The key difference between a physical change and a chemical change lies in the rearrangement of atoms.

Physical Change:

* No new substances are formed. The molecules or atoms simply change their arrangement or state of matter.

* Changes are usually reversible.

* Only affects the appearance or physical properties of a substance. These properties include things like shape, size, color, or state of matter.

Examples of physical changes:

* Melting ice (solid to liquid)

* Boiling water (liquid to gas)

* Crushing a can

* Dissolving sugar in water (sugar molecules are dispersed but remain intact)

Chemical Change:

* New substances are formed. Atoms are rearranged into different molecules with different properties.

* Changes are usually irreversible.

* Results in a change in the chemical composition of the substance.

Examples of chemical changes:

* Burning wood (wood reacts with oxygen to form ash, carbon dioxide, and water)

* Rusting iron (iron reacts with oxygen and water to form iron oxide)

* Baking a cake (ingredients combine and react to form a new substance)

* Digesting food (enzymes break down food molecules into smaller molecules)

Here's a helpful way to remember:

* Physical changes are temporary. You can often get the original substance back.

* Chemical changes are permanent. You can't easily get the original substances back.

Let me know if you'd like more examples or have any other questions!