Notes Ch. 13.4 Changes of State Chemistry

Sublimation The change directly from a solid into a vapor without passing through a liquid stage is called sublimation. Sublimation will occur when vapor pressures are greater than atmospheric pressure at or near room temperature. An example of this would be dry ice. Sublimation can be useful for many different things - one would be for separating substances.

Phase Diagrams A phase diagram is a graph that shows the relationships between solid, liquid, and vapor states (or phases) of a substance in a sealed container. It gives the conditions of temperature and pressure at which a substance exists as a solid, liquid, or gas (vapor). The conditions of pressure and temperature at which 2 phases exist in equilibrium are shown on a phase diagram by a line separating the phases.

In the phase diagram each color shows a different state of water In the phase diagram each color shows a different state of water. The line between the states shows when the 2 phases are in equilibrium. The point on the diagram where both curves meet shows the triple point. This is the only set of conditions where all 3 states (phases) can exist in equilibrium. For water the triple point is a temperature of 0.016 degree Celsius and a pressure of 0.61 kPa.

A phase diagram is very important in showing the relationship between temperature and pressure and its effect on phases of substances.