Chilling Out with Condensation

Description

Heat usually transfers from a location of a higher temperature to that of a lower temperature, such as when you feel chilly on a winter’s day. A refrigerator, designed to keep food cold, therefore must do the opposite: transfer heat from a place that is cooler than the outside.

A fridge does this by utilizing an expansion device and condenser coils to facilitate evaporation and condensation. Both of these processes can be simulated in a simple classroom lab.

Materials

A clear, airtight container of either glass or plastic

A smaller, open-mouthed container (i.e. beaker) that can fit within the sealed container

Water

Dry-erase marker

Optional: double-sided tape OR glue dots

Outline

1.      This activity shows the baseline properties of evaporation and condensation. It is appropriate for young children who have not been exposed to the terms before, or older students who need a refresher.

2.      Fill the beaker halfway with water. Mark the height of the water on the beaker with the dry-erase marker to refer back to later

3.      Place the beaker inside of the container, standing upright, and put the lid on. A small piece of double-sided tape can be used to keep the beaker upright. The lid should not cover the mouth of the beaker, there should be at least a little bit of space between the two.

4.      Place the container in a sunny window for a few days

5.      Return to observe the beaker and the container. Is the same amount of water still in the beaker?

6.      Without removing the lid or tipping the beaker, move the set-up somewhere cooler, such as a dark corner or closet. After some time (can be only a few hours) return to look. Is there still water in the beaker? Is there water anywhere else in the container?

Extended Activity

·        In a separate activity, stir a little bit of salt into the water before putting it in the beaker and proceeding with the experiment. Do the remainder of the steps as directed. When removing the container from the sun, take a look at the container. What happened to the water? What happened to the salt?