This is called a residual disinfectant. Another chemical that is sometimes used is sulphur dioxide. This removes excess chlorine, allowing the dosing to be carefully controlled. The quality of water is very carefully measured by water companies and also several regulating bodies. These processes are the most important in the water cycle .
Instructions Fill the mug with the freshly boiled water and hold the metal spoon above the liquid.
Water droplets should form on the spoon, get larger and finally drop back into the liquid. The evaporation is the transition of the water from liquid to gas. You can't see the gas, the steam you see is water droplets suspended in the air, much like clouds. The condensation is the transition back to liquid again as the vapour loses it's heat to the spoon. The precipitation is simply the way in which the drops deposit.