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CognitoGas pressure and the gas laws
Key facts & equations
Pressure in gases
- Gas pressure: caused by gas particles colliding with container walls.
- More collisions per second = higher pressure.
- Factors increasing pressure: more particles, higher temperature (faster particles), smaller volume.
- Pressure = force / area. P = F/A. Units: Pa (pascals) or N/m².
- In a sealed container: temperature increases → particles move faster → more frequent, harder collisions → pressure increases.
Absolute temperature and Kelvin
- Absolute zero (0 K) = -273°C. At absolute zero, particles have minimum possible energy.
- Kelvin (K) = Celsius + 273. K is used in gas law calculations.
- Temperature in Kelvin is proportional to average kinetic energy of particles.
- Double T (Kelvin) = double average KE = double pressure (constant V).
Gas laws (Higher tier)
- Boyle's Law (constant T): pressure × volume = constant. P1V1 = P2V2.
- Charles's Law (constant P): V/T = constant. V1/T1 = V2/T2 (T in Kelvin).
- Gay-Lussac's Law (constant V): P/T = constant. P1/T1 = P2/T2.
- Combined gas law: P1V1/T1 = P2V2/T2.
- Explanation: PV/T = constant for a fixed amount of gas.
Exam questions — 4 questions · 10 marks · AQA 8463 style
⚡ Show all working — the AI marks against the AQA mark scheme. Method marks awarded for correct working even if the final answer is wrong.
1 markWhy pressure increases with temperatureAQA 8463 style
A sealed gas container is heated. Explain why the pressure increases.
A Gas particles become larger at higher temperatures
B Gas particles move faster at higher temperatures, colliding more frequently and with more force with the container walls
C Heating creates new gas particles
D The container expands, releasing trapped pressure
3 marksBoyle's Law calculationAQA 8463 Higher style 🔢 Calculator
A gas at pressure 200,000 Pa has volume 0.3 m³ at constant temperature. The gas is compressed to volume 0.1 m³. Calculate the new pressure. (3 marks)
Hint: P1V1 = P2V2. Substitute known values and solve for P2.
+30 XP
3 marksConvert temperature and apply gas lawAQA 8463 Higher style 🔢 Calculator
A gas is at 27°C and 100,000 Pa in a sealed rigid container. It is heated to 127°C. Calculate the new pressure. (3 marks)
Hint: Always convert °C to K first (+273). For constant volume: P1/T1 = P2/T2.
+30 XP
1 markAbsolute zeroAQA 8463 style
What is absolute zero in Celsius?
A 0°C
B -100°C
C -273°C
D -373°C
Module complete! 🎉
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