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11th grade The laws of thermodynamics and heat engines worksheet

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The laws of thermodynamics and heat engines

Grade 11 Science Worksheet - Challenge Me

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Circle the best answer, or write your answer on the line.

  1. A model heat engine runs between a hot side at 227 °C and a cold side at 27 °C. What is its greatest possible efficiency, to 0.1%, Ari?

  2. A model heat engine runs between a hot side at 100 °C and a cold side at 20 °C. What is its greatest possible efficiency, to 0.1%, Bo?

  3. A model heat engine runs between a hot side at 527 °C and a cold side at 127 °C. What is its greatest possible efficiency, to 0.1%, Esme?

  4. A test report says a model engine running between 100 °C and 20 °C is 60% efficient. Is that possible, Jun?

    • No: its limit is about 21%
    • Yes, if it runs long enough
    • Yes: good engines can reach 60%

  5. Which change raises a heat engine's Carnot limit, Kira?

    • A warmer cold side
    • A bigger engine at the same temperatures
    • A hotter hot side

  6. Why must the temperatures in the Carnot limit be in kelvins, Luz?

    • Kelvins are bigger units than degrees Celsius
    • The ratio must count from absolute zero
    • Celsius can't measure hot engines

  7. Noah says a car engine's waste heat is energy lost from the universe. Agree or disagree?

    • Disagree: the heat still exists in the surroundings
    • Agree: engines use up energy
    • Agree: wasted energy is gone for good

  8. Pia says a toy Stirling engine can run forever on one cup of hot water. Agree or disagree?

    • Agree: it turns the cup's heat into work again and again
    • Agree: the engine makes its own heat
    • Disagree: it stops when the cup cools to room temperature

  9. A model engine between 227 °C and 27 °C has a Carnot limit of 40%. Tests show 28%. Why is it lower, Ren?

    • Friction and heat leaks waste extra energy
    • Real engines can beat the limit
    • The limit was worked out in Celsius

  10. A model engine takes in 500 J of heat and does 140 J of work. How much heat goes to its cold side, Zee?

    • 640 J
    • 360 J
    • 140 J
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11th grade The laws of thermodynamics and heat engines worksheet – printable
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About this worksheet

The laws of thermodynamics and heat engines. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can use the first law, ΔU = Q − W (Q is heat into the gas, W is work done by it), and find work out = heat in − heat to the cold side.
  • I can state the second law: heat flows by itself from hot to cold, a refrigerator needs work, and no engine turns all its heat into work.
  • I can find efficiency from a table and the Carnot limit, 1 − Tc ÷ Th, with temperatures in kelvins only.
  • I can explain why a toy Stirling engine needs a temperature difference, and why real engines fall below the Carnot limit.

Standard: supports HS-PS3-4

Words to know

internal energy (U): The total particle energy inside a system

heat engine: A device that turns some heat flowing from hot to cold into work

hot side / cold side: Where the engine takes heat in / gives heat out

Carnot limit: The highest possible efficiency between two temperatures: 1 − Tc ÷ Th

Stirling engine: An engine that runs on a temperature difference, like a cup of hot water

Common mistakes

Your child added the heats. The work is the heat taken in minus the heat given out.

Your child added the work. Work done by the gas takes energy out, so ΔU = Q − W.

Your child counted heat alone. Internal energy changes with heat and with work: ΔU = Q − W.

Questions parents ask

What is the most common mistake with the laws of thermodynamics and heat engines?

Your child added the heats. The work is the heat taken in minus the heat given out.

Are these 11th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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