Water is necessary to the softening of fiber, and the cooking of starch. It acts as a solvent for sugar and salt and for gelatin, and is the basis of meat soups, certain substances in the meat dissolving in the water. The flavors of tea and coffee are extracted by water.
It is not necessary to lift the cover of a kettle to see if the water boils, if one is familiar with the action of water nearing and at the boiling point. A simple experiment with the boiling of water in a Florence flask is always interesting, and from it one gains practical knowledge.