### How Greenhouse Gases Absorb Heat

Student Worksheet

In this experiment, you will observe the effects of higher concentrations of greenhouse gases.

Prior to your investigation
Think about and respond to the following:
• What do you predict will happen if we conduct an experiment where we vary the amount of greenhouse gas in a model atmosphere?
• What are the independent and dependent variables?
• What variables are we holding constant?
• Formulate a hypothesis with an explanation of the results that you expect.
Materials Per Team
• 15 ml of Bromothymol Blue (BTB), an acid and carbon dioxide indicator
• 1 small beaker or jar
• 2 large jars with lids
• 2 pieces of black construction paper of equal size to place inside the jars
• 2 thermometers to place inside the jars
• 1 Erlenmeyer flask (250-500 ml)
• 1 one hole stopper for above flask
• 1 straight piece of glass tubing
• 1 50 cm piece of flexible tubing (aquarium air tubing works fine)
• 100 ml of vinegar
• 4 heaping teaspoons of baking soda
• Watches or classroom clock to time readings
• Lamp with 100 watt bulb or sunny window sill

Investigation
1. Collect materials together. Assemble the flask, stopper, and tubing as seen in the illustration. Remove the stopper and place 100 ml of vinegar into the flask and add a half teaspoon of baking soda, then replace the stopper. Place the flexible tubing into the BTB solution and notice the color of the liquid as the gas bubbles through the indicator solution. What color change do you notice?

2. Set-up your two jars with equal pieces of black construction paper in the bottom and the thermometer in each.

3. Now remove the stopper and place the remaining 3 1/2 teaspoons of baking soda into the flask, replace the stopper and place the tubing into one of the large jars. Allow the tubing to stay in the jar for a minute or so.

4. Record your starting temperature and then turn on your lamp making sure that the jars are placed and equal distance from the light source and that they are getting equal amounts of light. Record the temperatures on the two jars every 2 minutes for 15-20 minutes.

5. Plot your results on a graph of Temperature vs. Time for each jar. What do you notice about the temperature in the two jars? Share and compare your results with other teams in your classroom.

6. What can be said about the results? Do they support the hypothesis that you formulated before you did the investigation?

What do your results imply about what might happen to Earth's atmosphere if we increase the concentration of greenhouse gases?

7. What sources of error do you think might have affected your results?

8. What follow-up experiments might you conduct that would help you understand greenhouse gases better?