Why does water vanish when it starts boiling?

First, the water does not vanish. It changes to another state. Matter has three forms: Solid, Liquid and Gas. Water is in liquid state in room temperature. When heat is applied to water and its temperature reach its boiling point (212 Fahrenheit) it changes it form to a light, thin gas, the gaseous form of water. Steam is a good example of this gas. Furthermore, if water gets cold enough (32 Fahrenheit), it will begin to change in its solid form. This solid object is also known as ice.