We usually think of chemicals as being special substances that might be used in cleaning liquids such as bleach, but really everything is made of chemicals. Usually one chemical is joined with one other chemical or a number of other chemicals. For example we breathe out carbon dioxide. This is a chemical made by two other chemicals. They are the elements carbon and oxygen.

Some people think that the word chemical means a dangerous substance. It is true that some chemicals are very dangerous, but many are harmles, and some are needed to keep you alive. In fact you are made entirely of many different chemicals.

Chemicals can take part in changes. When they do, they make new chemicals.

In a battery there is a special mixture of chemicals. When the battery is wired into a circuit, and the circuit is switched on, the chemicals change. As they change, they make electricity.