Essay --

When chemicals come together, they form a reaction. A chemical reaction is when one or more substances change into one or more new substances. The properties of the new substances are different from those of the original substances. You can tell a reaction has happened when you see these signs: a precipitate has formed, gas has formed, color has changed, or energy has been given off (blue book). If substances with new properties have formed, you know a chemical reaction has occurred. The substances that you start off with are called the reactants. The substances you get after a reaction has occurred are called the products. There are different types of chemical reactions. Exothermic reactions are a type of chemical reaction where energy is released and absorbed by nearby matter. Endothermic reactions are a type of reaction where energy is absorbed from from its surroundings (blue book). Chemical reactions happen at different rates. There are many factors that affect the speed of ch emical reactions. To make a reaction go faster you can increase the temperature, increase the concentr...