# Bubbles on Bottles

Students observe that a change in the temperature of air can impact the size of a bubble placed on a bottle that is cooled and/or heated.

Lower Elementary

## Time

• Teacher preparation: 20 minutes
• Introduction for students: 10 minutes
• Student activity: 30 minutes
• Class discussion/analysis: 10 minutes

## Learning Objectives

• Students observe that change in temperature of the air in a bubble will change the volume of the bubble
• Students will be able to describe the relationship between the change in a unit of air's temperature to its volume
• Students will understand that the Sun's energy creates movement in the air, and that motion is called a convective current

## Materials

For each pair of students:

• 2 clear plastic 1-liter bottles
• plastic shoebox or similar
• small plastic containers
• hot water in an open-top kettle
• ice water
• dishwashing soap - diluted

## Directions:

(This can be altered to a format that best fits the activity when necessary)

1. File a clear plastic shoebox with 3”-5” of ice water for each group of two to four students (have hot water on standby to fill a shoebox container in the same way for each group).

2. Add approximately 1/4” of diluted dishwashing soap to a small container for each group.

3. Demonstrate dipping the narrow open end of the bottle (mouth) into the soap container to form a film over it, then have students practice this. If the film pops, simply ask students to repeat the procedure.

4. Next place the bottom of the bottle into the cold water. Have students record what happens.

5. Carefully provide a shoebox with 3” - 5” of hot water in it to each group, making sure to review common safety precautions.

6. Have students experiment and record what happens when the bottom of a bottle with soap film over its mouth is placed in the hot water.

7. Encourage students to place their bottles in both the hot and cold water without breaking the bubble to see it rise and fall due to the temperature change.

## Reflection and Assessment

Ask the students the following questions:

1. Is the same amount of air in the bottle if the bubble does not pop?

2. Is the volume of air increasing or decreasing in the bottle when it is warmed? What happens when the air is cooled?

3. What could you do to make the bubble grow larger or smaller? Do you know?

## Background Information

Convection is the transfer of heat by the movement or flow of a substance from one position to another. Temperature is a measure of the average speed or kinetic energy of molecules. These are both demonstrated in this activity, as changes in the temperature of air inside the bottle make the air’s volume grow or shrink. The warm bath causes the air inside the bottle to warm and expand, thus increasing the volume that the air needs. The air pushes the bubble up above the bottle’s mouth. The cold bath creates a slower and consequently more densely packed air mass that sinks into the bottle, pulling the bubble inside the bottle’s neck. As the temperature in the bottle fluctuates between cold and warm, the bubble serves as a tracer of invisible air – showing students how the mass of air in the bottle remains the same, but the space it takes up (its volume) changes as a result of its temperature.