boiling means a substance changes from a liquid into a gas by increasing heat energy & a liquid is a kind of substance & boiling is when liquids are heated above their boiling point ->  a liquid will change from a liquid to a gas when its heated above its boiling point  a liquid will change from a liquid to a gas when its heated above its boiling point & water is a kind of liquid at room temperature -> water will change from a liquid to a gas when its heated above its boiling point