Chemical Reactions

6. A change that affects the form or appearance of a substance but does not create a new substance.
8. A reaction in which one substance is oxidized (loses electrons) and another is reduced (gains electrons).
9. Reactions in which a more reactive element takes the place of a less reactive element in a compound.
10. A chemical reaction in which a substance reacts quickly with oxygen and releases energy as heat and light.
11. The speed at which reactants are converted into products in a chemical reaction.

1. Elements found in the center of the periodic table that can form ions with different charges and act as catalysts.
2. A substance that speeds up a chemical reaction by lowering the activation energy, without being used up.
3. A number that shows how many electrons an atom has gained, lost, or shared in a chemical reaction.
4. A change in which a new substance is formed with different properties; also called a chemical reaction.
5. A theory that explains how chemical reactions happen when particles collide with enough energy.
7. The process by which atoms, ions, or molecules stick to a surface, often used to describe how catalysts work.