Temperature, Heat Transfer and Laws of Thermodynamics

Attempt the quiz above first, then review every question with its correct answer and a short explanation below.

1. Q1.The SI unit of temperature is:

   • A.degree Celsius
   • B.degree Fahrenheit
   • C.kelvin✓ Correct Answer
   • D.joule

   Explanation: Kelvin is the SI base unit for thermodynamic temperature.

2. Q2.Water boils at what temperature at standard atmospheric pressure?

   • A.0 °C
   • B.100 °C✓ Correct Answer
   • C.212 °C
   • D.37 °C

   Explanation: 100 °C equals 373 K and 212 °F.

3. Q3.0 °C corresponds to about how many kelvin?

   • A.273 K✓ Correct Answer
   • B.0 K
   • C.100 K
   • D.373 K

   Explanation: K = °C + 273.15.

4. Q4.Heat from the Sun reaches the Earth mainly by:

   • A.radiation✓ Correct Answer
   • B.conduction
   • C.convection
   • D.evaporation

   Explanation: Radiation needs no material medium.

5. Q5.Absolute zero is:

   • A.0 °C
   • B.-100 °C
   • C.0 K✓ Correct Answer
   • D.273 K

   Explanation: It equals about -273.15 °C.

6. Q6.The SI unit of specific heat capacity is:

   • A.J K^-1 only
   • B.J kg^-1 K^-1✓ Correct Answer
   • C.W m^-1
   • D.N m^-2

   Explanation: It is the heat needed to raise 1 kg by 1 K.

7. Q7.Water has its maximum density at:

   • A.0 °C
   • B.100 °C
   • C.4 °C✓ Correct Answer
   • D.-4 °C

   Explanation: This anomalous behaviour lets aquatic life survive under ice.

8. Q8.Latent heat is the heat absorbed or released during a change of state at:

   • A.rising temperature
   • B.constant temperature✓ Correct Answer
   • C.falling temperature
   • D.zero temperature

   Explanation: The energy changes the arrangement of molecules, not their average kinetic energy.

9. Q9.Convection occurs in:

   • A.liquids and gases✓ Correct Answer
   • B.solids only
   • C.a vacuum
   • D.metals only

   Explanation: It involves bulk movement of the fluid.

10. Q10.A black body is a perfect:

    • A.reflector of radiation
    • B.insulator of heat
    • C.transmitter of light
    • D.absorber and emitter of radiation✓ Correct Answer

    Explanation: Good absorbers are also good emitters (Kirchhoff).

11. Q11.The first law of thermodynamics is a statement of:

    • A.conservation of energy✓ Correct Answer
    • B.conservation of momentum
    • C.conservation of charge
    • D.increase of entropy

    Explanation: ΔU = Q - W.

12. Q12.The range of a clinical thermometer is about:

    • A.0 °C to 100 °C
    • B.-10 °C to 110 °C
    • C.35 °C to 100 °C
    • D.35 °C to 42 °C✓ Correct Answer

    Explanation: It covers the range of human body temperature.

13. Q13.The Celsius and Fahrenheit scales give the same reading at:

    • A.0 degrees
    • B.32 degrees
    • C.100 degrees
    • D.-40 degrees✓ Correct Answer

    Explanation: F = 9C/5 + 32 gives C = F = -40.

14. Q14.Mercury is used in thermometers because it:

    • A.expands uniformly with temperature✓ Correct Answer
    • B.is cheap and light
    • C.freezes at 100 °C
    • D.sticks to glass

    Explanation: It also does not wet glass and is a good conductor.

15. Q15.One calorie is approximately equal to:

    • A.1 joule
    • B.10 joules
    • C.4.18 joules✓ Correct Answer
    • D.100 joules

    Explanation: This is the mechanical equivalent of heat.

16. Q16.The silvered walls of a thermos flask reduce heat loss by:

    • A.conduction
    • B.reflecting radiation✓ Correct Answer
    • C.convection
    • D.evaporation

    Explanation: The silvered walls work by reflecting radiation back, and the vacuum gap between the double walls blocks the other modes of transfer.

17. Q17.The second law of thermodynamics (Kelvin-Planck) says that a heat engine cannot:

    • A.produce any work
    • B.absorb heat
    • C.work at all temperatures
    • D.convert all absorbed heat into work✓ Correct Answer

    Explanation: Some heat must always be rejected to a cold reservoir.

18. Q18.The efficiency of a Carnot engine working between T1 (hot) and T2 (cold) is:

    • A.T2/T1
    • B.1 - T1/T2
    • C.T1 - T2
    • D.1 - T2/T1✓ Correct Answer

    Explanation: Temperatures are in kelvin.

19. Q19.Entropy is a measure of the:

    • A.energy of a system
    • B.pressure of a system
    • C.disorder of a system✓ Correct Answer
    • D.mass of a system

    Explanation: The entropy of an isolated system never decreases.

20. Q20.The triple point of water is:

    • A.273.00 K
    • B.273.16 K✓ Correct Answer
    • C.373.15 K
    • D.0 K

    Explanation: Ice, water and vapour coexist at this temperature.