NORTHWEST WEATHER WATCH

Overview

As in the previous experiment, students will work in cooperative groups with one student recording information on to the Lab Sheet.

Materials for each group

• 1 liter clear glass jar with lid
• ice cubes or crushed ice
• hot water (not burning hot)
• matches
• black construction paper
• flashlight
• safety goggles
• 2 Lab Sheets
• for each student: Journal Sheet (Definitions)

The teacher will ask the students what "ingredient" they discovered in the air in their last experiment (water vapor). The teacher will then ask students how they made the drops of water appear (how they made the water vapor condense). They did this by cooling the air with ice.

Tell students that they have discovered 2 of the essential factors that must be present for clouds to form. Their task today will be to find the answer to the question:

Given the presence of water vapor and air that is cooling, what is the third ingredient that must be present in order for a cloud to form?

Now the teacher will ask students to get into groups and come up with a hypothesis to answer this question.

Experiment

Next the teacher will distribute the materials and explain the directions for the experiment which will be done in two parts using 2 Lab Sheets (Experiments 2-A and 2-B)

Procedure 2-A

1. Fill the jar with hot water (not hot enough to burn skin)
2. Pour out most of the hot water leaving about 2 cm in the bottom of the jar.
3. Turn the lid of the jar upside-down and fill it with ice.
4. Then place the lid filled with ice (upside-down) on top of the jar.
5. Let the jar sit this way for 10 minutes.
6. Now shine the flashlight on the jar.
   What do you see?
   (The students shouldn't see anything different.)

   The recorder will record all of the required information for the group on the first Lab Sheet - Experiment 2-A.

Here we go again! Students will conduct a second experiment identical to the first, but they will add one step at the end which will change the experiment's outcome.

Repeat steps 1-3 of the first experiment. then add one more step. Put on your safety goggles
1. Strike a match and drop the burning match into the jar.
2. Immediately cover the jar with the lid filled with ice.
   What do you see?
   Students should see a cloud forming within the jar.

   Once again the recorder will write down all information and group findings on the Lab Sheet (Lab Sheet #2-B) including the added step (lighting the match). The group will then rethink their original hypothesis in Hypothesis Revisited.

Students will come together to share observations and then return to their groups to record their concluding hypothesis. When finished, students hand in the Lab Sheet and return to their desks.

Seat Work

Students will write a definition in their Science Journals for the term:

Suspended particles
(condensation nuclei)

Students should have reached the conclusion that a cloud cannot form unless 3 factors are present:

• water vapor
• cooling air & suspended particles

• sand & dust particles
• salt from sea spray
• pollen

A cloud is composed of millions of water droplets. These water droplets were formed by water vapor as it condensed in cooling air.