Q.7 Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.

(1) When we burn wood, a new substance coal is formed.
Wood is converted to charcoal with the liberation of CO2.
Therefore, it is a chemical change.

(2) However, when we cut wood no new substance is formed.
Only the shape and size of the wood are changed. It does not change the nature of the wood.
Therefore, it is a physical change.