14.3. Specific heat capacity and specific latent heat
A subsection of Physics, 9702, through 14. Temperature
Listing 10 of 29 questions
Define specific latent heat of fusion. A student sets up the apparatus shown in in order to investigate the melting of ice. A V + – heater pure melting ice beaker water The heater is switched on. When the pure ice is melting at a constant rate, the data shown in are collected. voltmeter reading / V ammeter reading / A initial mass of beaker plus water / g final mass of beaker plus water / g time of collection / minutes 12.8 4.60 121.5 185.0 5.00 The specific latent heat of fusion of ice is 332 J g–1. State what is observed by the student that shows that the ice is melting at a constant rate. Use the data in to determine the rate at which 1. thermal energy is transferred to the melting ice, rate = W 2. thermal energy is gained from the surroundings. rate = W
9702_w18_qp_42
THEORY
2018
Paper 4, Variant 2
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State what is meant by specific latent heat. A student determines the specific latent heat of vaporisation of a liquid using the apparatus illustrated in . V pan of balance heater liquid A + – The heater is switched on. When the liquid is boiling at a constant rate, the balance reading is noted at 2.0 minute intervals. After 10 minutes, the current in the heater is reduced and the balance readings are taken for a further 12 minutes. From time 0 to time 10.0 minutes, the mass of liquid evaporated is 56 g. Use to determine the mass of liquid evaporated from time 12.0 minutes to time 22.0 minutes. mass = g Explain why, although the power of the heater is changed, the rate of loss of thermal energy to the surroundings may be assumed to be constant. Determine a value for the specific latent heat of vaporisation L of the liquid. L = J g–1 Calculate the rate at which thermal energy is transferred to the surroundings. rate = W
9702_w19_qp_41
THEORY
2019
Paper 4, Variant 1
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State what is meant by specific latent heat. A student uses the apparatus illustrated in to determine a value for the specific latent heat of fusion of ice. A V beaker melted ice pan of balance heater ice The balance reading measures the mass of the beaker and the melted ice in the beaker. The heater is switched on and pieces of ice at 0 °C are added continuously to the funnel so that the heater is always surrounded by ice. When water drips out of the funnel at a constant rate, the balance reading is noted at 2.0 minute intervals. After 10 minutes, the current in the heater is increased and the balance readings are taken for a further 12 minutes. From time 0 to time 10.0 minutes, 65 g of ice is melted. Use to determine the mass of ice melted from time 12.0 minutes to time 22.0 minutes. mass = g Explain why, although the power of the heater is changed, the rate at which thermal energy is transferred from the surroundings to the ice is constant. Determine a value for the specific latent heat of fusion L of ice. L = J g–1 Calculate the rate at which thermal energy is transferred from the surroundings to the ice. rate = W
9702_w19_qp_42
THEORY
2019
Paper 4, Variant 2
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State what is meant by specific latent heat. A student determines the specific latent heat of vaporisation of a liquid using the apparatus illustrated in . V pan of balance heater liquid A + – The heater is switched on. When the liquid is boiling at a constant rate, the balance reading is noted at 2.0 minute intervals. After 10 minutes, the current in the heater is reduced and the balance readings are taken for a further 12 minutes. From time 0 to time 10.0 minutes, the mass of liquid evaporated is 56 g. Use to determine the mass of liquid evaporated from time 12.0 minutes to time 22.0 minutes. mass = g Explain why, although the power of the heater is changed, the rate of loss of thermal energy to the surroundings may be assumed to be constant. Determine a value for the specific latent heat of vaporisation L of the liquid. L = J g–1 Calculate the rate at which thermal energy is transferred to the surroundings. rate = W
9702_w19_qp_43
THEORY
2019
Paper 4, Variant 3
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Define specific heat capacity. Two solid blocks X and Y are made from different metals. The blocks have different initial temperatures. Block Y is initially at room temperature. The blocks are placed in direct thermal contact with each other at time t = 0. shows the variation with t of the temperatures of the two blocks. 0.5 1.0 1.5 t / min 2.0 2.5 3.0 temperature / °C X Y State three conclusions that may be drawn from . The conclusions may be qualitative or quantitative. The ratio mass of block Y mass of block X is equal to 1.3. The metal in block Y has a specific heat capacity of 901 J kg–1 K–1. Determine the specific heat capacity of the metal in block X. specific heat capacity = J kg–1 K–1
9702_w24_qp_41
THEORY
2024
Paper 4, Variant 1
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Define specific latent heat. A dish containing 7.2 × 10–5 m3 of a substance rests on a laboratory bench. The substance is initially a liquid of density 710 kg m–3. Atmospheric pressure is 1.0 × 105 Pa. The liquid is heated at its boiling point so that it completely vaporises. The increase in the internal energy of the substance during this process is 17.6 kJ. The final volume of the vapour is 0.017 m3. Show that the magnitude of the work done on the substance when it vaporises is 1.7 kJ. Use the information in to calculate the thermal energy Q, in kJ, supplied to the substance to cause it to vaporise. Q = kJ Use your answer in to determine a value for the specific latent heat of vaporisation LV, in kJ kg–1, of the substance. LV = kJ kg–1 The substance in has a specific latent heat of fusion LF. Suggest and explain whether LF is likely to be less than, the same as, or greater than the answer in .
9702_w24_qp_42
THEORY
2024
Paper 4, Variant 2
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Define specific heat capacity. Two solid blocks X and Y are made from different metals. The blocks have different initial temperatures. Block Y is initially at room temperature. The blocks are placed in direct thermal contact with each other at time t = 0. shows the variation with t of the temperatures of the two blocks. 0.5 1.0 1.5 t / min 2.0 2.5 3.0 temperature / °C X Y State three conclusions that may be drawn from . The conclusions may be qualitative or quantitative. The ratio mass of block Y mass of block X is equal to 1.3. The metal in block Y has a specific heat capacity of 901 J kg–1 K–1. Determine the specific heat capacity of the metal in block X. specific heat capacity = J kg–1 K–1
9702_w24_qp_43
THEORY
2024
Paper 4, Variant 3
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Questions Discovered
29