# Learning Lesson: Sweatin' to the Coldies

## Overview

There are three states of matter; gas, liquid, and solid. Water in our atmosphere exists in these three states constantly. As the temperature of water vapor (a gas) decreases, it will reach the point at which it turns into a liquid (called the dew point or the point at which dew forms). This change of state from a gas to a liquid is called condensation.

Using some ice and a glass, the students will chill the glass to the point where water from the atmosphere will condense on the outside of the glass. This demonstrate the change of state of water vapor to liquid.

TOTAL TIME 30 minutes Glass cups or jars, Ice cubes None This can be done as a class demonstration or you can divide the students into pairs should you have enough glass jars. You can also shorten this experiment by using crushed ice instead of cubed ice. Crushed ice chills water quicker, causing condensation sooner. Flash Flood Safety

## Procedure

1. Fill the cups/jars with ice.
2. Add cold water to the cups/jars.
3. Let the cups/jar set for about 30 minutes.
4. Observe the outside of the glass for condensation.

## Discussion

Ask the students where the water on the outside of the glass came from. The answer is from the atmosphere. As air comes in contact with the glass, it is cooled to below the dew point temperature and the water vapor contained in the air condenses onto the glass.

The amount of water on the side of the glass depends upon the humidity which is the ratio of dry air to moist air. The higher the humidity the more moisture that air contains. The greater the moisture, the greater the water that can condense.

As an aside, you can repeat the process with different types of drinking containers, such as plastic and Styrofoam. Ask the students why there is a difference in the amount of water condensing onto each type.