We put ice into a cup.
Ice is a solid.
We put the cup into hot water.
The ice cubes melted away.
They became water.
Water is a liquid.
We put the water in a pan on the stove.
The water went away.
It became a gas.
The stove is hot.
Heat made the liquid change to a different state of matter.
We also put water in the freezer and it turned into an ice cube.
Cold changed a liquid to a solid.
Building Foundations of Scientific Understanding, Lesson A-2 part 2