Chemical and Physical Changes

A physical change is a change that does not alter the chemical composition of a substance. Examples include melting, freezing, and boiling.

A chemical change is a change that results in the formation of new chemical substances. The atoms in the reactants rearrange to form products with different characteristics.

Melting ice is a physical change.

The molecules may change their state (solid, liquid, gas) but their chemical structure remains the same.

Yes, physical changes can often be reversed, such as freezing water back into ice.

No, chemical changes usually cannot be reversed, as new substances are formed.

An example of a physical change is boiling water.

An example of a chemical change is rust forming on iron.

A physical change does not change the substance's chemical identity, while a chemical change results in new substances being formed.

The properties of the substance change because new substances with different characteristics are formed.