Phases of Matter

Question 1

Temperature - Pressure

What is Phase Equilibria?

Answer 1

Phase changes depend on temperature, pressure and composition.
* Phase changes occur when enough energy has been supplied or removed from a system.
* When a system is going through a phase change, it is at equilibrium

Question 1

Temperature - Pressure

What does pressure do to matter?

Answer 1

• Increasing pressure pushes matter together
• Typically matter is a gas at low pressures, and a solid at high pressures

Question 2

Temperature - Pressure

What does Temperature do to matter?

Answer 2

• Increasing temp. gives matter kinetic energy
• Typically matter is gas at high temperatures and solid at low temperatures

Question 3

Temperature - Pressure

List the features found on a Pressure-Temperature (P-T) phase diagram

Answer 3

• Temperature on the x-axis, pressure on the y-axis
• Three phase areas (solid, liquid, gas) separated by boundary lines
• A triple point – where all 3 phases are in equilibrium
• A critical point – where liquid and gas merge into a supercritical phase, and no phases are in equilibrium

The boundary lines represent where two phases are in equilibrium.

• Boiling, melting, sublimation points etc are found on the boundary lines
• Boundary lines all intersect at the triple point

Question 4

Temperature - Composition

Liquid - Solid Systems

Answer 4

• Cooling a two-component liquid (solution) system, A (solute) - B (solvent), will eventually lead to the separation of solid at a well defined temperature; the freezing point
• As solid separates, the liquid composition changes, hence the freezing point will change.

Question 5

Temperature - Composition

Temperature - Composition (T-C) Diagram

Answer 5

Temperature - Composition (T-C) Diagram of a binary solution of A and B
* Show freezing points of mixtures as a function of
composition
*refer to notebook for diagram examples

Question 6

Temperature - Composition

Cooling Curves

Answer 6

• demonstrates the cooling behaviour of two component mixtures
• determines when the freezing points occur, and when solid phase begins to separate from the solution mix at a specific mixture %

Question 7

Temperature-Composition Diagrams
for Liquid-Vapour Systems

Answer 7

A liquid mixture of two volatile (how easily a substance will vapourise) components, A and B:
* measure the boiling points of a series of A-B
mixtures and plot on graph
* results often show a smooth variation in boiling point
between the boiling points of the pure liquids

Question 8

Features of Liquid-Vapour Systems

Answer 8

Composition of the liquid and vapour will be
different at different boiling points
* Lower curve – liquidus equilibrium
* Upper curve – vaporus equilibrium
Vaporus curve is a mirror-image of the liquidus
curve
Lower Bpt is the more volatile component.