Edexcel IGCSE Physics: Solids, Liquids and Gases — Practice Questions

These are original questions written for Marlbridge, in the style and at the standard of the examination. They are not reproduced past-paper questions — examination boards hold copyright in their own papers. Use these alongside the official past papers available free from your board.

Related: Solids, Liquids and Gases revision notes

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Questions

1. Describe the arrangement, movement and relative energy of particles in a solid, liquid and gas. [6]

2. Explain, in terms of particles, how a gas exerts pressure on the walls of its container. [2]

3. A gas at 1.0 × 10⁵ Pa occupies 240 cm³. It is compressed to 80 cm³ at constant temperature.

(a) Calculate the new pressure. [3] (b) Explain, in terms of particles, why the pressure changes. [2]

4. A gas in a sealed rigid container is heated from 27 °C to 227 °C.

(a) Convert both temperatures to kelvin. [1] (b) The initial pressure is 2.0 × 10⁵ Pa. Calculate the final pressure. [3] (c) Explain, giving both effects, why heating raises the pressure. [3]

5. Describe an experiment to determine the density of an irregularly shaped stone. [4]

6. 0.40 kg of water at 20 °C is heated to 100 °C. (c = 4200 J kg⁻¹ °C⁻¹)

(a) Calculate the energy needed. [3] (b) The water is now heated further and begins to boil. State what happens to its temperature while it boils, and to the pattern of a temperature-time graph plotted for the whole heating process. [2] (c) Explain why the temperature does not rise while it is boiling. [2]

7. A dam holding back a lake is built much thicker at its base than at its top.

(a) Write the equation for the pressure difference between the surface and a point at depth h in a liquid, defining each term. [2] (b) Explain why the dam is built thicker at the base, in terms of what liquid pressure depends on. [2] (c) State whether the shape of the lake or the total volume of water it holds affects the pressure at the base. [1]

8. A metal rod is heated and its length is found to increase slightly.

(a) Explain this thermal expansion in terms of the particle model. [2] (b) A student claims the particles themselves get bigger when heated. Explain why this is incorrect. [1]

9. Explain what is meant by absolute zero, and why no temperature lower than this is possible. [2]

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Answers

1. Solid — regular close-packed arrangement [1], particles vibrate about fixed positions, lowest energy [1]. Liquid — close together but irregular [1], particles slide past one another, medium energy [1]. Gas — far apart and random [1], particles move rapidly in all directions, highest energy [1].

2. The particles collide with the walls [1], and each collision exerts a small force; the total force per unit area is the pressure [1].

3. (a) p₁V₁ = p₂V₂ [1] 1.0 × 10⁵ × 240 = p₂ × 80 [1] p₂ = 3.0 × 10⁵ Pa [1]. (b) The same number of particles occupies a smaller volume [1], so they hit the walls more frequently, increasing the pressure [1].

4. (a) 300 K and 500 K [1]. (b) p₁/T₁ = p₂/T₂ [1] p₂ = 2.0 × 10⁵ × (500 ÷ 300) [1] = 3.3 × 10⁵ Pa [1]. (c) The particles gain kinetic energy and move faster [1], so they collide with the walls more frequently [1] and each collision exerts a greater force [1]. Both effects are needed for full marks.

5. Measure the mass of the stone on a balance [1]. Partly fill a measuring cylinder with water and record the volume [1]. Lower the stone in and record the new volume; the difference is the stone’s volume [1]. Calculate density = mass ÷ volume [1].

6. (a) E = mcΔθ = 0.40 × 4200 × 80 [1] [1] = 1.3 × 10⁵ J [1]. (b) The temperature stays constant (at 100 °C) while boiling [1], so the graph shows a flat/horizontal section at 100 °C before rising further (if superheated) or continuing once boiling is complete [1]. (c) The energy supplied is used to overcome the forces between the particles and separate them [1], rather than to increase their kinetic energy, and temperature depends on kinetic energy [1].

7. (a) Δp = ρgh [1], where ρ is the density of the liquid, g is the gravitational field strength, and h is the depth below the surface — this gives the pressure difference between the surface and that depth; the total pressure at the depth also includes the pressure (e.g. atmospheric) already acting on the surface [1]. (b) Liquid pressure increases with depth [1], so the pressure (and hence the force) on the dam wall is greatest at the base, requiring more material there to withstand it [1]. (c) Neither — pressure at a given depth depends only on the density of the liquid and the depth, not on the shape of the container or the total volume of liquid [1].

8. (a) Heating makes the particles vibrate more vigorously [1], and this increased vibration means each particle takes up more space on average, so the rod expands [1]. (b) The particles themselves do not change size — it is the space between them, created by more vigorous vibration, that increases [1].

9. Absolute zero (0 K, −273 °C) is the lowest possible temperature, at which particles have the minimum possible kinetic energy [1]; since no further energy can be removed from the particles once they are at this minimum, no lower temperature can exist [1].

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Where marks are usually lost

• Using °C in the gas laws.
• Giving only one effect when a gas is heated at constant volume.
• Using E = mcΔθ during a change of state.
• Forgetting to record the initial water level in a displacement experiment.
• Saying liquid pressure depends on the shape of the container or the total volume of liquid, rather than only on depth and density.
• Saying particles themselves expand when a solid is heated, rather than the space between them increasing.

Work through the Solids, Liquids and Gases revision notes alongside these questions: the notes summarise the particle model, the gas laws and the pressure formulas in condensed form, while these questions test whether you can apply them to a specific, unfamiliar situation such as a dam wall or a heated rod, rather than just recall the definition.