Greenhouse Effect …
Building Our Own

In a Nutshell:

Students set up a simplified model of the earth and the greenhouse effect. By comparing temperatures inside a jar to temperatures outside the jar, they will be able to draw conclusions about how an envelope of greenhouse gases is affecting the earth.

Goal:

To have students understand the greenhouse effect as a physical phenomenon.

Background Learning:

Teachers should be familiar with the basic science of climate change and its anticipated impacts as reviewed in:

• High School Backgrounder #1: Climate Change: What’s The Big Deal?

Teachers should read the backgrounder that corresponds specifically to this lesson plan:

• High School Backgrounder #2: The Greenhouse Effect

Students should be familiar with the basic science of climate change and its anticipated impacts as reviewed in:

• Intermediate Backgrounder #1: Basics of Climate Change: What’s the Big Deal?
  

Learning Outcomes:

Click on the icon for your territory to review the learning outcomes that are addressed by this lesson:

Introduction to Lesson Plan:

Where does the term “greenhouse effect” come from? Well, picture a greenhouse, built with walls of glass or clear plastic. As sunlight passes through the walls, its heat is absorbed by both the soil and by the plants. Some of the heat is radiated back into the air, warming the greenhouse. The walls keep the warm air inside the greenhouse.

A similar trapping of heat happens in the earth’s atmosphere. Sunlight passes through the atmosphere and is absorbed by the earth’s surface. Some of that heat is later radiated back into the air where some of it is trapped by the atmosphere. Without the atmosphere, earth’s temperature would average about –18C. Greenhouse gases in our atmosphere, however, trap more of the radiating heat than the atmosphere normally does. This warming due to heat-trapping gases is called the “Greenhouse Effect”.

In the classroom experiment, the air around the exposed thermometer is constantly changing due to convection currents in the classroom. Warm air rises and is replaced by cooler air. The air trapped in the jar is unable to circulate to the rest of the room, however, and as a result the air gets warmer and warmer.

Activity:

1. Group the students and distribute the materials. (Click on Handouts to get the Student Handout: Greenhouse Effect …Building Our Own – Student Worksheet.)
2. Hold the two strips of cardboard together (face to face), and wrap the rubber band around what will now be the top ends. The two pieces are now attached.
3. Slide the thermometer between the pieces of cardboard, with the top end under the rubber bands, roughly flush with the top of the cardboard. You should now have a thermometer sandwich: the thermometer should be secured under the rubber band, between the two pieces of cardboard.
4. Bend the cardboard out a bit in a teepee shape so that the thermometer is suspended between the two pieces. Make sure the numbers on the thermometers are facing out.
5. Stand the teepee up to make sure it is self-supporting.

   

6. Place one of the thermometers inside the jar and put the lid on the jar.
7. Place the jar in a sunny window or beside a desk lamp. Place the second thermometer next to the jar. Be sure that both thermometers are shaded from direct light by the cardboard to get an accurate reading.
8. Wait for approximately three minutes so the thermometers will be giving accurate readings and then have the students record the initial temperatures from both thermometers.
9. Record the temperatures on the student worksheet every 10 minutes for one hour.
10. Plot a line graph with both sets of data on the same axes (temperature on Y, time on X). See the example below.

    

    Note about graphs: Line graphs can be used to show how something changes over time. They have an x-axis (horizontal) and a y-axis (vertical). Usually, the x-axis has numbers for the time period, and the y-axis has numbers for what is being measured. The data that gets plotted are called “values.” Line graphs are useful for plotting data that has peaks (ups) and valleys (downs), or that was collected in a short time period.

11. Lead a discussion on the results:
    
    
    • Why is it hotter inside the jar? (The glass lets the sun’s energy inside, and then traps the heat.)
    • What would cause the temperature in the jar to change at different times? (Different sun conditions)
    • In what ways is our mini-greenhouse like the sun’s atmosphere? In what ways is it different? (The jar traps heat, like the earth’s atmosphere. But the earth’s atmosphere is not solid, like glass. Some of the heat radiating from the earth’s surface escapes into space. Some is absorbed for a short time by greenhouse gases and then emitted back to the earth’s surface.)

Credits: Greenhouse Effect …Building Our Own was created using the following sources:

• Littlejohn, G. & Waters, A., “Gases and Greenhouses: Simple Activities for Exploring Key Concepts,” in Grant & Littlejohn (2003). Teaching about Climate Change, Green Teacher and New Society Publishers.
• “The Greenhouse Effect in a Jar” – The Franklin Institute Online – http://sln.fi.edu/tfi/activity/earth/earth-5.html

Handouts:

Click on the icon for the handout that supports this lesson – Student Handout: Greenhouse Effect…Building Our Own – Student Worksheet.

Student Web-Exchange:

Students can post graphs or reports on the student exchange portion of the website for others to read. Click on the icon for information on how to post to the Web-Exchange.

Evaluation:

• Have each student complete his or her data sheets and hand in.
• Ask each group to take the discussion questions above and answer them on chart paper to be hung up for further discussion.
• Ask each student to graph his or her findings on a piece of graph paper. After the follow up discussion above, ask each student to write a paragraph or two explaining what happened in their experiment and why. Ask them to answer the questions at the bottom of their worksheet as well.

Enrichment Ideas:

Science:

• Graphing is groovy! Students may want to continue the experiment and record the two temperatures every day at the same time for a week. Graph the data and discuss how the temperatures fluctuate from day to day.
• Stevenson who? For teachers who are below treeline, you may want to take this opportunity to introduce your students to standardized weather recording instruments, which have been used for decades to predict forest fire weather. Forest fires are expected to increase in numbers and intensity as the climate warms.
  
  The link to the experiment is the cardboard that is used to shield the thermometers from direct sun. In an official weather monitoring station, a Stevenson screen performs the same function. The Stevenson screen is a wooden box, painted white, with double louvered sides, and mounted on a stand four feet above the ground. Thomas Stevenson, a civil engineer (and father of Robert Louis Stevenson, author of Treasure Island) designed this instrument shelter. Any territorial or government office that does fire prediction will have a Stevenson screen and the weather recording instruments it protects. Ask someone to speak to your class about fire and climate change.

About the Author:

My name is Colleen O’Brien. I have been a teacher for 18 years and continue to enjoy the energy and excitement that students bring to class. For the past 13 years I’ve been working in Whitehorse, Yukon as an elementary teacher. The Yukon is an inspiring place to live with its vast wilderness at our fingertips. I believe the outdoors is a great classroom for our children and would like to see us do what we can to preserve that learning environment.

I enjoyed writing this lesson plan and being an advisor on various aspects of this project. I’d like to thank the YCS curriculum team for assistance on this lesson, and also the people from Green Teacher who provided me with the initial inspiration.