom will pair together
both atoms are then attracted to the same pair of electrons so the atoms will stay together
a covalent compound is formed when non-metallic atoms share electrons to form covalent bonds
a covalent molecule is a group of atoms in which the atoms are bound together by sharing one or more pairs of electrons
the pair of electrons involved in a covalent bond are sometimes called the bonding pair
a pair of electrons in the valence shell that is not used in bonding is sometimes called a lone pair
a Lewis diagram is a diagram that illustrates chemical bonding by showing only the valence shell and electrons of an atom, and the chemical symbol
they are sometimes called Lewis structures or electron dot diagrams
you can follow these rules to draw a Lewis diagram
write the element symbol
dots representing electrons are placed around the element symbol at the points of the compass
place the dots until the fifth dot is reached, then pair them
remember, only draw the valence electrons
To draw a Lewis diagram of an ion, follow these rules:
for positive ions, one electron dot is removed from the valence shell for each positive charge of the ion. this usually means all valence electrons are removed. only the element symbol remains incased in square brackets with a positive charge show at the top right
for negative ions, one electron dot is added to each valence shell for each negative charge of the atom. this usually means the element's symbol is now surrounded by 8 electron dots (or 2 for hydrogen). square brackets are placed around the diagram with a negative charge shown at the top right
Lewis diagrams can be used to show ionic compounds, such as barium bromide:
Lewis diagrams can also be used to show covalent compounds, such as HF:
When two atoms are sharing a pair of electrons, you can represent the shared pair by a line as show in these examples:
you can use a Lewis diagram to show why some non-metals exist naturally as a diatomic molecule
a diatomic molecule is a pair of atoms that are joined by covalent bonds because the double atom will be more stable than the single one
by joining together, the atoms will become more stable
ionic compounds are compounds that are composed of positive ions and negative ions
you can describe them using a name or a formula
a chemical formula indicates the elements present in the compound
The International Union of Pure and Applied Chemistry is the organization that represents chemists around the world and develops the rules for naming compounds
one rule is that every name must have two parts; one for each type of ion in it
the first part of "potassium iodide" names the positive ion, potassium
the positive ion is always a metal in a compound containing two elements
the positive, metal ion is always written first
the second part of potassium iodide names the negative ion, iodide, and ion of iodine
the negative ion is always a non-metal in a compound containing two elements
the negative, non-metal ion is always written second
the non-metal's name always ends with the suffix "-ide" (iodine changes to iodide)
the charge of each ion refers to how many more or less electrons there are in the atom

the chemical formula of an ionic compound contains a symbol to identify each ion
the formula also shows the number of ions of each element in the compound
the small number written to the right of the symbol of an element is called a subscript and it gives the ratio of each type of ion in the compound
if there is no subscript, assume the subscript is 1
Remember to put the subscript ratios in simplest form
multivalent metals are metals that can form ions in more than one way, therefore they have multiple ion charges
for example, is some compounds nickel has a charge of 2+, while in others it has a charge of 3+
the periodic table always lists the most common charges first
a polyatomic ion is an ion composed of more that one type of atom joined by covalent bonds
because they carry an electric charge, they cannot exist on their own
brackets are used in the formulas to insure that the ratios are correctly placed
Remember, in covalent compounds DO NOT reduce the ratio to simplest terms
a binary covalent compound contains two non-metal elements joined together covalent bonds
atoms in covalent compounds do not connect by forming ions, instead they combine chemically by sharing electrons
prefixes indicate the numbers of atoms of each element that appear in the formula of binary covalent compounds
these prefixes are used for naming only covalent compounds
The formulas and names for ionic and covalent compounds can look very similar, here is the method you should use for distinguishing and naming them both:
1. Examine the formula
if it begins with a metal or ammonium (NH4+) it is an ionic compound
if it starts with a non-metal, it is likely a covalent bond
watch out for polyatomic ions - they have a charge (like ammonium)

2. If the compound is covalent
if it is covalent and doesn't begin with hydrogen, use the prefix naming system
for example, P2F4 would be diphosphorus tetrafluoride

3. If the compound is ionic
if it's ionic, look on the periodic table to see how many ion charges it has
if it only has one charge, the ion simply takes the name of the element without any roman numerals

chemical change always involves the conversion of pure substances called reactants into other pure substances called products
the reactant are what you start with, and the product(s) are what you end up with
the product(s) will be different from the reactants
when one or more chemical changes happen at the same time, it is called a chemical reaction, which may be represented by a chemical equation
a chemical equation may be written in words or symbols
a symbolic equation is a set of chemical symbols and formulas that identify the reactants and the products in a chemical reaction

word equation: nitrogen monoxide + oxygen -----> nitrogen dioxide
symbolic equation:
a chemical equation may also show the following:
integers are placed in from of the formula or a chemical symbol for an element
the integers can be used to determine the ratios between the various compounds in a chemical reaction
state of matter
letters indicate what state each compound is in
(g) = gaseous
(l) = liquid
(aq) = aqueous (dissolved in water)
(s) = solid
John Dalton believed that during a chemical reaction, no atoms were created or destroyed, they only arranged themselves in new ways
the total number of each type of atom present at the start of the reaction equaled the total number of each kind of atom after the reaction
Antoine Lavoisier, a French chemist, formulated the law of conservation of mass
this law states that mass is conserved in a chemical reaction; the total mass of the products is always equal to the total mass of the reactants in a chemical reaction
the idea that atoms are conserved (neither made nor destroyed) is believed to be true for all chemical reactions
the simplest for of a chemical equation is a word equation
potassium metal + oxygen gas ---> potassium oxide
a word equation provides only limited information about a chemical reaction
you can write a more useful equation by replacing words with chemical symbols and formulas
a skeleton equation simply shows the formulas of the reactants and products, and it does not show the correct proportions in which the reactants will actually combine and the products will be produced
the next step is to balance the equation by making sure there is the same number of each atom on both sides of the equation
a balanced chemical equation shows the identities of each pure substance involved as well as the matching number of atoms of each element of both sides of a chemical equation
according to the law of conservation of mass, the mass of each element present is conserved during a chemical reaction
the balanced equation for the above reaction is below
you can read the above equation as: "four atoms of potassium will combine with one molecule of oxygen to produce two potassium oxides"
remember to use the smallest whole number ratio
when you convert a word equation into a skeleton equation, there are a few problems:
you cannot deduce the formula of a polyatomic ion or other complicated compounds from their name
diatomic molecules are naturally present in groups of two
when you translate a word equation into a skeleton equation, remember these points:
we use the chemical symbol for nearly all elements when they are not in a compound (Cu is the chemical symbol for pure copper)
three common compounds containing hydrogen that you can memorize are methane, ammonia, and water
there are seven diatomic element, all of which are non-metals
they form a 7 shape from N to F to I on the periodic table
you can this of them as the "gens": hydrogen, nitrogen, oxygen, and the halogens (excluding At)
when you write them in an equation, always write them with a subscript two, for they are naturally present that way
REMEMBER: hydrogen is also diatomic even though it is not part of the seven shape
Here are some strategies you can use to help you balance a skeleton equation:
use trial and error. If you don't know where to start, start anywhere
balance compounds first and single elements last
balance all atoms in one formula before moving on
ad coefficients only in front of formulas. NEVER change subscripts
sometimes, oxygen or hydrogen will appear in more than one place on the reactants side or on the products side. this is your signal to balance oxygen and hydrogen LAST. once you have balanced everything else, you may find that hydrogen and oxygen are already balanced
if a polyatomic ion is on both sides of the equation, you can balance them as one unit, instead of balancing the atoms inside separately
perform a final check after you have finished balancing to make sure you've got it right
acids and bases have useful properties, but they should be handled with care, as some are corrosive, which means they can burn your skin, throat, stomach, and eyes on contact
the pH scale is a number scale for measuring how acidic or basic a solution is
an acid is a chemical compound that produces a solution with a pH of less that 7 when it dissolves in water
a base is a chemical compound that produces a solution with a pH of more that 7 when it dissolves in water
if a solution has a pH of 7, it is said to be neutral (neither acidic nor basic)
using the "pH values of Common Substances" diagram, you can see examples of pH values
notice that the more acidic a solution is, the lower the pH is
substances with a pH higher that 7 are said to be basic or alkaline
pure water is neutral, with a pH of 7
the pH scale allows chemists to express a wide range of measurements using a small an easily understood range of numbers
on the pH scale, one unit of change represents a 10 times change in the degree of acidity or basicity
therefore, a 2 pH drop is like a drop of 10 to the power of 2, or 100x drop in pH
even a small change in the pH of water can cause certain organisms to suffer
many common acids and bases form colorless solutions that may looks just like water, but can be dangerous
a safe way to tell whether a solution is acidic or basic is it use a pH indicator, a chemical that changes color depending on the pH solution it is placed in
one pH indicator is litmus, a compound that is extracted from some lichens
litmus is often dried onto this strips of paper and placed in solutions
litmus paper comes in red and blue
when blue litmus paper is placed in an acidic solution, the blue paper turns red
when red litmus paper is placed in a solution that is basic, the red paper turns blue
either paper will keep its original color when placed in a neutral solution
universal indicator contains a number of indicators that turn different colors depending on the pH of the solution
universal indicator can be a solution or can be put on paper strips
not all pH indicators change color at pH 7
the table below shows at which pHs other indicators turn color
you can sometimes identify acids by their chemical formulas
many compounds, such as HCl, take on acid properties only when mixed with water
if (aq) is written after a formula, it means it is aqueous, or "dissolved in water to make a solution"
the chemical formulas for acids are usually written with an H on the left side of the formula, such as HCl
for acids containing the element carbon, the H may be on the right side, as in CH3COOH
acids can be named in several ways
if no state of matter is given, the name may be given beginning with hydrogen, as in hydrogen chloride (HCl)
if the acid is aqueous, a different name may be used that ends in "-ic acid" (hydrogen chloride would be hydrochloric acid)
there are many different kids of acids
some contain oxygen, and some do not
there is a basic pattern when oxygen is present in the formula
names that begin with hydrogen and end with the suffix "-ate" can be changed by dropping hydrogen from the name and changing the suffix to "-ide"
example: hydrogen carbonate is changed to carbonic acid
names that begin with hydrogen and end with the suffix "-ite" can be changed by dropping hydrogen from the name and changing the suffix to "-ous acid"
example: hydrogen sulfite is changed to sulfurous acid
you can identify bases by their chemical formula since they are usually written with and OH on the right side of the formula
some bases are stronger that others
solutions made from highly reactive bases are called caustic
a solution that is either acidic or basic can conduct electricity because it contains freely moving ions
acids produce hydrogen ions (H positive) when dissolved in solution
bases produce hydroxide ions (OH negative) when dissolved in solution
testing the pH of a solution is a way of measuring its concentration of hydrogen atoms
concentration of hydrogen ion refers to the number of ions in a specific volume of solution
high concentration of hydrogen ions means the solution is highly acidic
high concentration of hydroxide ions means the solution is highly basic
acids and basics are considered to be chemcal opposites because H+ ions and OH- ions react with each other and therefore a solution cannot be both highly acidic and highly basic at the same time

when separate solutions containing H+ ions and OH- ions are combined, they react to form water: H + OH ---> H(2)O (water)
when an acidic solution is mixed with a basic solution, the solutions can neutralize each other, which means that the acidic and basic properties are in balance
in may cases (but with some important exceptions), this reaction produces a neutral solution
a salt is made up of a positive ion from a base and a negative ion from a acid
salts are a class of ionic compounds that can be formed during the reaction of an acid and a base
there are many different types of salts and they are used in a variety of ways
many everyday products are produced through acid-base neutralization
neutralization (acid-base) is the name for the type of chemical reaction that occurs when an acid and a base react to form a salt and water
for example: HCl + NaOH ---> NaCl + H(2)O
(acid) (base) (salt) (water)
metals react with oxygen to form oxides
an oxide is a chemical compound that includes at least one oxygen atom or ion along with one or more other elements
a metal oxide is a chemical compound that contains a metal chemically combined with oxygen
when a metal oxide dissolves in water, the solution becomes basic
the most reactive metals appear on the left of the periodic table; they are the alkali metals and the alkaline earth metals
within these groups, the metals at the bottom react most vigorously
other metals such as gold and copper are much less reactive, and will only react with a certain combination of acids
when metals react with acids, they usually release hydrogen gas, such as shown in the following two examples
in the 19th century, chemists knew that organisms produced a huge number of carbon-containing compounds
today, we call almost all carbon-containing compounds organic compounds, even if they are synthesized in a laboratory
inorganic compounds include compounds that generally do not contain carbon and also a few exceptions to the organic classification, such as carbon dioxide, carbon monoxide, and ionic carbonates
organic chemistry is the study of compounds that contain carbon
well over half of all known compounds are classified as organic
carbon is an element in group 14 of the periodic table, has four valence electrons, and forms four covalent bonds
in almost all organic compounds, carbon atoms are bonded to hydrogen or other elements close to carbon on the periodic table
carbon can also bond with itself
because carbon can form four bonds, it forms complex, branched-chain structures, ring structures, and even cage-like structures
carbon can even make double or triple connections between two carbon atoms
no other element can match carbon's ability to make stable compounds with such a variety of shapes and arrangements
you can tell whether a compound is inorganic or organic by examining its chemical formula
organic compounds must contain carbon, and inorganic compounds contain carbonate, carbides, and oxides
hydrogen does not come first in the above formulas because if it did the formula would look like an acid (as in HCl - remember H is on the left side of a formula in and acid)
a hydrocarbon is an organic compound that contains only the elements carbon and hydrogen
there are thousands of know hydrocarbons
the simplest of all hydrocarbons is methane, with one carbon atom and 4 hydrogen atoms off each covalent bond
the larger the molecule of carbon, the more easily it becomes a liquid
pentane is a liquid at room temperature
an alcohol is one kind of organic compound that contains carbon, hydrogen, and oxygen
there are many kinds of alcohols
a solvent is a liquid that can dissolve other substances
methanol will dissolve many substances that water cannot
ethanol is used in some beverages, and is a poison when consumed in large amounts
in a chemical reaction, how quickly or slowly reactants turn into products is called rate of reaction
a reaction that takes a long time has a low reaction rate, and a reaction that occurs quickly has a high reaction rate
a rate describes how quickly or slowly a change occurs
every chemical reaction proceeds at a definite rate
however, you can speed up or slow down the rate of a chemical reaction
chemists can control the rate of reaction by increasing or decreasing the temperature
the rate of reaction increases as the temperature increases
heating causes the particles of the reactants to move more quickly, resulting in more collisions and more energy
lowering the temperature slows down the particles of the reactants, so that they collide with each other less frequently and with less energy
increasing the concentration of the reactants in a chemical reaction will increase the rate of reaction
concentration refers to how much solute is dissolved in a solution
we measure concentration by knowing the mass of a substance that is in 1L of the solution
in order for new substances to be formed, the reactant atoms and molecules must be able to make contact with each other
if there is a greater concentration of reactant atoms, then there will be more collisions
therefore, increasing the concentration of the reactants will usually increase the rate of reaction
surface area is the measure of how much area of an object is exposed
the greater the surface area of the reactants, the more the particles will collide, so greater surface area means an increased reaction rate
this means that a powdered solid will generally react more quickly than a chunk of the material
if both reactants are gases or liquids that mix together, then there is no surface, and surface area is not a factor
the temperature and the concentration of reactants affect the rate of a reaction however increasing temperature or concentration isn't always a good idea
using a catalyst is a good way to increase the reaction rate without increasing temperature or concentration
a catalyst is a substance that speeds up the rate of a chemical reaction without being used up in the reaction itself, and is generally not included when you write a chemical equation
catalysts help to speed up a reaction by increasing the amount of energy needed to break bonds in a chemical reaction
in the presence of a catalyst, molecules of reactants line up better so when they collide with each other a reaction is more likely to take place
all cars built since the 1980s have pollution control devices built into their exhaust systems
a catalytic converter is a stainless steel device, shaped like a muffler, located underneath the frame of a vehicle
inside it is a ceramic or wire honey-comb-like structure that provides a large surface area for reactions to take place
the surface of the honeycomb is coated with a thin layer of metallic catalysts
as exhaust passes through the catalytic converter, several reactions occur
much of the poisonous carbon monoxide, which is produced from the combustion of gasoline, reacts with oxygen and is changed into carbon dioxide
hydrocarbons react with oxygen to produce carbon dioxide and water
finally, the poisonous nitrogen oxides are converted into nitrogen gas and oxygen in the following reaction:
Chemists have identified six common types of reactions: synthesis, decomposition, single replacement, double replacement, neutralization (aid-base), and combustion
these six general types represent thousands of reactions
in a synthesis (combination) reaction, two or more reactants (A and B) combine to produce a single product (AB)
element + element ---> compound
A + B ---> AB
a decomposition reaction is the breaking down of a compound into smaller compounds or separate elements
a decomposition reaction is the reverse of a synthesis reaction
compound ---> elememt + element
AB ---> A+B
in a single replacement reaction, a reactive element an a compound react to produce another element and another compound
in other words, one of the elements in the compound is replaced by another element
the element that is replaced could be a metal or a non-metal
element + compound ---> element + compound
A + BC ---> B + AC where A is a metal OR
A + BC ---> C + BA where A is a non-metal
a double replacement reaction usually involves two ionic solutions that react to produce two other ionic solutions
one of the compounds forms a precipitate, which is an insoluble solid that forms from a solution
a precipitate floats in the solution, then settles and sinks to the bottom
the other compound may also form a precipitate, or it remain dissolved in the solution
ionic solution + ionic solution ---> ionic solution + ionic solution
AB(aq) + CD(aq) ---> AD (aq) + CB(s)
acids are compounds that produce H+ ions in solution, and have a pH of less that 7
the formula for an acid is usually written with an H on the left side, an exception is water, as it is neutral
bases are compounds that produce OH- ions in solution, and have a pH of more than 7
the formula for a base is usually written with a metal or NH(4)+ on the left and OH- on the right side
when an acid an a base are combined, they will neutralize each other
in neutralization (acid-base) reactions, an acid and a base will combine to form a salt and water
acid + base ---> salt + water
HX + MOH ---> MX + H(2)O
X = negative ion, M = positive ion
combustion is the rapid reaction of a compound or element with oxygen to form an oxide and to produce heat
organic compounds and carbohydrates both combine with oxygen to form carbon dioxide and water
hydrocarbon + oxygen ---> carbon dioxide + water
C(x)H(y) + O(2) ---> CO(2) + H(2)O
x and y are subscripts and represent integers
radioactivity is the release of high-energy particles and rays of energy from a substance as a result of changes in the nuclei of its atoms
the stream of high-energy, fast-moving particles or waves that is found in our environment is called natural background radiation
background radiation has the potential to interact with an atom and turn it into an ion
radiation refers to high-energy rays and particles emitted by radioactive sources
radiation includes radio waves, microwaves, infrared rays, visible light, and ultraviolet rays
most forms of radiation are invisible to the human eye, but they are present all around us all the time
light is one form of radiation that is visible to humans
in 1895, German physicist Wilhelm Roentgen discovered that an unknown kind of energy was emitted from certain materials when he bombarded them with electrons
these invisible rays could darken photographic film, just like visible light rays could
he called the newly discovered energy "X rays" where X stood for unknown
his work led to the discovery of radioactivity by a French physicist (Henri Becquerel) who found that uranium salts emitted rays that darkened photographic plates
this surprised Henri, because up to this point scientists had only found evidence for these rays when they directed radiation onto the material
chemists Marie Curie and her husband concluded that the darkening of the photographic plates was due to rays emitted from the uranium atoms present in the mineral sample, and they called this process radioactivity
isotopes are different atoms of a particular element that have the same number of protons but different numbers of neutrons
all isotopes of an element have the same atomic number, however, since the number of neutrons differ, they will have different atomic masses and mass numbers
the mass number is an integer (whole number) that represents the sum of an atom's protons and neutrons
the mass number of an isotope is found by adding the atomic number and the number of neutrons:
mass number = atomic number + number of neutrons
the atomic number is found by counting the number of protons
to find the number of neutrons in an isotope, subtract the atomic number from the mass number:
number of neutrons = mass number – atomic number
different isotopes of the same element have the same element symbol, the number of neutrons does not change the name, symbol, or atomic number of the element
you can use the mass number to tell different isotopes apart
chemist represent isotopes using standard atomic notation (fig. 7.5), which is a shortened for involving the chemical symbol, atomic number, and mass number
the mass number is written as a superscript on the left of the symbol
the atomic number is written as a subscript on the left
another name for the standard atomic symbol is the nuclear symbol
the the isotope below would be written as potassium-39, as 39 is the mass number
by emitting radiation, atoms of one kind of element can turn into atoms of another kind of element
radioactive atoms emit radiation because their nuclei are unstable (likely to decay)
unstable atoms gain stability by losing energy, and they lose energy by emitting radiation
radioactive decay is the process in which unstable nuclei lose energy be emitting radiation
unstable radioactive atoms undergo radioactive decay until they form stable non-radioactive atoms, usually of a different element
isotopes that are capable of radioactive decay are called radioisotopes
it is very hard to judge whether an isotope is stable or not just by looking at a nuclear symbol
the three most common types of radiation emitted during radioactive decay are alpha radiation, beta radiation, and gamma radiation
beta particles are negatively charged, alpha particles are positively charged, and gamma radiation had no charge at all
alpha radiation is a stream of alpha particles
alpha particles are positively charged atomic particles that are much more massive than either beta particles or gamma radiation
an alpha particle has the same combination of particles as the nucleus of a helium atom
we use the atomic notation for helium-4 to represent an alpha particle
the symbols show that an alpha particle has a mass number of 4 and an atomic number of 2, which means it has 2 protons and 2 neutrons
because it has two protons, an alpha particle has an electric charge of 2+
because of their mass and charge, they are relatively slow-moving compared with other types of radiation
they are not very penetrating, as they can be stopped by a single sheet of paper
the emission of an alpha particle form a nucleus is called alpha decay
notice that the nuclear equation shown below is balanced; the sum of the atomic numbers and the mass numbers is the same on both sides
also note that when the alpha particle leaves radium, radium loses two protons, becoming radon, which is two atomic numbers down on the periodic table
a beta particle is an electron
the two following symbols can be used to represent a beta particle:
the mass of an electron is so small that it is rounded to 0
a beta particle has an electric charge of 1-
they are lightweight and fast-moving, so they can penetrate paper, but a thin sheet of aluminum foil can block beta particles
some atoms undergo beta decay, which is when a neutron changes into a proton and an electron
the proton remains in the nucleus, and the electron shoots out form the nucleus with a lot of energy
since the proton remains in the nucleus, the atomic number goes up by on, and becomes the next higher element on the periodic table
the mass number does not change because although the nucleus lost a neutron, it gained a proton that was pretty much the same mass
see attached diagram for the equation for beta radiation
gamma radiation consists of rays of high-energy, short-wavelength radiation
gamma radiation is represented by the following symbol:
because gamma radiation has almost no mass and no charge, the release of gamma radiation does not change the atomic number or the mass number of a nucleus
gamma rays are the highest form of electromagnetic radiation, and thick blocks of lead or concrete are needed to stop gamma radiation
gamma decay results from a redistribution of energy within the nucleus
a high-energy gamma ray is given off as the isotope of as the isotope falls from a high-energy state to a lower energy state
see the example below:
a nuclear equation is a set of symbols that indicates changes in the nuclei of atoms during a nuclear reaction
the symbols used in a nuclear equation include element symbols (including atomic number and mass number) and symbols representing neutrons and electrons
like a chemical equation, a nuclear equation shows reactants on the left side and products on the right
you can use a nuclear equation to show changes in the nucleus due to radioactivity
when you write a nuclear equation, you need to include the mass number and the atomic number of every particle and every nucleus participating in the change
remember the following rules when you write a nuclear equation:
the sum of the mass numbers does not change
even when a neutron splits into a proton and an electron or when a large nucleus splits into smaller ones releasing protons or neutron or gamma rays, the total number of protons plus neutrons remains the same
the sum of the charges in the nucleus does not change
the atomic number of an element represents the total (positive) charge in a nucleus
each nuclear symbol, including electrons and neutrons, has a number in the bottom left
the charge number does not change across a nuclear reaction
we can measure how the radioactivity in plant or animal remains has changed over time and calculate the age of the remains
all organisms on Earth contain carbon, especially isotopes carbon-12 and carbon-14
when an organism dies, carbon-14 atoms decay without replacing, and so the ratio of carbon-12 atoms to carbon-14 atoms gets smaller and smaller
knowing this, we can estimate for how long an organism has been dead
radiocarbon dating is the process of determining the age of an object by measuring the amount of carbon-14 remaining in that object
only material from plants and animals that were alive within the past 50 000 years contain enough carbon-14 to be measured
the rate of radioactive decay can be compared using a quantity called half-life
a half-life is a constant for any radioactive isotope and is equal to the time required for half the nuclei in a sample to decay
see the table below for examples:
when the information in table 7.5 (previous slide) is graphed, a type of line called a decay curve is produced
a decay curve is a curved line on a graph that shows the rate at which radioisotopes decay
the decay curve below is what the graph for all radioisotopes decaying will look like, the only difference will be the half-life of the isotope
there are many different isotopes that can be used for dating fossils, including those shown in table 7.6
the isotope that undergoes radioactive decay is called the parent isotope
the stable product of radioactive decay is called the daughter isotope
the production of a daughter isotope can be a direct reaction or the result of a series of decays
notice in the table below that each patent isotope is paired with a daughter isotope
each isotope can be used for radioisotope dating, but the dating range is different for each depending on the half-life of the parent isotope
all nuclear energy used for power generation anywhere in the world is accomplished through nuclear fission
nuclear fission is the splitting of a more massive nucleus into two less massive nuclei, subatomic particles, and energy
heavy nuclei tend to be unstable due to the repulsive forces between the many protons
in order to increase their stability, atoms with heavy nuclei may split into atoms with lighter nuclei
the fission of a nucleus is accompanied by a very large release of energy
we can use this huge amount of energy to generate power to support our present lifestyle
although nuclear reactions reduce the need for burning fossil fuels, nuclear reactors produce wastes that need to be stored safely for hundreds of thousands of years
the physical deterioration of nuclear power plants is a significant problem, especially in Ontario
there is an added concern that nuclear material could be used for making nuclear weapons
mass is conserved in chemical reactions
in typical chemical reactions, the energy produced or used is so small that there is very little change in mass
in chemical reactions, we say that mass is conserved
for example:
Mass A (wood + air) = Mass B (carbon + carbon dioxide + water)
you have learned that the number of protons in the nucleus of an atom determines the identity of the element
in a chemical reaction, there are no changes in the nuclei of the reactants, so the identities of the atoms do not change
chemical reactions involve electrons and rearrangements in the way atoms and ions are connected to each other
reactions that involve a change in an atom's nucleus are called nuclear reactions
a nuclear reaction is a process in which an atom's nucleus changes by gaining or releasing particles of energy
a nuclear reaction can release one, two, or all three types of subatomic particles as well as gamma rays
however, in nuclear reactions, a small change in mass results in a large change in energy
there are other kinds of nuclear reactions besides the natural radioactive decay
in a process called an induced or forced nuclear reaction, scientists can make a nucleus unstable and undergo a nuclear reaction immediately
a nuclear reaction is induced by bombarding a nucleus with alpha particles, beta particles, or gamma rays
the nuclear reaction shown below has similarities to radioactive decay
the difference is that an alpha particle is this nuclear reaction is a reactant, not a product
in atomic notation, mass number is on the top, atomic number or charge is on the bottom
the rules for writing nuclear equations for induced nuclear reactions are the same as for radioactive decay:
the sum of the mass numbers on each side of the equation stays the same
the sum of the charges (represented by atomic numbers) on each side of the equation stays the same
it takes a lot of energy for an alpha particle (with a charge of 2+) to collide with a nitrogen-14 nucleus (with a charge of 7+) because the repulsion between the + charges is so great
another kind of collision that can happen at much lower energies involves a neutron colliding with a nucleus
the nuclear fission of uranium-235 is the main nuclear reaction in both fission-style nuclear weapons and in Canadian nuclear power plants
the equation for nuclear fission for uranium-235 is:
(+ energy)
the ongoing process in which one reaction initiates the next reaction is called a chain reaction
the number of fissions and the amount of energy released can increase rapidly and lead to a violent nuclear explosion
a chain reaction is shown below
Italian physicist Enrico Fermi realized that materials that absorb neutrons could be used to control the chain reaction
in 1942, Fermi built the first nuclear reactor by using cadmium rods to absorb neutrons
keeping the chain reaction going in a nuclear power plant, while preventing it from racing out of control, requires precise monitoring and continual adjusting
much of the concern about nuclear power plants focuses on the risk of losing control of the nuclear reactor, which could result in the accidental release of harmful levels of radiation or even an explosion
Canada is a leader in the peaceful use of nuclear technology for both medical uses and power generation
Canadian nuclear reactors are called CANDU reactors (Canadian Deuterium Uranium reactors)
deuterium is an isotope of hydrogen-1 that is twice as heavy as it has both a proton and a neutron in its nucleus
the design of the CANDU reactor is among the safest in the world, and the reactor can be shut down quickly if a problem arises
a CANDU reactor produces heat as a result of reactions like the following:
the fuel used to produce heat in a CANDU reactor is in the form of bundles of rod containing uranium pellets
each nuclear fuel bundle stays in a CANDU reactor for about 15 months, and used bundles, which are highly radioactive, are stored in water pools at the reactor for about 10 years before they can be transferred to shielded, above-ground dry storage containers
while the radioactivity of the bundles does decrease over time, they remain hazardous for many thousands of years and must be isolated
Canada is planning to put used nuclear fuel in metal containers deep underground in stable rock formations
some countries reprocess used nuclear fuel to recover material for new nuclear fuel
fusion is the process in which two low mass nuclei join together to make a more massive nucleus
this process occurs in the sun and other starts where there is lots of pressure and high temperature
although the most common isotope of hydrogen is hydrogen-1, there is also hydrogen-2 and -3 in the sun, and when hydrogen-2 and -3 combine, their energy is so huge that it brings light and heat to Earth
the nuclear equation for fusion in the Sun and in fusion reaction experiments is:

the kinetic molecular theory explains that all matter is composed of particles, and that the particles move around constantly in random directions
kinetic energy is the energy of a particle or an object due to its motion
when particles collide, kinetic energy is transferred between them
the particles of a substance are bonded together differently depending on the state of the substance
in a solid, the particles are close together and vibrate slowly
in a liquid, the particles are farther apart
in a gas, the particles spread even farther apart, and move very quickly
an increase in temperature means the particles in a substance will move more quickly
even within a pure substance, the kinetic energy of the particles will vary
the particles travel at different speeds and in different directions
temperature is a measure of the average kinetic energy of all the particles in a sample of matter
as the particles average kinetic energy increases, so will the temperature
particles in a cold substance will move slower that particles in a hot substance
three different number scales are used to measure temperature; Celsius, Fahrenheit, and Kelvin
the Fahrenheit scale has been used since 1724, and was designed by Daniel Gabriel Fahrenheit
water boils at 212 degrees F
water freezes at 32 degrees
absolute zero is at -459 degrees
the Celsius scale was invented by Anders Celsius, and has been used since 1745
water boils at 100 degrees C
water freezes at 0 degrees
absolute zero is at -273 degrees
the Kelvin scale was designed by William Thompson (later know as Lord Kelvin) in 1848
water boils at 373 degrees K
water freezes at 273 degrees
absolute zero is at 0 degrees
thermal energy is the total energy of all the particles in a solid, liquid, or gas
the more kinetic energy something has, the more thermal energy it has
a swimming pool of lukewarm water has more thermal energy that a small cup of hot tea, because the TOTAL ENERGY of all the particles is larger
potential energy is the stored energy of an object or particle, due to its position or state
example: as you lift a textbook higher and higher off the desk, its potential energy increases
as the molecules spread apart, their potential energy increases, and they speed up
heat is the amount of thermal energy that transfers from an area or object of higher temperature to an area of lower temperature
example: when you turn on the stove, HEAT from the stove element TRANSFERS to the pan, and then the heat once again transfers to the egg
heat can similarly transfer through oceans and the atmosphere
heat can be transferred in three ways: conduction, convection, and radiation
all three methods of heat transfer are illustrated below
conduction is the transfer of heat from one substance to another or within a solid by direct contact of particles
conduction transfers heat from matter with a higher temperature (and higher kinetic energy) to matter with a lower temperature (and lower kinetic energy)
this is how heat transfers from a stove onto a pan onto food
particles from the heat from the stove collide with particles from the pan, transferring energy an heat
most materials can transfer heat by conduction, but they transfer it at different rates
thermal conductors are material that transfer heat easily (metals like aluminum)
thermal insulators do not transfer heat easily (air, wood, snow, and Styrofoam)
liquids and gases are fluids
fluids are substances in which the particles can flow freely
this characteristic allows for a second type of heat transfer, called convection
convection is the transfer of heat within a fluid and the movement of fluid from one place to another
unlike conduction, convection transfers matter as well as heat
liquid in lava lamps move by convection
convection can be explained by the kinetic molecular theory; as particles move faster and their kinetic energy increases, they move farther apart
as the particles move farther apart, the fluid itself expands and its density decreases
when the density of a substance decreases, the mass remains the same but the volume increases
heating the air inside a hot air balloon causes the air to expand and become less dense
as the air becomes lighter, the volume increases, filling up the balloon and causing it to rise up off the ground
in a pot of water, water near the bottom (closest to the element) heats up, becomes less dense, and rises to the top
cooler water is more dense so it sinks down to replace it and also becomes heated and rises
this continual movement of water caused by heating, cooling, and reheating is called a convection current
a convection current is the movement of fluid caused by density differences
convection currents are used in a variety of household appliances including convection ovens and hot air furnaces
electromagnetic radiation is the transfer of energy by waves traveling outward in all directions from a source
electromagnetic waves radiate (travel by radiation) through space even though there is no matter there
radiant energy is the energy carried by electromagnetic waves
the only electromagnetic radiation we can see is visible light
most of the electromagnetic spectrum is invisible to the unaided human eye
infrared radiation (also known as heat radiation) is what you will experience when you stand close to a heat source, such as a campfire
when you stand in sunlight, you feel solar radiation, which is the transfer of radiant energy from the Sun
solar radiation is made up of visible light as well as infrared and other types of radiation
any material with a temperature greater that absolute zero (0 K) radiates some heat, even ice, snow, humans, and all other matter with a greater temperature than 0 Kelvin
materials absorb, reflect, or transmit radiation
an atmosphere is a layer or layers of gas(es) that extends above a planet's surface
of all the planets studied, only one is known to contain water in all three states; this planet is Earth
Earth's atmosphere is a complex system
scientists believe that millions of years ago, there may not have been oxygen gas in Earth's atmosphere
science suggests that oxygen gas first appeared when sunlight broke apart water molecules in the upper atmosphere
the next stage of oxygen production came much later, with the appearance of photosynthetic micro-organisms
like, plants, these single-celled organisms used sunlight to produce their own food
at the same time, the process of photosynthesis produced large amounts of oxygen gas and eventually the balance of carbon dioxide to oxygen in the atmosphere stabilized
what we call "air" is a combination of gasses in the lower atmosphere, near Earth's surface
the lower atmosphere is made up mainly of nitrogen and oxygen, and about 1% of air is made up of other trace gases
the composition of the atmosphere remains fairly constant to a height of about 80 km above sea level
the higher the elevation, the thinner (less dense) the air becomes, making it hard to breathe
Earth's atmosphere is made up of five layers, which all differ in average altitude, chemical composition, average temperature, and density
the average altitude of a layer will change depending on what time of day it is
the five layers of Earth's atmosphere are:
the troposphere
the stratosphere
the mesosphere
the thermosphere
the exosphere
the troposphere is the lowest layer of Earth's atmosphere
on average, it is about 10 km thick, but ranges from 8 km thick at the poles to about 16 km thick at the equator
because the troposphere is the bottom layer, the mass of the upper atmosphere compresses its gas molecules, making it the densest of all the layers
almost all water vapor in the atmosphere is found in the troposphere, which is why weather takes place in this layer
solar radiation and heat emitted from Earth's surface affect the air in the troposphere, causing air to move around continuously
the troposphere also contains most of the particulate matter (dust) that exists in the atmosphere
the temperature in the troposphere drops by about 6.5 degrees C for every 1 km increase in altitude
at the bottom of the troposphere the average temperature is 15 degrees C, and at the top it is about -55 degrees C
at the top of the troposphere is a transition zone, called the tropopause, which marks the boundary between the troposphere and the next layer– the stratosphere
transition zones are not absolute boundaries, as their altitudes differ depending on changes in patterns of air movement, temperature, and air density
the stratosphere has dry air and few clouds
at the bottom it is about -55 degrees C, and gets warmer as you go higher
at about 50km, temperatures can reach 0 again
passenger airplanes usually fly about 10km above sea level to avoid convection currents in the troposphere
the stratosphere acts as a barrier that helps contain moisture in the troposphere and also block out damaging radiation from the sun
the ozone layer is an important part of the stratosphere that absorbs much of the ultraviolet radiation from the sun
ozone is a molecule composed of three oxygen atoms
there are about 12 ozone molecules per million other molecules in the ozone layer, but it still helps absorb radiation, and this is what makes the stratosphere heat up
above the stratosphere is the mesosphere, which extends from about 50 to 80km above sea level
temperatures in the mesosphere can reach as low as -100 C
every day, millions of small pieces of dust and meteors crash through the mesosphere
as they collide with particles in the mesosphere, thermal energy is released and the space debris burns up
the burning pieces of matter are shooting stars
the fourth layer in the atmosphere is the thermosphere, which extends from about 80 to 500km above sea level
at the top of the thermosphere, where the solar radiation is the strongests, temperatures can reach 1500 - 3000 degrees C
when charged particles in Earth's magnetic field collide with particles in the thermosphere, a bright glow can be seen
in the northern hemisphere this glow is called the northern lights, or aurora borealis
the fifth layer of the atmosphere is the exosphere, and the top of it is not well defined and merges with outer space at an altitude of about 700 km
only a tiny portion of solar radiation reaches Earth, but even so almost all energy on Earth comes from the Sun
waves of solar radiation transfer their energy when they are absorbed by matter, whether solid, liquid, or gas
much of the solar energy is converted to thermal energy as particles move faster and transfer kinetic energy to each other
areas that receive the most solar radiation gain the most thermal energy
the amount of solar radiation that reaches a certain area is called insolation
insolation is measured in watts per square meter
particles of matter in the atmosphere interact with solar radiation, reducing insolation at Earth's surface
a region's location also affects how much isolation it receives
as a result, locations at higher latitudes receive less insolation
angle of incidence is the angle between a ray reaching a surgace and a line perpendicular to that surface
at the equator, the angle of incidence of the Sun's rays is 0 degrees, and at higher latitudes the angle is much larger
the smaller the angle of incidence, the more sunlight an area recieves
very little solar radiation heats the atmosphere directly
solar radiation comes in short wavelengths, some of which pass through the atmosphere to Earth's surface, where they are absorbed
Earth's surface reradiates some of this energy as longer, infrared waves, which the atmosphere absorbs
convection transfers the thermal energy throughout the atmosphere
conduction transfers heat in the lowest part of the troposphere, near Earth's surface
the ground transfers heat to particles in the air directly above it
the particles in the heated air collide with particles in the lowest level of the atmosphere and the temperature of the air increases
an average of 342 W/m squared of solar radiation reaches the top of Earth's atmosphere
if all this energy was kept in the atmosphere, the planet would be too hot
Earth has a radiation budget, which keeps incoming and outgoing energy in balance, so that the same amount of energy goes out and comes in
the incoming solar radiation is reflected by clouds (15%) and dust in the atmosphere (7%)
another 20% is absorbed by clouds and the atmosphere, and the remaining 58% reaches Earth's surface, but only some is absorbed by the land and the water
about 9% or incoming solar radiation is reflected back to outer space by Earth's surface
ultimately, the energy absorbed by Earth's surface and atmosphere will be radiated back into space
a number of sources emit the energy as longer wave radiation: evaporation and sublimation of water (23%), conduction and convection (7%), and infrared radiation (19%)
clouds and atmospheric gases temporarily trap much of the radiation from Earth's surface and then release it in all directions, including back into space
the physical characteristics of a substance affect how much radiation it will absorb or reflect
dark areas will absorb more than light ones
albedo describes the amount of radiation reflected by a surface, and is an important quality when discussing thermal energy in the atmosphere
the amount of reflection from land depends greatly on the ground cover
snow covered areas have high albedos, while many forests and soil covered areas have low albedos
if Earth were covered in snow, it would have a much higher albedo, and more solar radiation would be reflected back into space
if Earth were covered in water, it would have a much lower albedo, and more solar energy would be absorbed
weather is the condition of the atmosphere in a specific place and at a specific time
weather describes more that clouds, rain, lightning, and storms
weather describes all aspects of the atmosphere, including temperature, atmospheric pressure, amount of moisture in the air, and wind speed and direction
weather is closely connected to heat transfer in the atmosphere
convection moves air and thermal energy throughout the troposphere, causing various kinds of weather experienced at Earth's surface
atmospheric pressure plays a key role in the convection of air in the atmosphere
pressure is the amount of force per unit area
molecules in the air move continuously in all directions
as they collide with a nearby surface, such as you, they exert force on it
air pressure, or atmospheric pressure, is the pressure exerted by the mass of air above any point in Earth's surface
a barometer is an instrument that measures atmospheric pressure
the barometer was developed in 1643 by Torricelli
the SI unit for atmospheric pressure is the pascal (Pa)
pascals are used to measure the vertical force per unit area
one pascal has a force of one newton per square meter, and this is a very small amount so kilopascals (kPa) are usually used instead
there are 1000 Pa in one kPa
at sea level, the atmospheric pressure is about 101.3 kPa, which is equal to 1kg/cm squared
atmospheric pressure in you body counteracts the pressure outside your body, so you can stand Earth's atmospheric pressure
as a result, you usually don't notice it
as the altitude increases, the atmospheric pressure decreases, because they air is becoming less dense
higher altitude means lower density, which means lower atmospheric pressure
the kinetic molecular theory explains that as particles are heated they gain kinetic energy and move around more quickly
as a result, warm air is less dense that cold air because the gas molecules in it are farther apart
warm air is also lighter that cold air
the movement of air at different temperatures also affects atmospheric pressure
when warm air pushes into an area of cold air near the ground, the atmospheric pressure in that location decreases
when cold air pushes into a region of warm air, the atmospheric pressure in that location increases
humidity is a measurement that describes the amount of water vapor in air, and is a third cause of changes in atmospheric pressure
the more water vapor in the atmosphere, the lighter the air is
as water vapor is added to a region of the atmosphere, it displaces an equal volume of dry air
oxygen gas and nitrogen gas make up about 99% of dry air
they are heavier that water vapor, and so wetter air is lighter
therefore humid, or wet air exerts less atmospheric pressure, so more humidity equals less pressure
meteorologists use atmospheric pressure readings to predict changes in the weather
a decrease in atmospheric pressure means that warm, humid air is approaching and that the temperature will increase
an increase in pressure suggests that cool, dry weather is on the way
specific humidity is the number of grams of water vapor in 1 kg of air, or in 1m cubed of air
as the temperature of the air increases, its capacity to hold water vapor also increases
the air becomes saturated when the specific humidity equals the capacity of air to hold water at a specific temperature, also known as the dew point
when air is cooled below the dew point, water vapor condenses
usually, the amount of water vapor in the air is less that the amount required to saturate the air at a given temperature
relative humidity is the comparison of the amount of water vapor in the air with the amount of water vapor that the air could possibly hold
a relative humidity of 50% means that the air is 50% saturated, and 100% relative humidity means that the air is completely saturated
an air mass is a parcel of air with similar temperature and humidity throughout
conditions in an air mass change to become like the surface below it
an air mass can be thousands of km wide and several km thick
when an air mass cools over an ocean or a cold region on land, a high pressure system forms
some high pressure systems are large enough to cover most of North America
as the air mass cools, particles in the air lose kinetic energy and the air becomes denser
the air mass contract and draws in surrounding air from the upper troposphere
the added weight of the extra air increases atmospheric pressure
the dense, high pressure air moves outward towards areas of lower pressure, creating a wind
wind is the movement of air from an area of higher pressure to an area of lower pressure
Earth's rotation causes the wind to flow clockwise around the high pressure center
as the high prssure air sinks, it becomes warmer and drier
as a result, high pressure systems often bring clear skies
air masses that travel over warm land or oceans may develop into low pressure systems
when an air mass warms, it expands and rises, making the layer of air thicker
however, as the air rises, it cools, and water vapor in the air may condense, producing clouds or precipitation
this is why low pressure systems often bring wet weather
meanwhile, the expanding air mass pushes away air in the upper troposphere
directly below, at Earth's surface, the atmospheric pressure decreases
the lower pressure area at the surface draws in air from higher pressure areas
as higher pressure air in the atmosphere flows towards a lower pressure area, Earth's rotation causes the air flow to curve
as a result, the wind flows counterclockwise around the low pressure center in the northern hemisphere and clockwise in the southern hemisphere
prevailing winds are winds that are typical for a region
the prevailing winds of southern British Columbia are moist air masses from the Pacific Ocean that blow inland over the coastal mountains
cool temperatures and high altitudes cause water vapor in the air to condense, forming rain or snow
as a result, the air carried by these prevailing winds has lost most of its moisture by the time it reaches interior British Columbia
prevailing winds are influenced by several factors
over a short distance, winds follow a fairly straight path from areas of high to low pressure
over long distances, with massive high and low pressure systems, wind patterns are not so straightforward
geographic features such as mountains, oceans, and lakes greatly affect the characteristics of winds
sea breezes are local winds that are caused by the different rates at which land and water respond to heating and cooling
during the day, land heats up faster that water
the land radiates heat, which warms air at the surface
the warm air rises, replaced by cool air drawn in from over the water
the resulting wind, called an onshore breeze, usually occurs during the late morning along coastal regions
during the night, the land cools down faster than water
the relatively warm air over the water rises and draws in cool air from over the land
this nightly reversal of the sea breeze is called an offshore breeze
if Earth was much smaller and did not spin, warm air would rise at the equator, travel to the poles, and sink, creating two convection currents
Earth's actual size means that air sinks long before it reaches the poles
over long distances, wind is also affected by Earth's rotation
the Coriolis effect is a change in the direction of moving air, water, or objects due to Earth's rotation
as Earth rotates, any location at the equator travels much faster that a location near the poles
air rising from the equator travels east quickly in the same direction that Earth rotates
as a result, the Coriolis effect deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
wind systems are wide zones of prevailing winds
Earth's major wind systems result from convection currents and the Coriolis effect
Earth has three major wind systems, which occur in both hemispheres: the trade winds, the prevailing westerlies, and the polar easterlies
the trade winds were named by sailors, who historically used these dependable winds, along with the prevailing westerlies, to sail across the oceans in order to trade goods
the prevailing westerlies in the northern hemisphere are responsible for much of the weather in Canada and the United States
as you might expect, the polar easterlies are cold winds from the poles
in the troposphere, Earth's surface and the density of the air produce friction, which slows global winds
in the stratosphere, winds are subject to less friction, and so they can move much faster that winds in the troposphere
a jet stream is a band of fast-moving air in the stratosphere
jet streams are so strong and fast that airline pilots try to fly with these winds and avoid flying against them
several jet streams circle earth at various latitudes
as with other global winds, convection currents in the atmosphere produce the jet streams, and so temperature differences in the atmosphere greatly affects these winds
during cooler times of year, jet streams are faster and occur closer to the equator
the movement of the jet streams also affects the movement of the air beneath them
as a result, changes in the jet streams affect the weather
at any given time, several air masses over North America affect the weather in different regions
these air masses interact as they move
perhaps on a sunny day you have looked to the west and have seen an approaching wide band of clouds
this band of clouds would have indicated the boundary between two air masses, called a front
a weather front may be several hundred km wide and thousands of km long
each air mass has its own temperature and pressure, and these conditions change the front
an approaching front means a change in the weather, and the extent of the change depends on the degree of difference between conditions in the air masses
cold, dense air, for example, will slide under warmer air, bringing cooler temperatures and dry weather
fronts usually bring precipitation
warm air at the front is displaced by cold air
the warm, moist air rises, and as it cools water vapor in the air condenses, forming clouds
under the right conditions, the condensed water will fall as precipitation
one example of extreme weather is a thunderstorm
thunderstorms are named for the lightning, thunder, strong winds, and hair or rain that they produce
they occur when water vapor in rising warm air condenses, releasing thermal energy
the energy further heats the air, which continues to rise
the condensation produces large thunderheads (cumulonimbus clouds), which precede and accompany thunderstorms
these clouds can reach the top of the troposphere where the tops spread out and form anvil shapes
thunderheads can produce extremely heavy rain and even hail
the clouds may also discharge static electricity, known as lightning
lightning heats the air to 10 000 degrees C or more, causing it to expand rapidly
the expansion and sudden collapse of the air produced the sound we call thunder
thunderstorms occur where atmospheric conditions are unstable
moist air rising rapidly up a mountain or within a cold air mass can produce intense thunderstorms
sea breezes in the tropics, for example, often result in thunderstorms
advancing cold fronts and, less often, advancing warm fronts also cause thunderstorms
a tornado is a violent, funnel-shaped column of rotating air that touches the ground
it can form when high-altitude horizontal winds meet large thunderstorms
the horizontal winds cause the rapidly rising air in the thunderstorm to rotate, producing a spinning vortex of air called a funnel cloud
in some cases the funnel cloud touches the ground and becomes a tornado
the tornado follows a seemingly random path, hurling dust and debris all over
surface winds caused by tornadoes can reach speeds of 400 km/h
when tornadoes form over water, waterspouts can occur, which are funnel shaped rotating column of water
some of the world's most violent weather results from the exchange of thermal energy in the tropics
the tropics, the regions closest to the equator, are the ideal location for the formation of intense storms
together, warm ocean water and winds produce conditions that lift moist air high into the atmosphere
the water vapor condenses, producing clouds and rain
the precipitation releases large amounts of thermal energy transferred from the warm ocean water
at the same time, the rising air produced a low pressure area at the ocean's surface
warm air rushes towards the low pressure area to replace the rising air
the Coriolis effect forces the air to rotate counterclockwise in the southern hemisphere
the result is a massive, spinning storm known as a tropical cyclone
it gains speed and momentum as more and more air approaches the low pressure center, and more energy is released with condensation, and the cyclone rotates even faster
wind speeds may reach 240 km/h
tropical cyclones are known as cyclones to people living near the Indian Ocean, typhoons to those near the western Pacific Ocean, and hurricanes to those near the Atlantic Ocean
hurricane season extends from late summer to early fall, the period when the oceans store the greatest amount of thermal energy
in the early 20th century, German scientist Alfred Wegener proposed the continental drift theory, which states that the continents have not always been in their original positions, but have drifted there over millions of years
Wegener's first clue came from maps of the world
the apparent match on a world map between South America;s eastern coastline and Africa's western coastline was the first piece of evidence for Wegener's theory
Wegener thought the matching coastlines were to close to be coincidental, and he suggested that millions of years ago, the continents were joined in one super continent, which he called "Pangaea"
Pangaea comes from the Greek words pan (all) and Gaea (earth)
the coastlines do not match perfectly, a better alignment is obtained by matching the continental shelves, which are the submerged original shorelines of continents
Wegener also compared geological structures, fossils, and evidence of ancient glaciers on different continents
this clues didn't seem important until he visualized the continents together
Wegener's analysis of rocks and mountain ranges supported his idea that the continents were once joined
he noted mountain ranges that begin on one continent, end at the coastline, and then appear to continue on a continent across the ocean
there are also many similarities between rock structures, such as folds, and the ages of rocks on continents that are separated by thousands of km of ocean
Wegener reasoned that the continuous mountain ranges were once joined when pangaea existed
another piece of evidence for the continental drift theory is the matching fossils
similar fossils occur in various parts of the world
for example, fossils of the freshwater reptile Mesosaurus can be found in only two places: southeastern South America, and southwestern Asia
Because Mesosaurus was a small, freshwater animal, it seemed very unlikely that the animal would have survived crossing the 6000 km of open ocean between the two continents
this, along with other fossil evidence, supports Wegener's theory that the continents were once joined
work by many scientists has added support to Wegener's theory
the effects of ice ages on Earth's surface are one example
glaciers are vast masses of ice, found in our time at the poles and high in the mountains
during the ice ages, glaciers covered large areas of land
when glaciers advance or retreat, they mark the land with proof of their existence, leaving behind large, U-shaped valleys, deeply scratched rocks, and various types of patterns of rock formations
paleoglaciation refers both to the extent of ancient glaciers and to the rock markings they have left behind
scientists have found evidence that glaciers were located in tropical regions such as Africa and India
if the continents were once joined, Africa and India would be at different latitudes, and therefore have lower temperatures, maybe even low enough to have glaciers
there are coal deposits in Antarctica which doesn't make sense because in order to make coal you need living organisms and usually swampy plant material, which doesn't grow in Antarctica
this suggests that Antarctica as well was in a different location
although Wegener collected a great deal of evidence for his theory, he still could not explain how the continents moved
it would be over 30 years before his question was answered
the surface of Earth is broken into large, movable slabs of rock called tectonic plates
volcanoes are openings in Earth's surface, that, when active, spew out gases, chunks of rock, and melted rock
and earthquake is a sudden, ground-shaking release of built-up energy at or under Earth's surface
volcanic eruptions and earthquakes are dramatic events, and it would be reasonable to assume they occur everywhere
a plot of volcanoes and earthquake zones on a map outline boundaries between tectonic plates
oceanographers have discovered a long mountain range under the ocean called the Mid-Atlantic Ridge
from the 1940s onwards, the drive to map the ocean floor led to many discoveries
oceanographers made one such discovery when they took rock samples from the Mid-Atlantic Ridge to determine the age of the ocean floor
a peculiar pattern emerged: the youngest rocks were found closest to the ridge
in addition, the layer of ocean sediment became thicker the farther it was from the ridge
like a bar magnet, Earth has north and south magnetic poles and a magnetic field
the reason that a compass points north is because the needle lines up with the poles
iron and other magnetic metals in rocks also usually align with these field lines
over thousands of years Earth's magnetic field can completely reverse, a process known as magnetic reversal
there is no definite explanation for this
much like a compass needle that has been frozen in place, ancient rocks often preserve the strength and direction of Earth's magnetic field as it was when rocks were formed
paleomagnetism is the study of the magnetic properties of ancient rocks
scientists have discovered a surprising pattern of stripes in the direction that iron-containing metals pointed on the sea floor
the pattern, called magnetic striping, was repeated on both sides of the mid-Atlantic ridge
in 1960, Harry Hess proposed that magma, molten rock from beneath Earth's surface, rises because it is less dense than the material that surrounds it
the magma cools and hardens when it breaks through Earth's surface, at a spreading ridge, forming a new sea floor
as convection currents cause more magma to rise, the new magma forces apart the hardened material and, like a conveyer belt, continuously pushes older rock aside
this process is called sea floor spreading as was an important step in understanding tectonic plate movement
in the mid-1960s, Tuzo Wilson suggested that chains of volcanic islands, such as the Hawaiian Islands, were formed when a tectonic plate passed over a stationary hot spot
a geologic hot spot is an area where molten rock rises to Earth's surface
Wilson thought that the continents must break up at certain areas, move across Earth's surface, and then rejoin
his hypothesis explained the formation of mountains and ocean basins and the cause of earthquakes and volcanic eruptions
Wilson's hypothesis also gave a reason for the movement of tectonic plates and helped explain the transformation of rocks from one type to another in the rock cycle
later named the plate tectonic theory, it is considered the unifying theory of geology
scientists believe that Earth began as a molten ball over 4.5 billion years ago, and as it cooled, less dense materials floated to the top
the top layer of Earth is called the cruse
three quarters of Earth's crust is made from the elements silicon and oxygen, which combine to form a group of rocks called the silicates
Earth's outer layer is composed of several large, rigid but mobile chunks of rock known as tectonic plates
made up of the crust and the uppermost mantle, tectonic plates form the lithosphere, which ranges in thickness from 65 to 100 km
there are about 12 major tectonic plates and many smaller ones
there are two types of tectonic plates
oceanic plates contain the dense rock basalt
continental plates and continents themselves contain large amounts of granite
the crust is Earth's outermost layer, made from solid, brittle rock
the thickness and type of rock varies in different parts of the crust
continental crust is made from a lighter type of rock called granite and can be as thick as 70 km
oceanic crust is made from a dense, dark rock called basalt and can be as thick as 10 km
the mantle is Earth's thickest later; it is 2900 km thick an makes up 70% of Earth's volume
it is mostly solid and can be divided into the upper mantle and the lower mantle
the upper mantle is composed of partly molten rock containing iron and magnesium
the upper mantle magma flows like thick toothpaste
a transition zone separates it from the lower mantle, which begins at a depth of about 660 km
the lower mantle is made of solid, dense material that contains the elements magnesium and iron
the layer below the mantle is the outer core and it is a liquid
it is bot 2300 km thick and is composed of mainly a mixture of iron and nickel
the inner core lies at Earth's center and is a sphere with a radius of about 1200 km
composed mainly of iron and some nickel
although the temperatures range from 5000-6000 degrees C, far past the melting point of iron, the pressure keeps it solid
scientists believe that the outer and inner cores rotate at different speeds and may be responsible for Earth's magnetic field
below the lithosphere is the asthenosphere, a partly molten layer in the upper mantle
the temperature varies throughout, and geologists believe this is because large quantities of radioactive uranium are located here, and the radioactive decay heats the mantle in these spots
heated particles have more kinetic energy and so move around more, causing them to spread farther apart
a convection current results as the hotter, and therefore less dense, material in the mantle rises, cools, and then sinks again, only to be reheated
scientists hypothesize that mantle convection is one of the driving forces behind plate movement
currents in the asthenosphere move the tectonic plates, which carry the continents with them
rising currents of magma eventually reach Earth's surface at spreading centers
if a spreading center occurs in the ocean, it is called a spreading ridge, or an oceanic ridge; if it occurs on land, which is less common, it is called a rift valley
magma cools as it reaches the surface and becomes "new" rock
as new material at a ridge or a rift pushes older material aside, the tectonic plates move away from the ridge
this process is called ridge push
when tectonic plates are pushed apart, one or more will eventually bump into another plate
if a dense ocean plate collides with a continental plate, the heavy oceanic plate will dive deep under the lighter continental plate, an event known as subduction
subduction is the action of one plate pushing below the other
areas of subduction, called subduction zones, typically experience large earthquakes and volcanic eruptions
subduction zones themselves are thought to contribute to plate motion
the edge of a tectonic plate subducts deep into the mantle, and as it does so it pulls the rest of the plate with it
this process is called slab pull
along with convection currents and ridge push, slab pull helps keep tectonic plates in motion
a region where two tectonic plates are in contact is known as a plate boundary
the interaction of tectonic plates has played an important role in both the geological and the biological history of Earth
there are three main types of plate interaction: divergence (spreading apart), convergence (coming together), and transform (sliding by)
the way in which tectonic plates interact depends on two main factors: the type of plate and the direction the plates are moving relative to one another
divergent plate boundaries mark the areas where tectonic plates are spreading apart
plates that are spreading apart are known as diverging plates
in the ocean, sea floor spreading causes plates to separate
a similar process can occur on the continents
a convergent plate boundary occurs where tectonic plates collide
plates that collide are known as converging plates
the collision can have various results, depending on the nature of the converging plates
when a dense oceanic plate collides with a continental plate, the oceanic plate is forced to slide under the continental plate, forming a deep underwater valley called a trench
as the subduction plate moves deeper, large pieces melt off
much of this melted material cools and crystallizes into large rock masses below the surface of the continental plate
if conditions are right, magma can work its way to the surface, forming cone-shaped volcanoes, and sometimes even a volcanic belt, which is a long chain of volcanoes
the force of the collision between oceanic and continental plates creates mountain ranges as the continental rock crumples and folds
although the tectonic plates move slowly, great forces are involved
frequently, colliding plates resist the force of convection currents, ridge push, and slab pull
when the stress is too great to resist anymore, the energy is released, causing an earthquake
subduction also occurs where two oceanic plates converge
cooling will cause one plate to be denser than the other, and the denser one will slide deep into the mantle
in this case, a long chain of volcanic islands known as a volcanic island arc may form
when continental plates collide, subduction does not occur since the plates have very similar densities
as the plates collide, their edges fold and crumple, forming great mountain ranges
the mountains get bigger as the plates continue to move towards each other
convection currents in the mantle often cause tectonic plates to slide past each other, this is known as a transform plate boundary
at these boundaries, not mountains or volcanoes form since rock is sliding past rock
earthquakes and faults (breaks in rock layers due to movement on either side) may occur
a fault that occurs at a transform boundary is called a transform fault
friction between moving plates produces stress, or the build up of pressure
when the plates can no longer resist the pressure, there is an earthquake—a massive release of energy that shakes the crust
earthquakes can happen anywhere, but 95% of them occur at a plate boundary
about 80% occur in a ring bordering the pacific ocean
it is hard to predict the exact timing, size, and location of a particular earthquake
the focus is the location inside Earth where the earthquake starts
energy is released at the focus
the epicenter is the point on Earth's surface directly above the focus
earthquakes occur at various depths, depending on the type of plate interaction involved
more shallow focus equals more damage
vary few earthquakes have deep foci
energy released by an earthquake produced vibrations called seismic waves
seismology is the study of earthquakes and seismic waves
by studying seismic waves, scientists can deduct the composition of Earth's layers
not all waves are alike; some can only pass through certain layers of the Earth
see table below
you can use a seismometer to measure the amount of ground motion caused by an earthquake
a seismometer produces a record of ground motion called a seismogram, which provides information such as the time, duration, and amount of ground shaking of and earthquake
magnitude is a number that rates the strength of an earthquake
higher magnitude = more damage
there are three distinct types of volcanoes: composite volcanoes, shield volcanoes, and rift eruptions
the type of volcano depends on the type of plate interaction involved
a composite volcano is cone shaped and belches rock, ash, and lava
the cone shape results from repeated eruptions that caused magma to build up and cool
as magma approaches the surface, gas builds up underneath
when there is too much pressure, there is an explosive volcanic eruption
composite volcanoes are usually found near subduction zones
shield volcanoes are the larges on Earth and do not occur at plate boundaries but instead form over hot spots
a hot spot occurs where a weak part of the lithosphere allows magma to break through
the magma in shield volcanoes is much thinner and so shield volcanoes are often less explosive
shield volcanoes can occur in ocean basins, where the lithosphere is thinner
rift eruptions occur when magma erupts through long cracks in the lithosphere
curtain like fountains of lava erupt at spreading ocean ridges or at rifts
they are usually not very violent or explosive, but they produce a lot of lava
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