P1 02 Kinetic Theory
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P1 02 Kinetic Theory 74 minutes 74 marks Q1. The drawing shows water being heated in a metal saucepan. (a) Explain, in terms of the particles in the metal, how heat energy is transferred through the base of the saucepan. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (b) Energy is transferred through the water by convection currents. Explain what happens to cause a convection current in the water. The answer has been started for you. As heat energy is transferred through the saucepan, the water particles at the bottom ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (c) Some energy is transferred from the hotplate to the air by thermal radiation. What is meant by thermal radiation? ..................................................................................................................................... ..................................................................................................................................... (1) (Total 6 marks) Q2.(a) The graph shows how the temperature of a pure substance changes as it cools from 330 °C. Explain why the temperature of the substance is constant between the points marked Jand K. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (b) A book of scientific data contains the statement: ‘The specific latent heat of fusion of pure ice is 3.3 × 105 J/kg’. What does this statement mean? ........................................................................................................................ ........................................................................................................................ (1) (c) The diagram shows one method of measuring the specific latent heat of fusion of ice in a laboratory where the temperature is 20 °C. Two funnels, A and B, contain equal amounts of crushed ice at 0 °C. The mass of melted ice from each funnel is measured after 12 minutes. The joulemeter measures the energy supplied to the heater. (i) Why is it necessary to set up funnel B to obtain an accurate result? ............................................................................................................... ............................................................................................................... ............................................................................................................... (2) (ii) The measurements taken are given in the table. Mass of melted ice collected from funnel A 63 g Mass of melted ice collected from funnel B 24 g Joulemeter reading 17160 Use the data in the table to calculate the specific latent heat of fusion of ice. ............................................................................................................... ............................................................................................................... Specific latent heat of fusion of ice = ......................................... J/kg (2) (iii) Suggest one reason why the value obtained by this method and the value given in the data book are not the same. ............................................................................................................... ............................................................................................................... (1) (Total 8 marks) Q3. (a) The diagram shows a tray of marbles being shaken from side to side. As this happens some of the marbles jump out of the tray. Explain how the tray of marbles is acting as a model for the evaporation of a liquid. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (b) Before giving an injection, a nurse dabs some alcohol onto the patient’s arm. This makes the patient’s skin feel cold. Explain what happens to make the patient’s skin feel cold. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (c) The graph shows that the molecules in a liquid do not all have the same speed. Use the information in the graph to explain why a liquid cools down when it evaporates. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (5) (Total 9 marks) Q4. Marbles inside a box can be used as a model for the particles in a solid, a liquid or a gas. Use words from the box to complete the following sentences. Each word can be used once, more than once or not at all. gas (a) liquid solid The particles in a ............................................ vibrate about fixed positions. (1) (b) The particles in a .......................................... move at high speed in any direction. (1) (c) The particles in a ............................................ are arranged in a pattern. (1) (Total 3 marks) Q5. (a) The diagrams show the arrangement of the particles in a solid and in a gas. Each circle represents one particle. (i) Complete the diagram below to show the arrangement of the particles in a liquid. (2) (ii) Explain, in terms of the particles, why gases are easy to compress. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (b) The diagram below shows the model that a science teacher used to show her students that there is a link between the temperature of a gas and the speed of the gas particles. The ball-bearings represent the gas particles. Switching the motor on makes the ballbearings move around in all directions. (i) How is the motion of the ball-bearings similar to the motion of the gas particles? ........................................................................................................................ ........................................................................................................................ (1) (ii) The faster the motor runs, the faster the ball-bearings move. Increasing the speed of the motor is like increasing the temperature of a gas. Use the model to predict what happens to the speed of the gas particles when the temperature of a gas is increased. ........................................................................................................................ ........................................................................................................................ (1) (Total 6 marks) Q6.According to kinetic theory, all matter is made up of small particles. The particles are constantly moving. Diagram 1 shows how the particles may be arranged in a solid. Diagram 1 (a) One kilogram of a gas has a much larger volume than one kilogram of a solid. Use kinetic theory to explain why. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (4) (b) Diagram 2 shows the particles in a liquid. The liquid is evaporating. Diagram 2 (i) How can you tell from Diagram 2 that the liquid is evaporating? ............................................................................................................... ............................................................................................................... (1) (ii) The temperature of the liquid in the container decreases as the liquid evaporates. Use kinetic theory to explain why. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... (3) (Total 8 marks) Q7.(a) The diagrams, X, Y and Z, show how the particles are arranged in the three states of matter. (i) Which one of the diagrams, X, Y or Z, shows the arrangement of particles in a liquid? Write the correct answer in the box. (1) (ii) Which one of the diagrams, X, Y or Z, shows the arrangement of particles in a gas? Write the correct answer in the box. (1) (b) Draw a ring around the correct answer in each box to complete each sentence. vibrating in fixed positions. (i) In a gas, the particles are moving randomly. not moving. (1) stronger than (ii) In a solid, the forces between the particles are equal to the forces between weaker than the particles in a liquid. (1) (c) The picture shows a puddle of water in a road, after a rain shower. (i) During the day, the puddle of water dries up and disappears. This happens because the water particles move from the puddle into the air. What process causes water particles to move from the puddle into the air? Draw a ring around the correct answer. condensation evaporation radiation (1) (ii) Describe one change in the weather which would cause the puddle of water to dry up faster. ............................................................................................................... ............................................................................................................... (1) (Total 6 marks) Q8.The diagram shows three cups A, B and C. Energy is transferred from hot water in the cups to the surroundings. (a) Use the correct answer from the box to complete each sentence. condensation conduction convection Energy is transferred through the walls of the cup by ....................................... . In the air around the cup, energy is transferred by ........................................... . (2) (b) Some students investigated how the rate of cooling of water in a cup depends on the surface area of the water in contact with the air. They used cups A, B and C. They poured the same volume of hot water into each cup and recorded the temperature of the water at regular time intervals. The results are shown on the graph. Time in minutes (i) What was the starting temperature of the water for each cup? Starting temperature = ........................................ °C (1) (ii) Calculate the temperature fall of the water in cup B in the first 9 minutes. ................................................................................................................ Temperature fall = ........................................ °C (2) (iii) Which cup, A, B or C, has the greatest rate of cooling? Using the graph, give a reason for your answer. ................................................................................................................ ................................................................................................................ (2) (iv) The investigation was repeated using the bowl shown in the diagram. The same starting temperature and volume of water were used. Draw on the graph in part (b) another line to show the expected result. (1) (v) After 4 hours, the temperature of the water in each of the cups and the bowl was 20°C. Suggest why the temperature does not fall below 20°C. ................................................................................................................ (1) (c) (i) The mass of water in each cup is 200 g. Calculate the energy, in joules, transferred from the water in a cup when the temperature of the water falls by 8°C. Specific heat capacity of water = 4200 J / kg°C. Use the correct equation from Section B of the Physics Equations Sheet. ................................................................................................................ ................................................................................................................ ................................................................................................................ Energy transferred = ........................................ J (3) (ii) Explain, in terms of particles, how evaporation causes the cooling of water. ................................................................................................................ ................................................................................................................ ................................................................................................................ ................................................................................................................ ................................................................................................................ ................................................................................................................ ................................................................................................................ ................................................................................................................ (4) (Total 16 marks) Q9.Solid, liquid and gas are three different states of matter. (a) Describe the difference between the solid and gas states, in terms of the arrangement and movement of their particles. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (4) (b) What is meant by ‘specific latent heat of vaporisation’? ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2) (c) While a kettle boils, 0.018 kg of water changes to steam. Calculate the amount of energy required for this change. Specific latent heat of vaporisation of water = 2.3 × 106 J / kg. Use the correct equation from Section B of the Physics Equations Sheet. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... Energy required = .................................... J (2) (d) The graph shows how temperature varies with time for a substance as it is heated. The graph is not drawn to scale. Explain what is happening to the substance in sections AB and BC of the graph. Section AB ..................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... Section BC ..................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (4) (Total 12 marks) M1. (a) ions / electrons gain (kinetic) energy accept atom / particles / molecules for ion accept ions vibrate faster accept ions vibrate with a bigger amplitude accept ions vibrate more do not accept ions move faster 1 (free) electrons transfer energy by collision with ions or energy transferred by collisions between vibrating ions 1 (b) move faster or take up more space do not accept start to move / vibrate 1 (warmer) water expands or becomes less dense (than cooler water) do not accept answers in terms of particles expanding 1 warm water rises (through colder water) or colder water falls to take its place 1 (c) transfer of energy by waves / infrared (radiation) accept rays for waves do not accept transfer of energy by electromagnetic waves ignore reference to heat 1 [6] M2.(a) latent heat is evolved / transferred 1 because (the substance is) changing from a liquid to a solid accept because (the substance is) changing state 1 (b) that 3.3 × 105 (330 000) joules of energy are needed to change 1 kg of pure ice at 0 °C to water at 0 °C accept in terms of energy evolved / transferred in changing from water to ice 1 (c) (i) acts as a control 1 allowing the amount of ice melted without the heater to be measured or allowing the amount of ice melted by the air temperature to be measured 1 (ii) using correct mass and changing to kg, ie 0.039 1 4.4 × 105 or 440 000 correct answer with or without working gains 2 marks 1 (iii) accept any sensible suggestion that would lead to less ice being melted bythe heater than expected, eg: because heater not totally covered by iceorsome energy used to warm heater itselforsome energy lost to the surroundings / funnel 1 [8] M3. (a) the marbles model / act as molecules accept atoms / particles for molecules 1 molecules leaving a liquid = evaporation or marbles leaving tray = evaporation 1 (b) to evaporate the alcohol requires energy 1 this energy is taken from the skin and the skin feels cold accept heat for energy 1 (c) there are attractive forces between molecules 1 only the fastest molecules have enough energy to break away from other molecules 1 these molecules escape from the surface of the liquid 1 therefore the average speed / energy of the remaining molecules goes down 1 the lower the average speed / energy of molecules the lower the temperature of the liquid 1 [9] M4. (a) solid 1 (b) gas 1 (c) solid 1 [3] M5. (a) (i) random distribution of circles in the box with at least 50 % of circles touching 1 random distribution of circles occupies more than 50 % of the space judged by eye 1 (ii) (large) gaps between particles accept particles do not touch accept particles are spread out 1 (so) easy to push particles closer (together) or forces between particles are negligible / none an answer in terms of number of particles is insufficient 1 (b) (i) (both are) random accept a correct description of random eg unpredictable or move around freely or in all directions they take up all the space is insufficient they are spread out is insufficient they move in straight lines is insufficient 1 (ii) (speed also) increases 1 [6] M6.(a) there are strong forces (of attraction) between the particles in a solid accept molecules / atoms for particles throughout accept bonds for forces 1 (holding) the particles close together particles in a solid are less spread out is insufficient 1 or (holding) the particles in a fixed pattern / positions but in a gas the forces between the particles are negligible accept very small / zero for negligible accept bonds for forces 1 so the particles spread out (to fill their container) accept particles are not close together gas particles are not in a fixed position is insufficient 1 (b) (i) particles are (shown) leaving (the liquid / container) accept molecules / atoms for particles throughout accept particles are escaping particles are getting further apart is insufficient 1 (ii) accept molecules / atoms for particles throughout accept speed / velocity for energy throughout particles with most energy leave the (surface of the) liquid accept fastest particles leave the liquid 1 so the mean / average energy of the remaining particles goes down 1 and the lower the average energy (of the particles) the lower the temperature (of the liquid) 1 [8] M7.(a) (i) Z 1 (ii) X 1 (b) (i) moving randomly 1 (ii) stronger than 1 (c) (i) evaporation 1 (ii) any one from: • becomes windy • temperature increases accept (becomes) sunny “the sun” alone is insufficient • less humid 1 [6] M8.(a) conduction must be in correct order 1 convection 1 (b) (i) 70 accept ± half a square (69.8 to 70.2) 1 (ii) 15 accept 14.6 to 15.4 for 2 marks allow for 1 mark 70 − 55 ecf from (b)(i) ± half a square 2 (iii) C 1 biggest drop in temperature during a given time accept it has the steepest gradient this is a dependent 1 (iv) starting at 70 °C and below graph for C must be a curve up to at least 8 minutes 1 (v) because 20 °C is room temperature accept same temperature as surroundings 1 (c) (i) 6720 correct answer with or without working gains 3 marks 6 720 000 gains 2 marks correct substitution of E = 0.2 × 4200 × 8 gains 2 marks correct substitution of E = 200 × 4200 × 8 gains 1 mark 3 (ii) the fastest particles have enough energy accept molecules for particles 1 to escape from the surface of the water 1 therefore the mean energy of the remaining particles decreases accept speed for energy 1 the lower the mean energy of particles the lower the temperature (of the water) accept speed for energy 1 [16] M9.(a) solid particles vibrate about fixed positions 1 closely packed accept regular 1 gas particles move randomly accept particles move faster accept freely for randomly 1 far apart 1 (b) amount of energy required to change the state of a substance from liquid to gas (vapour) 1 unit mass / 1 kg dependent on first marking point 1 (c) 41000 or 4.1 × 104 (J) accept 41400 or 4.14 × 104 correct substitution of 0.018 × 2.3 × 106 gains 1 mark 2 (d) AB changing state from solid to liquid / melting 1 at steady temperature dependent on first AB mark 1 BC temperature of liquid rises 1 until it reaches boiling point dependent on first BC mark 1 [12] E1. This question was very poorly answered. (a) Many candidates stated that particles start to vibrate, rather than vibrate faster. (b) Candidates confused conduction and convection and frequently wrote about particles expanding and becoming less dense. (c) Answers were generally poor. Few candidates mentioned waves, rays or infrared and many wrote about heat transferring to the air, or heat moving from hot to cold. E5. (a) (b) E6.(a) (b) (c) (ii) A poorly answered question, with only the very best students scoring both marks. Many students simply stated that there were fewer particles in a gas. (i) Students found difficulty in describing the way in which the motion of the ball bearings was similar to that of the gas particles; the difficulty was often with the language rather than the science. (ii) Some students referred to the ball bearings in the model instead of to the particles in the gas. Some students simply said that the particles moved ‘more’. There were many students who failed to attempt this question. Whilst many answers referred to the arrangement of particles in solids and gases, fewer responses referred to the forces between the particles. (b) E7.(a) (i) Students found great difficulty in drawing a representation of a liquid - many of the diagrams looking like the structure of a gas rather than a liquid. (i) Just under half of the students answered correctly in terms of particles leaving the container / liquid. Other answers seen just referred to the particles ‘rising.’ (ii) Many answers referred to particles needing energy to escape, but often just stated ‘gaining energy’, without specifying that they had more energy than the particles that remained. Very few students gained the second marking point because they did not refer to “mean / average” energy. A fair number of students gained the third mark by linking a decrease in energy to the decrease in temperature. (i) Nearly all students answered this correctly. (ii) Nearly all students answered this correctly. (i) Nearly all students answered this correctly. (ii) Nearly all students answered this correctly. (i) The majority of students correcty chose evaporation. (ii) Most students knew that if the weather became warmer or more windy the puddle of water would evaporate faster. A few students were unspecific and simply wrote “temperature” or “the Sun”. E8.(a) (b) (c) Nearly all students recognised two situations that represented conduction and convection. (i) Almost all students were able to read the starting value of temperature from a cooling curve. (ii) Nearly all students correctly calculated the temperature fall from the cooling curve. Those who got it wrong gave the value of the temperature reached rather than the change in temperature. (iii) The given graph showed the cooling curves for three cups of different crosssectional areas. Students were asked which cup showed the greatest rate of cooling. Only half of the students were able to give a reason because they did not refer to temperature drop in a given time. (iv) A diagram of a fourth container was given and students had to draw the expected cooling curve on the same axes. This was well done with four-fifths of students scoring full marks. (v) Nearly all students recognised that the lowest temperature reached after four hours was also room temperature. (i) The calculation of energy transferred from the water, where the mass of water was given in grams, was correctly done by two-thirds of the students. (ii) The explanation of evaporation causing the cooling of water was very poorly answered with half of the students scoring zero marks. Many students described convection and very few referred to the reduction in the mean energy of the particles when the most energetic had escaped from the surface of the water. Only a tenth of students scored three or four marks.
