Intermolecular Forces Liquids, Solids, and Phase Changes

Intermolecular Forces Liquids, Solids, and Phase Changes 

Each type of phase change is reversible and has an enthalpy change that is positive in one direction and negative in the other. It takes more energy to convert a liquid to a gas than to convert a solid to a liquid, because the molecules are being more completely separated in the conversion to a gas. 

When a liquid vaporizes in a closed container at a given temperature, it reaches a state of equilibrium as the rates of vaporization and condensation become equal. At that point, the pressure of the gas (vapor pressure) becomes constant. 

A phase diagram for a substance shows the conditions of pressure and temperature at which each phase is stable and at which phase changes occur. 

A combination of intermolecular forces determines the properties of liquids—surface tension, capillarity, and viscosity. The unique properties of water allow it to play vital roles in bblogy and the environment. 

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