Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.

Burning of wood produces ash and smoke. Hence the properties of wood are changed, and new substances are formed. So, it is a chemical reaction. When a log of wood is cut into small pieces, there is no new substance formed. Each small piece bears the properties of wood. So, it's a physical change. Obviously, burning and cutting of wood are two different types of changes.