The laws of thermodynamics and heat engines

Answer Key - Grade 11 Science Worksheet - Building Confidence

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

1. 1.

   A model heat engine takes in 250 J of heat and gives 190 J of heat to its cold side. How much work does it do, Esme?

   60 J
3. 2.

   In the energy bar chart, how much work does the engine do, Jun?

   • 750 J, the bigger output bar
   • 250 J
   • 1000 J
4. 3.

   In the energy bar chart, how much heat goes to the cold side, Kira?

   Use the picture in question 2.

   • 0 J, since good engines waste nothing
   • 250 J
   • 750 J
5. 4.

   In the energy bar chart, what is the engine's efficiency, Luz?

   Use the picture in question 2.

   • 75%
   • 400%
   • 25%
6. 5.

   Which law says the energy put into a system equals the energy that leaves plus the energy stored, Milo?

   • The first law of thermodynamics
   • The second law of thermodynamics
   • Newton's first law of motion
7. 6.

   Which law says that, by itself, heat flows from hot to cold and not the other way, Noah?

   • The second law of thermodynamics
   • The first law of thermodynamics
   • Newton's third law of motion
8. 7.

   Why can't a heat engine turn all of its heat into work, Pia?

   • Some heat must flow out to the cold side
   • Work and heat use different units
   • Energy is destroyed inside the engine
9. 8.

   A toy Stirling engine sits on a cup of hot water. Why does it slow down as the water cools, Ren?

   • Its fuel tank slowly runs low as it works
   • The temperature difference shrinks
   • The water's mass drops
10. 9.

    When does a toy Stirling engine on a cup of hot water stop for good, Tala?

    • When the water reaches 50 °C
    • After exactly one minute
    • When the water reaches room temperature
11. 10.

    A toy Stirling engine can also run on a cup of ice water. Why, Zee?

    • There is still a temperature difference
    • Ice water holds more energy than the room
    • Ice gives off cold energy