14.1. Thermal equilibrium
A subsection of Physics, 9702, through 14. Temperature
Listing 7 of 7 questions
Explain what is meant by the statement that two bodies are in thermal equilibrium. Suggest suitable types of thermometer, one in each case, to measure the temperature of the flame of a Bunsen burner, the change in temperature of a small crystal when it is exposed to a pulse of ultrasound energy. Some water is heated so that its temperature changes from 26.5 °C to a final temperature of 38.0 °C. State, to an appropriate number of decimal places, the change in temperature in kelvin, change = K the final temperature in kelvin. final temperature = K
9702_s16_qp_42
THEORY
2016
Paper 4, Variant 2
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Two metal spheres are in thermal equilibrium. State and explain what is meant by thermal equilibrium. An electric water heater contains a tube through which water flows at a constant rate. The water in the tube passes over a heating coil, as shown in . heating coil water out water in tube The water flows into the tube at a temperature of 18 °C. When the power of the heater is 3.8 kW, the temperature of the water at the outlet is 42 °C. The specific heat capacity of water is 4.2 J g–1 K–1. Use the data to calculate the flow rate, in g s–1, of water through the tube. flow rate = g s–1 State and explain whether your answer in is likely to be an overestimate or an underestimate of the flow rate.
9702_w12_qp_41
THEORY
2012
Paper 4, Variant 1
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Two metal spheres are in thermal equilibrium. State and explain what is meant by thermal equilibrium. An electric water heater contains a tube through which water flows at a constant rate. The water in the tube passes over a heating coil, as shown in . heating coil water out water in tube The water flows into the tube at a temperature of 18 °C. When the power of the heater is 3.8 kW, the temperature of the water at the outlet is 42 °C. The specific heat capacity of water is 4.2 J g–1 K–1. Use the data to calculate the flow rate, in g s–1, of water through the tube. flow rate = g s–1 State and explain whether your answer in is likely to be an overestimate or an underestimate of the flow rate.
9702_w12_qp_42
THEORY
2012
Paper 4, Variant 2
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Two bodies are in thermal equilibrium. State what is meant by thermal equilibrium. The temperature of a body is found to increase from 15.9 °C to 57.2 °C. Determine, in kelvin and to an appropriate number of decimal places, the rise in temperature of the body, temperature rise = K the final temperature. temperature = K An ideal gas at a constant pressure of 1.2 × 105 Pa is heated from a temperature of 290 K to a final temperature of 350 K. The change in volume of the gas is 950 cm3. The total change in kinetic energy ΔEK, measured in joules, of the gas molecules is given by the expression ΔEK = 3 2 × 1.9 × ΔT where ΔT is the change in temperature in kelvin. Determine the thermal energy required to produce the change in temperature from 290 K to 350 K. energy = J
9702_w15_qp_43
THEORY
2015
Paper 4, Variant 3
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State what may be deduced from the difference in the temperatures of two objects, the basic principle by which temperature is measured. By reference to your answer in , explain why two thermometers may not give the same temperature reading for an object. A block of aluminium of mass 670 g is heated at a constant rate of 95 W for 6.0 minutes. The specific heat capacity of aluminium is 910 J kg−1 K− 1. The initial temperature of the block is 24 °C. Assuming that no thermal energy is lost to the surroundings, show that the final temperature of the block is 80 °C. In practice, there are energy losses to the surroundings. The actual variation with time t of the temperature θ of the block is shown in . θ/ °C t / minutes 1. Use the information in to draw, on , a line to represent the temperature of the block, assuming no energy losses to the surroundings. 2. Using , calculate the total energy loss to the surroundings during the heating process. energy loss = J
9702_w17_qp_41
THEORY
2017
Paper 4, Variant 1
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State what may be deduced from the difference in the temperatures of two objects, the basic principle by which temperature is measured. By reference to your answer in , explain why two thermometers may not give the same temperature reading for an object. A block of aluminium of mass 670 g is heated at a constant rate of 95 W for 6.0 minutes. The specific heat capacity of aluminium is 910 J kg−1 K− 1. The initial temperature of the block is 24 °C. Assuming that no thermal energy is lost to the surroundings, show that the final temperature of the block is 80 °C. In practice, there are energy losses to the surroundings. The actual variation with time t of the temperature θ of the block is shown in . θ/ °C t / minutes 1. Use the information in to draw, on , a line to represent the temperature of the block, assuming no energy losses to the surroundings. 2. Using , calculate the total energy loss to the surroundings during the heating process. energy loss = J
9702_w17_qp_43
THEORY
2017
Paper 4, Variant 3
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Questions Discovered
7