CA Standard 7C

7C:Students know energy is released when a material condenses or freezes and is absorbed when a material evaporates or melts.

When something condenses or freezes, energy is released. A substance is really cold because the energy, such as heat was released. An example would be from liquid water to ice. When you put the liquid in a really cold environment like the freezer, the energy is released because:

1. the molecules get closer together.
2. the molecules move slower.
   

Liquid Water

















Ice(solid)


















Steam (gas)


















When something evaporates or melts, energy is absorbed. An example is from water to steam. On a really really hot day, if you pour some water on the hot concrete, the water will turn into steam (aka water vapor) because the water will absorb the heat from the hot concrete. When energy is absorbed:

1. the molecules in the substance get farther apart.
2. the molecules move faster.

So when energy is released the substance is cooler, and when energy is absorbed, the substance is warmer.
To remember this stuff, think about a group of friends. When they don't move that much, they get cold and huddle close together to share their body heat (released). When they do move a lot, they get hot and they would want to get further apart from each other (absorbed).

The video below shows how hot water can turn to water vapor in a cool environment.