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					                                       Clouds

Objectives: We are going to learn how to make a cloud in the classroom. To do so, we
have to learn what ingredients are important for cloud-making.
Inroduction
Moisture condenses to form water droplets when moist air cools. Clouds and fog form
when this happens. If we took air with a lot of moisture in it and then cooled it down,
we should be able to make a cloud.
Vocabulary: Define the following terms:
dew point:


troposphere:



condensation nuclei:



expansional cooling



Activity 1 (Teacher Demonstration)
1. Your teacher will demonstrate how to make a cloud chamber with a flask, a beaker,
some ice and hot water. Watch carefully, since you will be doing the same thing later on.

2. Did clouds form? _____________

3. What is the important ingredient that we are missing? ___________________

This time we will redo the experiment and see if the clouds will form.

Activity 2 (Student Activity)
1. Cool down the flask with ice as before, for 2-3 minutes.
2. When you are ready, carefully pour enough hot water into the small beaker so it will
cover the mouth of the flask. Remove the ice from the flask.
3. Your teacher will light the string and blow out the flame, causing smoke to form.
4. Catch some of the smoke with the flask, so it gets into the wide part and quickly insert
the flask into the small beaker. Replace the ice.
5. Observe what happens. Write down your observations below:




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Activity 3: Clouds in a bottle

Materials

1 empty 2-liter plastic bottle (with cap, labels removed) per student

water

matches

Procedure

1. Place a very small volume of hot water into the 2-L bottle.

2. Cap the bottle tightly and shake the bottle to accelerate the evaporation of some
of the water inside.

3. Compress the air inside the bottle by squeezing the sizes.

4. Release the pressure on the sides of the bottle and observe any cloud formation
inside.

5. Open the cap of the bottle.

6. Light a match, extinguish the match, and attempt to draw some of the smoke into
the open end of the bottle.

7. Cap the bottle tightly and compress the air inside by squeezing the sides.

8. Release the pressure on the sides of the bottle and observe any cloud formation.




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Questions

1. Did you observe any cloud formation inside the bottle during your first trial?




2. Did you observe any cloud formation inside the bottle during the second trial when
smoke from the match had been added to the air inside?




3. For clouds to form in the atmosphere, tiny airborne particles called condensation
nuclei are needed. What served as condensation nuclei in your second trial?




4. Expansional cooling is the principal means of cloud formation in the atmosphere.
Explain how this activity demonstrates the concept of expansional cooling.




                                                                                       3
Questions

1. Why did you need the smoke to make the clouds form?




2. Why don’t clouds form in the higher reaches of the troposphere, even though it is very
cold?




3. Why does warm, moist air tend to rise?




4. In our atmosphere, there are no ice cubes to cool the rising warm air. Describe what
causes the air to get cooler as it gets higher:




5. What have you learned from doing this lab?




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                        Clouds – Teacher’s Notes
Objectives: To show that to make clouds, it is necessary to have both moist air that
cools down to below the dew point and the presence of condensation nuclei (some kind
of particulate).

In this lab, we will use ice to act as the cooling mechanism and smoke to provide
condensation nuclei. In Activity 1, the teacher will perform the experiment without
smoke, both to demonstate the procedure, and to show what happens if some form of
condensation nuclei are not provided. In Activity 2, the students will repeat the
procedure, only this time they will use smoke, provided by the teacher.

Materials
Erlenmeyer flask (we use a 500 ml flask, but a smaller one will work as well), beaker
that is small enough so the flask will fit in snugly and its mouth won’t touch the beaker
bottom., hot water from the tap or large water container, hot plate and oven mitt, string
(optional – makes better smoke than just matches), matches, ice cubes or crushed ice,
baggie (or ice-holder made out of a small cup with bottom cut out and plastic wrap),
paper towels for spills.

Activity 1 (Cloud formation without condensation nuclei)

1. Turn the Erlenmeyer flask upside down so the wide bottom end is up. Cool down the
wide part of the flask by laying ice on top for 2-3 minutes.
2. Pour a small amount of hot water into the beaker, then insert the upside down flask.
Leave the ice on the top of the flask. Make sure the top opening of the flask doesn’t
touch the bottom of the beaker. The water level in the beaker should cover the flask
opening.
3. Warm moist air will now rise up from the bottom of the beaker into the wide part of
the flask. This air will be cooled by the ice.
4. Show the students that even though the warm moist air is being cooled no clouds form
and ask why?

Activity 2 (Cloud formation with condensation nuclei)
Make sure the students set up their apparatus correctly, so that the hot water level in the
beaker covers the mouth of the flask.
Help the students with pouring hot water if necessary.
Make smoke by lighting the string or match and then blowing it out.



Your notes here:




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