Sometimes surface or subsurface water will contain dissolved lime (calcium hydroxide). We have made our own limewater by dissolving a very small amount of calcium hydroxide in a glass of tap water. In the photograph here you can see that this aqueous solution looks like ordinary water.

When carbon dioxide is bubbled through the limewater, it reacts with the calcium hydroxide. In the photograph here the milky color is caused by the calcium carbonate that is formed from the reaction between the dissolved calcium hydroxide and the carbon dioxide exhaled through the straw into the solution. Carbon dioxide is thus removed from the exhaled air and becomes fixed in the calcium carbonate.

In a similar manner, carbon dioxide can be removed from the atmosphere by natural carbon dioxide sinks.

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Properties of Liquids

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