| A | B |
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| chemical bond | an interaction that holds atoms or ions together |
| valence electron | an electron that is found in the outermost shell of an atom and that determines the atom's chemical properties |
| chemical reaction | the process in which atoms are rearranged and chemical bonds are broken and formed to produce a chemical change of a substance |
| exothermic reaction | a chemical reaction in which energy is released to the surroundings, usually as heat |
| endothermic reaction | a chemical reaction that requires energy input, usually as heat |
| law of conservation of energy | the law that states that energy cannot be created or destroyed but can be changed from one form to another |
| law of conservation of mass | the law that states that mass cannot be created or destroyed in ordinary chemical and physical changes |
| chemical formula | a combination of chemical symbols and numbers to represent a substance |
| chemical equation | a representation of a chemical reaction that uses symbols to show the relationship between the reactions and the products |
| reactant | a substance that participates in a chemical reaction |
| product | a substance that forms in a chemical reaction |
