The volume of a gas increases with increased pressure if the temperature stays constant. Gas laws like Boyles' law and Charles' law can be used to predict numerical changes in gas properties. Equal volumes of gas contain equal numbers of gas particles. STP means pressure of 1 atmosphere and temperature of 273 Kelvin. The dipole-dipole forces exist only between polar molecules.
All hydrogen containing molecules show hydrogen bonding.
Hydrogen bonding exists when molecules have any of the following combinations. Strong interactions between molecules result in low melting points. All liquids have a vapor pressure. Vapor pressure is high above a volatile liquid. All solids have a definite crystal structure.