Lesson Plans: Making Clouds

Objective

The objective of this activity is to investigate the conditions that must be present for clouds to form.

Materials

Each student or group of students will need the following:

  • 1 liter (or larger) clear glass jar with lid (large mouth jars work best)
  • Ice cubes or crushed ice
  • Hot water
    Caution: Even very warm water will do. Do not use water that is hot enough to burn your skin.
  • Matches
  • Can of aerosol spray (air freshener is suggested)
  • Black construction paper
  • Safety goggles
  • Flashlight (optional)

Important Points to Understand

  • Three things are necessary for cloud formation: cooling of air, water vapor, and condensation nuclei.
  • Water vapor must have something to condense on in order to form the droplets that compose clouds.
  • Many things can serve as condensation nuclei. Some of the most common include dust, pollen, salt from ocean spray, and smoke.

Preparation

Before the lesson begins, discuss cloud formation with the class to determine the students' ideas on how clouds form. Ask students what they think a cloud is made of, then ask them how it forms.

Be sure that all materials are either centrally located or already distributed to the groups of students. Perhaps the students could bring clear glass jars, such as mayonnaise jars, pickle jars, canning jars, etc., from home. The jars do not have to be the same shape, but clear glass works the best. The larger the mouth of the jar, the better the experiment.

Depending on the students, the teacher may choose to light all matches for them to reduce the risk of accidents and the temptation for horseplay. Be careful: Flames and aerosol cans are an explosive combination. Holding a lighted match in front of an aerosol can makes a very effective flame thrower. Students must never have access to both the matches and the aerosol at the same time. If in the teacher's opinion, this represents too great a risk for his or her students, it is strongly recommended that the aerosol not be used at all. The important points of the activity can still be made using only smoke.

Procedure

  1. Fill the jar with hot water. Do not use water that is hot enough to burn
    your skin.
  2. Pour out most of the hot water, but leave about 2 centimeters of water
    in the bottom of the jar. Hold the black paper upright or prop it up against
    some books behind the jar.
  3. Turn the lid of the jar upside down and fill it with ice. Now place the
    lid on the jar as shown below. Observe the jar for 3 minutes. If you have
    a flashlight, darken the room, and shine the flashlight on the jar while
    you observe it. Record your observations in the table, under "Control."

  4. Pour the water out of the jar and repeat steps (1) and (2).
  5. Prepare the lid so that you can immediately cover the mouth of the jar
    during the next step.
  6. Move all loose papers away from the jar, put on your safety goggles then
    strike a match and drop the burning match into the jar. Cover the mouth
    of the jar immediately (with the ice-filled lid). Record your observations
    in the table, in the box marked "Match." Be extremely careful with the matches.
  7. Pour out the water in the jar and repeat steps (1) and (2).
  8. Spray a very small amount of the aerosol in the jar and immediately cover
    the mouth of the jar with the ice-filled lid.
  9. Observe what happens in the jar for three minutes and record your observations
    in the table in the box marked "Aerosol."
Trial Observations
Control
Match
Aerosol

Questions

  1. In all the trials of this experiment, the jar contained water vapor and cooled air. Where did each come from?
  2. Did a cloud form the first time you put the lid over the mouth of the jar? How about the second and third times?
  3. Define aerosol.
  4. Based on the definition of aerosol, would you classify smoke as an aerosol?
  5. Based on your observations and your answers, what is the other condition besides moisture and cool air necessary for cloud formation?