Grade 8 Science Experiment

Test for the presence of carbon dioxide in exhaled air.

Our topic is photosynthesis and respiration.  Carbon Dioxide plays a very important role in both these processes.  We conducted a simple experiment to test for the presence of carbon dioxide in exhaled air.

• Prepare clear lime water by mixing a solution of calcium hydroxide and water.  
• Let the solution rest until it is clear and filter all the excess lime.  
• Place a straw in the lime water and exhale (breathe out) through the straw.  
• The clear lime water turns milky when carbon dioxide is dissolved in it.