Reaction between Calcium and Water

This demonstration shows the reaction between calcium and water.

As with group 1, the products are the metal hydroxide and hydrogen. Notice that calcium hydroxide is only partially soluble in water, leading to the cloudy appearance. Calcium hydroxide is used by farmers to increase the pH of soil. The calcium hydroxide is soluble enough to be absorbed by the crops, but insoluble enough not to be immediately washed away by the rain. Interestingly, the solubility of calcium hydroxide at 70 °C is about half its value at 25 °C. The reason for this rather uncommon phenomenon is that the dissolution of calcium hydroxide in water is an exothermic process. This effect obeys le Chatelier's principle. This counter-intuitive temperature dependence of the solubility is referred to as "inverse" solubility.

Similar to group 1, reactivity increases down group 2. There are a greater number of protons in the nucleus and this makes the group 2 elements less reactive than the corresponding elements in group 2.