Edexcel A Level Physics
Edexcel A Level Physics Topic 9: Thermodynamics Exam Questions
Free Edexcel A Level Physics exam questions for Topic 9: Thermodynamics, with a mark scheme for every pack. Covers specific heat capacity, specific latent heat, internal energy, absolute zero, kinetic theory, the ideal gas equation and black body radiation.
Topic 9: Thermodynamics exam questions
3 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel A Level Physics Topic 9: Thermodynamics
Topic 9: Thermodynamics in Edexcel A Level Physics covers thermal energy transfer, kinetic theory and ideal gases, and black body radiation. You calculate energy changes using specific heat capacity and specific latent heat, explain internal energy and absolute zero, and use pV = NkT and ½m<c^2> = (3/2)kT. The black body section introduces the Stefan-Boltzmann law and Wien's law, which are used again in Topic 10: Space. Core practicals include determining the specific latent heat of a phase change and investigating the relationship between pressure and volume of a gas at fixed temperature. It is assessed in Paper 2: Advanced Physics II.
What you need to know
- Thermal energy transfer ΔE = mcΔθ and ΔE = LΔm. Specific latent heat is the energy needed to change the state of 1 kg without a temperature change.
- Internal energy Internal energy is the sum of the random kinetic and potential energies of the molecules. Absolute zero is the temperature at which molecules have minimum internal energy.
- Ideal gas laws pV = NkT with T in kelvin. Boyle's law (pV constant at fixed T) and the pressure law follow from it.
- Kinetic theory Pressure arises from molecules changing momentum when they collide with the container walls. Mean molecular kinetic energy ½m<c^2> = (3/2)kT.
- Black body radiation A black body absorbs all incident radiation and is the best possible emitter. Stefan-Boltzmann law L = σAT^4; Wien's law λmaxT = 2.898 × 10^-3 m K.
Common mistakes in Topic 9: Thermodynamics
- Using °C instead of K in gas laws, Wien's law or Stefan's law.
- Saying temperature rises during a change of state. Energy increases molecular potential energy, so temperature is constant.
- Confusing N (number of molecules) with n (number of moles). Edexcel uses pV = NkT.
- Forgetting the fourth power of T in L = σAT^4.
- Leaving out energy losses to the surroundings when evaluating a specific heat capacity or latent heat experiment.
Try three Topic 9: Thermodynamics exam-style questions
1. Calculate the number of molecules in 1.0 m^3 of an ideal gas at 1.0 × 10^5 Pa and 300 K. (2 marks)
Show the mark scheme answer
N = pV/kT = 1.0 × 10^5 × 1.0/(1.38 × 10^-23 × 300); N = 2.4 × 10^25.
2. Calculate the mean kinetic energy of a gas molecule at 300 K. (1 mark)
Show the mark scheme answer
½m<c^2> = (3/2)kT = 1.5 × 1.38 × 10^-23 × 300 = 6.2 × 10^-21 J.
3. Describe how to determine the specific latent heat of fusion of ice. (4 marks)
Show the mark scheme answer
Place crushed ice in a funnel with an immersed electrical heater; measure the mass of meltwater collected in a set time with the heater off (control) and with the heater on; energy supplied = VIt (or joulemeter reading); L = energy/(mass melted by heater - mass melted in control).
Topic 9: Thermodynamics FAQs
What does Edexcel A Level Physics Topic 9: Thermodynamics cover?
It covers specific heat capacity, specific latent heat, internal energy, absolute zero, kinetic theory, the ideal gas equation and black body radiation.
Which paper is Topic 9 examined in?
It is assessed in Paper 2: Advanced Physics II, and like every topic it can also appear in Paper 3: General and Practical Principles in Physics.
Which core practicals are in Thermodynamics?
Determining the specific latent heat of a phase change, and investigating the relationship between pressure and volume of a gas at fixed temperature.
