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Date November 2011 Marks available 4 Reference code 11N.2.HL.TZ0.11
Level Higher level Paper Paper 2 Time zone Time zone 0
Command term Explain Question number 11 Adapted from N/A

Question

Part 2    Properties of a gas

A fixed mass of an ideal gas is at an initial volume of 2.0×10–3 m3. It undergoes an adiabatic expansion to a volume of 5.0×10–3 m3. An identical ideal gas undergoes the same change of volume but this time isothermally.

The graph shows the variation with volume V of the pressure P of the two gases.

Using data from the graph above, identify which gas, A or B, undergoes the isothermal expansion.

[2]
a.

Using the graph opposite, estimate the difference in work done by each gas.

[4]
b.

Explain, with reference to the first law of thermodynamics, and without further calculation, the change in temperature of the gas undergoing the adiabatic change.

[4]
c.

Markscheme

choice of two data points;
to show P×V constant for gas A / not constant for gas B;

a.

identifies area between lines as work done;
counts squares (14 squares);
each square 12.5;
175 J; (allow answers in the range of 150 to 200 J)

b.

QU+W and Q=0; (both needed)
so ΔU+W=0;
work done by gas is positive;
so ΔU decreases therefore temperature decreases;

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Option B: Engineering physics » Option B: Engineering physics (Core topics) » B.2 – Thermodynamics
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