CHAPTER 8: Phase diagram
PHASE
Substances can exist in a variety of forms depending on the conditions of the surroundings. The form when matter is uniform in chemical composition and physical state is called a phase, for example liquid, solid and gas (all three have the same composition but are arranged different)
Phases can be converted spontaneously (depending on the Gibbs free energy, remember?) at a certain temperature. The minimum temperature at which two phases are in equilibrium is called transition temperature.
Phases can be converted spontaneously (depending on the Gibbs free energy, remember?) at a certain temperature. The minimum temperature at which two phases are in equilibrium is called transition temperature.
PHASE CHANGE
Imagine you have water in a piston-cylinder at environmental conditions, where water is in its fluid form, called compressed liquid. Then heat is now transferred to the piston-cylinder until the temperature rises at 100 C. At this point the liquid is about to vaporize, and it is called saturated liquid.
Once the liquid starts to boil, the temperature remains constant during the phase-change process. As heat continues to be transferred to the piston-cylinder, the entire liquid becomes vapor that is about to condense, called saturated vapor. A substance that is in between the saturated liquid and saturated vapor boundaries is called a saturated liquid-vapor mixture. As heat continues to be added to the system, temperature increases and the vapor is no longer about to condense and it is denominated superheated vapor.
PHASE DIAGRAM
Aplication by thermocuates
Cengel, Y. Thermodynamics. Phase change. McGrawHill. 2012. pp 111