Thermal Properties of Matter

Define temperature

A measure of the concentration of thermal energy of a material OR the average kinetic energy of particles of a body

Define thermal equilibrium

Net heat flows from a hotter to colder object until both are of the same temperature

What is the Zeroth law

Body A thermal equilibrium with body B, body B thermal equilibrium with body C, hence body A thermal equilibrium with body C

Define internal energy

Total energy of a body due to the motion of molecules and the total potential energy due to intermolecular forces in the body

What do intermolecular forces of energy depend on

• Forces between particles

• Distance between particles

How does temperature affect kinetic energy

High temperature — More vigorous vibration of particles in solids and vigorous movement of particles in liquids and gases

Low temperature — Less vigorous vibration of particles in solids and less vigorous movement of particles in liquids and gases

Define heat capacity

The quantity of energy needed to cause the temperature of a body to change by 1ºc or 1K

High C → A lot of energy needed

Low C → Less energy needed

What is the formula for heat capacity

Q = cΔθ

Define specific heat capacity

Quantity of energy required to change the temperature of 1kg of a substance by 1ºc or 1K

What is the formula for specific heat capacity

Q = mcΔθ

Q = heat energy added

c = specific heat capacity

Define melting

Change in state from solid to liquid without temperature change

Define boiling

Change in state from liquid to gas without temperature change

Define freezing/solidification

Change in state from liquid to solid without temperature change

Define condensation

Change in state from gas to liquid without temperature change

Define latent heat

Amount of thermal energy absorbed/released during a change in state without temperature change

Define latent heat of fusion

Amount of thermal energy required to change a substance from solid to liquid or vice versa without temperature change

What happens to thermal and potential energy during melting

• Thermal energy absorbed to weaken the bonds of solid particle

• Potential energy is increased to break the intermolecular bonds of liquid particles

What happens to thermal and potential energy during solidification

• Thermal energy is released to strengthen bonds of liquid particles

• Potential energy decreases

What happens to thermal and potential energy during boiling

• Thermal energy is absorbed to weaken the bonds with liquid particles

• Potential energy is increased to break the intermolecular bonds of liquid particles

What happens to thermal and potential energy during condensation

• Thermal energy is released to strengthen the bonds of gas particles

• Potential energy decreases

What happens to kinetic energy during state change

Remains constant so temperature is constant

Define specific latent heat

Energy needed to change the state of m/kg of a substance without temperature change

What is the formula for specific latent heat

Q = mlf or mlv

what is the difference between boiling and evaporation in terms of temperature

Boiling — Occurs at a fixed temperature

Evaporation — Occurs at any temperature

What is the difference between boiling and evaporation in terms of where it occurs

Boiling — Throughout the liquid

Evaporation — Liquid surface

What is the difference between boiling and evaporation in terms of the speed

Boiling — Slow

Evaporation — Quick

What is the difference between boiling and evaporation in terms of whether bubbles are formed

Boiling — Bubbles formed in the liquid

Evaporation — No bubbles

What is the difference between boiling and evaporation in terms of where thermal energy is supplied from

Boiling — Supply from an energy source

Evaporation — Supply from the surrounding

How does evaporation occur

1. Energetic molecules escape, carrying heat away and leaving less energetic molecules behind

2. Some molecules rebound into the liquid due to collisions with air molecules or other escaping liquid molecukes

3. Evaporation causes cooling due to thermal energy loss

What factors increase the rate of evaporation

• Higher temperature

• Bigger surface area

• Lower humidity

• Lower pressure

• Nature of liquid

What factors decrease the rate of evaporation

• Lower temperature

• Smaller surface area

• Higher humidity

• Higher pressure

• Nature of liquid