Edexcel IGCSE Physics (d) Ideal gas molecules

[Maximum number: 6]

This question is about gas pressure.

(a)

Diagram 1 shows some of the molecules of a gas in a sealed container.

Diagram 1

The molecules collide with all the surfaces of the container. This exerts an outward force on the container and causes pressure.

Describe how the motion of the gas molecules causes an equal pressure on all the walls of the container.

You may add to diagram 1 to help your answer.

[ 2 ]

(b)

The width of the container is slowly decreased so that the volume of the container is smaller than before.

Diagram 2 shows the width of the container before and after this change. All other dimensions of the container remain the same.

The initial volume of the gas is 130 cm^3.
The initial pressure of the gas is 100 kPa.
Calculate the pressure of the gas after the width of the container is decreased.
Assume the temperature of the gas remains constant.

pressure = ............ kPa

[ 4 ]

Marking points:
- evaluation of new volume
- substitution into $p_{1}V_{1}=p_{2}V_{2}$
- rearrangement
- evaluation of new pressure

Example:
$V_{2}=130\times\frac{5.0}{8.4}=77\ \mathrm{cm^{3}}$ $100\times130=p_{2}\times77$ $p_{2}=\frac{100\times130}{77}$ $p_{2}=170\ \mathrm{kPa}$

Accept:
- $V_{2}=77.38\ldots\ \mathrm{cm^{3}}$
- any value that rounds to $170\ \mathrm{kPa}$
- ECF different yet incorrect volume

Marking guidance:
- Deduct 1 mark for a power-of-ten error.

[Maximum number: 9]

A student uses a computer simulation to investigate the motion of particles in a gas.
He records the pressure of the gas and the mean speed of the particles in the gas at different temperatures.

The graphs show his results.

Graph 1

Graph 2

(a)

Describe the relationships shown by the graphs.

[ 3 ]

(b)

Explain why the value of temperature chosen in the simulation should not decrease below $-273^{\circ} \mathrm{C}$ .

[ 2 ]

(c)

The student then calculates the kinetic energy of a single gas particle at each temperature.

[ 4 ]

(i)

Using the curve of best fit on graph 2, determine the mean speed of a gas particle when the gas temperature is 100 degrees C.

mean speed = ............ m/s

[ 1 ]

(ii)

Calculate the temperature of the gas in kelvin when its temperature is 100 degrees C.

temperature = ............ K

[ 1 ]

(iii)

On the axes, sketch a graph of the average kinetic energy of the gas particles against temperature in kelvin.

Figure for Question (iii) — Edexcel IGCSE Physics

[ 2 ]

[Maximum number: 7]

The diagram shows a manometer, a device used for measuring differences in pressure.

Figure for Question 3 — Edexcel IGCSE Physics

(a)

The temperature and pressure of the trapped gas increase when it is warmed.

[ 7 ]

(i)

Explain, in terms of particles, why the pressure of the trapped gas increases.

[ 3 ]

(ii)

The pressure of the trapped gas in the manometer is $9.95 \times 10^{4} \mathrm{~Pa}$ and the temperature is $16^{\circ} \mathrm{C}$ .

Calculate the new pressure of the trapped gas if the temperature increases to $32^{\circ} \mathrm{C}$ .
[assume volume of the trapped gas remains constant]
new pressure = Pa

[ 4 ]

Marking points:
- conversion of temperatures to kelvin
- substitution
- rearrangement
- evaluation

Example:
$T_1=289\ \mathrm{K},\qquad T_2=305\ \mathrm{K}$ $\frac{9.95\times10^{4}}{289}=\frac{p_2}{305}$ $p_2=\frac{9.95\times10^{4}\times305}{289}$ $p_2=1.1\times10^{5}\ \mathrm{Pa}$

Marking guidance:
- not converting to kelvin giving $199000\ \mathrm{Pa}$ gains 2 marks maximum

Accept:
- $1.05\times10^{5}\ \mathrm{Pa}$
- $105008.65\ldots\ \mathrm{Pa}$

[Maximum number: 2]

This question is about gas pressure.

Diagram 1 shows some of the molecules of a gas in a sealed container.

Diagram 1

The molecules collide with all the surfaces of the container. This exerts an outward force on the container and causes pressure.

Describe how the motion of the gas molecules causes an equal pressure on all the walls of the container.

You may add to diagram 1 to help your answer.

[Maximum number: 2]

A student uses a computer simulation to investigate the motion of particles in a gas.
He records the pressure of the gas and the mean speed of the particles in the gas at different temperatures.

The graphs show his results.

Graph 1

Graph 2

Explain why the value of temperature chosen in the simulation should not decrease below $-273^{\circ} \mathrm{C}$ .

[Maximum number: 1]

A student uses a computer simulation to investigate the motion of particles in a gas.
He records the pressure of the gas and the mean speed of the particles in the gas at different temperatures.

The graphs show his results.

Graph 1

Graph 2

The student then calculates the kinetic energy of a single gas particle at each temperature.

Calculate the temperature of the gas in kelvin when its temperature is 100 degrees C.

temperature = ............ K

[Maximum number: 1]

A student uses a computer simulation to investigate the motion of particles in a gas.
He records the pressure of the gas and the mean speed of the particles in the gas at different temperatures.

The graphs show his results.

Graph 1

Graph 2

The student then calculates the kinetic energy of a single gas particle at each temperature.

Using the curve of best fit on graph 2, determine the mean speed of a gas particle when the gas temperature is 100 degrees C.

mean speed = ............ m/s

[Maximum number: 2]

A student uses a computer simulation to investigate the motion of particles in a gas.
He records the pressure of the gas and the mean speed of the particles in the gas at different temperatures.

The graphs show his results.

Graph 1

Graph 2

The student then calculates the kinetic energy of a single gas particle at each temperature.

On the axes, sketch a graph of the average kinetic energy of the gas particles against temperature in kelvin.

Figure for Question 8 — Edexcel IGCSE Physics

[Maximum number: 3]

The diagram shows a manometer, a device used for measuring differences in pressure.

Figure for Question 9 — Edexcel IGCSE Physics

The temperature and pressure of the trapped gas increase when it is warmed.

Explain, in terms of particles, why the pressure of the trapped gas increases.

[Maximum number: 4]

The diagram shows a manometer, a device used for measuring differences in pressure.

Figure for Question 10 — Edexcel IGCSE Physics

The temperature and pressure of the trapped gas increase when it is warmed.

The pressure of the trapped gas in the manometer is $9.95 \times 10^{4} \mathrm{~Pa}$ and the temperature is $16^{\circ} \mathrm{C}$ .

Calculate the new pressure of the trapped gas if the temperature increases to $32^{\circ} \mathrm{C}$ .
[assume volume of the trapped gas remains constant]
new pressure = Pa

Marking points:
- conversion of temperatures to kelvin
- substitution
- rearrangement
- evaluation

Example:
$T_1=289\ \mathrm{K},\qquad T_2=305\ \mathrm{K}$ $\frac{9.95\times10^{4}}{289}=\frac{p_2}{305}$ $p_2=\frac{9.95\times10^{4}\times305}{289}$ $p_2=1.1\times10^{5}\ \mathrm{Pa}$

Marking guidance:
- not converting to kelvin giving $199000\ \mathrm{Pa}$ gains 2 marks maximum

Accept:
- $1.05\times10^{5}\ \mathrm{Pa}$
- $105008.65\ldots\ \mathrm{Pa}$

[Maximum number: 4]

This question is about gas pressure.

The width of the container is slowly decreased so that the volume of the container is smaller than before.

Diagram 2 shows the width of the container before and after this change. All other dimensions of the container remain the same.

The initial volume of the gas is 130 cm^3.
The initial pressure of the gas is 100 kPa.
Calculate the pressure of the gas after the width of the container is decreased.
Assume the temperature of the gas remains constant.

pressure = ............ kPa

Marking points:
- evaluation of new volume
- substitution into $p_{1}V_{1}=p_{2}V_{2}$
- rearrangement
- evaluation of new pressure

Example:
$V_{2}=130\times\frac{5.0}{8.4}=77\ \mathrm{cm^{3}}$ $100\times130=p_{2}\times77$ $p_{2}=\frac{100\times130}{77}$ $p_{2}=170\ \mathrm{kPa}$

Accept:
- $V_{2}=77.38\ldots\ \mathrm{cm^{3}}$
- any value that rounds to $170\ \mathrm{kPa}$
- ECF different yet incorrect volume

Marking guidance:
- Deduct 1 mark for a power-of-ten error.

Edexcel IGCSE Physics D Ideal Gas Molecules Questions

Exam points

Covered syllabus points

Covered syllabus points

Question 1

Question (a)

Question (b)

Question 2

Question (a)

Question (b)

Question (c)

Question (i)

Question (ii)

Question (iii)

Question 3

Question (a)

Question (i)

Question (ii)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11