Describe an experiment to show that an expired air contains carbon dioxide
To demonstrate that expired air contains carbon dioxide, you can conduct a simple experiment using easily available materials such as a container, a straw, lime water, and a source of expired air (like your breath).
Here's a step-by-step description of the experiment:
1. Get a clear container (a glass or a plastic bottle with a tight-fitting lid will work) and fill it about halfway with clear lime water. Lime water is a solution of calcium hydroxide in water and turns milky/cloudy when exposed to carbon dioxide.
2. Insert a straw vertically into the container, ensuring that one end of the straw reaches close to the bottom of the container where the lime water is.
3. Seal the container tightly with the lid, making sure no air can escape.
4. Take a deep breath and exhale through the straw into the container for about 10-15 seconds. This will allow your expired air, containing carbon dioxide, to enter the container.
5. Wait for a few minutes and observe the lime water. If the breath you blew into the container contained carbon dioxide, the lime water will turn milky/cloudy due to the formation of calcium carbonate (a product of the reaction between carbon dioxide and calcium hydroxide in the lime water).
6. As a control experiment, repeat the same steps using fresh air (by blowing into the container without exhaling). You will notice that the lime water remains clear as there is no carbon dioxide present in fresh air.
This experiment shows that expired air contains carbon dioxide, which reacts with the lime water to form a visible precipitate of calcium carbonate, causing it to appear milky/cloudy.