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Topic 2: Atoms and Their Interactions
Transcript of Topic 2: Atoms and Their Interactions
Smallest part of an element that has the characteristics of that element. Both living and nonliving things are composed of atoms What is an element?
An element is a substance that cannot be broken down into simpler chemical substances Oxygen (O) makes up 61% of our body
Carbon (C) makes up 23% of our body
Hydrogen (H) makes up 10% of our body
Nitrogen (N) makes up 2.6% of our body
Calcium (Ca) makes up 1.4% of our body
Phosphorus (P) makes up 1.1% of our body
other elements make up the remaining 1% Of the naturally occurring elements, only 25 are essential to living organisms. Animals obtain trace elements from foods they eat.
Plants obtain trace elements by absorbing them through their roots. Elements that are present in very small amounts are called trace elements.
examples include: iron (Fe) and Copper (Cu) Mammals use iodine, (I) to produce hormones which are substances that affect chemical activity in the body. Plants use Magnesium, (Mg) to form chlorophyll which captures light energy for sugar production Isotopes have the same number of protons and electrons, but different numbers of neutrons
scientists refer to isotopes by stating the combined number of protons and neutrons in the nucleus
example: carbon-12 or C-12 has 6 protons and 6 neutrons
carbon-13 has 6 protons and 7 neutrons
carbon-14 has 6 protons and 8 neutrons Atoms are made up of
(+) protons in the nucleus
neutral neutrons in the nucleus
(-) electrons surrounding the nucleus Carbon-14 is very unstable and its nucleus tends to break apart
as nuclei break apart, they give off radiation
radiation is detectable and can damage or kill cells
radioactive isotopes are used to diagnose and/or treat diseases When two or more atoms of different elements are combined chemically, a compound is formed.
the properties of a compound are different from those of the individual elements
example: salt, NaCl Why do atoms combine to form compounds?
Atoms combine to become more stable.
Stability for atoms means having 8 electrons in their outer energy level, or having an octet.
Compounds are written with chemical symbols and subscripts. Atoms will share their outer electrons or valence electrons in a covalent bond or they will give away or take electrons from other atoms as in an ionic bond. Most compounds in organisms are covalent.
examples: sugar, fats, proteins, water
Covalent compounds are also called molecules. Ions are atoms with an overall charge as they have lost or gained electrons
Ions will form ionic bonds to become more stable
Ionic bonds are less common in living organisms, but ions are found within organisms
Sodium and potassium ions are required for transmission of nerve impulses.
Calcium is needed for muscle contraction
plant roots absorb essential minerals in the form of ions Chemical reactions occur when bonds are broken causing substances to recombine into different substances.
In organisms, chemical reactions occur within cells. These reactions are referred to as that organism's metabolism.
Metabolic reactions breakdown and build molecules that are needed for the organism to function.
Chemical reactions are represented by chemical equations. Let's look at a few reactions.... What happens when substances are just mixed and don't chemically combine?
When substances are mixed and do not chemical combine, they are called only mixtures.
A mixture is a combination of substances in which the individual components retain their own properties
you can easily separate the components
examples: sand and sugar mixture
salt and pepper A solution is a mixture in which one or more substances (called solutes) are distributed evenly in another substance (solvent)
example sweet tea, kool-aid, soda pop
the more solute that is added, the greater the concentration
living organisms must maintain specific concentrations in their bodies.
examples: insulin and glucagon are produced by the body to keep the amount of sugar in the body within a critical range Chemical reactions occurs when conditions are right
you need to have the right amount of energy, temperature, a certain concentration of a substance, or a certain pH
the pH is a measure of how acidic or basic a solution is
a scale with 0-14 is used
an acid is a substance with a pH below 7 that forms hydrogen ions in water
example: HCl in water
many fruits we eat are acidic
a base is a substance greater that 7 that forms hydroxide ions in water
example: NaOH in water http://learn.genetics.utah.edu/content/begin/cells/scale/