Thermal Energy Transfer
Physics: AQA A Level, topic 6.2.1
Internal Energy
Internal energy is the sum of the randomly distributed kinetic energies and potential energies of all the particles in a gas.
Particle energies
- Kinetic energy comes from the random movements of particles in a gas.
- Potential energy comes from the interactions between the particles.
Adding energy
- The internal energy can be increased by adding energy to the system.
- If you add heat to a system it increases in energy but NOT always in temperature.
Specific Heat Capacity
The specific heat capacity is the amount of energy needed to raise one kilogram of material by 1 degree Kelvin.
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Heat capacity
- Energy required = mass x specific heat capacity x change in temperature
Temperature
- All temperatures should be calculated in Kelvin.
- For changes in temperature, the change in degrees is the same as the change in Kelvin.
Specific Latent Heat
The energy required to change the state of an object is the specific latent heat.
Changing state
- To make an object go from a solid to a liquid or a liquid to a gas you need to add some energy. This energy is the latent heat.
- The energy goes into weakening the intermolecular bonds NOT into changing the temperature. The equation for the energy is:
- The energy needed = mass x specific latent heat
Kinetic energies
- When the latent heat is added to a solid to melt it, the bonds between molecules are weakened.
- Because all of the energy goes into weakening the bonds, there is no gain in kinetic energy and there is no gain in temperature.
Test yourself on Thermal Energy Transfer
What is the internal energy of a gas?
Which statements about internal energy are true?
What is the correct form for the equation for specific heat capacity?
Which statements about specific heat capacity are true?
What does the energy used to change the state of a substance do?