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Gas pressure and volume: GCSE Combined Science Physics practice questions

Foundation and Higher · Grade 7

A second set of questions on gas pressure and volume. They are different from the ones on the topic page. Try each, then open the answer and compare your working.

More questions

Question 1 Hard

A gas at 300 kPa has a volume of 2 m³. It is compressed to 1.5 m³ at constant temperature. Work out the new pressure.

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Answer: 400 kPa

  1. p₁ × V₁ = p₂ × V₂
  2. 300 × 2 ÷ 1.5 = 400 kPa

Question 2 Hard

A gas at 120 kPa has a volume of 5 litres. It expands to 8 litres at constant temperature. Work out the new pressure.

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Answer: 75 kPa

  1. p₁ × V₁ = p₂ × V₂
  2. 120 × 5 ÷ 8 = 75 kPa

Question 3 Hard

Explain why a bicycle pump gets warm when the air is compressed quickly.

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Answer: Work is done on the air, which increases its internal energy, so its temperature rises.

  1. Work is done on the air by the piston.
  2. The energy raises the internal energy of the gas, so the temperature rises.

Question 4 Hard

A sealed aerosol can is left in a hot car. Explain why the pressure inside rises and why this is dangerous.

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Answer: The particles move faster and hit the walls harder and more often, so the pressure rises and the can could burst.

  1. Heating makes the particles move faster.
  2. They hit the walls harder and more often, so the pressure rises and the can could burst.

Quick checks

Short questions with options. Choose one before you open the answer.

Check 1

How do the particles in a gas move?

  1. fast and randomly, in all directions
  2. in fixed positions, only vibrating
  3. in a regular layer, sliding past each other
Show answer

fast and randomly, in all directions Gas particles are free to move until they collide with something.

Check 2

How far apart are the particles in a gas?

  1. far apart, with mostly empty space between them
  2. touching each other in a regular pattern
  3. packed tightly together
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far apart, with mostly empty space between them That is why a gas can be squashed.

Check 3

What causes gas pressure?

  1. particles colliding with the walls of the container
  2. particles sticking to the walls
  3. the gas getting heavy
Show answer

particles colliding with the walls of the container Each collision gives a tiny force. Together they make the pressure.

Check 4

In which direction does gas pressure act on a wall?

  1. at right angles to the wall
  2. along the wall
  3. only upwards
Show answer

at right angles to the wall The force of the collisions acts at 90 degrees to the wall.

Check 5

Why does a blown-up balloon stay round?

  1. The rubber is round already.
  2. The gas pushes outwards equally on every part of the rubber.
  3. The gas only pushes at the top.
Show answer

The gas pushes outwards equally on every part of the rubber. Gas pressure is the same in all directions.

Check 6

What happens to the speed of gas particles when the gas is heated?

  1. They move slower.
  2. They stop moving.
  3. They move faster.
Show answer

They move faster. Heating gives the particles more kinetic energy.

Check 7

A sealed gas of fixed volume is heated. What happens to the pressure?

  1. It increases.
  2. It decreases.
  3. It stays the same.
Show answer

It increases. Faster particles hit the walls harder and more often.

Check 8

Why does heating a sealed gas increase the pressure?

  1. The particles hit the walls harder and more often.
  2. There are more particles in the container.
  3. The particles get bigger and take up more space.
Show answer

The particles hit the walls harder and more often. Both effects push up the pressure.

Check 9

A sealed gas is cooled. What happens to the pressure?

  1. It decreases.
  2. It increases.
  3. It stays the same.
Show answer

It decreases. Slower particles hit the walls less hard and less often.

Check 10

What stays the same when a sealed gas is heated?

  1. the number of particles
  2. the speed of the particles
  3. the pressure
Show answer

the number of particles Nothing is added or taken away from a sealed container.

Check 11

What does the temperature of a gas tell you about the particles?

  1. their average kinetic energy
  2. their size
  3. how many there are
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their average kinetic energy A higher temperature means a higher average kinetic energy.

Check 12

What is absolute zero in degrees Celsius?

  1. −273 °C
  2. 0 °C
  3. −100 °C
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−273 °C Absolute zero is 0 K, the coldest temperature possible.

Check 13

What is 27 °C in kelvin?

  1. 300 K
  2. −246 K
  3. 27 K
Show answer

300 K Add 273 to the Celsius temperature.

Check 14

A gas at constant temperature has its volume halved. What happens to the pressure?

  1. It doubles.
  2. It halves.
  3. It stays the same.
Show answer

It doubles. Pressure × volume is constant, so halving V doubles p.

Check 15

Why does reducing the volume of a gas increase its pressure?

  1. The particles hit the walls more often.
  2. The particles move faster.
  3. The particles get bigger.
Show answer

The particles hit the walls more often. The same particles have less room, so they reach the walls sooner.

Check 16

What is constant for a fixed mass of gas at constant temperature?

  1. pressure × volume
  2. pressure + volume
  3. pressure ÷ volume
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pressure × volume p × V stays the same when the volume changes.

Check 17

What is the equation for two states of a gas at constant temperature? (Higher tier)

  1. p₁ × V₁ = p₂ × V₂
  2. p₁ ÷ V₁ = p₂ ÷ V₂
  3. p₁ + V₁ = p₂ + V₂
Show answer

p₁ × V₁ = p₂ × V₂ The first pressure times the first volume equals the second pressure times the second volume.

Check 18

A gas at 150 kPa and 4 m³ is compressed to 2 m³ at constant temperature. What is the new pressure? (Higher tier)

  1. 300 kPa
  2. 75 kPa
  3. 152 kPa
Show answer

300 kPa 150 × 4 = p₂ × 2, so p₂ = 600 ÷ 2 = 300 kPa.

Check 19

A gas at 240 kPa and 1 m³ expands to 4 m³ at constant temperature. What is the new pressure? (Higher tier)

  1. 60 kPa
  2. 960 kPa
  3. 236 kPa
Show answer

60 kPa 240 × 1 = p₂ × 4, so p₂ = 240 ÷ 4 = 60 kPa.

Check 20

Why can a gas be squashed into a smaller space?

  1. Its particles are touching and can be pushed into each other.
  2. Its particles are far apart, with mostly empty space between them.
  3. Gas particles shrink when they are squashed.
Show answer

Its particles are far apart, with mostly empty space between them. There is room for the particles to be pushed closer together.

Check 21

What two conditions are needed for p × V to be constant? (Higher tier)

  1. constant temperature and a fixed mass of gas
  2. constant pressure and constant volume
  3. high pressure and low volume
Show answer

constant temperature and a fixed mass of gas If the temperature changes or gas leaks out, the rule fails.

Check 22

A student says squashing a gas into half the space halves its pressure. What is wrong?

  1. The pressure doubles, because the particles hit the walls twice as often.
  2. Nothing is wrong. The pressure halves.
  3. The temperature must be halved too.
Show answer

The pressure doubles, because the particles hit the walls twice as often. Halving the volume doubles the pressure at constant temperature.

Check 23

Why does a bicycle pump get warm? (Higher tier)

  1. Work done compressing the gas increases its internal energy.
  2. The gas gets heavier.
  3. The pump makes new gas.
Show answer

Work done compressing the gas increases its internal energy. The energy goes to the particles, so the temperature rises.

Check 24

Why is a sealed aerosol can dangerous in a hot car?

  1. Heating raises the pressure inside until the can could burst.
  2. The gas inside gets lighter and floats out.
  3. The metal can melts at room temperature.
Show answer

Heating raises the pressure inside until the can could burst. The faster particles hit the walls harder and more often.

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