Break the class into groups of four to five students. Have the students heat water in the beaker to boiling. (Each group of students should heat 200 mL of water.)
As the water is heating, ask students:
- What is happening to the water?
- What is heat?
- Why does it matter that the water is heated?
- As the water heats, what is happening to the water particles?
- What is happening between the particles?
After the water has heated to boiling, students should carefully pour the water (200 mL) into the plastic bottle and tightly cap the top. They should observe what happens to the container for a 20 minute time period.
Note: The milk container will almost immediately begin to expand because of the increased particle movement of the water vapor.
As the students are making observations, ask:
- What is happening to the plastic bottle?
- Why is this happening?
- What is making thebottle do this?
- How could we test this idea?
As the water begins to cool and the milk container goes through another change, ask students:
- Now what is happening to the bottle?
- Why is this happening?
- What is the difference between the water at this time versus the water when we initially poured it into the container?
- What change is happening to the water to make this event occur?
Note: As the water begins to cool and particle movement decreases, the bottle will begin and continue to collapse until it is actually concave.
