Thermodynamics (HL IB Physics)

An ideal gas in a simple engine begins in state X. It then undergoes a cyclic process with 4 stages.

Stage 1: The gas is isothermally compressed

Stage 2: The gas gains thermal energy without doing any work

Stage 3: The gas does work isobarically

Stage 4: The gas expands adiabatically

Which diagram correctly shows this cyclic process?

In a box containing an unknown number of partitions, 15 particles are kept in a single section of the box behind one of the partitions.

When a small hole is opened in each of the partitions, the entropy increases by 1.12 × 10⁻²² J K⁻¹. 

What is the final number of microstates of the system?

A simple heat engine contains 3 moles of an ideal gas. When the gas is cooled, the mean kinetic energy per particle drops by 3.11 × 10⁻²¹ J.

Additionally, 2 kJ of work is done on the gas. 

What is the thermal energy transferred from the gas to its surroundings?

A refrigerator in its surroundings does work and freezes a small amount of liquid water. Which row of the table is correct?

	entropy of the water	temperature of the surroundings	entropy of the surroundings
A	increases	increases	increases
B	decreases	increases	increases
C	stays the same	decreases	decreases
D	decreases	increases	stays the same

The pressure-volume diagram below shows a cyclic process. The grey dashed lines represent isotherms.

Which option best describes the stages of the cyclic process, which begins at Z?

A electrical heater is has a current of 1.5 A passing through it and has a potential difference of 200 V across it. 

It heats a gas in a piston at a constant pressure of 30 kPa. After 15 s the volume of the gas has increases by 0.020 m³ and its internal energy has increased by 2000 J.

The electrical heater is 70% efficient. What proportion of the thermal energy output by the electric heater is transferred to the gas?

At 78.0°C, 12.0 g of liquid ammonia is converted to a gaseous state. The entropy change of this process is 0.0470 J K⁻¹.

What is the latent heat of vaporisation of ammonia?

In an adiabatic process, a gas in a piston does work.

The cylindrical chamber increases in length from 1.5 m to 290 cm.

Which expression, in terms of original pressure p, most closely represents the new pressure?

An idealised heat engine has an efficiency of η and is supplied with heat energy Q_H from an external hot reservoir.

The cycle is described as follows:

Stage 1: The gas undergoes isobaric compression at a pressure of p₁. The volume decreases by z and the final temperature is T₁.

Stage 2: The gas then undergoes isovolumetric heating. The final temperature is T₂.

Stage 3: The gas undergoes isobaric expansion. The volume increases by z.

Stage 4: Finally, the gas undergoes isovolumetric cooling and returns to its state at the beginning of stage 1.

Which is the correct expression for z?

A researcher is studying phase changes of different materials.

They plot the following graph of heat supplied and entropy change for different masses of a material being vaporised. Their axes are incomplete. 

Using the following table, which material was being studied?

Material	Melting point / °C	Boiling point / °C
A.	375	560
B.	0	100
C.	N/A	−270
D.	0	230