• understand the concept of relative humidity, absolute humidity, and dew point temperature
• interpret phase diagrams
• explain why relative humidity typically falls and rises during a 24-hour period

Beaker

Crayons

Graphs of relative humidity over a 24-hour period

Ice

Phase diagrams

Plastic wrap

Rubber band

*White Board (Optional)

Differentiation Strategies

• Varying academic levels: uses mixed-ability groups to allow students to learn from one another, uses small- and whole-group discussions to ensure all students participate
• Visual learners: incorporates phase diagrams and demonstrations of relative humidity
• Auditory learners: uses guided questions to help students formulate predictions, make observations, and brainstorm explanations
• Kinesthetic learners: engages students in coloring a phase diagram to label solid, liquid, and gas phases

• Distribute a water phase diagram (in black and white) with the phases labeled.
• Have students color in each of the phases.
• Ask students to describe the relative amounts of solid, liquid, and gas water at several different temperatures.
• Note that as the temperature increases the amount of gas water increases.

• Fill a beaker half-way with water. 
• Place three pieces of ice into the beaker.
• Cover it with a thick plastic wrap so that it does not sag and secure it tightly with a rubber band.
• Have students describe the relative amounts of solid, liquid, and vapor.
• Give students a few minutes to predict what will happen to the relative amounts of solid, liquid, and vapor in the beaker after ten minutes (standing at room temperature). Have them write their prediction in their science journals.
• Ask volunteers to share their predictions with the class. Write their predictions on the board.
• Write and define the concept of relative humidity on the board.
• Explain why the concept of relative humidity, rather than absolute humidity, is used by weather experts.
• After the ten-minute period, have the students describe the relative amounts of solid, liquid, and vapor in the beaker, and write their observations in their science journal.
•  Ask the students to explain the result.  You may need to guide the students by asking the following questions:

• What happened to the temperature of the beaker?
• As the temperature increased, what happened to the relative amount of solid, liquid, and gas?
• How could they use the phase diagram to explain this result?

• Revisit students’ predictions. Remind students that all predictions, even the incorrect ones, are a valuable and necessary contribution to the scientific method.

• Create mixed-ability pairs.
• Distribute graphs showing relative humidity in a city, or several cities, during a 24-hour period.
• Ask the pairs to work together to write a paragraph in their science journals explaining how and why the relative humidity changes during a 24-hour period.

•  Ask pairs to share their explanations with the whole group. If no group provides a complete explanation, use guided questions to lead students. Here are a few question to ask:

• What happens to temperature during a 24-hour period?
• Will the amount of moisture in the air radically change during a 24-hour period?
• If the amount of moisture stays about the same, what will happen to relative humidity as temperature increases?

• Have students revise the explanation they wrote in their journals.

•  Define dew point temperature and discuss the advantages and disadvantages of each measure and how these measures are used by weather experts.