PHZ3400 Phase Transition

Phases of Matter

Matter can exist in many phases. The phases most common are solids, liquids, and gases. In Physics, a phase can be described as a region of space in which all physical properties of a material remain constant, or uniform. Having consistent physical properties and chemical uniformity allow one to distinguish between the various phases, or states of matter.

Gas-Liquid-Solid Phase Diagram

Phase Diagram of Water

When studying phase transitions, it is important to be able to read and understand a phase diagram. A phase diagram is a pressure vs. temperature graph of an element or compound and which phase we can expect it to be in. The lines represent the boundaries between phases, and at any point on these lines we can expect two (or even three) phases to exist simultaneously in equilibrium.

Phase Separation and Nucleation

This we'll cover on Friday, Jan. 30

Van der Waals Equation

Johannes Diderik van der Waals

The Van der Waals Equation is an equation of state, that is a modification of the ideal gas law:

$PV=NkT\!$

Johannes van der Waals proposed two modifications to the ideal gas law:

$(P+{\frac {aN^{2}}{V^{2}}})(V-Nb)=NkT$

Van der Waals Equation:

$P={\frac {T}{\nu b}}-{\frac {a}{\nu ^{2}}},\!$ where $\nu \equiv {\frac {N}{V}}\!$

$P$ is pressure

$T$ is temperature

$N$ is the number of particles

$V$ is volume

$a$ and $b$ are constants dependent on the material