Chemical changes involve changes in the connections between substances. A chemical reaction can form a new substance. However, a chemical change involves the formation of a new substance, requires energy and cannot be reversed.
Chemical Change = Irreversible change = cannot be changed back
Cooking can cause an irreversible change. For example: an egg can be heated and cannot be returned to its previous state.
- Burning materials, such as wood, paper, natural gas, causes an irreversible change.
- Irreversible changes can form new materials that can be useful e.g. plaster of Paris and water.
- Dead plants and animals decay and some metals rust. These chemical changes are permanent.