The state of a gas is universally, if approximately, described by the Ideal Gas Equation of State. Surfaces and Interfaces Surfaces of liquids or solids in contact with gases are less stable than the bulk of the condensed phase. The surface of a liquid is in contact with some of the vapor phase, and ths is called an interface, a place where two phases meet. Each time neighbor 'bond' is broken, energy is required. The greater the viscosity, the 'more slowly it flows ' Viscosity is a measure of the ease with which molecules move past one another.
Viscosity depends on the attractive force between the molecules.
Viscosity decreases with increasing temperature - the increasing kinetic energy overcomes the attractive forces and molecules can more easily move past each other. Surface tension determines the pressure inside of a bubble. If I have a liquid bubble with gas on the inside and outside, the bubble will try to collapse on the gas inside and cause an increase in pressure inside. Our understanding of surface tension can be made more complete by knowing the energetics of making and breaking of molecular neighbors. This can be done by calorimetry, or the measure of the heat flow during an isothermal process.