Definition:
- Physical Change: A physical change is a change in the state or form of a substance without any change in its chemical composition. It can be reversed by physical means.
- Chemical Change: A chemical change is a process in which one or more substances are converted into new substances with different chemical properties. It cannot be easily reversed.

Examples:
- Physical Change: Melting of ice, boiling water, crushing a can, dissolving sugar in water.
- Chemical Change: Burning wood, rusting of iron, cooking an egg, digestion of food.

Reversibility:
- Physical Change: Physical changes are usually reversible. For example, melting ice can be refrozen to form ice again.
- Chemical Change: Chemical changes are usually irreversible. Once a chemical reaction occurs, it is difficult to revert the substances back to their original form.

Energy Change:
- Physical Change: Physical changes generally do not involve a significant change in energy. For example, melting ice requires heat energy.
- Chemical Change: Chemical changes often involve a release or absorption of energy. For example, burning wood releases heat energy.

Composition:
- Physical Change: In physical changes, the composition of the substance remains the same.
- Chemical Change: In chemical changes, the composition of the substance changes to form new substances with different properties.

Summary:
In summary, physical changes involve a change in the state or form of a substance without altering its chemical composition, and they are usually reversible. On the other hand, chemical changes result in the formation of new substances with different properties and are often irreversible.