Definitions: Define the Following Terms And/Or Concepts

Thermal Energy Study Guide Name: ______

8th Grade PSI

Definitions: Define the following terms and/or concepts.

1. Temperature

2. Kinetic Energy

3. Thermal expansion

4. Thermal contraction

5. Potential Energy (between molecules)

6. Thermal Energy

7. Heat

8. Thermal Equilibrium

9. Conduction

10. Radiation

11. Convection

12. Conductors

13. Insulators

14. Specific heat

15. Thermodynamics

16. Work

17. 1st law of thermodynamics

18. 2nd law of thermodynamics

19. Entropy

20. Heat engine

Multiple Choice: Select the answer choice that best completes the statement or answers the question.

21. When a liquid is cooled, the liquid molecules

a. spread farther apart.

b. move slower than before.

c. experience thermal contraction.

d. increase their kinetic energy.

22. This type of heat transfer can occur in outer space.

a. Conduction

b. Convection

c. Radiation

d. Entropy

23. An insulator is a material that has molecules that

a. are closely packed together.

b. move easily past one another.

c. do not transfer heat easily.

d. will shrink when heated.

24. The following objects are all heated from 10°C to 30°C. Which object will transfer the most energy to your hand?

a. 5kg apples

b. 2kg apples

c. 5kg gold

d. 2kg gold

25. Two objects of the same material but different masses are subjected to the same thermal energy input.

a. The object with less mass will experience a greater change in temperature.

b. The object with more mass will experience a greater change in temperature.

c. They will both experience the same change in temperature.

d. It is impossible to compare their changes in temperature without knowing the specific heats of the objects.

26. All of the following are examples of conductors except ___.

a. silver

b. water

c. air

d. aluminum

27. A 80°C object and a 60°C object sit (not touching) in a 21°C environment. Which best explains what will happen?

a. Both objects will get warmer.

b. The warmer object will exchange heat with the environment at a slower rate.

c. The environment will get warmer.

d. The warmer object will cool down while the cooler object will stay the same temperature.

28. Which is an example of heat transfer by convection?

a. Touching a hot pan and burning your finger

b. Water boiling in a pot on the stove

c. Feeling the warmth of a campfire on your face

d. The sun warming the roof of a house

29. Which of the following is an example of energy conservation?

a. An apple hangs suspended from a tree.

b. A person stands on tiptoes.

c. A car waits at a red light.

d. A hockey puck slides to a stop due to friction.

30. When energy is transferred as heat, the amount of useable energy ___.

a. decreases

b. remains the same

c. increases

d. is always zero

Short Response: Answer the following thoroughly. A table of specific heats is attached for reference.

Substance / Specific Heat (J/kg °C)
Aluminum / 897
Apples / 3,300
Bricks / 800
Carbon / 709
Copper / 385
Gold / 129
Iron / 449
Mercury / 140
Steam / 1,870
Tin / 230
Water / 4,186
Wood / 1,700

31. How are temperature and kinetic energy related?

32. Describe what happens to motion and spacing of molecules when heated or cooled for a:

a. liquid

b. solid

c. gas

33. What does a thermometer measure?

34. Describe characteristics of the three temperature scales including freezing and boiling point of water for each.

35. Complete the following conversions:

a. 37°C to Fahrenheit

b. 384 Kelvin to degrees Celsius

c. -45°C to Kelvin

d. 45 °F to degrees Celsius

36. Using the ideas of thermal expansion and contraction, describe how a liquid thermometer works.

37. Recall the video shown in class of the bimetallic strip that was bent when it was heated. Explain why it bent. (HINT: Remember that the strip was made of two different metals.)

38. What state of matter has the most potential energy? The least?

39. What two types of energy do molecules possess?

40. Explain why thermal energy and temperature, though related, are different.

41. Provide an example of when two substances might have the same temperature but different thermal energy.

42. How are heat flow and temperature differences related?

43. Which will cool fastest initially in a room temperature room? Boiling water or lukewarm water?

44. Will heat flow between two objects touching that have the same temperature? Why or why not?

45. Which direction does heat flow? Give an example.

46. What are the three methods of thermal energy transfer? Give two examples of each.

47. Do all objects emit the same amount of radiation? Why or why not?

48. Conduction occurs primarily in solids. Why?

49. What is the primary difference between conductors and insulators?

50. Give several examples of conductors and insulators.

51. If you wanted water to boil quickly in a tea kettle, what kind of material would you use for the tea kettle?

52. If you wanted to maximize heat transfer, what kind of material would you use? How about if you wanted to minimize heat transfer?

53. If you have several spoons made of conducting materials and insulating materials, which will feel cooler to the touch and why?

54. Suppose you took a bite of pie that was at a certain temperature. The crust doesn’t burn you but the filling does. Using the idea of specific heat, explain why the filling burned you but the crust didn’t even though they had the same temperature.

55. State whether the variable is “inversely” or “directly” proportional to the temperature change. Provide an illustrative example for each.

a. mass

b. specific heat

c. thermal energy transferred

56. Calculate the heat input (or output) required to change the temperature of 3kg of iron by 3 degrees Celsius.

57. Calculate the final temperature of 0.020 kg of mercury that loses 500J of thermal energy and started with a temperature of 400Kelvin.

58. Calculate the change in temperature of 10kg of wood that gains 3,000J of thermal energy.

59. Give an example of the 1st law of thermodynamics in action.

60. What energy conversions are involved in a heat engine?