At boiling point the vapour pressure of a fluid becomes equal to the atmospheric pressure. Water boils at 100°C at sea level therefore at 100°c at sea level the vapour pressure is equal to the atmospheric pressure.
Surface tension is caused by the force of cohesion between liquid molecules. 
Viscosity is exhibited by fluids only, under dynamic conditions. 
Air is about 20,000 times more compressible than water.