Under low pressure condition we can boil water at room temperature.
When we heat the water, the temperature of the water rises. Due to this the water molecule “gains kinetic energy” and starts to move and escapes to the atmosphere in the form of vapor.
At room temperature the water has specific vapor pressure. The boiling of water depends upon the external pressure of the water. When the external pressure of the water is lowered, the water will start to boil at room temperature. For this purpose vacuum is used.