PAPER 2 THEORY QUESTIONS 1 Fig. 1.1 shows the arrangement of atoms in a solid block. Fig. 1.1 (a) End X of the block is heated. Energy is conducted to end Y, which becomes warm. (i) Explain how heat is conducted from X to Y by the atoms.... [2] (ii) Explain why the solid block expands when it is heated. (b) The block is heated and becomes a liquid. Describe the changes that occur to the arrangement and the motion of the atoms............ [2] 2 Fig. 2.1 shows a metal pan containing water on a cooker. The hotplate heats the water. Fig. 1.2 (a) (i) State the method of heat transfer through the metal pan. (ii) Describe how the molecules transfer heat through the metal pan. MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 1
(b) (i) On Fig. 2.1, draw an arrow to show the direction of movement of the water at point X.[1] (ii) Explain why the water moves in this direction.... [3] 3 Fig. 3.1 shows a metal roof. One side is facing the Sun. Fig. 3.1 (a) State the means by which thermal energy (heat) is transferred from the Sun to the Earth and explain why other means of thermal energy transfer are not involved...... [2] (b) Describe how thermal energy is transferred through the metal roof from the heated surface......... [2] (c) During the night, the metal roof loses 1.2 10 6 J of thermal energy and its temperature falls by 20 C. The specific heat capacity of the metal in the roof is 400 J / (kg C). Calculate the mass of metal in the roof. mass =... [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 2
4 Three horizontal rods are placed with one end just above a Bunsen flame. The other end of each rod is coated with wax, as shown in Fig. 4.1. Fig. 4.1 (a) Describe how you would use the apparatus to discover which rod is the best conductor of heat............ [2] (b) Two metal teapots are identical except that one is black on the outside and the other is white on the outside, as shown in Fig. 4.2. Fig. 4.2 The teapots each contain the same amount of hot water. State and explain which teapot will cool down more quickly......... [2] 5 Heat is transferred by conduction, convection and radiation. (a) (i) State which of the three methods is responsible for the transfer of heat from the Sun to the Earth. (ii) Explain why the other two methods cannot be involved in this transfer.. [2] (b) A hand feels hot when placed above a lighted match, as shown in Fig. 5.1. Explain in detail how convection causes this to happen................ [2] Fig. 5.1 MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 3
(c) Fig. 5.2 shows a layer of fibreglass placed between the ceiling of a room and the roof of a house. Fig. 5.2 Explain how the layer of fibreglass helps to keep the room warm when it is cold outside......... [2] 6 Fig. 6.1 shows a refrigerator. Fig. 6.1 Inside the pipes in the ice-box, a liquid boils and takes in latent heat. The gas condenses in the pipes at the back of the refrigerator and thermal energy (heat) leaves through the black metal fins. (a) (i) State one similarity and one difference between boiling and evaporation. (ii) Explain, in terms of the molecules involved, why latent heat is needed to boil the liquid... [5] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 4
(b) (i) Explain how the ice box at the top of the refrigerator keeps the whole of the food compartment cool. (ii) Explain why the fins are black... [4] (c) A plastic ice tray has 16 sections filled with water. When placed in the ice box, the water freezes to form ice cubes. Each section contains a mass of 20 g of water that is initially completely liquid at a temperature of 0 C. The specific latent heat of fusion of ice is 330 J/g. (i) Calculate the amount of energy that must be taken from the tray of water to enable all the water in the tray to become ice at 0 C. energy =. (ii) State why the heat capacity of the plastic tray does not affect the answer to (i). (iii) The ice box takes energy from the water at a rate of 30W. Estimate the time taken for all the water in the tray to become ice. time taken =. [6] 7 A heat pipe is a device that transmits thermal energy along its length. It can transmit energy thousands of times faster than a solid copper rod. Fig. 7.1 shows a heat pipe attached to black metal fins. The fins absorb energy from the Sun. The sealed pipe transmits this energy along its length into a tank of cold water. Fig. 7.1 MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 5
(a) (i) Describe how molecules in the copper conduct energy to the alcohol. (ii) Explain how boiling and condensation within the heat pipe cause the transfer of energy. (iii) Explain why the heat pipe is able to transfer energy at a fast rate.... [4] (b) In one minute, a mass of 25 g of alcohol condenses at the end of the heat pipe. The specific latent heat of vaporisation of alcohol is 840 J/g. (i) Define specific latent heat of vaporisation. (ii) Clculate the amount of energy released when 25 g of alcohol condenses. You may neglect any change in the temperature of the alcohol. energy =.. (iii) Calculate the maximum rise in temperature that the energy calculated in (ii) produces when used to heat 500 g of cold water. The specific heat capacity of water is 4.2 J/(g C). temperature = [6] (c) Black surfaces absorb and emit infra-red radiation better than white surfaces. (i) Describe an experiment that shows black surfaces absorb radiation better than white surfaces. (ii) Describe an experiment that shows black surfaces emit radiation better than white surfaces at the same temperature... [5] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 6
8 Fig. 8.1 shows an electric boiler in a school kitchen. Fig. 8.1 The boiler contains 35 kg of water at 22 C. The specific heat capacity of water is 4200 J / (kg C). (a) (i) Calculate the thermal energy (heat) needed to raise the temperature of the water from 22 C to its boiling point. energy = [3] (ii) The water in the boiler is heated with a 2600 W immersion heater. Calculate the minimum time for the heater to bring the water to its boiling point. time taken =. [2] (iii) Suggest one reason why the actual time is greater than the time calculated in (ii).. [1] (b) (i) The immersion heater is placed in the water at the bottom of the boiler. Explain in detail how this ensures that the thermal energy (heat) is transferred throughout the water.... [4] (ii) The boiler is made of steel and has two large plastic handles. When the water is boiling, the steel surface at X is hot while the plastic handle at Y is cool. Explain why.... [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 7
(c) Before the water reaches boiling point, water vapour is seen escaping from the boiler. (i) State the name of the process that produces this water vapour. (ii) State two differences between this process and boiling.... [2] 9 When a house is heated, energy is lost to the outside. Fig. 9.1 shows where the energy is lost from the house. Fig. 9.1 (a) (i) Calculate the percentage of the energy lost through the roof. [1] (ii) Energy is lost through the roof by conduction and from the roof by convection and by radiation. Explain in detail how this happens... [6] (iii) Fitting carpets on the floor reduces energy loss. Explain how a carpet reduces energy loss... [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 8
(b) The table gives information about three methods of reducing energy loss. (i) Calculate the values of X and Y. [2] (ii) Which one of these three methods should the house owner choose? Explain your answer... [2] (iii) State two other ways, not already mentioned, of reducing energy loss from the house... [2] 10 The Aluminium bar is placed in a small furnace. Fig. 10.1 shows how the temperature of the bar varies with time t. Fig. 10.1 (i) State what happens to the bar between t = 600 s and 1000 s. MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 9
(ii) Explain what effect the energy supplied to the bar has on its molecules between t = 0 and 1000 s. (iii) The mass of the bar is 0.030 kg and the specific heat capacity of aluminium is 880 J/(kg C). Calculate the energy supplied to the bar between t = 0 and 600 s. energy = (iv) Between t = 600 s and 1000 s the furnace supplies 30 joules of energy per second to the bar. Calculate the specific latent heat of fusion of aluminium. specific latent heat of fusion = 11 A lead bullet of mass 1.9 g is fired from a rifle in a sports club. The bullet misses the target and embeds itself in a wall behind the target. The bullet melts as it is stopped by the wall. The specific latent heat of fusion of lead is 2.2 10 4 J / kg. (a) State what is meant by melting point...... [1] (b) (i) Calculate the energy required to melt the bullet, at its melting point, without raising its temperature. energy =... [3] (ii) Assume that the energy that melts the bullet is equal to its kinetic energy just before it strikes the wall. Calculate the speed of the bullet just before it strikes the wall. speed =... [3] (iii) Suggest two reasons why the speed of the bullet as it leaves the rifle is greater than the value calculated in (ii)... [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 10
(c) Describe how the molecular structure of the lead changes as it melts............... [3] (d) On another occasion, lead bullets of twice the mass are used. One of these heavier bullets hits the wall with the speed calculated in (b)(ii). State and explain whether this bullet melts as it is stopped by the wall......... [3] 12 Fig. 12.1 shows a thermometer. Fig. 12.1 (a) Explain how to calibrate a thermometer..................... [3] (b) (i) State the range of the thermometer in Fig. 12.1. (ii) State how you know that the scale of the thermometer in Fig. 12.1 is linear. (c) Fig. 12.2 shows a thermometer which is more sensitive than the thermometer in Fig. 8.1. Only 0 C is marked on this new thermometer. On Fig. 12.2, draw the temperature markings for 10 C and 20 C. [1] Fig. 12.2 MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 11
13 Fig. 13.1 shows a laboratory thermometer. Fig. 13.1 (a) (i) State the range of the thermometer. (ii) State one change in the design of the thermometer to increase its range. (b) (i) Describe how the behaviour of a more sensitive thermometer is different from a less sensitive thermometer. (ii) State one change in the design of the thermometer to make it more sensitive. (c) Describe how a clinical thermometer differs from a laboratory thermometer. A diagram may be included in your answer............ [3] (d) (i) In the space below, draw a labelled diagram of a thermocouple thermometer. [2] (ii) State two reasons why a thermocouple thermometer is sometimes a better choice than a laboratory thermometer.... [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 12
(e) Fig. 13.2 shows a copper block of mass 1.8 kg with two holes in the top. An 80 W heater is placed in one hole and a thermometer in the other. Fig. 13.2 The heater is switched on for 5.0 minutes. Assume that no energy is lost from the block. (i) Calculate the energy supplied to the block. energy supplied =... [2] (ii) The specific heat capacity of copper is 390 J / (kg C). Calculate the rise in temperature of the block. 14 Thermal expansion can be a problem temperature rise =... [2] Fig. 14.1 Small gaps are left in railway lines and in bridges, as shown in Fig. 14.1. (a) Explain in detail why the gaps are needed......... [2] (b) State one other problem caused by thermal expansion and explain how it can be solved...... [1] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 13
15 A mercury thermometer uses the expansion of mercury to measure temperature. The thermometer is calibrated by placing it in pure melting ice, and then in steam at 100 C. This is illustrated in Fig. 15.1. Fig. 15.1 (a) State the temperature of the thermometer when it is in pure melting ice... [1] (b) The length of the mercury column is 4.0 cm in pure melting ice and 28.0 cm in the steam. Calculate the temperature for a length of 22.0 cm. temperature =... C [2] (c) The heat capacity of the thermometer is 2.4 J/ C. Calculate the amount of energy needed to heat the thermometer from the temperature of pure melting ice to 100 C. energy =... J [1] (d) State one other physical property of a substance that may be used to measure temperature... [1] 16 A student notices puddles of water on a road, as shown in Fig. 16.1. Fig. 16.1 MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 14
Later in the day, he passes the puddles again and some of the water has evaporated. (a) State two changes to the atmospheric conditions that would cause the water to evaporate faster. 1.... 2.... [2] (b) Explain, in terms of molecules, what happens during evaporation......... [2] 17 Fig. 17.1 shows the arrangement of molecules in a solid and in a liquid. Fig. 17.1 (a) State one difference between the two arrangements......... [1] (b) By writing about the forces between molecules and the motion of molecules, explain why (i) the molecules of a solid and of a liquid have different arrangements, (ii) the evaporation of a liquid cools the liquid,... [2] (iii) the rate of evaporation is greater when a liquid is hotter.... [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 15
18 Fig. 18.1 illustrates the arrangement of the molecules of a substance in its solid, liquid and gaseous states. Fig. 18.1 (a) State which arrangement, A, B or C, contains molecules with the most energy... [1] (b) Explain, in terms of the forces between the molecules and their separation, why (i) gases are easier to compress than liquids,.. [2] (ii) latent heat is needed to change the substance from solid to liquid... [2] (c) Define the term specific latent heat of fusion of a substance......... [2] MS / Sh.M / FT 12 / Gr 10/ Physics / Theory questions / Thermal physics 16