Describe an experiment carried out to show that air contains carbon dioxide
To demonstrate that air contains carbon dioxide, one can conduct a simple experiment called the lime water test. Lime water, or calcium hydroxide solution, reacts with carbon dioxide to form a white precipitate called calcium carbonate.
Here's how you can carry out the experiment:
1. Obtain a clear glass or plastic container with a lid, such as a clear bottle or a small jar.
2. Fill it with lime water, which can be made by dissolving a small amount of calcium hydroxide (available at gardening stores or online) in water until it becomes a milky solution.
3. Securely close the container with the lid, ensuring it is airtight.
4. Shake the container to mix the lime water.
5. Collect a sample of air by filling a balloon or using a syringe without a needle.
6. Carefully introduce the air sample into the container without letting any of it escape.
7. Shake the container again to ensure proper mixing of the air and lime water.
8. Leave the container undisturbed for some time, allowing the reaction to occur.
Observations:
If the air sample contains carbon dioxide, you will notice a change in the lime water. Carbon dioxide reacts with calcium hydroxide to form calcium carbonate, which appears as a white precipitate or a cloudiness in the lime water.
Explanation:
When carbon dioxide is introduced into the lime water, carbon dioxide molecules (CO2) chemically react with the calcium hydroxide (Ca(OH)2) in the lime water to produce calcium carbonate (CaCO3) and water (H2O). This reaction causes the formation of a white precipitate or cloudiness in the lime water, indicating the presence of carbon dioxide.
To conclude, conducting the lime water test is a straightforward way to demonstrate that air contains carbon dioxide. The white precipitate formed during the reaction is a visible indicator of the presence of carbon dioxide gas in the air sample.