A LEVEL PHYSICS
PAPER 2 ALL IN ONE NOTES
AQA Physics
2024 Summer Exams
Chapter 19 Thermal Physics
Internal energy = sum of all the kinetic energies and potential energies of all its
particles
Molecular kinetic energy increases with temperature
Potential energy increases if an object changes state from solid to liquid or liquid
to gas
In gases, molecules are so far apart that there are no intermolecular interactions =>
no potential energy (too far away for forces to exist) and entirely kinetic
Heat = energy that flows from a high temperature object to a lower temperature
object
When something absorbs heat => internal energy increases ( or energy of its atoms
& molecules increase)
When something releases energy => internal energy decreases
Heating an object result in:
- Temperature changing (reason of expand or contract as molecular motion
changes)
1
, - Object changing phases (s,l,g)
Temperature = measure of degree of hotness of a substance
Heat energy normally moves from regions of higher to lower temperature
Conditions for thermal equilibrium:
- No net transfer of heat energy between two objects
- Only occur if both objects are at the same temperature
NEWTON’S FIRST LAW OF THERMODYNAMICS
Internal energy due to temperature => thermal energy
Internal energy can be increased by:
- Energy transfer by heating the object
- Work done on the object
Change in internal energy = energy gained by heating + energy gained by working
ΔU=ΔQ+ΔW
States of molecules
- Solid:
● Atoms and molecules are held together by forces due to the electrical
charges of the protons and electrons in the atoms
● Vibrate randomly about fixed positions
● Higher the temp of the solid, the more the molecules vibrate
● Energy supplied to melt a solid raises the potential energy of the molecules
as they break free from each other
2
, - Liquid:
● Molecules move about at random in contact with each other
● Forces between the molecules are not enough to hold the molecules
together in fixed positions
● Higher temp of liquid, faster the molecules move
● Energy supplied to a liquid to raise its temperature increases its kinetic
energy of the molecules => enough KE to break free and move away (gas)
- Gas or vapour:
● Molecules move randomly but much further apart on avg than liquid
● Heating cause the molecules to speed up and gain KE
Absolute Zero = lowest possible temperature where objects have minimal KE
Absolute scale of temperature: in Kelvins (K)
- Absolute Zero: 0 K => lowest possible temperature
- Triple point of water: 273.15 K => temp where three phases of water (s,l,g) co-
exist in equilibrium (allow simultaneous presence and transition between
states without any phase becoming more dominant than others)
Specific Heat Capacity = the energy needed to raise the temperature of unit mass
of the substance by 1K without change of state
Energy needed Δ Q = mc ΔT where c is the specific heat capacity
Specific Latent Heat of Fusion = energy needed to melt a solid at its melting point
Specific Latent Heat of Vaporisation = energy needed to vaporise a liquid
* without change of temperature
Q = ml
3
, Chapter 20 Gases
Pressure of a gas = force per unit area that the gas exerts normally on a surface
Unit: Pascals (Pa) = Nm^-1
Boyle’s Law
pV = constant at constant temperature
* pressure and volume are inversely proportional
Charles’ Law
V
=k at constant pressure
T
* volume is directly proportional to absolute temperature
The Pressure Law
p
=k at constant volume
T
* pressure is directly proportional to absolute temperature
Ideal Gas Law
pV = nRT
4
PAPER 2 ALL IN ONE NOTES
AQA Physics
2024 Summer Exams
Chapter 19 Thermal Physics
Internal energy = sum of all the kinetic energies and potential energies of all its
particles
Molecular kinetic energy increases with temperature
Potential energy increases if an object changes state from solid to liquid or liquid
to gas
In gases, molecules are so far apart that there are no intermolecular interactions =>
no potential energy (too far away for forces to exist) and entirely kinetic
Heat = energy that flows from a high temperature object to a lower temperature
object
When something absorbs heat => internal energy increases ( or energy of its atoms
& molecules increase)
When something releases energy => internal energy decreases
Heating an object result in:
- Temperature changing (reason of expand or contract as molecular motion
changes)
1
, - Object changing phases (s,l,g)
Temperature = measure of degree of hotness of a substance
Heat energy normally moves from regions of higher to lower temperature
Conditions for thermal equilibrium:
- No net transfer of heat energy between two objects
- Only occur if both objects are at the same temperature
NEWTON’S FIRST LAW OF THERMODYNAMICS
Internal energy due to temperature => thermal energy
Internal energy can be increased by:
- Energy transfer by heating the object
- Work done on the object
Change in internal energy = energy gained by heating + energy gained by working
ΔU=ΔQ+ΔW
States of molecules
- Solid:
● Atoms and molecules are held together by forces due to the electrical
charges of the protons and electrons in the atoms
● Vibrate randomly about fixed positions
● Higher the temp of the solid, the more the molecules vibrate
● Energy supplied to melt a solid raises the potential energy of the molecules
as they break free from each other
2
, - Liquid:
● Molecules move about at random in contact with each other
● Forces between the molecules are not enough to hold the molecules
together in fixed positions
● Higher temp of liquid, faster the molecules move
● Energy supplied to a liquid to raise its temperature increases its kinetic
energy of the molecules => enough KE to break free and move away (gas)
- Gas or vapour:
● Molecules move randomly but much further apart on avg than liquid
● Heating cause the molecules to speed up and gain KE
Absolute Zero = lowest possible temperature where objects have minimal KE
Absolute scale of temperature: in Kelvins (K)
- Absolute Zero: 0 K => lowest possible temperature
- Triple point of water: 273.15 K => temp where three phases of water (s,l,g) co-
exist in equilibrium (allow simultaneous presence and transition between
states without any phase becoming more dominant than others)
Specific Heat Capacity = the energy needed to raise the temperature of unit mass
of the substance by 1K without change of state
Energy needed Δ Q = mc ΔT where c is the specific heat capacity
Specific Latent Heat of Fusion = energy needed to melt a solid at its melting point
Specific Latent Heat of Vaporisation = energy needed to vaporise a liquid
* without change of temperature
Q = ml
3
, Chapter 20 Gases
Pressure of a gas = force per unit area that the gas exerts normally on a surface
Unit: Pascals (Pa) = Nm^-1
Boyle’s Law
pV = constant at constant temperature
* pressure and volume are inversely proportional
Charles’ Law
V
=k at constant pressure
T
* volume is directly proportional to absolute temperature
The Pressure Law
p
=k at constant volume
T
* pressure is directly proportional to absolute temperature
Ideal Gas Law
pV = nRT
4
