1-2 Phase Change, Slide 3

To change a thing from solid, like ice, to liquid, like water, or to gas, like steam, we need energy. This energy helps the tiny pieces that everything is made of to move apart from each other.

When something is changing from one form to another, like ice melting to water, we can add or take away energy, but it won't get hotter or colder until it has completely changed.