CAIE A-Level Physics 16.1.1 Internal Energy of a System

Practise explaining internal energy as random molecular kinetic and potential energy, recognising it as a state property and comparing thermodynamic states.

Exam points

explain internal energy as the sum of the random molecular kinetic and potential energies in a system
recognise that internal energy is a state property determined by the state of the system
compare internal-energy changes or microscopic energy distributions in stated thermodynamic situations

[Maximum number: 2]

A sample of $0.26 \mathrm{~m}^{3}$ of an ideal gas is at pressure $2.0 \times 10^{5} \mathrm{~Pa}$ and temperature 290 K .

Determine:

the internal energy of the gas. Explain your reasoning.
internal energy =

internal energy = total KE + PE of molecules

or

PE = 0 so internal energy = total KE of molecules

B1

internal energy $=1.3 \times 10^{25} \times 6.0 \times 10^{-21}$ $=7.8 \times 10^{4} \mathrm{~J}$

A1

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16.1.1—Internal energy is determined by the state of the system and that it can be question 1