IB Physics SL B 1 5 Kelvin Temperature and Kinetic Energy Questions

Practise linking kelvin temperature to molecular kinetic energy and speed, including gas mixtures, compression and particle graphs.

Exam points

Relate Kelvin temperature to average molecular kinetic energy using the proportional relationship Ēk = 3/2 kBT.
Interpret how changes in absolute temperature affect particle motion and average kinetic energy using complete evidence.

[Maximum number: 2]

A mass of 1.0 kg of water is brought to its boiling point of $100^{\circ} \mathrm{C}$ using an electric heater of power 1.6 kW .

The molar mass of water is $18 \mathrm{~g} \mathrm{~mol}^{-1}$ . Estimate the average speed of the water molecules in the vapor produced. Assume the vapor behaves as an ideal gas.

$E_k=\frac32(1.38\times10^{-23})(373)=7.7\times10^{-21}\ \mathrm{J}$ .
$v=\sqrt{\frac{3\times1.38\times10^{-23}\times6.02\times10^{23}\times373}{0.018}}=720\ \mathrm{m\ s^{-1}}$ .

v=\sqrt{\frac{3(1.38\times10^{-23})(6.02\times10^{23})(373)}{0.018}}=720\ \mathrm{m\ s^{-1}}

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IB Physics SL B 1 5 Kelvin Temperature and Kinetic Energy Questions question 1