Comprehension Check 5-4

Describe the action of molecules in a solid.

Molecules vibrate very slowly and are bonded together tightly.

What causes molecules to move more rapidly?

Heat.

What happens when the motion of the molecules in a solid or liquid becomes stronger than the attraction of the molecules to each other?

The molecules stray away from each other causing the matter to change state.

What is water's melting point? Boiling point?

Water melts at 0°C (32°F), and boils at 100°C (212°F).

What happens to most liquids when they become cooler? What happens to water? Why is this unusual characteristic of water important?

Most liquids become denser when they are cooled, but water becomes less dense (hence allowing solid ice to float on liquid water).