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UCE (O-Level) Ideal gases — practice questions

Explore 5 free Ideal gases questions in UCE (O-Level) Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Ideal gases questions and exercises with answers

Showing questions 1–5 of 5.

The temperature of a substance is a measure of what?Read the answer and worked solution →The pressure of a gas is a measure of what?Read the answer and worked solution →The volume of a fixed quantity of gas is halved while the temperature is kept constant. What happens to its pressure?Read the answer and worked solution →Charles' law states that the volume of an enclosed gas is directly proportional to its temperature on which scale?Read the answer and worked solution →Under which conditions does a real gas stop behaving like an ideal gas?Read the answer and worked solution →

Worked practice questions

The temperature of a substance is a measure of what?

  1. Total mass of the gas
  2. Average kinetic energy
  3. Number of gas molecules
  4. Volume of the container
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Correct answer: B. Average kinetic energy

1. The particles of a gas are constantly moving and so carry kinetic energy. 2. Temperature is a measure of the average kinetic energy of those particles. 3. Heating a gas raises the average kinetic energy and the particles move faster. 4. Cooling a gas far enough slows them so much that the gas liquefies. _Source: Siyavula Physical Sciences Grade 11 (Everything Science, CC BY 4.0), Chapter 7: Ideal gases_

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The pressure of a gas is a measure of what?

  1. Colour of the particles
  2. Charges on particles
  3. Collisions of particles
  4. Weight of the particles
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Correct answer: C. Collisions of particles

1. Gas particles move in straight lines and keep bumping into things. 2. Pressure measures the number of collisions of the particles with each other and with the container walls. 3. Squeezing the same gas into a smaller space makes those collisions more frequent. 4. More frequent collisions therefore mean a higher pressure. _Source: Siyavula Physical Sciences Grade 11 (Everything Science, CC BY 4.0), Chapter 7: Ideal gases_

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The volume of a fixed quantity of gas is halved while the temperature is kept constant. What happens to its pressure?

  1. It halves in size
  2. It stays unchanged
  3. It falls to zero
  4. It doubles in size
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Correct answer: D. It doubles in size

1. Boyle's law applies because the amount of gas and the temperature are both fixed. 2. Pressure is inversely proportional to the volume the gas occupies. 3. Halving the volume therefore doubles the pressure. 4. The particles now hit the walls twice as often in the smaller space, which is the same result seen from the particle picture. _Source: Siyavula Physical Sciences Grade 11 (Everything Science, CC BY 4.0), Chapter 7: Ideal gases_

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