Properties of Phases

Properties of Phases is the ninth lecture within the Properties of Matter section of PH1011. It covers

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Phases
The most common phases of matter are solids, liquids and gases. Solids retain shapes, are generally incompressible and have ordered molecules; liquids are disordered and will lose their shape whilst retaining volume, and gases are disordered and will fill a given container. One definition of "phase" is a chemically and physically homogeneous part of a system. Matter is almost always able to pass from one phase to another.

Heating Matter
The change in temperature of solids or liquids must be calculated differently to that of gases. It is dependent upon the mass of material, which material and energy suppplied in the relationship Q = cmΔT; c is the specific heat capacity of the material, different to the molar heat (c is the energy required to heat 1kg of matter; Cv or p was the energy required to heat one mole.

If a material is heated enough, a change in phase will occur as the atoms gain enough energy to break their intermolecular bonds. This is the latent heat of transformation, L, and relates to the energy required for a phase change by Q = mL. L is given in J/kg. Vapourising a substance requires more energy than melting it, and sublimation requires the sum of the two. Phase changes do not release energy - the temperature of a substance will not chance whilst its phase is changing.

Phase Diagrams
This is the phase diagram of water in a constant volume environment. Along each boundary between phases there is a curve at which they sit at equilibrium, during which dynamic processes occur at an equal rate. For most diagrams the green line (solid-liquid boundary) has a positive gradient - water is abnormal as it expands upon freezing.

Exotic Phases
When matter is heated or cooled greatly exotic phases can occur - at high temperatures plasmas happen (electrons are removed from the nucleus) and at low temperatures Bose Einstein Condensates occur (atoms behave coherently).

Summary
Liquids and solids are dense and cannot expand to fill an available volume. The specific heat capacity of a material refers to the amount of energy it must take in to increase in temperature. Heating matter far enough causes a phase change, over the duration of which temperature change stops. Exotic phases occur at very high or very low temperatures.