Limewater is used in many science experiments and is easy to make on your own. Put 1 teaspoon of calcium hydroxide in a clean glass jar, up to 1 gallon in size. (Limewater is a saturated solution, which means there will be some extra chemical that doesn't dissolve. A teaspoon will result in a fully saturated solution whether you use a gallon jar or a smaller one.) Fill the jar with distilled or tap water. Shake the jar vigorously for 1-2 minutes, then let it stand for 24 hours. Being careful not to stir up the sediment, pour the clearer solution off the top of the jar through a clean coffee filter or filter paper. Repeat the filtering step if necessary to obtain a clear limewater solution. Store in a clean jar or bottle.
When carbon dioxide is bubbled into limewater, calcium carbonate (CaCO3) is produced. It precipitates out as a white suspended solid, making the solution appear cloudy.