ABSTRACT
Water has three states: solid, liquid, and gaseous. They all exist at common Earth temperatures. At standard atmosphere (760 mmHg) and at about 0°C, all three states of water are in equilibrium when the partial pressure of water vapor is 4.6 mmHg. Changes from one state to another depend on water temperature and atmospheric pressure. Increases in air pressure will lower the freezing point and raise the boiling point of water. When atmospheric pressure is below 760 mmHg and temperature is lower than 0°C, water can change from the solid state directly into the vapor state, a phenomenon called sublimation (Figure 4.1).
