Thermal Physics

Question 1

Boyle’s Law, pressure and volume are inversely proportional

Answer 1

pV = constant

p1 x V1 = p2 x V2

p is pressure in Pa
V is volume in m^3

Question 2

Charle’s Law, Volume is directly proportional to absolute temperature

Answer 2

V / T = constant

V1/T1 = V2/T2

V is volume in m^3
T is temperature in kelvin

Temperature and k.e are directly proportional

Question 3

Pressure Law, Pressure of gas is directly

proportional to the absolute temperature

Answer 3

p / T = constant

p1 / T1 = p2 / T2

p is pressure in Pa
T is temperature in kelvin

Question 4

Gas law

Answer 4

(pV) / T = constant

(p1 x V1) / T1 = (p2 x V2) / T2

1. Constant pressure
   - temperature and volume increase
2. Constant volume
   - temperature and pressure increase
3. Constant temperature
   - volume decreases and pressure increases

Question 5

Specific Heat Capacity, Amount of heat energy required to raise the temperature of 1 kg mass by 1ºC.

Answer 5

c = Q / (m x ∆θ)

c is specific heat capacity in J/(kg ºC),
Q is heat energy supplied in joules (J),
m is mass in kg
Δθ is change in temperature

Question 6

Thermal Capacity, amount of heat required to raise the temperature of a substance of any mass by 1ºC

• 2 formulas

Answer 6

Thermal capacity = m x c

Thermal capacity = Q / ∆θ

m is mass in kg
c is specific heat capacity in J/(kgºC)
Q is heat energy supplied in Joules (J)
∆θ is change in temperature

Question 7

Specific latent heat of fusion

1. Solid to liquid
2. Liquid to vapour

Answer 7

L {f or v} = Q / m

Lf is specific latent heat of fusion in J/kg
Q is total heat in Joules
m is mass of state change in kg

Question 8

Thermal or heat transfer through states and mediums

Answer 8

Solid = conduction

Liquid and gas = convection and also convection current (hot matter goes up and cold matter comes down)

In vacuum = radiation

Question 9

Emitters and Radiators

Answer 9

Dull black surface = good emitter and radiator, bad reflector
Bright shiny surface = poor emitter and radiator, good reflector

Question 10

Another name for heat radiation

Answer 10

Infrared radiation or radiant heat

Question 11

Melting point

Answer 11

Change solid into liquid, energy weaken the molecular bond, no
change in temperature, molecules move around each other

Question 12

Boiling point

• change of state
• molecules
• kinetic energy
• temp

Answer 12

Change liquid into gas, energy break molecular bond and
molecules escape the liquid, average kinetic energy increase, no
change in temperature, molecule are free to move

Question 13

Condensation

Answer 13

Change gas to liquid, energy release, bonds become stronger

Question 14

Solidification

Answer 14

Change liquid to solid, energy release bonds become very strong

Question 15

Evaporation

change of state
temperature
area of occurence

Answer 15

Change liquid to gas at any temperature, temperature of liquid decreases, happens only at the surface

Question 16

Temperature of water between states graph

Answer 16

NB.
The graph has a gradient of zero (flat) where a change of state is occurring
The graph has a positive gradient (upwards sloping) as a state of matter is being heated or cooled