Chemical Changes

4. ____________ is sometimes taken in or given out during a chemical reaction.
5. During a chemical reaction, mass is conserved.
7. A change in which new substances are formed is called a ____________ change.
8. During respiration, ____________ is broken down in the presence of oxygen to form carbon dioxide and water.
10. Substances that react with each other are known as ____________.
14. Rusting occurs when _________ reacts with oxygen and water.
15. Light and heat are usually given out during ____________.
16. In a word equation, products are shown are shown on the ______-hand side.
17. Word equations include the reactants, products and ____________ under which a chemical reaction occurs.
18. The mass of the reactants is ____________ to the mass of the products in a chemical reaction.

1. During combustion, a substance is heated in the presence of ____________ to form a one or more new susbtances.
2. Thermal ____________ occurs when a substance breaks down into simpler substances upon heating.
3. Chemical changes are usually ____________.
6. An example of an oxidation reaction is cellular _______________.
9. When a substance gains oxygen, it undergoes ____________.
11. An ____________ instead of an '=' sign is used in qord equations.
12. Substances formed at the end of a reaction are known as ____________.
13. Calcium ____________ is an example of a substance that undergoes thermal decomposition upon heating.
19. In a word equation, reactants are shown on the ______-hand side.