Chemical reactions involve the rearrangement of atoms. There are two main types of chemical changes - synthesis reactions which combine simpler substances into more complex ones, and decomposition reactions which break down a substance into simpler parts. Chemical equations are used to represent chemical reactions, and must obey the law of conservation of mass by being balanced. Reactions can release or absorb energy depending on whether the bonds in the products are stronger or weaker than the bonds in the reactants. Living things and industry rely on exothermic and endothermic chemical processes.

2. Section 3.1 Chemical Reactions Alter Arrangements of Atoms

5. Page 71 Bonds are broken in reactants, and new bonds are formed in the products.

6. Page 72 Evidence of a chemical reaction includes a change in color or temperature or the formation of a precipitate or a gas .

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14. Section 3.2 The Masses of Reactants and Products are Equal.

24. Section 3.3 Chemical Reactions Involve Energy Changes.

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32. A plant absorbs energy from the sun during photosynthesis. 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Endothermic Equation If the plant burns, the energy is released. C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O Exothermic Reaction Combustion Page 90

33. Section 3.4 Life and Industry Depend on Chemical Reactions

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