• A narrow-neck bottle (such as a beer bottle)
• Vinegar
• Baking soda
• Matches
• 1 candle
• 1 straw
• Hot Stuff! Activity 1 Worksheets, 1 per student (Use this worksheet for Class Demo 1, 2, 3, and Student Activity 1.)

• A narrow-neck bottle (such as a beer bottle)
• 50 ml vinegar
• 45 grams baking soda
• 1 small, round balloon
• 1 straw
• 50 ml BTB n (solution = 6 drops per 1/3 cup water). BTB is bromothymol blue (BTB), a dye used as an acid-base indicator solution. (Available at a chemistry equipment store or a well-equipped hardware store. Or, order from the online chemistry equipment supply company such as Fischer Scientific International.
• 1 clear beaker (large enough to hold 50 ml of BTB solution)
• Hot Stuff! Activity 1 Worksheets, 1 per student (Use this worksheet for Class Demo 1, 2, 3, and Student Activity 1.)

Each student needs:

• 1 small, round balloon
• 1 straw
• 1 small cup of ~50 ml of BTB solution (solution = 6 drops per 1/3 cup water) (Paper Dixie cups or small beakers are suitable)
• Hot Stuff! Activity 1 Worksheet (Use this worksheet for Class Demo 1, 2, 3, and Student Activity 1.)

• 2 medium-size beakers, each half full of BTB solution (solution = 6 drops per 1/3 cup water)
• 1-2 small pieces of ice (cubes)
• 1-2 small pieces of dry ice
• Hot Stuff! Activity 1 Worksheets, 1 per student (Use this worksheet for Class Demo 1, 2, 3, and Student Activity 1.)

Each group needs:

• Hot Stuff! Activity 2 Investigation Worksheet and Instructions (provide each group with the specific instruction sheet for the investigation that the group is conducting)
• Masking tape and pen
• Graph paper, 1 sheet per group
• Supplies for the specific investigation the group is conducting (see below).
• Investigation #1 supplies:

1. 2 identical, large plastic jars
2. 2 outdoor thermometers (must fit in jar)
3. 25g baking soda
4. 1 cup vinegar
5. Plastic wrap (2 large squares to fit over jar openings)
6. 2 rubber bands

• Investigation #2 supplies:

1. 2 identical, large jars
2. 2 outdoor thermometers (must fit in jar, below rim)
3. Hot water
4. Hot mitt
5. Plastic wrap (1 large square to fit over jar opening)
6. 1 rubber band

• Investigation #3 supplies:

1. 2 identical, large jars
2. 2 outdoor thermometers (must fit in jar, below rim)
3. Cold water chilled with ice cubes
4. Plastic wrap (1 large square to fit over jar opening)
5. 1 rubber band

• Investigation #4 supplies:

1. 2 identical, large jars
2. 2 outdoor thermometers (must fit in jar, below rim)
3. 2 cups of garden soil
4. Plastic wrap (1 large square to fit over jar opening)
5. 1 rubber band

This activity is composed of three teacher-led class demonstrations and two student-conducted activities. Students use the Hot Stuff! Activity 1 Worksheet for Class Demos 1, 2 and 3, and Student Activity 1. Students use the Hot Stuff! Activity 2 Investigation Worksheet and Instructions for Student Activity 2.

Bromothymol blue (BTB) changes from dark blue to light blue, green or yellow, depending on the concentration of carbon dioxide present.

Dry ice is solid carbon dioxide at -110ºF.

• Prepare the BTB solution (6 drops BTB per 1/3 cup water).
• Gather materials and make copies of the worksheets.
• Make arrangements to transport ice and dry ice, and heat the hot water.

Class Demo 1: Carbon Dioxide Extinguishes a Flame

1. Explain the steps of the demonstration to the students. Ask them to make predictions about what will happen and record them on their Hot Stuff! Activity 1 Worksheets.

Figure 1. Class Demo 1. Carbon dioxide extinguishes a flame. click for copyright

2. Light the candle.
3. Mix vinegar and baking soda in a bottle. This works best if you put the vinegar in the bottle first and then add the baking soda.
4. Tilt the bottle slightly over a burning candle so that the gas gently flows out and extinguishes the candle. It may help to use a straw from the bottle to direct the CO₂ towards the flame, see Figure 1. Do not tilt the bottle so much that the liquid runs out and extinguishes the flame.
5. Ask students to record their observations on their worksheets.
6. Ask the students to explain why the flame went out. Discuss each theory.
7. Repeat the demonstration, explaining what is happening at each step. (Explanation: CO₂ pushes away the O₂ needed by the candle to keep burning.) Explain to students that they will create this same CO₂ gas for another experiment.

Demo 2: Creating and Testing for Carbon Dioxide

1. Explain the steps of the demonstration to the students. Ask them to make predictions about what will happen and record their predictions on their Hot Stuff! Activity 1 Worksheets.

Figure 2. Class Demo 2. Capturing in a balloon the carbon dioxide gas created from the reaction of vinegar and baking soda in the bottle. click for copyright

2. Pour 50 ml of vinegar into a narrow-necked bottle.
3. Place 45 grams of baking soda in a balloon.
4. Secure the rim of the balloon over the mouth of the bottle without releasing any of the baking soda into the vinegar.
5. Tip the balloon so that the baking soda falls into the vinegar.
6. Observe the inflation of the balloon (see Figure 2).
7. Carefully twist the balloon shut so that the gas does not escape.
8. Insert a straw into the balloon and squeeze the opening closed with your fingers. A little carbon dioxide might escape, but try to keep most of it in the balloon.
9. Pour 50 ml of the BTB solution into a clear beaker.
10. Explain to the students that this BTB solution is an acid-base indicator. (They should remember about these from Air Pollution unit, Lesson 6.) What do they think it will show? (Answer: BTB indicates the presence of carbon dioxide [an acid] with a color change; turning from blue to green or yellow.)
11. Place the opposite end of the straw into the solution.
12. Slowly allow the carbon dioxide to be released into the BTB solution.
13. Have students observe what happen and record it on their worksheets. (Explanation: The BTB solutions turns from blue to green or yellow.)

Student Activity 1: Testing for Carbon Dioxide from Our Own Breath

1. Explain the steps of the activity to the students. Ask them to make predictions about what will happen and record them on their Hot Stuff! Activity 1 Worksheets.
2. Ask students to name the gas that animals exhale. (Hopefully, they know that it is CO₂.)
3. Distribute a small balloon, a straw, and a small cup of BTB solution to each student.
4. Ask the students to predict if the concentration of CO₂ that they exhale will be greater or less than the concentration from the vinegar and baking soda.
5. Repeat the steps in Class Demo 2, picking up from step #8 as described above, except this time ask the students to blow up their balloons.
6. Observe and record results on their worksheets. (Explanation: The BTB turns from blue to green or yellow.) What happens? How is using CO₂ from their breath different from Demo 2?

Class Demo 3: Testing Ice

1. Explain the steps of the demonstration to the students. Ask them to make predictions about what will happen and record them on their Hot Stuff! Activity 1 Worksheets.
2. Fill two medium-sized beakers half-full of BTB solution.
3. Ask the students to predict what will happen when you place a small piece of ice into a beaker.
4. Place the ice into the beaker. (Nothing should happen.)
5. Ask students to predict what will happen when you place a small piece of dry ice into a beaker.
6. Place the dry ice (solid CO₂) into the beaker.
7. Ask students to record their observations on their worksheets. (Answer: BTB changes color, from blue to green or yellow, due to the presence of CO₂.)
8. Can students explain the difference in reactions? (Explanation: The BTB turns from blue to green or yellow in the presence of CO₂. Regular ice is frozen water. Dry ice is frozen CO₂.)

Student Activity 2: Team Investigations

1. Divide the class into investigation teams of three students each.
2. Assign each group to one of the four different investigations in the attached Hot Stuff Activity 2 Investigation Worksheet and Instructions. Have at least two groups working on each investigation.
3. Distribute the appropriate instructions to each group.
4. Ask each group to carefully read through their instructions and make their initial predictions about what will happen in their investigation.
5. Have students gather their supplies, set up and begin. Investigation recaps and explanations:

Investigation #1

CO₂ is released in the reaction (just like in the demos). This models an increase in greenhouse gas. While the jars heat up at about the same rate, the one with CO₂ cools down much more slowly.

Investigation #2

This models how CO₂ and water vapor in the atmosphere affect the rate at which the Earth loses heat (the plastic wrap acts as the CO₂ and water vapor during the experiment).

Investigation #3

This is similar to Investigation #2. This models how CO₂ and water vapor in the atmosphere affect the rate at which the Earth gains and loses heat (the plastic wrap acts as the CO₂ and water vapor during the experiment).

Investigation #4

This models how the temperature of the actual Earth changes (as opposed to water in investigations #2 and #3). The plastic wrap acts as the greenhouse gases.

6. Give students time to create graphs and think about their results.
7. Suggest that each team make a presentation to the class. They could start with a brief outline for their presentation. Require each team member to participate in the presentation.
8. After all the presentations are given, conduct a class discussion. Ask the students which model they think is the best representation of the greenhouse effect? Global warming? How would they improve the models?

Predictions: Using the attached worksheets, have students make and record predictions about what will happen.

Observations: Have students observe what happens during the activity and record it on their worksheets.

Conference Presentations: Have students prepare and give oral presentations on their investigations. Often engineers are asked to present their research to a group of their peers or interested persons in a way that is understandable and clearly expresses the conclusions of their research. Have students pretend to be engineers who are presenting their recent findings about the effects of carbon dioxide at an EPA (U.S. Environmental Protection Agency) conference. Ask the students how the model they investigated is the best representation of the greenhouse effect? Global warming? How would they improve the models?

Discussion Questions: Ask students to summarize what they have learned in this activity. Do this as an informal discussion or a written homework assignment.