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Date November 2016 Marks available 2 Reference code 16N.2.SL.TZ0.3
Level Standard level Paper Paper 2 Time zone 0 - no time zone
Command term Define Question number 3 Adapted from N/A

Question

Define internal energy.

[2]
a.

0.46 mole of an ideal monatomic gas is trapped in a cylinder. The gas has a volume of 21 m3 and a pressure of 1.4 Pa.

(i) State how the internal energy of an ideal gas differs from that of a real gas.

(ii) Determine, in kelvin, the temperature of the gas in the cylinder.

(iii) The kinetic theory of ideal gases is one example of a scientific model. Identify one reason why scientists find such models useful.

[4]
b.

Markscheme

mention of atoms/molecules/particles

sum/total of kinetic energy and «mutual/intermolecular» potential energy

Do not allow “kinetic energy and potential energy” bald.
Do not allow “sum of average ke and pe” unless clearly referring to total ensemble.

a.

i
«intermolecular» potential energy/PE of an ideal gas is zero/negligible


ii
THIS IS FOR USE WITH AN ENGLISH SCRIPT ONLY
use of  T = P V n R or T = 1.4 × 21 0.46 × 8.31

Award mark for correct re-arrangement as shown here not for quotation of Data Booklet version.
Award [2] for a bald correct answer in K.
Award [2 max] if correct 7.7 K seen followed by –265°C and mark BOD. However, if only –265°C seen, award [1 max].

7.7 K
Do not penalise use of “°K”

ii
THIS IS FOR USE WITH A SPANISH SCRIPT ONLY
T = P V n R


T = 1.4 × 2.1 × 10 6 0.46 × 8.31

T = 7.7 ×10-6 K
Award mark for correct re-arrangement as shown here not for quotation of Data Booklet version.
Uses correct unit conversion for volume
Award [2] for a bald correct answer in K. Finds solution. Allow an ECF from MP2 if unit not converted, ie candidate uses 21 m3 and obtains 7.7 K
Do not penalise use of “°K”

 

iii
models used to predict/hypothesize

explain

simulate

simplify/approximate
Allow similar responses which have equivalent meanings. Response needs to identify one reason.

b.

Examiners report

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

Syllabus sections

Core » Topic 3: Thermal physics » 3.1 – Thermal concepts
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Core » Topic 3: Thermal physics
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