Thermal energy transfer

9.What is a vacuum?

10.Which type of thermal energy transfer is responsible for the Earth being heated by the Sun?

11.A student places a metal rod in a flame. After a few seconds, the end away from the flame becomes hot. Which process explains this?

12.A pan of water is heated on a stove. Which statement correctly describes the movement of water?

13.A metal pan with a plastic handle is used for cooking. Why is the handle made of plastic?

14.Which of the following is an example of convection?

15.Which material is the best conductor of thermal energy?

16.Which type of thermal energy transfer does not require particles?

17.A vacuum flask keeps hot drinks hot. Which method of thermal energy transfer is prevented by the vacuum layer?

18.In a convection current, what happens to the density of a fluid when it is heated?

19.A student wraps two identical metal cans with different materials: one with shiny aluminium foil and one with matt black paper. Both cans contain the same amount of hot water at the same initial temperature. After 10 minutes, which can is likely to have cooled more?

20.In an experiment to compare thermal conductivity of different materials, a student places rods of copper, iron, and glass into a beaker of hot water. Which rod would you expect to feel hottest at the end outside the water after the same time?

21.A student investigates how the colour of a surface affects the rate of cooling. They use two identical metal plates, one painted white and one painted black, both at the same initial temperature. They measure the temperature of each plate every minute. Which graph shape would you expect?

22.A student sets up an experiment to demonstrate convection in a liquid. They place a few crystals of potassium permanganate at the bottom of a beaker of cold water and then gently heat the beaker from below. What will the student observe?

23.Which of the following is a method of thermal energy transfer?

24.Conduction occurs primarily in which state of matter?

25.Which of the following is an example of a good conductor of thermal energy?

26.Which of the following is an example of a good insulator?

27.In which two states of matter does convection occur?

28.What happens to the density of a fluid when it is heated?

29.Which type of thermal energy transfer can travel through a vacuum?

30.All objects emit infrared radiation. True or false?

31.A student wraps two identical metal cans with different materials: one with shiny aluminium foil and one with matt black paper. Both cans contain the same amount of hot water. After 10 minutes, which can will have the lower temperature?

32.In an experiment to compare thermal conductivity of different materials, a student places rods of copper, iron, and glass into a beaker of hot water. Which rod will become hot at the far end first?

33.A student investigates how the colour of a surface affects the rate of cooling. They use two identical metal plates, one painted white and one painted black, both at the same initial temperature. Which plate cools faster?

34.A student sets up an experiment to demonstrate convection in a liquid. They place a few crystals of potassium permanganate at the bottom of a beaker of cold water and gently heat the bottom of the beaker. What will they observe?

35.A student sets up an experiment with a metal rod and a Bunsen burner. The rod is wrapped in three different materials: paper, cloth, and aluminium foil, each covering a section of the rod. The student heats one end of the rod and measures the temperature at the other end. Which material is expected to be the best insulator?

36.In an experiment to investigate convection, a student places a few crystals of potassium permanganate at the bottom of a beaker of water and heats the beaker gently. The purple colour is observed to rise in the centre and sink at the edges. Which statement best explains this observation?

37.A student investigates the rate of cooling of two identical metal plates, one painted matt black and the other painted shiny silver. Both plates are heated to the same initial temperature and allowed to cool in the same room. Which plate cools faster, and why?

38.A vacuum flask is designed to keep hot drinks hot. Which method of thermal energy transfer is primarily prevented by the vacuum layer?

39.In an experiment to compare thermal conductivity, four rods of equal length and thickness (copper, iron, glass, and wood) are placed in a beaker of hot water. The temperature at the far end of each rod is measured after 5 minutes. Which rod is expected to show the smallest temperature increase?

40.Which of the following is NOT one of the three methods of thermal energy transfer?

41.Conduction happens mostly in solids.

42.Metals are good conductors.

43.Convection currents happen only in liquids.

44.Thermal energy cannot be transferred through a vacuum.

45.Only hot objects emit infrared radiation.

46.Match each method of thermal energy transfer with its description.

47.Arrange the steps of convection current formation in the correct order.

48.Which of the following statements about thermal energy transfer are correct? (Select all that apply)

49.A student places a metal rod in a flame. The end away from the flame becomes hot. Which statement best explains why metals are good conductors?

50.A student places a metal rod of length 0.5 m in a flame. After 10 seconds, the temperature at the far end rises by 2°C. If a rod of the same material but 1.0 m long is used, how long will it take for the far end to rise by 2°C?

51.State three ways thermal energy can be transferred.

52.Describe why gases are good insulators.

53.Describe how a convection current forms.

54.Describe how conduction transfers thermal energy.

55.State which colour of object absorbs infrared radiation the best.

56.Describe what a vacuum is.

57.A metal rod is 0.5 m long. One end is placed in a flame. After 10 seconds, the temperature at the other end rises by 2°C. If the rod were twice as long, how many seconds would it take for the temperature at the far end to rise by 2°C, assuming the same rate of heat transfer?

58.Complete the sentences about thermal energy transfer.

59.Describe what a conductor is.

60.A metal rod has a thermal conductivity of 200 W/m·K. Its cross-sectional area is 0.002 m² and its length is 0.5 m. The hot end is at 100°C and the cold end at 20°C. Calculate the rate of thermal energy transfer (in watts) through the rod. Use the formula: Rate = k × A × (T_hot - T_cold) / length.

61.A student investigates how the colour of a surface affects the rate of cooling. Two identical metal cans are filled with hot water at 80°C. One can is painted matt black, the other shiny silver. They measure the temperature every minute for 10 minutes. Describe the expected results.

62.Describe how a convection current forms in a liquid.

63.A metal rod is 0.5 m long. One end is placed in a flame. After 10 seconds, the temperature at the other end rises by 2°C. If the rod were twice as long, how many seconds would it take for the temperature at the far end to rise by 2°C, assuming the same rate of heat transfer?

64.A metal rod has a thermal conductivity of 200 W/m·K. Its cross-sectional area is 0.002 m² and its length is 0.5 m. The hot end is at 100°C and the cold end at 20°C. Calculate the rate of thermal energy transfer (in watts) through the rod. Use the formula: Rate = k × A × (T_hot - T_cold) / length.