What is the difference between a physical change and a chemical change? Give one example of each.

A physical change is a change in the form, shape, or state of matter without forming a new substance. The molecules remain the same, and the change is often reversible. For example, melting of ice into water is a physical change. In this case, ice (solid) changes into water (liquid), but both are still H₂O molecules, and the process can be reversed by freezing.

A chemical change, on the other hand, results in the formation of a new substance with different chemical properties. The molecular composition changes, and the process is usually irreversible. For example, when paper burns, it turns into ash, carbon dioxide, and water vapor. The paper cannot be brought back once burned, and completely new substances are formed

In summary, physical changes only affect appearance or state, while chemical changes alter the substance itself. Understanding this difference helps us classify various processes in daily life.