CO2 Absorption - Experiment

Breathe in…Breathe out…Inhale…Exhale.…

This is something each of us does many times every minute of the day. With every breath we inhale, we remove oxygen from the air for our own use. With every breath we exhale, we add to the amount of carbon dioxide in the atmosphere. Carbon dioxide is one of the greenhouse gases, so named because it helps to keep earth’s heat from escaping into outer space.

Over the past several hundred years, the proportion of carbon dioxide in the atmosphere has been increasing. There are more people living on the surface of the earth now than ever before. In addition to more people exhaling, many of our industrial activities are adding carbon dioxide to the atmosphere, such as through the burning of fossil fuels. This increase in carbon dioxide is likely a major factor in the rising average temperature of the earth.

If the amount of carbon dioxide in the atmosphere continues to increase, it could have a major impact on our global climate and life as we know it. To prevent this, we can find ways to decrease our carbon dioxide production, mainly through regulating our industrial activities.

However, there is also the possibility of removing carbon dioxide from the air and storing it in other places, such as in plants, rock formations, or water. In this activity, you can experiment with storing some of your own carbon dioxide in water.

Tools and Materials

two small transparent cups (about 100 ml or 3 ounces) or other similar containers
drinking straw
safety goggles
sheet of paper or transparent plastic wrap
paper towels
pH indicator, such as cabbage water

What To Do

1. Prepare two small cups or containers of cabbage water. The initial purple color of the cabbage water indicates a pH of around 7.0, which is typical.

2. Cover the mouth of one cup with paper or transparent plastic wrap. Insert a drinking straw and gently blow bubbles into the water for several minutes. We recommend the use of safety goggles for any activity in which liquid might splash into the eyes.

3. Compare the color of the bubbled cabbage water with the color of the cabbage water in the other cup.

Compare your observations with our results.

Course:

Science

Result/Solution(s)

Cabbage water with straw When we blew gently into the cabbage water for several minutes, we observed that the color of the cabbage water changed from its original purple to a slightly lighter color. This indicates that the water is slightly more acidic.

What’s happening here? When carbon dioxide is bubbled through water, some of it dissolves into the water. That is, some of the carbon dioxide goes into the spaces between water molecules. A small proportion of this dissolved carbon dioxide creates carbonic acid, a weak acid. The slight change of color of the cabbage water caused by the carbonic acid indicates that some of the carbon dioxide is being stored in the water.

Plain water with straw You can see this effect more clearly by using plain water and pH testing tablets..

Plain water with straw After blowing into the water on the left for several minutes, we used the pH tablets to test a sample of water from each glass. The difference between the color of the water in the two tubes was very noticeable.

Plain water with pH test According to the pH card that came with the test kit, the water on the left that we blew into had a pH value of about 6.0, indicating a slight acidity. The original water was between 7.0 and 8.0, typical values for water from a faucet.

earth science

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