Humidity Lesson Plan: Condensation & Dew Point Experiment

Lesson Procedure:

1. Display the KWL Chart chart on the whiteboard. Ask students what they know about humidity and what causes it. You can also ask them to think of places that are humid and ask them why they think that is. Write their responses in the K column.
2. Tell students that today they will learn all about humidity--what it is, what it has to do with weather, and its role in the water cycle. Ask students what they hope to learn about humidity. Write their responses in the W column. Next, invite a volunteer to read the movie description that appears below the movie player.
3. Next show the movie Humidity on an interactive whiteboard or other larg e display, pausing as needed to explain or review key terms and concepts, such as molecules, vapor, condensation, dew point, saturation, evaporation, equilibrium, and precipitation.
4. After the movie, ask students to recall why dew sometimes appears on the grass in the morning. They should understand that overnight, the air temperature drops causing water vapor to change states to liquid “dew”. Remind them that this is called condensation. Ask what would happen if the temperature doesn’t drop. They should recall that if the air doesn’t get colder, the water vapor will not change to liquid, and there won’t be dew. Review that dew point is the temperature at which condensation happens. Lastly, ask whether there is more humidity when the dew point is high or low? Have them make a prediction, then tell them they will conduct an experiment to find out the answer.
5. Next, divide the class into pairs or small groups to conduct an experiment to see how temperature affects condensation and dew point. Distribute the materials to each pair or group: cup, ice water, thermometer, warm water, and a syringe.
6. First, have students use their thermometers to measure the air temperature. On the whiteboard, open www.weather.com and put in the zip code for your school. Point out the relative humidity.
7. Next, instruct students to fill the cup a third of the way with the warmer water (it should be approximately 85 degrees) and put the thermometer in the water.
8. Now have one student in each pair/group, use the syringe to add small amounts of ice water as another watches the temperature on the thermometer. They should continue to add ice water until the temperature drops with each new drop.
9. When condensation forms on the outside of the cup, ask them what it is. Point out that the liquid formed for the same reason dew appears on the grass in the morning.
10. Have the groups repeat the experiment on a day when the relative humidity is much different than today. Ask if they had to add more or less ice water for condensation to form.
11. Finally, bring the class together, and ask them to review their predictions about whether there is more humidity when the dew point is high or low.