amazon.co.ukThermal Physics
A-Level Physics revision: Thermal Physics. Learning objectives, key points, worked examples and practice questions across AQA, Edexcel, OCR, WJEC and CCEA.
๐ Key Points
Key Fact: Internal energy U = ฮฃ(KE + PE) of molecules; Temperature โ mean KE per molecule
Key Fact: Q = mcDeltaฮธ (no phase change); Q = mL (phase change); L_fusion, L_vaporisation
Key Fact: 1st law: DeltaU = Q + W; W = โซPdV (work done ON gas); Q +ve into system, W +ve on system
Key Fact: Ideal gas: pV = nRT = NkT; Boyle pโ1/V (isothermal), Charles VโT (isobaric), Pressure pโT (isochoric)
Key Fact: Kinetic theory: pV = โ
Nm<c^2> -> p = โ
ฯ<c^2>; <c^2> = 3RT/M
Key Fact: RMS speed: c_rms = sqrt(3RT/M); M = molar mass in kg/mol
Key Fact: Degrees of freedom: monatomic 3 (translational); diatomic 5 (+2 rotational) at room temp
Key Fact: Equipartition: each quadratic term contributes ยฝkT per molecule
๐ฏ Learning Objectives
- Distinguish heat, internal energy, and temperature
- Use specific heat capacity c and specific latent heat L
- Apply first law: DeltaU = Q + W (sign conventions)
- Use ideal gas laws: Boyle, Charles, Pressure, Combined, PV = nRT
- Understand kinetic theory: pressure from molecular collisions
- Relate microscopic (molecular) to macroscopic (PV=nRT)
- Calculate root-mean-square speed: c_rms = sqrt(3RT/M)
- Understand degrees of freedom and equipartition of energy
๐ก Worked Example
Exam-Style Question
Question: 2 moles of ideal gas at 300 K compressed isothermally from 0.02 m^3 to 0.01 m^3. Find work done
Model Answer:
Isothermal: W = โซPdV = โซ(nRT/V)dV = nRT ln(Vโ/Vโ) = 2x8.31x300xln(0.5) = -3457 J. Work done ON gas = +3457 J
โ Practice Questions
Questions:
- Heat to raise 500 g water from 20 deg C to 80 deg C (c=4180)
- 1 mole gas at 27 deg C, V=0.022 m^3. Find pressure
- Explain why C_p > C_v for ideal gas
- RMS speed of Nโ at 300 K (M=0.028 kg/mol)
- Derive pV = โ Nm<c^2> from momentum change on wall
๐ฌ Video Resources
- Thermal Physics - Overview -- YouTube Search
- Thermal Physics - Exam Questions -- YouTube Search
๐ Past Papers & Exam Resources
๐ Further Reading & Resources
- Physics & Maths Tutor - Thermal Physics -- Free notes, worksheets, and past paper questions by topic
- Dr Frost Maths - Thermal Physics -- Free resources, slides, and interactive questions
- BBC Bitesize - Thermal Physics -- BBC Bitesize revision resources
๐ Lesson Plan (50 minutes)
- Starter (5 min): Recall prior knowledge of thermal physics with quick questions.
- Teaching (15 min): Work through each of the learning objectives, explaining principles step by step.
- Key points review (5 min): Revisit the key points together, confirming understanding.
- Worked example (10 min): Model the example question: 2 moles of ideal gas at 300 K compressed isothermally from 0.02 m^3 to 0.01 m^3. Find work done. Solution: Isothermal: W = โซPdV = โซ(nRT/V)dV = nRT ln(Vโ/Vโ) = 2x8.31x300xln(0.5) = -3457 J. Work done ON gas = +3457 J
- Practice (10 min): Students attempt the practice questions independently; circulate and support.
- Plenary (5 min): Review answers and address misconceptions.
๐ Homework
- Heat to raise 500 g water from 20 deg C to 80 deg C (c=4180)
- 1 mole gas at 27 deg C, V=0.022 m^3. Find pressure
- Explain why C_p > C_v for ideal gas
- RMS speed of Nโ at 300 K (M=0.028 kg/mol)
- Derive pV = โ Nm<c^2> from momentum change on wall
๐งพ Assessment
Check practice answers against the model answer; use the built-in practice questions as formative assessment.