Physical Change:
A physical change is a type of change in which the form of matter is altered, but not its chemical composition. This means that the substance involved in the change remains the same on a molecular level. Examples of physical changes include changes in state (solid to liquid to gas), changes in shape or size, and dissolving.

Key points:
- No new substance is formed during a physical change.
- The change is usually reversible.
- Physical properties such as color, shape, size, and state may be altered.

Chemical Change:
A chemical change, on the other hand, involves a transformation of one or more substances into different substances with new properties. This type of change is often irreversible and results in the formation of new chemical bonds. Common examples of chemical changes include rusting of iron, burning of wood, and baking a cake.

Key points:
- New substances are formed during a chemical change.
- The change is usually irreversible.
- Chemical properties such as reactivity, flammability, and toxicity may be altered.
In summary, physical changes involve alterations in the form of matter without changing its chemical composition, whereas chemical changes result in the formation of new substances with different properties. Understanding the differences between these two types of changes is crucial in various fields such as chemistry, physics, and biology.