Examples of chemical changes include burning of wood, digestion of sugar, an exploding firecracker, reactions between salts and acids and lighting a matchstick. A chemical change involves changes at the atomic and molecular level.
When a chemical change takes place, new products are formed as a result of chemical reactions. At the molecular level, bonds between atoms and molecules are broken and new bonds are formed. This results in the formation of new compounds.
Most chemical changes are irreversible. However, there are some chemical changes that are reversible. The formation of ammonia from hydrogen and nitrogen is an example of a reversible chemical change. Some chemical changes are rapid, such as the burning of a magnesium ribbon. Others are slow, such as the rusting of iron.