1. Thermal Physics
1. The Kinetic Model of Matter
2. Heat versus Temperature
3. Measuring Temperature
4. Heat Processes
5. Heat Capacity
6. Latent Heat Brownian Motion:
https://www.youtube.com/watch?v=FAdxd2Iv-
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2. 1. The Kinetic Model of Matter
• All matter is made of atoms or molecules.
• These have energy.
• This energy is found in the chemical bonds and in their
kinetic energy.
• Their chemical energy defines the state of the material
• The kinetic energy defines their temperature, pressure
and volume.
3. Particles
What happens to the kinetic energy of the particles when a gas is
heated?
The heat energy is transferred to the kinetic energy of the gas
particles.
What sort of graph would you get if you plotted ‘Kelvin temperature (Tk)’
against ‘the average kinetic energy (KEave)of the particles’.
Zero Kelvin temperature equals zero
gas molecule kinetic energy.
At what temperature is zero
Kelvin?
-273°C
Tk
KEave
4. Pressure(P) and temperature(T)
T
P
P T
As long as it is Kelvin
temperature
P – pressure (Pascals) T – Temperature(K)
P1/T1 = P2/T2
Recall:
(P = F/A)
5. 2. Heat versus Temperature
These are NOT the same thing.
• Heat is a type of energy. It flows from a hot
place to a cold.
• Temperature is a measure of the average
kinetic energy of the molecules.
8. Evaporation
Since the average speed of the remaining molecules must now
be lower, the temperature of the liquid drops (since
temperature is a measure of the kinetic energy of the
molecules).
10. Heat can travel by Conduction
Hot particles vibrate more, so collide with
adjacent particles. The heat energy travels
from hot to cooler areas.
hot
cold
11. 1. Conduction in metals
Metals have atoms inside them and lots of free
electrons.
The free electrons can move around and
vibrate.
The heat energy is passed on by
neighbouring particles vibrating along the
metal.
There are too few free electrons in a non-metal
for this to happen.
Energy : heat transfer
12. 4. Radiation
Heat can move by travelling as Infra Red waves
These are electromagnetic waves, like light waves, but with a longer wavelength.
This means that infra red waves act very much like light waves:
They can travel through a vacuum
They travel at 300,000,000 m/s
They can be reflected
They can’t travel through opaque materials.
Energy : heat transfer
14. 2.Why does take-away food often come in aluminium
containers?
3.Why do elephants have big ears?
4.Radiation
Energy : heat transfer
1.How does a cup of tea lose heat by conduction,
convection, evaporation and radiation?
15. 5. Heat Capacity
This is the measure of a substance’s capacity to
absorb heat.
A large heat capacity means the substance can
absorb a lot of heat but only change
temperature by a small amount.
EH= c.m.(Tf – Ti)
17. Latent heat
When the molecules of a substance settle into
the regular patter of a solid, energy is released
as bonds are formed. This energy released is
called latent heat. This stops the temperature
from falling.
(“latent” = “hidden”)
18. Solid Liquid
Liquid Gas
Time
Melting
Freezing
Boiling
Condensing
Changes of State
19. Example
• The specific latent heat of fusion (melting) of
ice is 334 000 J/kg. How much energy is
needed to melt 5kg of ice at 0°C to 5 kg of
water at 0°C?
• Energy = mL = 5 x 334 000 = 1670000 J
