Kinetic Model + Thermal Properties of Matter

Solid

• Strong forces of attraction hold particles in fixed positions.

• Particles are closely packed together.

• Particles vibrate and rotate about fixed positions.

Liquid

• Forces of attraction are less strong than in solids but stronger than in gases. Particles do not have fixed positions.

• Particles are randomly arranged and are slightly further apart from each other than in solids.

• Particles may slide over one another.

Gas

• Weak and negligible forces of attraction.

• Particles are randomly arranged and are very far apart from each other, hence they can be compressed.

• Particles move about freely at high speeds.

Kinetic model of matter

The tiny particles that make up matter are always in continuous, random movement.

Relationship between motion of particles and temperature

The total kinetic energy of particles of a body is directly proportional to the absolute temperature of the body. The average kinetic energy of the particles are proportional to the temperature.

How gases exert pressure

1. By the kinetic model of matter, gas particles are always in continuous, random motion.

2. When the gas particles collide with the walls of the container, they exert a force on the container.

3. Since pressure is the perpendicular force exerted per unit area, the pressure of the gas is the average force exerted by the gas particles on the container per unit area.

Internal energy consists of:

• Kinetic energy due to the motion of particles.

• Potential energy due to the intermolecular forces of attraction between the particles.

Specific heat capacity (c)

The amount of thermal energy absorbed/emitted per unit mass per unit temperature change; the energy absorbed/emitted is used to increase/decrease the internal kinetic energy of particles; Q = mcΔT, where Q is energy, m is mass, c is specific heat capacity, ΔT is change in temperature

Specific latent heat (l)

The amount of energy absorbed/emitted per unit mass to change the state of matter, at constant temperature; the energy absorbed/emitted is used to overcome/strengthen the forces of attraction between particles; latent heat of fusion for melting/freezing, latent heat of vapourisation for boiling/condensation; Q = ml, where Q is energy, m is mass, l is specific latent heat