Chapter 5

1. A reaction that absorbs energy.
3. A substance formed as a result of a chemical reaction.
8. A change in which one or more substances combine or break apart to form new substances.
9. A substance that enters into a chemical reaction.
11. A short, easy way to show a chemical reaction, using symbols.
12. A reaction in which one element replaces another in a compound or when two elements in different compounds trade places.
14. A material that increases the rate of a reaction by lowering the activation energy.
15. A chemical reaction in which two or more simple substances combine to form a new, more complex substance.
17. The minimum amount of energy needed to start a chemical reaction.
18. A chemical reaction that breaks down compounds into simpler products.

2. A reaction that releases energy, usually in the form of heat.
3. A change that alters the form or appearance of a material but does not make the material into another substance.
4. A number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction.
5. The principle that the total amount of matter is neither created nor destroyed during any chemical or physical change.
6. A system in which no matter is allowed to enter or leave.
7. A type of protein that speeds up a chemical reaction in a living thing.
10. A system in which matter can enter from or escape to the surroundings.
11. The amount of one material in a certain volume of another material.
13. A solid that forms from a solution during a chemical reaction.
16. A material that decreases the rate of a reaction.