14. Temperature
A section of Physics, 9702
Listing 10 of 51 questions
Use Use the kinetic theory of matter to explain why melting requires energy but there is no change in temperature. Define specific latent heat of fusion. A block of ice at 0 °C has a hollow in its top surface, as illustrated in . hollow ice A mass of 160 g of water at 100 °C is poured into the hollow. The water has specific heat capacity 4.20 kJ kg–1 K–1. Some of the ice melts and the final mass of water in the hollow is 365 g. Assuming no heat gain from the atmosphere, calculate a value, in kJ kg–1, for the specific latent heat of fusion of ice. specific latent heat = …………………………. kJ kg–1 Examiner’s Use In practice, heat is gained from the atmosphere during the experiment. This means that your answer to is not the correct value for the specific latent heat. State and explain whether your value in is greater or smaller than the correct value.
9702_s07_qp_4
THEORY
2007
Paper 4, Variant 0
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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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During melting, a solid becomes liquid with little or no change in volume. Use kinetic theory to explain why, during the melting process, thermal energy is required although there is no change in temperature. An aluminium can of mass 160 g contains a mass of 330 g of warm water at a temperature of 38 °C, as illustrated in . warm water aluminium can ice A mass of 48 g of ice at –18 °C is taken from a freezer and put in to the water. The ice melts and the final temperature of the can and its contents is 23 °C. Data for the specific heat capacity c of aluminium, ice and water are given in . c / J g–1 K–1 aluminium ice water 0.910 2.10 4.18 Assuming no exchange of thermal energy with the surroundings, show that the loss in thermal energy of the can and the warm water is 2.3 × 104 J, use the information in to calculate a value L for the specific latent heat of fusion of ice. L = J g–1
9702_s18_qp_42
THEORY
2018
Paper 4, Variant 2
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State the reason why two objects that are at the same temperature are described as being in thermal equilibrium. shows the variations with temperature of the densities of mercury and of water between 0 °C and 100 °C. density temperature / °C mercury density temperature / °C water Temperature may be measured using the variation with temperature of the density of a liquid. Suggest why, for measuring temperature over this temperature range: mercury is a suitable liquid water is not a suitable liquid. A beaker contains a liquid of mass 120 g. The liquid is supplied with thermal energy at a rate of 810 W. The beaker has a mass of 42 g and a specific heat capacity of 0.84 J g–1 K–1. The beaker and the liquid are in thermal equilibrium with each other at all times and are insulated from the surroundings. shows the variation with time t of the temperature of the liquid. temperature / °C t / s State the boiling temperature, in °C, of the liquid. temperature = °C Determine the specific heat capacity, in J g–1 K–1, of the liquid. specific heat capacity = J g–1 K–1 The experiment in is repeated using water instead of the liquid in . The mass of liquid used, the power supplied, and the initial temperature are all unchanged. The specific heat capacity of water is approximately twice that of the liquid in . The boiling temperature of water is 100 °C. On , sketch the variation with time t of the temperature of the water between t = 0 and t = 60 s. Numerical calculations are not required.
9702_s23_qp_41
THEORY
2023
Paper 4, Variant 1
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State the reason why two objects that are at the same temperature are described as being in thermal equilibrium. shows the variations with temperature of the densities of mercury and of water between 0 °C and 100 °C. density temperature / °C mercury density temperature / °C water Temperature may be measured using the variation with temperature of the density of a liquid. Suggest why, for measuring temperature over this temperature range: mercury is a suitable liquid water is not a suitable liquid. A beaker contains a liquid of mass 120 g. The liquid is supplied with thermal energy at a rate of 810 W. The beaker has a mass of 42 g and a specific heat capacity of 0.84 J g–1 K–1. The beaker and the liquid are in thermal equilibrium with each other at all times and are insulated from the surroundings. shows the variation with time t of the temperature of the liquid. temperature / °C t / s State the boiling temperature, in °C, of the liquid. temperature = °C Determine the specific heat capacity, in J g–1 K–1, of the liquid. specific heat capacity = J g–1 K–1 The experiment in is repeated using water instead of the liquid in . The mass of liquid used, the power supplied, and the initial temperature are all unchanged. The specific heat capacity of water is approximately twice that of the liquid in . The boiling temperature of water is 100 °C. On , sketch the variation with time t of the temperature of the water between t = 0 and t = 60 s. Numerical calculations are not required.
9702_s23_qp_43
THEORY
2023
Paper 4, Variant 3
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A student states, quite wrongly, that temperature measures the amount of thermal energy in a body. State and explain two observations that show why this statement is incorrect. 1. 2. A thermometer and an electrical heater are inserted into holes in an aluminium block of mass 960 g, as shown in . thermometer connections to electrical circuit aluminium block The power rating of the heater is 54 W. The heater is switched on and readings of the temperature of the block are taken at regular time intervals. When the block reaches a constant temperature, the heater is switched off and then further temperature readings are taken. The variation with time t of the temperature θ of the block is shown in . t θ Suggest why the rate of rise of temperature of the block decreases to zero. After the heater has been switched off, the maximum rate of fall of temperature is 3.7 K per minute. Estimate the specific heat capacity of aluminium. specific heat capacity = J kg–1 K–1
9702_w09_qp_41
THEORY
2009
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_41
THEORY
2012
Paper 4, Variant 1
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Questions Discovered
51