You can test for the presence of carbon dioxide gas by bubbling it through limewater. If carbon dioxide is present, the limewater will develop a cloudy appearance.

Carbon dioxide is a common gas produced in various chemical reactions. A straightforward test for its presence can be conducted using limewater, which is an aqueous solution of calcium hydroxide. The test relies on the reaction between carbon dioxide ($\text{CO}_2$) and calcium hydroxide ($\text{Ca(OH)}_2$), resulting in the formation of calcium carbonate ($\text{CaCO}_3$) and water ($\text{H}_2\text{O}$). Calcium carbonate is insoluble in water and precipitates out of the solution, leading to the cloudiness or milky appearance of the limewater.

To perform this test, first collect the gas that you suspect contains carbon dioxide. This can be achieved by directing the gas through a delivery tube into a test tube or container filled with limewater. If the limewater turns cloudy, it indicates the presence of carbon dioxide. Conversely, if the limewater remains clear, then the gas does not contain carbon dioxide.

It is important to note that this test is specific to carbon dioxide; other gases will not cause the limewater to become cloudy. However, if the limewater initially turns milky and then clears upon continued bubbling, this may suggest the presence of excess carbon dioxide, which can form a soluble compound with calcium carbonate.

Always remember to handle chemicals safely and under the supervision of a teacher or another responsible adult. Safety goggles should be worn to protect your eyes, and the test should be conducted in a well-ventilated area to minimize the risk of inhaling any gases.