Principle
Water is liquid in the range from 0°C to 100°C. Below the freezing point at 0°C it is solid, above the boiling point at 100°C it is gaseous. If water is brought to boiling point, bubbles of gaseous water rise from the bottom of the vessel where the boiling point has already been reached. The rising of the gas through the liquid causes the noise. If hot water is dripped onto an ice cube, the three physical states of water - solid, liquid and gas - can be observed simultaneously.