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| List the most common elements in living things. |
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| Life requires 25 chemical elements. |
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| Compare and contrast elements and compounds |
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| anything that occupies space and has mass. The physical stuff in the universe. Ex. rock, wood, air, metal, water. Humans and everything around them are examples of matter. |
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| a pure substance that cannot be broken down into other substances by chemical means. |
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| elements that make up less than 0.01 % of your body mass, are nevertheless critical to yoru health. Ex. you need about 0.15 miligrams of iodine each day. |
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| a substance containing two or more elements that are hemically combined in a fixed ratio. Ex. H2O water or NaCl sodium chloride/salt |
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| (gets its name from the Greek work atomos/"indivisible")Smallest particle of an element. |
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| a subatomic particle with a single unit of positive electrical charge (+) |
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| a subatomic particle with a single unit of negative electrical charge (-) |
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| a subatomic particla which is electrically neutral, meaning it has no electrical charge. |
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| a central core of the atom where the protons and neutrons are tightly packed together. |
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| number of protons in an atom's nucleus; is unique for each element. |
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| one of several forms of an element, each containing the same number of protons in thier atoms but a different number of neutrons. |
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| isotope in which the nucleus decays (breaks down) over time, giving off radiation in the form of matter and energy. |
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| chemical bond that occurs when an atom transfers an electron to another atom. |
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| chemical bond that forms when two atoms share electrons. |
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| two or more atoms held together by covalent bonds. |
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| breaking of old and formation of new chemical bonds that result in new substances. |
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| starting material for a chemical reaction. |
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| material created as a result of a chemical reaction. |
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| molecule in which opposite ends have opposite elecric charges. |
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| bond created by the weak attraction of a slightly positive hydrogen atom to a slightly negative portion of another molecule. |
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| tendency of molecules of the same kind to stick to one another. |
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| attraction between unlike molecules. |
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| total amount of energy associated with the random movement of atoms and molecules in a sample of matter. |
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| measure of the average enery of random motion of particles in a substance. |
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| substance in a solution that dissolves the other substance and its present in the greater amount. |
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| solution in which water is the solvent. |
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| substance in a solution that is dissolved and is present in a lesser amount. |
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| compound that donates H+ ions to an aqueous solution and measures less than 7 on the pH scale. |
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| compound that removes H+ ions from an aqueous solution and that measures more than 7 on the pH scale. |
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| a range of numbers used to describe how acidic or basic a solution is; ranges from 0 (most acidic) to 14 (most basic). |
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| substance that maintains a fairly constant pH in a solution by accepting H+ ions when their levels rise and donating H+ ions hwen their levels fall. |
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| basic unit of living matter; separated from its environment by a plasma membrane. |
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