Matter changes all the time.  Ice cubes change to water. After the ice cubes change to water the water evaporates and turns into a gas. Matter changes when the temperature changes. When something is a solid like the ice cube, the molecules are packed tightly together. But, when they are liquids like the water, the molecules start to get looser and move around more. After water evaporates, it turns into gas and the molecules get very loose and start bouncing all over the place.  Everything, including you, is made from molecules.

Changing Matter in Action 

The Golf Ball

There are three layers of a golf ball.  The first layer is made of a firm rubber layer that is soft to the touch.  The second layer is a layer of string.  The last layer is made of a hard rubber with dimples on it.  We learned that when we heat, the molecules spread apart.  The result is that the ball travels an extra distance.  When the ball is frozen, the molecules are stuck together, which does not give the ball a spin.   The ball that is left at room temperature goes farther than the frozen ball because the molecules are farther apart and the ball has more of a spin to it.