A chemical change is when matter converts from one type to another type. Some examples of chemical changes:

  • Formation of rust: Rust is a different kind of matter than the iron, oxygen, and water present before the rust formed.
  • The explosion of nitroglycerin: Gases produced are very different kinds of matter from the original substance.
  • All form of combustion
  • Food is cooked, digested, or rotting.

A physical change is a change in the form of a substance but not its composition. It occurs when matter changes among solid, liquid, or gaseous states. You can see a physical change when you freeze or boils water. The water turns states, but it is still composed of H2O molecules.

During chemical change or physical changes, there is no detectable change in the total quantity of matter. This phenomenon is called the law of conservation of matter.