Thermodynamic State

Procedure to Define a State

Identify the phase
Find two independent properties (State Postulate)
Then, there will be a process leading to another state
If we define a state under the vapour dome, we need to know how much of it is liquid or vapour

Quality

Defines how much vapour there is by mass in a 2-phase mixture.

$Q u a l i t y = x = \frac{m _{v a p or}}{m _{t o t a l}} = \frac{m _{g}}{m _{f} + m _{g}}$
Saturated liquids: x = 0
Saturated vapours: x = 1

You can apply the lever rule to find the mass average of properties at saturated states

!!! IMPORTANT EQUATION !!!
$v = v_{f} + x (v_{g} - v_{f}) = v_{f} + x v_{f g}$ or
$x = \frac{v - v _{f}}{v _{g} - v _{f}}$

Quality

Note that quality only really exists under the vapour dome

First, you make a table like this with the values you want to interpolate with

x_1	y_1
x	y
x_2	y_2

Then apply the following formula:
$\frac{x - x _{1}}{x _{2} - x _{1}} = \frac{y - y _{1}}{y _{2} - y _{1}}$