1. Students will be able to explain the greenhouse effect both in words and diagramatically.
2. Students will be able to explain the usefulness of models in understanding phenomena and will be able to provide an example of a model.
3. Students will be able to test for the presence of carbon dioxide in a sample of gas.
4. Students will be able to compare relative amounts of carbon dioxide in different samples of gas by testing the samples in the laboratory.
The science portion of this interdisciplinary unit focuses on providing students with a sound background on the greenhouse effect. Students are introduced to the global climate change theory as well. In activity 1, students are introduced to the idea that a greenhouse traps in heat. Students build a greenhouse model in which they make temperature comparisons between the greenhouse model and a regular container. Using basic knowledge of how a greenhouse works, they then compare their model to what is actually happening in our atmosphere. In activities 2 and 3 students are introduced to the "greenhouse gases". They learn that carbon dioxide plays a large role in trapping heat in the Earth's atmosphere. Students conduct tests on samples of gas to determine the relative carbon dioxide content of the gases. These activities give students a good idea of the amounts of carbon dioxide that are exhaled in human breath and which are emitted in car exhaust. In the final activity, students use the knowledge gained from the first three activities in constructing a diagram designed to clearly illustrate the greenhouse effect.
Global warming is a term which many students have heard, but most likely do not understand. This is not surprising, given that there is a great deal of uncertainty among scientists about global warming. Some scientists are very worried by a recent increase in average annual temperatures around the world. They are afraid that this warming trend will severely alter climates here on the planet Earth. These scientists believe that this warming trend is largely the result of human activities. Other scientists believe that the evidence is weak for a variety of reasons. The temperature on Earth has greatly fluctuated for millions of years. The observed increase in temperature may just be part of this natural fluctuation and have little tie to human activities. This would mean there would be very little, if anything, that could be done to stop the temperature changes. This uncertainty among the scientific community forces each person to make their own judgments about what may be happening to our environment. Students need to ask themselves: Is it better to continue emitting large amounts of CO2 and other harmful gases into the environment, hoping that global warming will not really occur, or, would it be safer to take steps to reduce the production of harmful gases, hoping that the temperature changes can be curbed?
The activities in the science portion of this module are designed to introduce students to the greenhouse effect and global climate change. In the laboratory, students will learn about how a greenhouse works to trap heat. They will also learn how to test gases for the presence of carbon dioxide. However, there is not a great deal of reading on the student pages related to global climate change and the greenhouse effect. The teacher must play a major role in presenting students with the background knowledge they will need to make sense out of their laboratory experiences. Each activity contains background information, written for the teacher. It is important that some of this information be shared with students, through class discussion. Specific suggestions for doing this are provided in the teacher notes of each of the four science activities. It will be important for you to set the tone of the unit by introducing each activity and by providing time for discussion following the gathering of data.
The concepts involved with global climate change are rather complex. To help students to sort out the important concepts, ask the class to construct a global climate change information board. Ask the students what format they would like the information board to take. For example, would they like one corner dedicated to related newspaper and magazine clippings? Would they like to prepare a diagram illustrating how greenhouse gases trap heat in the Earth's atmosphere? This is something that students will continue to work on as they learn new ideas throughout the unit. Ask students if they would like to be able to refer to their information board during their test over this unit. Encourage creativity and the use of diagrams.
Teacher Notes
Objective:
By completing this activity, students will increase their understanding of the greenhouse
effect and will be able to explain the usefulness of models in understanding phenomena.
Materials:
2-liter plastic bottles. Cut the tops of the bottles off at the point where the neck begins to
narrow.
thermometers (2 per student group)
masking tape
rubber bands (one per student group)
clear plastic wrap
index cards or other small pieces of card stock
soil
Background:
Most students have seen greenhouses. However, they would likely have trouble if asked to
explain how greenhouses work. Greenhouses are used for growing plants out of season and
for plants with special growth requirements. The walls are made of glass and allow radiant
energy from the sun to enter the greenhouse. This radiant energy is absorbed by the contents
of the greenhouse. The absorbed energy is re-emitted by the contents of the greenhouse, but
is not transmitted back out through the glass. Thus, although the air temperature outside the
greenhouse may be cold, the temperature inside the greenhouse will be much higher due to
the trapped heat. In summer, the panes of greenhouses are often covered with slat shades or
whitewashed to reduce the amount of light entering. This helps to keep the greenhouse from
getting too hot.
The greenhouse effect is the term for the role the atmosphere plays in helping warm the Earth's surface. The atmosphere is largely transparent to incoming solar radiation. The Earth's surface absorbs this energy. Much of this radiation is then reflected back to the atmosphere. However, certain gases can reflect this heat back toward the Earth. Carbon dioxide, methane, nitrous oxide, halocarbons, and ozone in the atmosphere can act as a "lid" by trapping heat. The amount of carbon dioxide in the atmosphere has been increasing by 0.4% a year since the late 1800's because of the use of fossil fuels such as coal, oil, and gas and the slash-and-burn clearing of tropical forests. Other gases that contribute to the greenhouse effect, such as methane and chlorofluorocarbons, are increasing even faster. The net effect of these increases could be a worldwide rise in temperature, estimates at 2 deg C to 6 deg C over the next 100 years. Warming of this magnitude would alter climates throughout the world, affect crop production and cause sea levels to rise significantly. If this happened, millions of people would be adversely affected by major flooding.
Teaching Strategies:
Begin by discussing models with your students. Ask students to share their ideas of what a
model is and to give examples of models they have seen or heard about. Scientists use
models to help them understand things that are difficult to test in the lab. Since the
atmosphere is too large and cannot be controlled, a model can be used to help scientists see
what can happen on a smaller scale. Models are not perfect replicas of the "real thing", but
can be helpful in understanding the ideas involved.
Allow students some freedom in setting up their greenhouse models. Most students will know that a greenhouse has clear walls and ceilings that allow the sun's energy to enter the greenhouse. This should be sufficient knowledge for them to guess that one container should have a clear covering and the other should be left open. Rather than giving students this information, allow them to figure it out for themselves. Directions are provided on the student page, however, you may wish to save paper by presenting students with directions using an overhead. The degree of direction you wish to provide will be up to you and will be dependent upon the expertise of your class in controlling variables. The student page provides a research question for students as well as a short list of factors students may wish to think about in setting up their experiment.
In order to get good results, students should set their experiments up in direct sunlight. The best results can be obtained if it is not a real hot day. Outside temperatures less than 72 degrees F are best, with cold temperatures working very well. The experiment may be set up either outdoors or on an indoor window sill or counter. The maximum temperature is likely to be reached within a maximum of 15 minutes. If your classroom does not receive direct sunlight, and you cannot wait for a sunny day to go outdoors, a lightbulb may be substituted for the sun. If you do use lightbulbs, give students safety pointers on handling hot bulbs. Students should experiment with different arrangements of the bulb. You will need only one bulb per student group, as one bottle may be set on each side of the light bulb. Distances of only a few centimeters between the light bulb and the bottles work best. Check to see that the thermometers are oriented in the same position relative to the light bulb. Students should read the thermometers every 1 minute and always read the same thermometer first.
It works best to cover the bulb of the thermometer with a small square of card stock. This prevents unusual temperature readings that result from the metal parts of the thermometers absorbing more heat than would the rest of the contents of each bottle. When setting up the experiment, simply tape a small square of card stock onto the back of the thermometer, near the region of the bulb.
In order to answer "Summing Up" question 3, students will need some knowledge of the greenhouse effect. Rather than providing this information prior to the lab, allow students to collect their data and to answer "Summing Up" questions 1 and 2 first. The closed container helps to illustrate how heat is trapped by the CO2 lid on our atmosphere. This "lid" prevents heat from escaping into the environment. This causes the air inside the bottle to become warmer faster than in the "control", which has no lid. Emphasize to students that this is a model of what may be happening to our global temperature.
Sample Answers to Summing Up:
2. Why did the temperature in each bottle go up? (Both light and heat energy from the
sun passed through the plastic and warmed the air and soil inside the bottle.)
3. Explain why the final temperatures of the two bottles were different? (The air inside each of the bottles is heated up. The air in the open container can mix with the cooler air in the room, so it has a chance to stay cooler. The air in the closed container is trapped, so the warm air stays warm.)
4. The plastic bottles in your experiment were acting as a model of the greenhouse
effect. Good models try to use things that behave similarly to the "real thing". In this
case, the real thing is the Earth's atmosphere and the sun. List those parts of your model
that were the same for the real greenhouse effect and those parts that only represented
what might be happening in the actual atmosphere.
Parts that were the same
both are exposed to direct sunlight
both involve air heating up
both have soil present
Both have moisture in the air
Parts that were different
plastic bottles represent the Earth & its atmosphere
plastic wrap was used to represent CO2 gas trapping in the heat
the Earth's surface is not covered with soil everywhere
the temperature of the Earth varies at different times of the year
the Earth's atmosphere does not have a physical barrier, like plastic wrap. Instead, it is
held down by gravity
the real atmosphere is much larger than the layer of air trapped in the bottle.
5. Imagine a second grader asks you to explain how a greenhouse works. How would you go about answering her question? (Student answers will vary to this question.)
Home/Community Connection:
Extensions:
Student Page
Problem:
Design and test a model for comparing the inside air temperature of a "greenhouse" to
that of an open container.
Materials:
2 liter plastic bottles with the tops cut off
soil
2 thermometers with card stock squares
plastic wrap & rubber band
masking tape
other things you may need depending on the design of your experiment
Let's Investigate:
People have been using greenhouses to help plants flourish for a long time. Light enters
the greenhouse through the glass. The light and heat energy from the sun is absorbed by
the objects within the greenhouse. While light easily passes into and out of the glass,
heat does not. A greenhouse has also been called a "hot house" because the heat becomes
trapped inside the glass room. The greenhouse effect is the name given to the role the
atmosphere plays in warming the Earth. Many believe that certain gases in the
atmosphere trap heat in the air. This could lead to a gradual "warming up" of the
Earth.
In this activity, your job is to develop and test a model that will illustrate what
happens to the temperature of the air around the Earth when heat is trapped within the
Earth's atmosphere. Your job is to discover the answer to the following question.
Research Question:
How does the air temperature in an open container compare to that of a closed container,
both of which are exposed to direct light from the sun?
To answer this question, you will need to design your own experiment. Here are a few hints about what your model might look like. You will be working with the materials listed above. If you need any other items, just ask your teacher.
As is the case with any good experiment, you must be very careful to control
variables. Here are some of the things you will need to think about in your model.
Summing Up:
1. Make a drawing of your experiment. Be sure to label all of the parts. Design a data
table in which to record your data. Be sure to place labels on any numbers you
record.
2. Diagram and/or describe why the containers heat up.
3. Explain why the final temperatures of the two bottles were different.
4. The plastic bottles in your experiment were acting as a model of the greenhouse effect. Good models try to use things that behave similarly to the "real thing". In this case, the real thing is the Earth's atmosphere and the sun. List those parts of your model that were the same for the real greenhouse effect and those parts that only represented what might be happening in the actual atmosphere.
5. A second grader asks you to explain how a greenhouse works. How would you go about answering her question? Remember, you are talking to a second grader! (You may include drawings in your explanation and should also try to tie in some everyday experiences the second grader might have had with the greenhouse effect.)
Teacher Notes
Objective:
By completing this activity, students will increase their understanding of the reaction
between exhaled carbon dioxide and water to form carbonic acid. They will also be able to
test a sample of gas for the presence of carbon dioxide.
Materials:
balloons (one per student group)
one gallon dilute bromothymol blue solution (BTB) - place into dropper bottles
20 or 25 ml graduated cylinder (one per student group)
8 oz plastic cups, small baby food jars, small beakers, large test tubes, or clear vials (4 per
student group)
ammonia solution - place in dropper bottles
** do not wash any of the materials in soap, as soap residue will affect the gas test. Make
certain that all bottles have been rinsed very well to remove any soap residue.
Preparation of BTB Solution:
NOTE: while tap water will work, using distilled water results in a more vivid color. If
distilled water is available, use it. If you have access of BTB that is in concentrated liquid
form, simply pour this into dropper bottles.
To make BTB solution from powdered BTB:
Weigh 0.50 grams of BTB powder and place it in container. Add 8.0 ml of 0.1 M sodium
hydroxide (NaOH) to dissolve the BTB crystals. Once dissolved, add 500 ml of water to the
mixture. (0.1 M NaOH can be prepared by dissolving 1.0 grams of NaOH in 250 ml of
water.) Place this solution in dropper bottles.
Testing your BTB solution:
It is important to test your solution to make certain that it is within an acceptable range. Do
this by placing 15 ml of water into a clean cup or beaker. Add 10 drops of the BTB solution
to the water. Using a straw, bubble one lungfull of breath through the straw into the solution.
If the solution turns green, it is okay. If it stays blue, or turns only slightly bluish-green, it is
too concentrated. Add some more water to the BTB stock solution and retest it. If it turns
yellow, it is too weak. Add a little more BTB concentrate and retest it. Make certain that
your dropper bottles of BTB each contain solutions of the same strength. Test and adjust your
stock solution, before filling your dropper bottles with BTB solution. Once you are satisfied
with your BTB solution, pour the BTB solution into dropper bottles, one for each group.
Preparation of Ammonia Solution:
Prepare a dilute solution of ammonia by adding 10 ml of household ammonia to 100 ml of
water. Since not all brands of household ammonia are the same, it may be necessary for you
to adjust the concentration of your ammonia. Conduct this simple test on your diluted
ammonia before placing the ammonia into dropper bottles: Blow up a balloon. Using a twist
tie, secure the balloon around one end of a pen casing. Let out air until the balloon just fits
through the center of a roll of masking tape. Seal the end of the pen casing with a lump of
clay. Bubble the exhaled air through a solution of 15 ml of water and 10 drops of BTB. If
more than 15-20 drops of ammonia are needed to turn the solution yellow, remake the
ammonia by adding less water to the ammonia. Make certain that all of the ammonia
solutions are of the same strength before placing them in dropper bottles, or comparisons of
findings between groups will be difficult.
Safety Warning:
Students should wear goggles while using BTB and ammonia solutions. The solution may be
irritating to the skin and eyes. Any spills should be washed off immediately. Remind students
to be careful and to report any spills as soon as they occur.
Background:
Bromothymol blue (BTB) is an acid/base indicator that changes color between pH 5 (yellow)
and pH 7.6 (blue). The indicator is green between these pH values. When carbon dioxide
(CO2) is added to water, it reacts with the water to create carbonic acid. The more CO2
present, the more carbonic acid forms and the lower the pH. pH values below 7 are considered
acidic. The lower the pH, the stronger the acid.
Some carbon dioxide is needed in the atmosphere, or the Earth would freeze. The
problem is one of balance. Many researchers believe that too much carbon dioxide is being
added to the atmosphere from burning fossil fuels such as gasoline, natural gas, coal, and oil.
Scientists who have measured the amount of carbon dioxide from different sources have
found that carbon dioxide in the United States comes from the following sources:
Cars and Other Transportation 27%
Homes and Businesses 16%
Industry 29%
Electric Power Plants 28% (these provide power to homes, businesses & industry)
Since 1850 there has been a mean rise in global temperature. This rise could be part of a natural fluctuation. Such fluctuations have occurred for tens of thousands of years. Temperature fluctuations can be short-term as well as long-term cycles. Because of the difficulty of distinguishing human-made causes of carbon dioxide emissions from natural sources, governmental legislation regarding their control has been slow in coming. However, the potential consequences of global warming are so great that many of the world's top scientists have urged immediate action and have called for international cooperation on the problem.
Suggested Teaching Strategies:
Students will be observing the color changes that occur in BTB as they exhale into the
solution. They will need to be able to observe differences in the colors of blue, green and
yellow. Colorblind students will have difficulty observing the differences between the various
shades of BTB. Be sure to have these students work in an appropriate group setting.
This activity should not require a great deal of teacher direction. Emphasize safety while using ammonia and insist that students wear safety goggles throughout the experiment. Students may wish to do the experiment more than one time. This should be encouraged. It can be done quickly and does not involve expensive materials. You will find that several students will attempt to compare the CO2 content of each other's breath. This is a good lab to allow students some freedom to experiment!
Sample Answers to Summing Up:
1. As more CO2 was bubbled through the BTB solution, the color changed from blue to green
to yellow.
2. Approximate color scale students develop may look like the one below, although it is not necessary that they list all the colors shown:
3. The air in the auto garage contains large amounts of CO2. This is probably from leaving car engines running while tuning up engines. This high CO2 is not good for those working in the garage. A better ventilation system is needed for the safety of the workers in the garage. The greenhouse has a low amount of CO2. This is likely due to the fact that plants take in CO2 and give off oxygen. The greenhouse air is healthy for those working there.
Home/Community Connections:
Extensions:
Do all people exhale the same amount of CO2? Challenge students to design an experiment
that will help them answer this question. Ask them to carry out their experiment. They should
record their data and write a short summary of their findings.
Student Page
Problem:
Find out how the amount of carbon dioxide affects the color of BTB solution.
Materials:
BTB solution
sheet of white paper
4 plastic cups
1 straw
stirring stick
ammonia solution
graduated cylinder
Let's Investigate:
In this activity, your job is to discover how the amount of carbon dioxide is related to the
color of a special solution. It is a solution which changes color, depending on how much
acid is in it. When carbon dioxide (CO2) is dissolved in water, it turns into an acid called
carbonic acid. The more CO2 present in a gas, the more carbonic acid it forms when mixed
with water. How can you tell how much CO2 you have? You can use a chemical called
bromothymol blue, or BTB for short. Your job in this lab is to discover how the amount of
CO2 is related to the color of BTB.
Begin by preparing 4 test cups. Place 15 ml of water into each cup. Be sure to measure the amount of water carefully using a graduated cylinder. Now add 10 drops of BTB solution to each cup. Line up your cups on a white piece of paper. Label the cups as shown in the drawing below.
Be careful not to add bubbles to the control cup. This will be your color comparison for the other three cups. Take a deep breath and slowly exhale the breath through a straw and into the BTB solution. As the bubbles go through the solution, notice the color change. Exhale two full breaths into the next cup. Exhale three full breaths into the last cup. Record the color of the BTB solutions in a data table.
You can add ammonia to each test cup to get its color to change back to blue. The more ammonia you need to add, the more CO2 it must contain. Add drops of ammonia solution to the 1 breath test cup. Gently stir the solution after each drop. Keep adding ammonia until the color of the test solution matches that of the control. Record this number of drops in the data table.
Once all your data has been recorded, clean up your cups and other materials.
Summing Up:
1. Describe how the color of the BTB changed as more CO2 was bubbled through it.
2. Develop a color scale key which a person could use to determine the amount of carbon dioxide in a sample of gas. Write the names of the correct color on the scale below.
3. Imagine that you are a scientist testing the CO2 content of two samples of air. Sample 1 is collected from inside an auto repair garage. Sample 2 is from inside a greenhouse which is stocked with large plants. Based on the data provided below, write a summary describing how the amounts of CO2 compare between the two samples. What recommendations about air quality would you make to the management of each place?
Number of drops of ammonia neeed to turn the sample back to blue:
Sample 1: 35 drops
Sample 2: 6 drops
Teacher Notes
Objective:
By completing this activity, students will be able to compare the relative amounts of CO2
present in the air, human breath, car exhaust and pure CO2.
Materials:
trays (1 per student group)
plastic cups (5 per student group)
25 ml graduated cylinder (1 per student group)
pea-sized piece of modeling clay (1 per student group)
empty pen casing (1 per student group)
different colored balloons (4 per student group)
permanent marker (1 per student group)
twist ties (5-6 per student group)
bicycle pump (2-3 per classroom)
stirring sticks (popsicle sticks work well)
small funnel & modeling clay for collecting car exhaust
12 or 16 ounce plastic pop bottle (1 per student group)
dropper bottles of weak ammonia (1 per student group)
safety goggles
1 box baking soda (place into baby food jars for student use)
dropper bottles of BTB (1 per student group)
1 gallon white vinegar (place into smaller containers which hold between 300-500 ml)
100 ml graduated cylinder (one per student group) or measuring cup
SAFETY WARNING:
Students should wear safety goggles throughout this activity, as students have a tendency to
splash as they are stirring. Remind students that if ammonia is spilled or gets on their skin,
they should immediately wash the area with water.
Background:
The main greenhouse gases are considered to be carbon dioxide, methane, nitrous oxide,
ozone, and chlorofluorocarbons (CFC's). Of these, carbon dioxide and water vapor are the
most important gases in creating the insulating or "greenhouse effect" on the atmosphere.
CO2 accounts for nearly half of the warming potential caused by human activity. It is
released by burning fossil fuels, (oil, coal, and natural gas), flaring of natural gas, changes in
land use (deforestation, burning and clearing land for agricultural purposes), and the
manufacture of cement. Methane accounts for about 16% of the global warming. Methane
comes from landfills, wetlands, bogs, domestic livestock, coal mining, wet rice growing,
natural gas pipeline leaks, biomass burning, and termites. Molecule for molecule, methane
traps heat 20--30 times more efficiently than CO2. CFC's account for about 20% of the
global warming. CFC's come from industrial products developed 60 years ago. They are
used in refrigerators, car air conditioners, solvents, aerosol, propellants, and insulation. One
molecule of CFC has about 20,000 times the heat-trapping power of a molecule of CO2.
CFC's also degrade the ozone layer. One CFC molecule can destroy as many as 100,000
ozone molecules. The thinning of the ozone layer may have a cooling effect on Earth, since
this allows additional radiation to reach the Earth's surface. It allows more penetration of
ultraviolet rays, which can cause skin cancers and cataracts in humans, as well as damage
plants. Nitrous oxide accounts for about 6% of global warming. Nitrous oxides come from
burning coal and wood. The amounts of each of these gases have been increasing for many
years. The amount of carbon dioxide in the atmosphere has been increasing rapidly. The
preindustrial level of CO2 was about 275 ppm, while in 1986 the concentration of CO2 in the
air was about 343 ppm.
Suggested Teaching Strategies:
This lab requires a good deal of advanced preparation. It works best to organize materials
using trays, with one tray per student group. Each item from the list of materials should be
placed on a tray. Remind students that their tray is to look the same at the end of the class!
Organized clean-up will make your job much easier, especially if you need the materials for
your next hour class.
Activity 2 familiarized students with the BTB test. Ask students to reiterate their findings from that experiment. (They should indicate that the more yellow the BTB solution becomes, the more CO2 the solution contains. It is also true that the more drops of ammonia added to turn the color back to blue, the more CO2 must be present.)
This laboratory requires specific techniques for collecting and bubbling the gas through the BTB solution. While the procedure is briefly outlined on the student page, a demonstration of the techniques would be most efficient. As the demonstration may require 15 or so minutes, it would be best to conduct your demonstration the day before students begin testing their own gases. Use one of the trays of materials. This will allow students to see that all of the materials they will need are there. Be sure to demonstrate and emphasize good clean-up as you proceed.
While it was easy for students to bubble exhaled air through the BTB solution using a straw, the process becomes more difficult with other gases. To help illustrate the importance of controlling variables, ask two different students to exhale into two different balloons. Hold the two inflated balloons up, asking the class if it would be fair to compare these two samples for CO2. (Make certain that the balloons differ greatly in size!) Students will immediately notice the difference in the sizes of the two balloons. Ask the class to come up with a way to make certain all the balloons contain the same amount of air. Use whichever of their suggestions sounds the most manageable. An excellent choice is to use the center of a roll of masking tape. When the balloon just fits through, it is the correct size. Students will likely want to keep the balloon a very large size. This is not necessary and, in fact, a smaller size works best. Whatever method you decide upon, you may refer to this as your "balloon sizer".
When you exhaled through the straw, you were not controlling how much air was bubbled through the solution. For this experiment, you must know that that amounts of each gas being tested are the same. To do this, you will need to use a method which will allow the gas to be trapped, then bubbled through the BTB solution. The steps and drawings shown below illustrate a good method for doing this. Go through each step, demonstrating to students as you proceed.
Steps for Gas Collection and Testing:
If time remains following the demonstration, you may wish to have students draw their circles and labels on a clean sheet of white paper, as indicated in the directions on the student page. It is suggested that each student keep their own data, rather than handing in group data. This helps to keep each student focused on the activity.
Allow students to begin collecting and testing their gases at the beginning of the class, the day after your demonstration. It is best to have students work in groups of three, with each group receiving their own tray of materials. Remind students that they will be testing each gas with BTB solution and counting the number of drops of ammonia needed to change the color back to its original blue.
Collecting Samples of Car Exhaust
Once the data has been collected, provide students with an opportunity to compare their results with those of other students. You may want to make a chart on the chalkboard to pool the results from each student group.
Sample Answers to Summing Up:
1. Number of drops of Ammonia Needed to Return Color to Blue
2. Vinegar and baking soda has the highest CO2 content. The room air has the least CO2.
3. Of the gases tested, car exhaust would contribute the most to high CO2 levels in our atmosphere. Vinegar and baking soda produced more CO2, but this reaction is not common-place and would not be expected to add much CO.
Home/Community Connections:
Ask students if they think that all cars contain the same amount on CO2 in their exhaust. Do
they think there are measurable differences between the amount of CO2 emitted from a 4-cylinder and an 8-cylinder engine? Challenge students to design an experiment to find the
answers to these questions. Ask them to have one of their parents or other adult family
member help collect the data needed to answer this question.
Extensions:
Do some research to discover which countries contribute the most to the various greenhouse
gases. Display your findings in the form of a chart or graph.
Reference: "The Greenhouse Effect in a Vial" by Richard Golden & Cary Sneider, The Science Teacher, May, 1989.
Student Page
Problem:
How does the amount of CO2 in exhaled air, car exhaust, classroom air, and pure CO2
compare?
Materials:
4 different colored balloons sheet of white paper
5 plastic cups
graduated cylinder
BTB solution
ammonia solution
empty pen casing
4-6 twist ties
lump of clay
stirring stick
baking soda
vinegar
plastic pop bottle
bicycle pump
sample of car exhaust
SAFETY WARNING:
The BTB and ammonia solutions can cause burning if spilled on the skin and are dangerous
when in contact with the eyes. Wear your safety goggles at all times during this lab. Report
any spills to your instructor right away.
Let's Investigate:
You will be collecting gas from 4 different places and determining which has the most CO2
and which has the least. Here is a list of the gases and where they will come from:
Pure CO2: vinegar & baking soda
Room Air: bike pump
Breath: your lungs
Auto exhaust: your teacher's car
It works best to collect all of the gas samples first before testing each sample for CO2 . Make certain that you fill and seal each balloon using the techniques which your teacher demonstrated to you. Use a magic marker to label each balloon once you have filled it with the gas. Try to fill each balloon with more gas than you need in case some leaks out. Don't forget to stretch out each balloon first!
Collecting samples of room air:
Use a bicycle pump to inflate a balloon. Be sure to inflate the balloon to a size larger than
what you will need. Seal the balloon by twisting the end of the balloon and securing it with a
twist tie. Use a magic marker to label the balloon "room air".
Collecting samples of human breath:
Devise a way to collect human breath that will allow you to test the same amount of human
exhaled gases as you collected from the classroom.
Collecting Pure CO2:
Mix 100 ml of vinegar with 1 Tbs. of baking soda in a plastic pop bottle. Quickly pull a
balloon over the bottle opening. If your balloon does not seem full enough, add more vinegar
and baking soda and try again. Collect the gas in a balloon, sealing it tightly with a twist tie.
Be sure to label the balloon "pure CO2".
Collecting a Sample of Car Exhaust:
Your teacher will fill your balloon with car exhaust. Have a twist tie and marker handy. If
your balloon breaks, do not inhale the gas!
Testing the Gas Samples
Summing Up:
1. Prepare a bar graph showing the amounts of ammonia needed to return the color of each
BTB solution back to its original blue.
2. Which gas has the highest CO2 content? Which gas contains the least CO2?
3. High levels of CO2 are believed to be linked to global climate change. Which of the gas samples tested do you believe contributes the most to the high levels of CO2 in our atmosphere? Explain your choice.
Teacher Notes
Objective:
By completing this activity, students will be able to illustrate, in diagram form, how the
greenhouse effect works.
Materials:
clean sheet of white paper
glue
scissors
rulers
Activity 4 picture in Appendix A
** You will need one of each of the above items per student group.
markers or colored pencils
Background:
The atmosphere is divided into layers according to major changes in its temperature. The
layers of air that surround the Earth are held close to it by the force of gravity. The layer
of the atmosphere closest to Earth is the troposphere. Almost all of the Earth's weather
occurs in the troposphere. The height of the troposphere varies, but averages around 8-17
kilometers.
As heat energy from sunlight travels through the atmosphere, only a small amount of the heat energy is trapped by the atmosphere. Most of the heat energy is absorbed by the ground. The ground then warms the air above it.
The next layer of the atmosphere is called the stratosphere. The stratosphere contains winds called the jet stream. This layer also contains the ozone layer. Most of the ozone layer is located between 16 and 60 kilometers above the Earth's surface. Ozone acts as a shield for the Earth's surface, absorbing most of the ultraviolet radiation from the sun. Overexposure of the skin to ultraviolet radiation has been linked to skin cancer.
Above the stratosphere is the mesosphere, the layer in which most meteoroids burn up as they enter Earth's atmosphere. Above this layer, there is one more layer, the thermosphere. This layer has no well defined outer limit. The air in this layer is extremely thin and the air pressure is only about one-millionth as great as it is on Earth's surface.
Suggested Teaching Strategies:
This activity should require little teacher direction. Students will be cutting out pieces of
the greenhouse effect diagram and then organizing those pieces to illustrate how all of the
parts fit together. Emphasize to students that there is no one right answer. The class may
end up with 20 different diagrams, each of which "makes sense". That is the key. Their
diagrams should make sense. Diagrams are used to make complex relationships more
easy to understand. If their diagrams are confusing and disorganized, then they have not
achieved the goal of succinctly illustrating the concepts involved in the greenhouse
effect.
Remind students that only the "basics" are provided for their diagram. Give each student group a copy of the picture in Appendix A. Encourage them to make additions that will add color and understanding to their diagram. If some students would rather use larger sheets of paper for their diagrams, this would be acceptable. The cut-outs are designed to fit on a 8x10 sheet of paper which has been turned side-ways. If students use larger sheets of paper, they will have more room to add explanations and arrows to their drawings. Ask for student volunteers to share their diagrams with the class and to explain the important parts.
Answers to Summing Up:
Student answers will vary, as no two diagrams will likely be alike.
Home/Community Connections:
Extensions:
Make a real global warming puzzle. First draw and color your picture. Add labels and
explanations. Cut out the picture to make interesting shaped puzzle pieces. Challenge
one of your classmates or someone at home to put your puzzle together.
Student Page
Problem:
Develop a diagram illustrating the greenhouse effect, using the materials provided.
Materials:
clean sheet of white paper
page containing cut-outs of greenhouse components
scissors
glue
ruler
markers or colored pencils
Let's Investigate:
In the previous three activities, you picked up bits and pieces of the global warming
puzzle. You will now attempt to pull your ideas together to construct a diagram showing
how the greenhouse effect works. Your teacher will provide you with a page of
drawings, labels, and pictures. Cut each of these out and arrange them on a sheet of paper
in order to illustrate the greenhouse effect. Once you have arranged all of the cut-outs on
a blank sheet of paper, glue them down.
Summing Up:
1. Add arrows to your drawing showing heat from the sun hitting the Earth's surface.
2. While most of the sun's energy reaches the Earth, about 30% of this energy is reflected back into space. Add more arrows showing energy being reflected just inside the ozone layer back into space.
3. The greenhouse gases form a "blanket" which traps heat energy inside the Earth's atmosphere. Add arrows showing heat energy being trapped and reflected around the atmosphere and back to Earth.
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