The term 'TURN TO GAS' can be broken down into two crossword solutions: BOIL (4 letters) and EVAPORATE (9 letters). Boiling is the process of heating a liquid until it reaches its boiling point, which is when the vapor pressure of the liquid is equal to the atmospheric pressure. Evaporation is the process of a liquid turning into a gas at any temperature below its boiling point. Both processes are used to turn a liquid into a gas.