GCSE Physics: Pressure in gases

All questions and answers

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1. In which direction does gas pressure act on the wall of its container?

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   At right angles (perpendicular) to the wall, or to any surface.

2. What does the pressure of a gas produce on the walls of its container?

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   A net force acting at right angles to the wall.

3. A gas can be compressed or expanded by ? changes.

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   pressure

4. Why does increasing the volume of a gas at constant temperature decrease its pressure?

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   The particles have more space, so they collide with the container walls less often, giving a smaller force per unit area.

5. What is the equation relating pressure and volume for a fixed mass of gas at constant temperature?

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   pV = constant (pressure × volume = constant).

6. For a fixed mass of gas at constant temperature, pressure × volume = ?.

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   constant

7. What two conditions must hold for pV = constant to apply?

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   A fixed mass of gas held at a constant temperature.

8. What is the SI unit of pressure in the equation pV = constant?

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   Pascals (Pa).

9. What is the SI unit of volume in the equation pV = constant?

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   Metres cubed (m³).

10. A gas at 100 kPa in 2 m³ is compressed to 0.5 m³ at constant temperature. What is the new pressure?

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    400 kPa. p₁V₁ = p₂V₂ → 100 × 2 = p₂ × 0.5 → p₂ = 400 kPa.

11. At constant temperature, what happens to a fixed mass of gas's pressure if its volume is halved?

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    The pressure doubles, because pV stays constant.