Thermal Properties of Matter — 50 High-Yield MCQs (NCERT / NEET)

Topics: temperature & heat, specific & latent heat, thermal expansion, heat capacity, conduction, convection, radiation, blackbody laws, ideal gases, thermometry. Correct answer shown after each question.

50 MCQs
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Heat & Temperature Specific & Latent Heat Heat Transfer Thermal Expansion
1. Temperature is a measure of:
A. Total internal energy
B. Average kinetic energy of particles
C. Heat content
D. Mass
Answer: B
2. Heat (Q) added to a system is energy transferred due to:
A. Work only
B. Temperature difference
C. Mass transfer only
D. Pressure only
Answer: B
3. Specific heat capacity (c) has SI units:
A. J/kg
B. J/kg·K
C. K/J
D. J/K
Answer: B
4. Heat required to raise mass m by temperature ΔT is Q = m c ΔT. This assumes:
A. c constant over ΔT
B. No heat losses and uniform temperature
C. Both A and B
D. Neither
Answer: C
5. Latent heat of fusion L_f is energy required to:
A. Raise temperature by 1 K
B. Convert unit mass from solid to liquid at constant temperature
C. Vaporize unit mass
D. Compress a gas
Answer: B
6. In calorimetry, specific heat of substance is found by equating:
A. Heat lost by hot body = heat gained by cold body
B. Heat gained = zero
C. Heat lost > heat gained
D. Heat lost < heat gained
Answer: A
7. Coefficient of linear expansion α relates change in length ΔL to temperature change ΔT as:
A. ΔL = α L ΔT
B. ΔL = α ΔT
C. ΔL = L / (α ΔT)
D. ΔL = α L
Answer: A
8. Approximate relation between volume expansion coefficient β and linear coefficient α for isotropic solids is:
A. β = α
B. β = 2α
C. β = 3α
D. β = α/3
Answer: C
9. Thermal stress in a rod prevented from expanding is proportional to:
A. Young's modulus × α × ΔT
B. α / E
C. ΔT only
D. E only
Answer: A
10. Heat conduction in a material is described by Fourier's law: q = −k A (dT/dx). Here k is:
A. Thermal conductivity
B. Specific heat
C. Stefan-Boltzmann constant
D. Density
Answer: A
11. SI unit of thermal conductivity k is:
A. W/m·K
B. J/kg·K
C. K/W
D. N/m
Answer: A
12. Convective heat transfer coefficient depends mainly on:
A. Fluid properties and flow conditions (velocity, viscosity)
B. Solid density only
C. Emissivity only
D. Specific heat of solid only
Answer: A
13. Stefan–Boltzmann law states power radiated per unit area of a blackbody is proportional to:
A. T
B. T^2
C. T^4
D. ln T
Answer: C
14. Stefan–Boltzmann constant σ has approximate value:
A. 5.67 × 10^-8 W·m^-2·K^-4
B. 9.8 N/kg
C. 6.63 × 10^-34 J·s
D. 1.38 × 10^-23 J/K
Answer: A
15. Emissivity of a perfect blackbody is:
A. 0
B. 0.5
C. 1
D. >1
Answer: C
16. Wien's displacement law gives wavelength of maximum emission λ_max proportional to:
A. 1/T
B. T
C. T^2
D. T^4
Answer: A
17. Newton's law of cooling states that rate of cooling is proportional to:
A. Temperature of object
B. Temperature difference between object and surroundings
C. Square of temperature difference
D. ln of temperature
Answer: B
18. Specific heat at constant volume (C_v) for ideal monoatomic gas (per mole) equals:
A. (3/2) R
B. (5/2) R
C. R
D. 0
Answer: A
19. Relation between molar specific heats for ideal gas: C_p − C_v =
A. R
B. 0
C. 2R
D. R/2
Answer: A
20. Internal energy of ideal monoatomic gas depends on:
A. Pressure only
B. Temperature only
C. Volume only
D. Both pressure and volume
Answer: B
21. Latent heat of vaporization is generally ______ than latent heat of fusion for same substance.
A. Smaller
B. Larger
C. Same
D. Zero
Answer: B
22. Thermal conductivity of metals is generally high because:
A. High density
B. Free electrons transport heat efficiently
C. High specific heat
D. Low melting point
Answer: B
23. Thermal diffusivity α_th = k/(ρ c) measures:
A. Rate of heat conduction relative to storage
B. Specific heat only
C. Density only
D. Emissivity
Answer: A
24. Boyle's law and Charles's law combine to give the ideal gas law PV = nRT. Here R is:
A. Universal gas constant
B. Specific gas constant
C. Gas constant dependent on pressure
D. Stefan-Boltzmann constant
Answer: A
25. Anomalous expansion of water means that between 0°C and 4°C water:
A. Contracts on heating
B. Expands on heating
C. No change
D. Freezes
Answer: A
26. Heat engine's efficiency is defined as ratio of:
A. Work output to heat input
B. Heat input to work output
C. Heat rejected to heat input
D. None
Answer: A
27. For a blackbody, absorptivity equals:
A. 0
B. Emissivity (Kirchhoff's law)
C. Twice emissivity
D. 1/emissivity
Answer: B
28. Thermal contact resistance arises due to:
A. Perfect contact surfaces
B. Imperfect contact and microscopic gaps between surfaces
C. High conductivity materials only
D. Vacuum only
Answer: B
29. For a rod heated at one end, thermal waves propagate with speed dependent on:
A. Thermal diffusivity and frequency
B. Only thermal conductivity
C. Only density
D. None
Answer: A
30. Heat transfer by radiation does NOT require:
A. Medium (it can occur in vacuum)
B. Temperature difference
C. Emissivity
D. Surface area
Answer: A
31. Molar specific heat at constant pressure for diatomic ideal gas (approx, room T) is:
A. (3/2) R
B. (5/2) R
C. (7/2) R
D. R
Answer: B
32. Heat required to raise temperature of 1 kg of water by 1°C is approximately:
A. 4.18 kJ
B. 418 J
C. 1000 J
D. 1 J
Answer: A
33. When two bodies at different temperatures come into thermal contact, net heat flows from:
A. Colder to hotter
B. Hotter to colder
C. Depends on mass only
D. No net flow
Answer: B
34. Heat capacity of calorimeter must be accounted for in:
A. All calorimetry experiments
B. None
C. Only when calorimeter is ideal
D. Only at high temperatures
Answer: A
35. Conduction is dominant heat transfer mode in:
A. Vacuum
B. Stationary solids and stationary fluids
C. High-speed flows only
D. Radiation-dominated systems only
Answer: B
36. Thermal expansion mismatch between joined materials can cause:
A. Thermal stress and possible failure
B. Improved conductivity
C. No effect
D. Increased emissivity
Answer: A
37. Kirchhoff's law of thermal radiation relates emissivity and absorptivity for a body in thermal equilibrium. It implies for a body in thermal equilibrium emissivity =
A. 0
B. Absorptivity
C. 1/absorptivity
D. Emissivity independent
Answer: B
38. Heat transfer coefficient for free convection is generally ______ than for forced convection.
A. Larger
B. Smaller
C. Same
D. Infinite
Answer: B
39. Thermal radiation intensity from a grey body is less than that of a blackbody at same T by factor:
A. Emissivity
B. Absorptivity
C. Reflectivity
D. Transmissivity
Answer: A
40. When a gas expands adiabatically and reversibly, its temperature:
A. Increases
B. Decreases
C. Remains same
D. Depends on container color
Answer: B
41. Thermal conductivity of insulating materials (like wood, foam) is:
A. Very high
B. Very low
C. Same as metals
D. Infinite
Answer: B
42. In steady one-dimensional conduction through plane wall of thickness L, heat flux is proportional to:
A. Temperature difference / L
B. Temperature difference × L
C. L only
D. Temperature difference^2
Answer: A
43. Heat transfer in vacuum between two bodies occurs mainly by:
A. Conduction
B. Convection
C. Radiation
D. None
Answer: C
44. Thermal contact conductance improves when surfaces are:
A. Rough and dirty
B. Polished and clamped firmly
C. Separated by air gap
D. Coated with insulator
Answer: B
45. Specific heat of solids generally _____ with increasing temperature (at moderate ranges).
A. Decreases
B. Increases slightly then approaches Dulong–Petit limit
C. Drops to zero
D. Oscillates
Answer: B
46. When heat is added at constant pressure to an ideal gas, work done by the gas equals:
A. P ΔV
B. ΔU
C. Zero
D. n R T
Answer: A
47. Clapeyron equation relates slope of coexistence curve to latent heat. It is used to find:
A. Phase boundary slope dP/dT
B. Specific heat only
C. Thermal conductivity
D. Emissivity
Answer: A
48. When two blackbodies at different temperatures face each other, net radiative heat transfer depends on:
A. Difference of T^4 (T1^4 − T2^4)
B. Difference of T
C. Sum of temperatures
D. None
Answer: A
49. In radiation heat transfer, spectral distribution depends on:
A. Temperature only
B. Material only
C. Temperature and surface properties
D. Geometry only
Answer: C
50. Practical insulation often uses multiple layers because:
A. Multiple layers reduce conduction and radiation losses better than single thick layer
B. Single layer is always better
C. Layers increase emissivity
D. Layers reduce mass only
Answer: A