This common misconceptions covers Common Misconceptions within Gas Pressure & Temperature for GCSE Physics. Revise Gas Pressure & Temperature in Particle Model for GCSE Physics with 19 exam-style questions and 30 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 7 of 12 in this topic. Use this common misconceptions to connect the idea to the wider topic before moving on to questions and flashcards.
⚠️ Common Misconceptions
Misconception 1: "Pressure increases because particles get bigger when heated"
Particles do not change size when heated. Pressure increases because the SAME particles move FASTER — they hit the walls more frequently and with more force. Size of particles is unchanged.
Misconception 2: "Pressure and temperature are linked using Celsius"
Gas law calculations MUST use Kelvin (absolute temperature), not Celsius. −273°C = 0 K. If you use Celsius, calculations will be completely wrong. Always convert: T(K) = T(°C) + 273.
Misconception 3: "Pressure in a liquid is the same at all depths"
Pressure in a liquid increases with depth (P = ρgh). This is why deep-sea divers face enormous pressures and submarines must have thick walls. Greater depth = more weight of liquid above = greater pressure.
Quick Check: Convert 27°C to Kelvin and explain why Kelvin must be used in gas pressure calculations.
27°C + 273 = 300 K. Kelvin must be used because the relationship between pressure and temperature (p ∝ T) only holds when using the absolute temperature scale. Kelvin starts at absolute zero (−273°C), where particles have minimum kinetic energy and pressure would theoretically be zero. Celsius is an arbitrary scale that doesn't start at zero kinetic energy.
Practice questions for Gas Pressure & Temperature
A sealed gas container is heated. What happens to the pressure of the gas inside?
A sealed gas cylinder is heated. Explain, using particle theory, why the pressure of the gas increases when the temperature increases.