2.1.8 thermal physics

Question 1

The internal energy, U, of a system

Answer 1

the sum of the kinetic and potential energies of the molecules in that system.

Question 2

the significance of ‘absolute zero’ with regard to internal energy

Answer 2

At absolute zero, the internal energy of a system is the minimum possible. It is impossible to extract energy from the system.

Question 3

Explain how the internal energy of an ideal gas is different from that of systems in general

Answer 3

All energy is kinetic because the molecules of an ideal gas’ potential energy forces are negligible, so there is no potential energy component to the internal energy.

Question 4

Describe what is meant by the term ‘heat’

Answer 4

Heat is the flow of energy from one system to another due to a temperature difference. The flow is into a system with a lower temperature.

Question 5

State what thermal equilibrium means in terms of heat and temperature.

Answer 5

that there is no heat flow between the systems; their temperatures are the same.