Final answer:
A chemical reaction is a process that changes substances into others. Indications of a chemical reaction include temperature changes, light, unexpected color changes, and the formation of bubbles.
Step-by-step explanation:
A chemical reaction is a process that changes some chemical substances into others. A substance that starts a chemical reaction is called a reactant, and a substance that forms as a result of a chemical reaction is called a product. During a chemical reaction, the reactants are used up to create the products.
Indications of a chemical reaction include temperature changes, light given off, unexpected color changes, and the formation of bubbles. Bubbles indicate the formation of a gas, which is a new substance. However, a chemical reaction can produce substances that are solid, liquid, or gas.