Cobalt chloride (CoCl2) has a dramatic color change when combined with water, making it a great water indicator. A concentrated solution of cobalt chloride is red at room temperature, blue when heated, and pale-to-clear when frozen. The cobalt chloride we’re using is actually cobalt chloride hexahydrate, which means that each CoCl2 molecule also has six water molecules (6H2O) stuck to it.


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2 Responses to “Cobalt Colors”

  1. Good question! Try it and let me know what happens!!

  2. Another idea: what if you just blow on it with your mouth?