StatesOfMatter

The Particle Theory of Matter (The Kinetic Theory of Matter)

Matter is composed of tiny particles (atoms, ions or molecules) The state of matter depends on the ‘movement’ of the particles. In a solid the particles are very close but do not move out of position, they ‘vibrate’ or ‘jog on the spot’. In a liquid the particles are very close but they are in constant ‘random rapid rolling’ over each other. In a gas the particles are relatively very far apart but are in constant ‘haphazard state flying and hitting’ off each other.

The Temperature of a substance is a measure of the average movement energy of its particles. The higher the temperature the greater the average movement energy of its particle i.e. the greater the vibration of the solid particles or the great the speed of movement of the particles of a liquid or gas.

Temperature and Change of State. (See Heat in Physics)

Matter changes state because of a change in the movement of its particles.

(a) Solid » Liquid » Gas;

Change in movement: fixed » rolling » flying

heat gain, increasing temperature, increasing motion of the particles

(b) Gas » Liquid » Solid

Change in movement: flying » rolling » fixed

heat loss, decreasing temperature, decreasing motion of the particles.

Diffusion is the movement of the free particles of a substance throughout a liquid or gas resulting in their equal distribution. The direction of diffusion is from an area where the concentration of the particles is higher to where they are in lower concentration. Diffusion is said to have stopped when the concentration of the particles of the substance is the same in all places in the liquid or gas. Diffusion in gases is about 10,000 faster than in liquids.

The faster diffusion in gases is due to the much higher speed of the particles plus the much more open space for the particles to move.