Phase Changes and Phase Diagrams

• Phase changes are transformations of matter from one physical state to another
• Phase changes occur when energy is added or removed from a substance
• Carbon dioxide cannot exist as a liquid at atmospheric pressure, the dry ice sublimates and instantly produces a gas, condensing water vapor, creating a thick white fog
• Liquefied petroleum gas is a flammable mixture of hydrocarbon gases
• Phase diagrams are graphical representation of physical states of a substance under different conditions of temperature and pressure
• Phase diagrams gives the possible combinations of pressure and temperature at which certain physical state of states a substance would be observed
• Phase diagrams are plots of pressure (usually in atmospheres) versus temperature (degrees Celsius or Kelvin)
• The three areas are marked solid, liquid, and vapor.
• The three lines serve as boundaries between physical states represent the combinations of pressures and temperatures at which two phases can exist in equilibrium
• Green line - melting and freezing
• Blue line - vaporization and condensation
• Red line - sublimation and deposition
• The triple point is the combination of pressure and temperature at which all three phases o matter are at equilibrium
• The critical point terminates the liquid/gas phase line
• The critical point is a set of temperature and pressure on a phase diagram where the liquid and gaseous phases of a substance merge together in a single phase
• Beyond the temperature of the critical point, the merged single phase is known as a supercritical fluid