Sodium is a highly reactive metal reacting vigorously with water to produce sodium hydroxide and hydrogen gas. To prevent its reaction with water, oxygen etc., and to retain it as a pure metal, it is kept under a layer of oil. Unlike other metals, sodium is not much hard. It is a soft metal and can be cut with the help of a shaving blade. In the laboratories, when required in experiments, the students are advised to cut a piece of sodium quickly and replace the rest in the oil.