Thermal Properties of Matter for NEET UG
Heat makes things expand, warm up, melt and boil, and it travels by conduction, convection and radiation. This chapter puts numbers on all of it.
PhysicsClass 1164 MCQs3 lessons12 flashcards3 memory tricks
Practise Thermal Properties of Matter free
What you'll learn
- Thermal expansion
Calculate changes in length and volume with temperature, and explain water's unusual behaviour. - Specific heat, latent heat and calorimetry
Use Q = mcΔT and Q = mL, and solve mixing problems using heat lost = heat gained. - Heat transfer: conduction, convection, radiation
Explain the three modes of heat transfer and use the conduction and Stefan–Boltzmann laws.
Key formulas
| Linear expansion | ΔL = αL ΔT |
|---|---|
| Area expansion | ΔA = βA ΔT, β = 2α |
| Volume expansion | ΔV = γV ΔT, γ = 3α |
| Heat to change temperature | Q = mcΔT |
| Heat to change state | Q = mL |
| Calorimetry (no losses) | Heat lost by hot body = heat gained by cold body |
| Rate of conduction | H = KA(T₁ − T₂)/L |
| Stefan–Boltzmann law | Power radiated = σeAT⁴ |
Memory tricks
Conduction passes heat through a material without bulk movement; convection carries it with moving fluid; radiation needs no medium.
Rate of cooling ∝ (T − T_surroundings), for small differences. The closer to room temperature, the slower it cools.
Water contracts from 0 °C to 4 °C. The coldest water and ice float on top, so lakes freeze from the surface down and the water below stays at about 4 °C.
Try 3 NEET-style questions
Q1. The temperature of a black body rises from 27 °C to 327 °C. The power it radiates increases by a factor of
- 2
- 4
- 16
- 12
Show answer
Answer: (3) 16
In kelvin, T rises from 300 K to 600 K, doubling. By Stefan's law P ∝ T⁴, so P increases 2⁴ = 16 times.
Q2. A bimetallic strip bends when heated because
- its two metals have different coefficients of linear expansion
- one of the metals melts
- its two metals have different densities
- heat flows in only one direction through it
Show answer
Answer: (1) its two metals have different coefficients of linear expansion
The two metals expand by different amounts, so the strip bends toward the metal with the smaller coefficient.
Q3. The heat needed to raise the temperature of 2 kg of water from 20 °C to 70 °C is (specific heat 4200 J/kg °C)
- 210 kJ
- 840 kJ
- 42 kJ
- 420 kJ
Show answer
Answer: (4) 420 kJ
Q = mcΔT = 2 × 4200 × 50 = 420,000 J = 420 kJ.
Practise all 64 questions Free · explanations for every option · see where you go wrong