Consider supporting us on Patreon. Help us keep revisedeck free.
14. Temperature
A section of Physics, 9702
Listing 10 of 51 questions
A microwave cooker uses electromagnetic waves of frequency 2450 MHz. The microwaves warm the food in the cooker by causing water molecules in the food to oscillate with a large amplitude at the frequency of the microwaves. State the name given to this phenomenon. The effective microwave power of the cooker is 750 W. The temperature of a mass of 280 g of water rises from 25 °C to 98 °C in a time of 2.0 minutes. Calculate a value for the specific heat capacity of the water. specific heat capacity = J kg−1 K−1 The value of the specific heat capacity determined from the data in is greater than the accepted value. A student gives as the reason for this difference: ‘heat lost to the surroundings’. Suggest, in more detail than that given by the student, a possible reason for the difference.
9702_s14_qp_42
THEORY
2014
Paper 4, Variant 2
View
Define specific latent heat. An electrical heater is immersed in some melting ice that is contained in a funnel, as shown in . heater melting ice water The heater is switched on and, when the ice is melting at a constant rate, the mass m of ice melted in 5.0 minutes is noted, together with the power P of the heater. The power P of the heater is then increased. A new reading for the mass m of ice melted in 5.0 minutes is recorded when the ice is melting at a constant rate. Data for the power P and the mass m are shown in . power of heater P / W mass m melted in 5.0 minutes / g mass m melted per second / g s−1 Complete to determine the mass melted per second for each power of the heater. Use the data in the completed to determine 1. a value for the specific latent heat of fusion L of ice, L = J g−1 2. the rate h of thermal energy gained by the ice from the surroundings. h = W
9702_s15_qp_41
THEORY
2015
Paper 4, Variant 1
View
Define specific latent heat. An electrical heater is immersed in some melting ice that is contained in a funnel, as shown in . heater melting ice water The heater is switched on and, when the ice is melting at a constant rate, the mass m of ice melted in 5.0 minutes is noted, together with the power P of the heater. The power P of the heater is then increased. A new reading for the mass m of ice melted in 5.0 minutes is recorded when the ice is melting at a constant rate. Data for the power P and the mass m are shown in . power of heater P / W mass m melted in 5.0 minutes / g mass m melted per second / g s−1 Complete to determine the mass melted per second for each power of the heater. Use the data in the completed to determine 1. a value for the specific latent heat of fusion L of ice, L = J g−1 2. the rate h of thermal energy gained by the ice from the surroundings. h = W
9702_s15_qp_43
THEORY
2015
Paper 4, Variant 3
View
Define specific latent heat of vaporisation. The specific latent heat of vaporisation of water at atmospheric pressure of 1.0 × 105 Pa is 2.3 × 106 J kg–1. A mass of 0.37 kg of liquid water at 100 °C is provided with the thermal energy needed to vaporise all of the water at atmospheric pressure. Calculate the thermal energy q supplied to the water. q = J The mass of 1.0 mol of water is 18 g. Assume that water vapour can be considered to behave as an ideal gas. Show that the volume of water vapour produced is 0.64 m3. Assume that the initial volume of the liquid water is negligible compared with the volume of water vapour produced. Determine the magnitude of the work done by the water in expanding against the atmosphere when it vaporises. work done = J Use your answers in and to determine the increase in internal energy of the water when it vaporises at 100 °C. Explain your reasoning. increase in internal energy = J Use the first law of thermodynamics to suggest, with a reason, how the specific latent heat of vaporisation of water at a pressure greater than atmospheric pressure compares with its value at atmospheric pressure.
9702_s22_qp_42
THEORY
2022
Paper 4, Variant 2
View
Define specific latent heat of fusion. Some crushed ice at 0 °C is placed in a funnel together with an electric heater, as shown in . ××× crushed ice funnel beaker heater joule- meter supply The mass of water collected in the beaker in a measured interval of time is determined with the heater switched off. The mass is then found with the heater switched on. The energy supplied to the heater is also measured. For both measurements of the mass, water is not collected until melting occurs at a constant rate. The data shown in are obtained. mass of water / g energy supplied to heater / J time interval / min heater switched off heater switched on 16.6 64.7 10.0 5.0 State why the mass of water is determined with the heater switched off. Suggest how it can be determined that the ice is melting at a constant rate. Calculate a value for the specific latent heat of fusion of ice. latent heat = kJ kg–1
9702_w08_qp_4
THEORY
2008
Paper 4, Variant 0
View
State what is meant by specific latent heat. A beaker of boiling water is placed on the pan of a balance, as illustrated in . A V boiling water heater balance pan d.c. supply The water is maintained at its boiling point by means of a heater. The change M in the balance reading in 300 s is determined for two different input powers to the heater. The results are shown in . voltmeter reading / V ammeter reading / A M / g 11.5 14.2 5.2 6.4 5.0 9.1 Energy is supplied continuously by the heater. State where, in this experiment, 1. external work is done, 2. internal energy increases. Explain your answer. Use data in to determine the specific latent heat of vaporisation of water. specific latent heat = J g–1
9702_w17_qp_42
THEORY
2017
Paper 4, Variant 2
View
Questions Discovered
51