Q3(c)(ii). Why a tyre gets hot when it is pumped
Why does a tyre get hot when air is pumped into it? Can a tyre be inflated without a rise in temperature?
Answer in brief
Each stroke compresses the air too fast for heat to escape (nearly adiabatic), so the work done raises its internal energy and temperature; yes, if compressed slowly enough for heat to leave, the tyre fills without warming.
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The full model answer
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Coversadiabatic compressionfirst law of thermodynamicsisothermal processinternal energytyre pump
All parts of Question 3
- 3(a)(i) Viscosity of air at 298 K and at 0 K10 marks
- 3(a)(ii) Boyle temperature of Ar, CH₄ and C₆H₆5 marks
- 3(b)(i) Surface tension: ethanol or dimethyl ether5 marks
- 3(b)(ii) Pressure difference across a water droplet of radius 150 nm5 marks
- 3(c)(i) Change in Helmholtz energy on reversible isothermal compression10 marks
- 3(c)(ii) Why a tyre gets hot when it is pumped5 marks
- 3(c)(iii) Pressure of O₂ over NiO at 25 °C5 marks
- 3(c)(iv) Final temperature after Joule–Thomson expansion5 marks