2. Any change from a solid to a liquid is called melting. In most pure substances this occurs at a specific temperature, called the melting point. Thermal energy makes the molecules in a substance vibrate faster, raising their temperature. At its melting point, the particles of a solid substance are vibrating so fast that they break free of their fixed positions. Water’s melting point is 0 ˚ C.

3. The change of state from liquid to solid is called freezing (it is just the reverse of melting). At its freezing temperature, the particles of a liquid are moving so slowly that they begin to form regular patterns. When you put water in a freezer, it slowly loses energy in the cold air. The molecules move more and more slowly until they become locked into place. Water freezes at 0 ˚ C. Even wax turning back into a solid is considered “freezing.”

4. Freezing Hot Water vs Cold Water Shooting a super-soaker at -45F

5. Changing from a liquid to a gas is called vaporization. It takes place when particles in a liquid gain enough energy to form a gas. The particles speed up from the thermal energy and break their loose bonds with each other. There are two types of vaporization: Evaporation Boiling

6. Evaporation is when vaporization only takes place on the surface of the liquid. A shrinking puddle is an example, water in the puddle gains energy from the ground, the air, or the sun, and the surface molecules can turn to gas.

7. Boiling occurs when a liquid changes to a gas below its surface as well as at the surface. You can see this because the liquid bubbles. The temperature at which a substance will boil is called its boiling point. The boiling point of water is 100 ˚ C, unless the air pressure is lower, then the boiling point drops.

8. The opposite of vaporization is condensation. Condensation occurs when particles in a gas lose enough thermal energy to form a liquid. The molecules slow down as they cool, and form loose bonds with each other, creating a liquid. You cannot see water vapor. It is a colorless gas that is impossible to see. The steam you see above a boiling pot is not water vapor, neither are clouds. They are tiny droplets of liquid water.

9. Sublimation Accelerated Sublimation