Explains chemical changes, which occur when two or more materials combine to form new substances. It describes various examples of chemical changes, such as burning wood, digestion, and ...

In a chemical reaction, new materials are always formed. Sometimes these new materials are useful to us. Irreversible changes are permanent. They cannot be undone. For example, you cannot change a ...

Instead, the atoms rearrange themselves to form new chemicals. This is known as a chemical change. The other kind of change in chemistry is a physical change, which is when a substance changes ...