* Physical changes alter the form or appearance of a substance but not its chemical composition.

* Chemical changes result in the formation of new substances with different chemical properties.

When you change the temperature of a substance, you're only changing the amount of kinetic energy (energy of motion) of the molecules within the substance. This can cause changes in states (solid, liquid, gas), volume, or density, but it doesn't alter the actual chemical makeup of the substance.

Examples:

* Ice melting: Ice (H₂O) and water (H₂O) have the same chemical composition. The temperature change causes a change in state, not a change in the chemical formula.

* Heating a metal rod: The metal rod expands when heated, but it remains the same metal (e.g., iron).

Important Note: While temperature change is a physical change, there are some cases where extreme temperature changes can lead to chemical reactions (like burning wood). However, the temperature change itself is still considered a physical change.