1 cc of water at its boiling point absorbs 540 cal of heat to become steam with a volume of 1671 cc. If the atmospheric pressure is
, the energy spent (in cal) to overcome molecular attractive forces is nearly (mechanical equivalent of heat = 4.2 J/cal)
540
500
40
zero
Work done against the atmospheric pressure
Water absorbs 540 cal of heat out of which 40 cal used in doing work against the atmospheric pressure. Therefore, work done to overcome the molecular attraction