Kinetic Particle Theory

The kinetic particle theory states all matter is made up of tiny particles and that these particles are in constant random motion.

Solid state

The particles of a solid are closely packed in an orderly manner (Arrangement), are held together by very strong forces of attraction (Bonding), have enough kinetic energy to only vibrate and rotate about their fixed positions (Kinetic energy level) and cannot move about freely (Movement).

Liquid state

The particles of a liquid are arranged in a disorderly manner (Arrangement), have weaker forces of attraction than the particles of a solid (Bonding), have more kinetic energy than particles of the same substance (Kinetic energy level) and can move freely throughout the liquid (Movement).

Gaseous state

The particles of gas are spread far apart from one another (Arrangement), have weaker forces of attraction than the particles of a liquid (Bonding), have a lot of kinetic energy and are not held in fixed positions (Kinetic energy level) and in any direction (Movement).

Melting

Heat energy is absorbed.
Heat energy is converted into kinetic energy.
Particles start to vibrate faster about their fixed positions.
When the temperature is high enough, vibrations become sufficient to overcome forces of attraction.
Particles start to break away from fixed positions
Particles can now move freely throughout the liquid.

Freezing

Energy is given out.
Particles lose kinetic energy and move slower.
Particles have not enough energy to move freely.
Particles start to settle in fixed positions.
Particles can only vibrate about their fixed positions.

Boiling

Heat energy absorbed by particles.
Heat energy is converted into kinetic energy.
Particles have enough energy to overcome the forces of attraction.
Particles can now move about in any directions.

Evaporation

Evaporation is the process by which a liquid changes to a gas at temperatures lower than its boiling point.
Happens because some particles have enough energy to escape as a gas from the surface of a liquid.
Liquids that evaporate quickly at room temperature are called volatile liquids. (E.g. Petrol, perfumes...)

Condensation

Heat energy is given out by the gas particles.
As temperature drops, particles lose energy and move slower.
Eventually, movement of particles is slow enough for gas to change to liquid.

Sublimation

Particles at the surface of the solid have enough energy to break away and escape as a gas.
E.g. Ammonium Chloride. iodine, dry ice...
Dry ice is used for industrial refrigeration and transporting frozen food.

Diffusion

The movement of particles from a region of higher concentration to a region of lower concentration.
The higher the relative molecular mass (Mr), the lower the rate of diffusion.
The higher the temperature, the higher the rate of diffusion.

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GCE 'O' Level Pure Chemistry chapter notes