Substances can undergo physical changes or chemical changes. what is the difference between these two kinds of changes

There are several differences between a physical and chemical change in matter or substances. A physical change in a substance doesn't change what the substance is. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.

Physical changes are those change which just externally or physically change the state of the object. for example : water boils and evaporates ... here the state is just changing from liquid to vapour while the composition is the same.

chemical changes are those which bring about a change in the composition of a substance. for example: burning of paper changes into ash.