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Chemistry - Chapter 2
Transcript of Chemistry - Chapter 2
Chemistry - Chapter 2
What is matter?
The Classification of Matter
Scripture tells us that the matter that makes up the physical universe was created out of nothing.
Matter is anything that occupies space and has mass (this is an operational description).
Volume and mass are the two measurable properties common to all matter.
Matter is the basic building block of the universe.
All scientifically observable things are made of matter.
Pure substances and mixtures
We can make distinctions between the two categories based on the physical and chemical properties of matter.
There are two major categories of matter:
are determined by how the particles that compose the material relate to one another.
can be measured or observed without changing the actual composition of the material.
include color, shape, texture, physical state, odor, taste, etc
other common physical properties that you will define in your notes include: density, malleability, ductility, and conductivity
A physical change occurs in a material without changing the identity of the material. (Like a change in state.)
describe how matter acts in the presence of other materials or how it changes composition when sufficient energy is added to it.
Scientists must know the kind of changes a chemical can undergo in order to know its chemical properties.
A chemical change will change the identity of a material and result in a different material with a different composition and properties. (Like iron rusting.)
Energy is the ability to do work.
Work is when energy is expended doing something.
*Both are measured in joules (J).
Energy and Matter
As we said before, there are two categories of matter...
consist of only one type of matter (elements and compounds)
could be separated by a chemical change in some cases
can be separated into two or more pure substances by physical changes
heterogeneous mixtures, if examined, appear to consist of two or more materials segregated into distinct regions called phases
homogeneous mixtures show only a single phase.... if it is uniform and made of particles of two or more pure substances with the same physical properties throughout it is called a solution
and their symbols
An element is a pure substance that can't be broken down int0 a simpler substance by ordinary chemical means and only consists of one kind of atom.
Atoms are the basic particles that make up elements.... they consist of a nucleus containing protons and neutrons and a cloud of electrons
If the charges in an atom are balanced it is neutral, if not it's an ion.
Elements in their natural state can be monatomic, diatomic, or polyatomic.
Distinct groups of atoms bonded together are called molecules - these can be of one or many different elements.
Each element has a chemical symbol.
like H, N, O, C, Ca, Cd
The first letter is ALWAYS capitalized, and the second letter is ALWAYS lower case.
Careless writing of symbols can result in BIG errors
For example: Co is cobalt..... CO is carbon monoxide, a poisonous gas
Pure substances that consist of two or more elements chemically combined are called compounds - these can create molecules or formula units.
Compounds are represented by a chemical formula
In compounds that form molecules, each molecule has a definite number of atoms.
Since the molecule is the smallest distinct particle of the compound, the molecular chemical formula will indicate the number of atoms of each element present in each molecule
CO has one carbon atom and one oxygen atom
Chemical subscripts are numbers written at the lower right of a chemical symbol that indicates the number of atoms or group of atoms in a chemical formula.
Coefficients are standard sized numbers in front of a chemical formula that applies to the whole formula immediately following it, multiplying each subscript.
and their formulas
Energy is related to the force that matter generates and the resulting actions of that forces.
A few different kinds of energy include: mechanical, thermal, sound, acoustic, electrical, electromagnetic, chemical, and nuclear.
Every form of energy can change the motion of matter to do work. When energy is absorbed by matter, it has done some kind of work.
Forms of Energy
Energy is continuously transferred and converted from one form to another.
Thermodynamics is the study of the movement and conversion of energy (especially thermal energy).
There are laws of thermodynamics that seem to govern nearly all areas of science; no exception to these has ever been observed in natural processes.
The conservation of energy:
Matter and energy can neither be created nor destroyed, only converted from one form to another.
1st Law of Thermodynamics:
Apart from divine intervention, the total amount of mass and energy has remained constant since the end of the sixth day of creation. (Genesis 2:1-3)
All natural processes tend toward the highest entropy (greatest disorder) and minimum usable energy.
2nd Law of Thermodynamics:
We analyze entropy within systems.
Every natural and artificial system is subject to the second law.
It is impossible to reach absolute zero.... we'll come back to this in a minute.
3rd Law of Thermodynamics:
Thermal Energy, Temperature, and Heat:
Matter consists of tiny particles in constant motion (kinetic-molecular theory).
This motion can occur in different ways, but the sum of all these motions determines the total kinetic energy (KE) of the particle.
Temperature is a measure of "hotness" or "coldness" proportional to the average kinetic energy of its particles.
Thermal energy is the sum of the kinetic energy of an object's particles because it can be transferred.
Heat is the quantity of thermal energy transferred from one object to another.
All chemical changes either release or absorb some form of energy.
Measuring temperature and thermal energy:
Since all matter has some form of kinetic energy, instruments convert this KE into a measurement using a property of matter directly related to temperature.
For example, a thermometer works because volume changes proportionally with temperature changes.
Celsius scale - uses two reference points to anchor the temperature scale (freezing and boiling point of pure water)
Kelvin scale - reference points are the triple point of water (273.16 K) and absolute zero (0K) which is the theoretical temperature at which all molecular and atomic movement ceases
To convert between Celsius, Kelvin, and Fahrenheit, see conversions in textbook.
joule (J) - energy and work
calorie (cal) - amount of heat transfer required to change the temperature of one gram of water one degree Celsius
kilocalorie (kcal) - one Calories which refers to the energy content of foods
have relatively little kinetic energy compared to the attractive forces that are present between particles so the particles stay in relatively fixed positions with set distances between them.
fixed volume, rigid shape, relatively incompressible
The States of Matter:
particles are still close together so the volume is relatively constant but its shape is determined by its container, can flow when a force is applied
particles possess a large amount of kinetic energy, they move rapidly and randomly, are highly compressible, have no definite shape, eventually diffuse to occupy a closed container, flow when forced to or in the absence of a force
gas like state at very high temperatures, particles are ions, electrons, and neutral atoms traveling at extremely high speeds, no definite shape or volume, can be affected by a magnetic field
Changes in common states of matter: