Chapter 2 Flashcards
What is pure substance ?
A pure substance is one that has homogeneous and invariable chemical composition. It may exist in more than one phase, but chemical composition is the same in all phases.
Thus liquid water, a mixture of liquid and water vapour steam, and a mixture of ice and liquid water are all pure substances; every phase has the same chemical composition. Where as a mixture of liquid air and gaseous air are not pure substances because the composition of the liquid phase is different from that of vapour phase.
Saturation temperature ?
Term saturation temperature designates the temperature at which vaporization takes place at a given pressure or the system forms more ice and less liquid at given temperatures these two saturation temperatures are called boiling point and freezing point.
What is sublimation line, vaporization line and fusion line?
In phase diagram it separates the vapour phase and solid phase. Fusion line separates the solid phase and liquid phase. Vaporization line separates the liquid and vapour phase.
What is triple point ?
Triple point is the only point where all three phases solid, liquid and gas can exist.
What is critical point?
Above this point substance is referred to as supercritical liquid. For water it is 22.19 Mpa above this pressure there is no boiling and heating a liquid will produce a vapour without boiling in smooth transition. Also at critical point distinction between the liquid and gas phases of substance disappear. At this point substance exists as a single phase called superficial fluid which exhibits properties of liquid and gas.
What is degree of superheat?
Difference between a given T and the saturated temperature for the same pressure is called the degree of superheat.
What is general principal for a simple pure substance ?
The state is defined by two independent properties. In a saturation state pressure and temperature are not independent because they are in a phase equilibrium with each other. However, other independent pairs such as pressure and specific volume or pressure pane quality are required to specify a saturation state of a pure substance.
What subscripts are used to designate the property of saturated liquid and saturated Vapor ?
Sat liq f and sat vap g
When is liquid state compressed ?
The state is a compressed liquid state when a liquid has a higher pressure than saturation pressure
When is liquid called subcooled liquid?
Temperature is lower than saturation temperature for a given pressure on the fusion line gives a solid state that is subcooled liquid.
When is solid compressed ?
For a given temperature the pressure is higher than saturated sublimation pressure, we have a compressed liquid.
Solids are mainly function of the temperature as the solid is nearly incompressible meaning that the pressure cannot change the intermolecular distances and the volume is unaffected by pressure.
When is Vapor expanded Vapor ?
A state with a pressure lower than saturated pressure for given T = expanded Vapor
When is Vapor superheated Vapor?
A state with a temperature higher than saturated temperature = superheated vapour
