al ce dse by-topic pastpaper PHYSICS ' ' I B2- Newto:n: ::>'""' -� . 7:�{� B·3- Moment of "'./1(1;!t,,' ,{ ,, ,; • "np, B4� Work, Energy6 P'o I"' .. BS- Mom1!ntum •. ·' B6- �rojectile Motion B7- Circular Motion B8-Gr,vitation DSE Physics - Section A : M.C. PA-HGl-M/02 DSE Physics - Section A : M.C. PA-HGl-M/01 HGl : Temperature, Heat and Intemal Energy HGl : Temperatw:e, Heat and Internal Energy 6. < BKCE 1989 Paper II - 20 > The following list of formulae may be found useful : A heater supplies energy to a liquid of mass 0.5 kg and specific heat capacity 4000 J kg""1 0C-1 contained in a vessel of negligible heat capacity. Amu:iw that the heat exchange with the SUIIoundings can be neglected. If the temperature of the Energy transfer during heating or cooling E= mcb.T liquid rises from 10°C to 70°C in 100 s, the power of the heater is A. 200W B. 1200W Part A : BKCE examination questions C. 1400W D. 12000W 1. < BK.CE 1980Paper II - 15> 7. <BKCE1992Paperll-20> When a mercury thermometer is immersed in melting ice and then in steam, the lengths of the mercury thread in the stem are respectively 2 cm and 22 cm. When the thermometer is put in a water bath, the length of the thread is 11 cm. What is the temperature of the water bath ? A. 40°C B. 45 °C C. 50 °C D. 55°C Heater 2. < HKCE 1984 Paper II - 13 > Water An equal quantity of heat is supplied to each of the following substances and the corresponding rises in temperature are recorded. Which of the following substances has the smallest specific heat capacity? In the diagram shown, the water is :initially at room temperature. The electric heater is switched on for 300 s and then switched off. Which of the following graphs correcily describes the variation of the reading of the thermometer ? Substance Mass (kg) Rise in temperature {°C) A Temperature/"C B. A. p 2.5 5 B. 3.0 4 r.±b: c Q R 4.5 3 . :I-. D. s 5.0 3 3. < BKCE 1986 Paper 11-16 > �:'. �--, . ,.• The heat capacity of an object depends on its 200 600 Time / s 200 400 600 (1) material (2) mass D (3) shap e . Temperature/ °C A. (1) only B. (3) only C. (1) & (2) only D. (2) & (3) only 4. <HKCE 1987 Paper II- 25 > zoo 400 600 Tbne/ s Which of the following pairs of objects have different specific heat capacities ? A. l kg ofwaterand2kgofwater 8. <BKCE 1993 Paper 11-18> B. 1 kg ofliquid naphthalene and 1 kg of solid naphthalene C. 1 kg of oil in a glass container and 1 kg of oil in a metal container An energy of 16500 J is supplied to a metal block of mass 0.5 kg and its rise in temperature is 64 "C. The specific heat D. 1 k g ofwater at 15°Cand 1 kg ofwater at30°C capacity of the metal is A . 16500x0.5 Jkg""l<>C-1 B. 16500 x 64 Jkg'"l cc-1 64+273 05 5. < HKCE 1988 Paper Il-12> C. 1650 0 Jk g-l oC-l D. 16500 Jkg""' oc-1 The graph shows the relationship between temperature and ti.me temperature / °C 64x 05 (64 + 273) X 0.5 when 1 kg ofa liquid is heated by a 500W immersion heater. Assuming no loss of heat, what is the specific heat capacity of 60 ---------------------- •• < HKCE 1993 Paper II - 16 > the liquid 1 40 Water is used as a coolant in motor car engines because A. 0.01 Jk g-1 oc-1 A water has a low specific heat capacity. B. 250 J kg-I oc-1 20 B. water has a high specific heat capacity. C. water has a low specific latent heat of vaporization. C. 420 J 1cg-1 oC-1 + 0< '----+----110--+,-- -�• time/ s D. water has a high specific latent heat of vaporization. D. 2500 J kg'"1 0C-1 0 1 20 DSE Physics - Section A : M.C. PA-HGl-M/04 DSE Physics - Section A : MC. PA-HGl-M/03 HG1 : Temperature, Heat and Internal Energy HGI : Temperature, Heat and Internal Energy 1s. <HKCE 1998 Paper n- 21 > 10. < HK.CE 1994 Paper II - 16 > Temperature / °C An equal amount of energy is supplied to each of the following substance. Which one of them has the smallest rise in 25 ----------------------- temperature ? 20 Substance Mau/kg Specific heat capacity / J kg'"1 0c-1 15 A. p 1 4200 B. Q 2 2300 10 C. R 3 2200 5 D. S 4 900 o '-----------�---+ 20 40 60 Time/s 11. <HK.CE 1995PaperlI- 18 > The graph shows the variation of the temperature of liquid with time when the liquid is heated by a 400 W heater. The mass Which of the following statements about heat is/are true ? of the liquid is 2 kg. Find the specific heat capacity of the liquid. Assume all the energy given out by the heater is absorbed (1) Heat is used to descnDe the total enetgy stored in a body, by the liquid. A. 83 Jkg""l cc-1 (2) Heat is used to descnDe the energy transferred from one body to another as a result of a temperature difference B. 480 Jkg-t oc-1 between them. 1 C. 1200 J Jcg-1 oc - (3) A body's interoal. energy is increased when it is heated. D. 2400Jicg-1 0C-1 A. (1) o,Jy B. (2) only C. (1J & (3) only 16. < BKCE 1998 Paper ll-19 > D. (2) & (3) only Which ofthe following statements about internal energy, heat and temperature is/are true? 12. < HKCE 1996 Paper n- 18 > (1) The intemal energy of a body is a measure of the total kinetic energy and pctential energy of the molecules in the body. Which of the following phenomena concerning water can be explained by its high specific heat capacity ? (1) Water is used as a coolant in car engines. (2) Two bodies ofthe same temperature always have the same amount ofintemal energy. (2) Inland areas generally have hotter summers and colder winters than coastal areas of similar latitude and altitude. (3) Heat is a measure of the energy tnmsferred from one body to another as a result of temperature difference between (3) The body temperature of human beings changes slowly even when the surrounding temperature changes sharply. the two bodies. A. (2) only B. (I) & (2) only A. (1) only C. (1) & (3) only B. (2) only D. (1), (2) & (3) C. (1) & (3) o,Jy D. (2) & (3) only 13. < HK.CE 1997 Paper II -19 > 17. <HKCE1999Paperll-16> The apparatus is used to find the specific heat capacity of a liquid. Which of the following can improve the accuracy of To power supply Thermometer the experiment? (1) Take the final temperature of the liquid immediately Cup after switching offthe power supply. (2) Cover the cup with a lid. (3) Stir the liquid throughout the experiment. Liquid A. (1) only B. (1) & (2) only C. (2) & (3) only D. (1),(2)&@) Temperature 14. < HKCE 1997 Paper n- 20 > Equal masses of liquids X, Y and Z are separately heated. The graph shows the variation of the energies absorbed by the liquids with their temperatures. Let ex, ey and cz be the specific heat capacities ofX, Y and Z respectively. Which of the An heater with a power of 100 Wis used to heat 0.3 kg ofa liquid which has a specific heat capacity of 2000 J kg-1 0C--1 • following relations is correct? Ji the initial temperature of the liquid is 23°C, find its temperature after 2 minutes. Assume all the energy given out by the heater is absorbed by the liquid. A. cx = e y>cz B. 03x2000x23x2 o cx = ey<ez A. (� + 23) °C B. ( ) c 03x2000 100 C. cx < cv = ez IO0x120x03 • 03x2000 'C C. D D. cx>cv cz ( 2000 +2 3) c 23) = . <1oox120 + DSE Physics - Section A: M.C. PA-HGl-M/06 DSE Physics - Section A : M.C. PA-HGl-M/05 HGl : Temperature, Heat and Internal Energy HG 1 : Temperature, Heat and Inte.tna1 Energy Questions 21 and 22 : The specific beat capacity of a metal is measured using the following method: 18. <BKCE 2000 Paper n- 22> An objectP bal;. a higher temperature than. another object Q. Which of the following statements is/are correct? Step 2: ! Hotmetalblock (1) The internal energy ofP must be higher than that of Q. i� /n (2) The specific heat capacity ofP must be higherthan that of Q. Cup (3) There will be a heat flow from P to Q when they are in contact. Thennometer A. (3) only B. (1) & (2) only d w"°' C. (2) & (3) only D. (1), (2) & (3) A metal block is first immersed in boiling water for some time. The block is then transferred to a cup of cold water. After a while, the temperature ofthe water is measu:red. 19. <RKCE 2000 Paperll- 20 > 21. <HKCE 2002 Paper Il- 20 > Equal amount of four difierent liquids are separately heated at the same rate. The initial temperatures of the liquids are all 20 °C. The boiling points and specific heat capacities of the liquids are shown below. 'Which one of the following liquids The result ofthe experiment is as follows : will boil first? Mass of metal block= 0.8 kg Liquid Boiling point/ 0C Specific heat capacity/ J i.g-1 0 C-1 Mass of water in the cup = 0.3 kg Initial temperature of water inthe cup = 23° C A. p 50 1000 FinaltemperatureofwaterintheCllp = 38"C B. Q 60 530 Find the specific heat capacity offue metal (m J k:g-1 CC-1). c. R 80 850 (Given: Specific heat capacity of water = 4200 J !qf1 0C- 1 ,) D. s 360 140 A. 236 B. 381 20. <HKCE 2001 Paperll-17 > c. 622 D. 9S3 22, <BXCE 2002 Paper 11-21> Immersion heater ...--Copper block The result obtained in the last question is found to be higher than the true value of the specific heat capacity of the metal. Which oftbe following is a probable reason? A. Some bot water is still adhered to the metal block when the block is transferred to the cold water. B. Some energy is lost to the sun;oundings when the metal block is transfmcd to the cold water. C. Some energy is absorbed by the cup. The apparatus shown is used to measure the specific heat capacity of a cylindrical copper block. The result of the experiment D. The temperature of the metal block is still higher than 38 °C when the final temperature of the water in the cup is is as follows : mo""""1 Mass ofcopperblock mkg Initial temperature 21 °c 23. < BKCE 2003 Paper ll-19 > Final temperature 47°c Ifthere is no heat flow between two bodes when they are in contact, then the two bodies must have the same Initial joulemeter reading R,J A. temperature. Finalj oulemeter readlllg R,J B. intemal energy. C. specific heat capacity. Which of the fol lowing expressions gives the specific heat capacity of copper in J kg·l 0C- 1 ? D. specific latent heat ofvaporization. m(Ri_ -Ri ) A. 26 24. < HKCE 2003 Paper ll- 22 > B. R,-R,_ 26m A student uses an electric kettle to heat 0.5 kg of water at 20°C. The water boils in 4 minutes. Estimate the output power of the Jrettle. The specific heat capacity of water is 4200 J kg"1 0C-1• A. 175W c. R,_ -R, 26m B. 700W C. 875W D. m(R, ·R,_) D. 1400W 26 DSE Physics - Section A : M.C. PA-HGl-M/08 DSE Physics - Section A : M.C. PA-HGl-M/07 HGl : Temperature, Heat and Int.emal Energy HG1 : Temperature, Heat and Internal Energy 30. <BKCE2010Paperll-33> 25. <HKCE2007PaperII-10> Four liquids P, Q, Rand Swith the same mass are heated Temperature/ °C The figure shows the t=pcerature-time graph oftwo objectsXand Y Temperature/ °C when they are heated at the same power. Which of the following at the same rate. The graph below shows the variation of deductions are correct ? X their temperatures with time. (I) The heat capacity ofX is smaller, Which liquid has the highest specific heat capacity? (2) IfX and Y are made of the same material, the mass of X y A. p is smaller. B. Q (3) The specific heat capacity ofXis smaller. '-------➔ o C. R A. (1)& (2) oruy Time/ minute B. (I)& (3) oruy D. S c. (2) & (3) only D. (1), (2) & (3) 26. < BKCE 2008 Paper II-35 > What physical properties does the temperature ofan object represent? 31. <HKCE201IPaperil-8> (1) A measure of the degree ofhotness of the object. Two liquidsXand Y are heated by two different heaters. The energy supplied, the mass of the liquid and the temperature (2) A measure of the intemal energy of the object. rises are recorded as follows. (3) A measure of the average kinetic energy ofthe molecules of the object Liquid¾ LiquidY A. (1)& (2) on1y :Energy supplied/ J 24000 18000 B. (I) & (3) oruy C, (2) & (3) oruy Mass/kg 0,3 02 D. (1), (2)& (3) Telllperature rise/ "C 20 25 Wbich of the following statements are correct? 27. < HK.CE 2008 Paper II -10 > (1) The heat capacity ofXis larger than that ofY. A 100 W immersion heater is used to heat 0.5 kg of water, which is thennonleter (2) The specific heat capacity ofXis larger than that of.Y. being stirred by a stirrer. After 3 minutes, the water temperature (3) Toe heat capacity ofX determined remains the same if the experiment is repeated by doubling the mass ofX increases from 25°C to 30°C. What is the estimated energy loss in this A. (!)& (2) on1y period? Given: specific heat capacity of water = 4200 J kg--1 °C-1 stin'er B. (!) & (3) on1y A. 7500 J C. (2 ) & (3) on1y B. 10500 J D. (1),(2)&(3) C. 18000 J beaker--16�.!::'.:J D. 285001 28. <HKCE2009Paperll-9> Part B : Supplemental exercise Which of the following descriptions about internal energy are correct? (1) Different masses ofwater at the same temperature lwve the same amount of.internal energy. 32. What is the advantages ofusingniercury in a liquid-in-glass thermometer? (2) A copper block has greater interoal energy when it is hot than when it is cold (l) It expands evenly with rise .in temperature. (3) Water at 0°C has greater internal energy than a block of ice of the same mass at OOC. (2) It is liquid over a convenient range. A. (1) & (2) only (3) Itis mmsparent. B. (!)& (3) on1y A. (!) & (2) only C. (2) & (3) only B. (1) & (3) only D. (!), (2) & (3) c. (2) & (3) on1y D. r), (2) & (3) 29. <BK.CE 2009 Paper II-33 > A bottle of 0.5 kg water and a bottle of 0 .75 kg water have been stored in a refrigerator for a few days. Which of the 33, Which of the following can increase the heat capacity ofa cup of water? following statements are correct? (I) Increase the mass of the water (1) The temperatures of the two bottles of water are equal. (2) Increase the temperature of the water (2) The average kinetic energy ofthe water molecules in the two bottles is equal (3) Change the water to another cup (3) The total potential en.e:rgy ofthe water molecules in the two bottles is equal A. (1) only A. (I) & (2) only B. (3) only B. (1) & (3) only C. (1) & (2) only C. (2) & (3) on1y D. (2) & (3) on1y D. (1), (2) & (3) DSE Physics - Section A : M.C. PA-HGl-M/10 DSE Physics - Section A : M.C. PA-HGl-M/09 HGl : Temperature, Heat and Jnterna1 Energy HGl : Temperature, Heat and Internal Energy 41. 34. What happens when a cup of water at room temperature is heated 'I R/fJ. (1) An increase in the total nwnber of water molecules 8.4 (2) An increase in molecular size (3) An increase in the average kinetic energy of the molecules A. (1) only 36 B. (3) only . --------------------- C. (!) & (2) only �-------�-+8!°C D. (2) & (3) only 0 100 The variation of electrical resistance can be used to determine temperature . Suppose a thermistor has resistances of 8.4 n 35. Which of the following physical properties cannot be used to measure temperature? and 3.6 0 at ice point and steam point respectively, Assume that the change of resistance with temperature is unifonn as A. Liquid volume shown in the figure . W'hat would be the temperature if the resistance of the of the metal wire is 5.8n? A. 42"C B. Resi.statlce ofmetal B. 46°C C. Mass C. 54"C D. Gas pressure D. 58°C 36. The length between the 0°Cmarkand·tbe lO0"Cmark is 20 cm. 'When the mercury level is S cm below the l00"C mark. the temperature is A. 25°C B. S0°C Part C : HKDSE examination questions c. 60°C D. 75°C 42. < BKDSE Practice Paper IA - 2 > In the figure below, a training pool B is located next to the main pool A. The training pool B has a smaller area and is 37. When a mercury thermometer is immersed in melting ice, the length of the mercury thread is 2 cm. When it is put into the shallower. If the pools are underthe sunlight at the same time, which of the following statements about the rise in the water steam above boiling water, the length of the thread is found to be 24 cm. What is the difference between each 1°C mark on temperature of the two pools is correct? Assume that the initial water temperatures of the pools are the same. the thennometer 'I A. 0.22cm B. 0.24cm training poolB C. 2.20cm D. 22.0cm main poolA 38. Heat is supplied at the same rate to equal amo1mt of water and oil placed in similar containers. The temperature of the oil rises faster. Which of the following is the possiDle reason 'I A Oil has a lower density than water . B. Oil has a higher boiling point than water. C. Oil bas a smaller specific beat capacity than water. D. Oil evaporates less readily than water. A. The water temperature of training poolB rises faster because it is shallower. B. The water temperature of training poolB rises faster beeause it has a smaller surface area. 39. It talces 8 minutes to raise the temperature of2 kg of a liquid by 40"Cusing a 2.5 kW heater . How long would it take to raise C. The watertemperature of main pool A rises faster because it is deeper. the temperature of 4 kg of the liquid by 20"Cusing a 5.0 kW heater? (Assume no heat loss to the surroundings.) D. The water temperature of Illall1 pool A rises faster because it has a largersurface area. A 2minutes B. 4minutes C. 16 minutes 43. < BKDSE Practice Paper IA - 3 > D. 32minutes Peter adds 50 g of milk at20°Cto 350 g of tea at 80°C, what is the final temperature of the mixture? Given: Specific heat capacity ofmilk = 3800 J kg -1 0C -1 40. A beaker contains 0.5 kg of water at 60°C. A cup containing 0.3 kg of water at 18°Cis poured in1D the beaker. When the Specific heat capacity oftea = 4200J kg-1 OC-1 mixture reaches the final common temperature, 200 J ofheat is lost to the surroundings. Calculate the final temperature of the mixture. Given : specific heat capacity of water is 4200 J kg-1 "C- 1 • A. 50.0°C A. 3S.6�C B. 72.5°C B. 44.2°C c. 73.l °C C. 48.5°C D. 77.4°C D. 54.2°C DSE Physics - Section A : M.C. PA-HGl-M/12 DSE Physics - Section A : M.C. PA-HGl-M/11 HGl : Temperature, Heat and Inlemlll Energy HGl : Temperature, Heat and In1emlll Energy 47. <.BKDSE2015PaperIA-2> 44. <HKDSEPracticePaperIA-1 > The graph below show how the electrical resistance R of three different circuit elements change with temperature B. Whicli X of the cireu.i.t elements can be used to measure temperature ? y 80 (1) 60 40 20 o�---------• ti, (2) Two objects Xand Y are heated separately by heaters of the same power. They are made of the same material, The graph ·�·" shows the variation of temperature 0ofX and Ywith time I. What is the ratio of mass ofXto that of Y? A. 3: 1 B. 2: I C. 1 :2 D. 2:3 ( 3) 48. <HKDSE 2020 Paper IA-2> An electric kettle which ccntains I kg of water at room temperature takes 168 s to heat up the water to boiling point. The kettle's rated value is '220 V, 2000 W'. Assume that all the electrical energy consumed by the kettle is 1Iansf<rred to the water. Which of the following statements is/are correct? Given: specificheatcapacityofwater=4200Jkg-1 'C-1 A (1) only B. C. (2) only '6,.,, (1) & (3) only (!) The initial temperatureofthewateris20 'C. (2) The resistance of the kettle's heating element is about 24 n. D. (2) & (3) only (3) Ifthe electric kettle is operated with llO V. the time taken to heat up the water to boiling point will be doubled. 45. <BKDSE2012PaperlA-1> Two metal blocks X and Y of the same mass and of initial temperatures 40 °C and 30°C respectively are in good thermal A. (!}only I I eontact as shovm.. The specific heat capacity ofXis greater than that of Y. Which statements is correct when a steady state is B. (3)only reached? Assume no heat loss to the smroundings. C. (1) and (2) only D. (!), (2) and (3) 40'C 30'C BlockX Block Y A. The temperature ofblockX is higher than that ofblock Y. B. Their temperature becomes the same and is lower than 35°C. C. Their temperature becomes the same and is higher than 35°C. D. Their temperature becomes the same is equal to 35 °C. 46. <HKDSE201SPaperlA•3> 'When two objects P and Qare in contact, heat flows fromPto Q. P must have a higher (1) temperature. (2) intemal energy. (3) specific heat capacity. A. (1) ooly B. (3) only C. (1) & (2) only D. (1) & (3) only DSE Physics • Section A : MC. Solution PA-HGl-MS/02 DSE Physics - Section A : M.C. Solution PA-HGl-MS/01 HGl : TemperatUre, Heat and Internal Energy HGl : TemperatUre, Heat and Intemal Energy HKEAA's MatkiDg Scheme is prepared for tho mad:ets' refetence. It should not be :regaroed as a set of model answetS. 6. B Students and 1eachers who are not illwh'edin tbe.znar.kmg process ate advised to int:elpretthe Madcini: Scheme with cme. By E=Pt=mcl::.T M.C. Answers P (100) = (05)(4000)(70-10) P= 1200W 1. B 11. D 21. B 31. A 41. C 2. D 12. D 22. A 32. A 42. A 7. D 3. C 13. C 23. A 33. A 43. C At time= 300 s, the heater is still hot and still transfers heat to the water 4. B 14. A 24. B 34. B 44. D :. water temperature rises fora short while as shown in C and D 5. B 15. C 25. C 35. C 45. C A short while after the heater switched off, water starts to cool down, 26. B 36. D 46. A 6. B 16. C the temperature of water drops and finally equals the initial room temperature asshowh in D. 7. D 17. D 27. A 37. A 47. C 8. C 18. A 28. C 38. C 48. C 8. C By E=mct:.T 9. B 19. B 29. A 39. B c = _!E_ = � Jkg-1 oc-1 10. C 20. C 30. A 40. B m·aT 0.5x64 M.C. Solution 9. B Water, withbigh specific heat capacity, can absorb large amoun.t of the heat in the engine. I. B :. Waterisused ascoolant. By 0 £-£a 0 11-2 0 = 45"C WO = e ioo -.e o 100 = 22-2 10. C By E=mct:.T 2. D 1 :. M'=_!_�_l_ By c=_!_oc-- m•c m·c m-!::,.T m·l::,.T :. The smallest rise in temperature corresponds to the largest product of mass and specific heat capacity. :. The smallest specific heat capacity corresponds to the largest product of mass and rise in temperature. :. R would be the substance with the smallest rise in temperature. .·. S would be the substance with the smallest specific heat capacity. 11. D 3. C X (1) lntemal energy is the total energy stored in a body, heat is a process to transfer energy. As heat capacity = mass x specific beat capacity ( C = m c) ✓ (2) It is the definition of heat Heat capacity depends on mass m and the material c but does not depend on shape. ✓ (3) When a body is heated, energy is transferred to the body and its internal energy must increase. 4. B 12. D A Same type of material (water) bas the same specific beat capacity. ✓ (1) Water has a high specific heat capacity to absorb beat in car e.ngines. ✓ B. Different states of the same substance have different specific beat capacities. C. Specific heat capacity is independent of the container ✓ (2) Since water has a high specific beat capacity, its temperature change is smaller and thus coastal areashave less change of temperature D. Specific beat capacity is independent of the temperature while inland areashave larger change of temperature between summer and winter. ✓ (3) Since human beings contain large amount ofwater and water bas a high specific heat capacity, 5. B therefore, body temperature changes more slowly than the surroundings. By B=Pt=mc!::,.T (500) (20) = (1) , (60 - 20) c = 250 J kg-1 "C-1 DSE Physics · Section A : M.C. Solution PA-HGl-MS/04 DSE Physics · Section A : M.C. Solution PA-HGl -MS/03 HG1 : Temperature, Heat and Internal Energy HGl : Temperature, Heat and Interruu Energy 20. C 13. C Since E=mcl::,,T (1) Heater is still hot and still ttansfersheat to the liquid after switched off Thus the temperature should not be taken immediately (�-R1) = mc(47-21) but should wmt for a short while until the liquid reaches the final temperature. ✓ (2) Covering the cup with a lid can reduce energy loss to surmundings and improve the aceuracy ✓ (3) Stirring can ensure uniform temperature ofthe liquid 21. B Heat lost by the metal block = heat gained by water 14. A By E""Pt = mc/J.T (0.8) '> (100- 38) - (03) (4200)(38- 23) (100)(2 x 60) - (0.3)(2000)(T- 23) Cl,= 381 J�l "C-1 T=(�+23) 0c 0.3 x2000 22. A By q,=m., c,,, !::..Tw 15. C mbMi, By E= Pt= mcliT ✓ A Ifsomehotwatcr is adhered to the metal block, l::,.Tw is greater and thus Cb is higher than the true value. .. (400)(60) = (2), (25-15) B. Ifsome energy is lost to the surroundings, !:.Tw is smaller and 1:lrus Cb should be lower than the true value. c = 1200 J kg-1 0C-1 C. Ifsome energy is absorbed by the cup, LlTw is smaller and thus ci, should be lower than the tru.e value. 16. C D. If the temperature of the metal block is stillhighertban 38°C when the water reaches 38°C, ✓ (1) It is the dclinition ofintemal. energy. heat gained by the water is smaller and thus 4.Tw is smaller :. ci, should be lower than the true value. (2) Two bodies of different masses have different internal energy even if they are at the same temperature. ✓ (3) It is the definition of heat. 23. A Heat must flow from a body ofhigher temperature to a body oflower tempetatu:re until they are at the same temperature. 17. D Ifthere is no :heat flow, the two bodies must be at the smne temperature. As E""mcAT 24. B slope = ..!!_=mco::c ST E = m c Af' = (0.5)(4200)(100-20) = 168 000 J As slope ofX > slope of Y "" slope ofZ P = §_ = 168000 = ?00W cx>ey = cz. I 4x60 18. A 25. C (1) Internal energy also depends on mass of the body and the type of material. ByE=Pt= mc!J.T (2) SinceP and Qare two different objects, they should have clifferent specific heat capacity. Slope = !J.T = t L me ec ..!. c ✓ (3) Heat would always flow from a body ofhigh temperature to another body of lower-temperature. Since R bas the smallest slope, R has the highest specific heat capacity c. 19. B By E=Pt=mc!:.T 26. B :. t = � o:: c-liT ✓ (1) Temperature is a measure of the degree ofhotness of an object. p (2) Internal energy depends on temperat'll:re, but also depends on mass, material and state. where ATis the difference oftemperatures between the boiling point and 20° C ✓ (3) Temperature and average kinetic energy ofthe molecules are int.er-related. Among the four liquids, Q has the smallest c /J.T, thus Q boils fust. DSE Physics • Section A : M.C. Solution PA-HGl-MS/06 DSE Physics - Section A : M.C. Solution PA-HGl-MS/05 HGl : Temperature, Heat and Inrernal Energy HGl : Temperature, Heat and Internal Energy 33. A 27. A ✓ (1) Heat capacity = mass x specific heat capacity Q) E = Pt= (100)(3 x 60) = 18000 J (2) Heat capacity is independent of the tempetature ofthe object Heat capacity is independent of the container "' E = m c !::.T = (0.5) (4200) (30 - 25) = 10500 J (3) @ Energy loss = 18000-10500= 7500 J 34. B 28. C (1) Total number of water molecules should remain unchanged. (1) Internal energy depends on the mass ofwater, (2) Molecular size would not in.crease when temperature is increased. water of greater mass contains more internal energy. ✓ (3) When water is heated. its temperature increases; thus the average K.E. of water mokcules increases. ✓ (2) Jntenwl energy depends on temperature, water ofhigher temperature contains more intemal. energy. 35. C ✓ (3) Internal energy depends on tlte state, ✓ A The expansion of liquid causes the liquid volume to increase with temperature water at liquid state contains more internal energy than that in solid state. ✓ B. Resistance of metal increases with temperature. X c. Mass remaios constatlt when temperature increases. 29. A ✓ D. Gas pressure in a fixed container increases with temperature. ✓ (!) After a long time, the temperature of the water should be same as the environmental temperature, i.e. temperature inside the refrigerator, thustheir temperatures should be equal 36. D ✓ (2) Average kinetic energy depends on the temperature, thustheir average KE is equal Ifthe mercury level is 5 cm below lOOoC marl., then it is 15 cm above 0 °C mark. 8 15 (3) Total PE depends on the state, and also depends on the number of molecules, By.!._=� 0=7s oc 100 £100 -£ 0 100 = 20 the bottle containing greater mass of water has more molecules, thus it has more total PE. 30. A 37. A Length of mercmy thread between 0 c mark and 100 C mark ° ° = 24 - 2 = 22 cm ✓ (1 ) ByE=Pt=CAf' :.slope= = fccl. 6.T tC C Length of mercury thread between each 1 "C marlc = � = 0.22cm ObjectXbas greater slope, thusXhas smaller beat capacity C. 100 ✓ (2) If they are made of the same material, they have the same specific heat capacity c. 38. C By C = me oc: m AI> XhasthesmallerC,Xbasthe smaller massm. By E=mc/::.T X (3) As the two objects may have different masses, their relation of specific heat capacity c C3mlot be known. a smaller value of specific heat capaci1,y c causes a greater :rise of temperature AT. 31. A 39. B ✓ (1) . C= .§._ Cx=�=1200J 0C-1 and Cy = �=720J 0C- 1 :. Cx>Cy AT 20 25 By E=Pt=mcAT ✓ (2) c = 2- .. ex= 24000 = 4000 Jkg'"tcc-t and ey= 18000 = 3600Jkg-1cc-1 :. cx>ey mct:.T t=--oc-- mAT .t = 3-.Ei..� m•AT 0.3x20 0.2x25 p p t, m, 6T, (3) Heat capacity depends on the mass. If the mass is doubled, the beat capacity will also be doubled. (8) = (2). (40). (5.0) .. t i = 4 minutes (4) (20) (2.5) 32. A 40. B ✓ (1) Mercury expands uniformly when temperature rises. Heat lost by the bot water= beat gained by the cold water + beat lost to surroundings ✓ (2) Mercury :remains as liquid at least from 0°C to 100 °c which is suitable for our daily application. .-. (O.S)(4200) (60- 0) = (0.3)(4200) (0-18) + (200) :. e= 44.2 °c X (3) Mercury is opaque. DSE Physics - Section A : M.C. Solution PA-HGl-MS/08 DSE Physics - Section A : M.C. Solution PA-HGl-MS/07 HGl : TemperatUre, Heat and Internal Energy HGl : Temperature, Heat and Internal Energy 47. C 41. C By Pt= mct:,,B 0 = S .B-S. 4 x 100 = 54°C 3.6-8.4 Since the two objects are made of the same material, they have the same specific heat capacity c. For the same time t and same power P, 42. A mx.:tny = t.0y:tl8x = (60-40):(60-20) = 20:40 = I :2 ✓ A. Since pooIB is shallower, the mass of water is Jess, by E-:. m c t:,,T, the rise of temperature is taster. B. PoolB absorbs Jess solar energy due to the SJDaller surface area. it is not the reason for the faster rise ofteinperature. C. Since pool A is deeper, the mass of water is more, thus the rise oftemperatw:e should not be faster. D. Although pool A absorbs more solar energy due to latger sur:face area, larger surlace area also implies more mass, thus fue rise oftemperature cannot be faster. 43. C By conservation of energy and assume no heat lost to the container and SUirOUil.ding air. Heat gained by the milk "" heatlost by the tea (0.050) (3800)(0-20) • (0.350)(4200) (80- 0) .. 0 = 73.1 °C 44. D (1) Since the resistance is constant and does not change with the ten:Jperature, it is not suitable. ✓ (2 ) As the resistance increases with the temperature, it is suitable to be used to measure temperature. ✓ (3) As the resistance decreases with the temperature, itis suitable to be used to measure temperatm:e. 45. C At steady state, the temperature must be the same. By conservation of energy and assume no heat lost to the surroundings. Heat lost by blockX = heat gained by block Y mcx.ATx = meyt:J'y :. ex > cv :. ATx < aTy Thus, the final temperature should be closer to 40 °C, that is, higherthan35 °C. 46. A ✓ (!) Heat must flow :from object ofhighedemperature to that oflower temperature. Thus, temperature of Pil'.lllSt be higher than that ofQ. (2) A body may have less internal energy than another body but higher temperature. Thus, no conclusion can be drawn about the internal energy ofP and Q. (3) The specific heat capacity depends on the material Different specific heat capacity would not affect the direction of flow of heat I DSE Physics - Section A : Question HGl : Temperature, Heat & Internal Energy PA-HGl - QI 02 II DSE Physics - Section A : Question HGl : Temperature, Heat & Internal Energy PA-HGl-Q/01 2. < BK.CE 1986 Paper I - 4 > The folloWUlg list of formulae may be found useful : The below figure shows the apparatus which may be used to measure the specific heat capacity ofwater. Energy transfer during heating or cooling E= mco:I' --ti Part A : BKCE examination questions 1. < HKCE 1984 Paper I - 4 > 12V O' To joulemeter TCIIlperature / °C 0 0 � Polystyrene cup Them,mn'°"' Low voltage supply Thexmoroeter (a) Draw a simple diagram to show how the apparatus can be set up for the experiment. Lid - Ill�-+-"'- LiquidX (b) The following are readings taken in the experiment: (7 marl<,) Theratingoftbe heater 12 V 40W The figure 1 above shows an experimental set-up to find the specific heat capacity of a liquid. The liquid X, contained in the Mass ofwaterused = 200 g plastic cup, is heated from room temperature by an innnersion heater. The energy transferred through the beater is measured by ajoulell1eter. The heater is switched on for 330 sand then switched off. The variation ofth.e temperature of the liquidX Initial temperature ofthe water 25.1 °C with time is plotted in a graph shown in figure 2. Final temperature of the water 53.2cc (a) After the heater is switched off. the temperailtte of the liquid rises for a while and then falls. Bxplajn why. (3 marks) Time taken to heat up the water 10 minutes (i) Calculate the specific beat capacity of water as measured from the experiment, given that the waq:t is we11-stined throughout the experiment. (b) What is the maximum increase in the tempcmtnre ofliquidX in this experiillent ? (2n,,,h) (ii) Give two reasons vvby a polystyrene cup should be used in the experiment. (c) The initial and final readings ofthejoulemeter are 74050 J and 83770 J respectively. The mass of the liquid Xis 0.2 kg. What is the specific heat capacity of the liq:uid, as fuund from this experiment 'l Assume the heat capacity of the apparatus and the heat lost to the SUIIoundings are negligible. (4 marks) (iii) Why should the water be stirred throughout the experiment ? (d) Although the plastic cup is made of poor conducting material, some energy is still lost to the swroundings. Should the (c) Descn"be, with the aid ofa diagram, a method to check whether the power output of the heater is 40 W. Show how the result obtamed in (c) be higher or lower than the true value of the specific heat capacity of the liquid X? Explam. actual power output of the heater can be calculated. (5 marks) briefly. (3 marks) Diagram (e) If a student forgets to cover the plastic cup with the lid, would he expect the maximum increase in temperature to be higher than, equal to or lowertha:o. the value obtained in (b)? Explain briefly. (3 marks) DSE Physics - Section A : Question PA-HGl - Q/04 DSE Physics - Section A : Question PA-HGI -Q/03 HGl : Temperature, Heat & Intern.al Energy HGl : Temperature, Heat & Intern.al Energy 4. <HKCE1991PaperI-5> 3. < HKCE 1987 Paper I- 6 > The specific heat capacity of water is 4200 J kg-1 0 C-1 . (a) What does this statement mean? Ca,bon dioxide Ak FlaskA FI,,kB (b) Describe briefly, with the aid ofa diagram, an experiment to measure the specific heat capacity of water. (5 madcs) The figure above shows the appa?atus of an experiment to study the abscn:ption of solar energy by gases. Identical flasks A andB are filled with carbon dioxide and air respectively. They are placed under sunlight and their temperatures are taken at Diagram. 3-nrillute intervals. The results are as follows: TllllC / murutes 0 3 6 9 12 15 18 T....,..,erature :inA I °C 28.0 38.4 44.0 46.2 47.8 48.8 48.8 TFfflnmture in BI °C 28.0 37.7 41.8 43.7 452 46.0 46.0 (a) Using a scale that 2 cm represents 5 C mi 2 cm represents 3 minutes, plot the temperature-time graphs for carbon ° dioxide and air on the same graph paper. (5 marks) (c) A kettle with 1.6 kg of water is placed on top of an electric heater at 1000 W. It takes 14 minutes for the temperature of the water to increase from 2o<'C to 100°C. (i) Find (I) the energy released by the heater, and (II) the energy absorbed by the water d>Jring that time. (ii) Give TWO reasons to account fur the difference of the values you obtained in (i) and (ti). (b) Why does each of the gases reach a steady temperature? (2.marks) (d) The specific heat capacity of water is higher than most of the other liquids. Name TWO practical importance of this in daily life. (2 marks) (c) The mass of carbon dioxide in :flask A is 0.00196 kg and the mass of air in flask B is 0.00125 kg. The specific heat capacities of carbon dioxide and air are 640 J kg-1 0C-1 and 740 J kg- 1 0C-1 respectively. Which flask of gas gains more energy to reach its steady temperature ? Show your calculations. (5 Jlll!IXS) I DSE Physics · Section A : Question HG 1 : Temperature, Heat & Internal Energy PA-HGl -Q / 06 II . DSE Physics - Section A : Question HGl : Temperature, Heat & Intemal Energy PA-HGl -Q / 05 6. < BK.CE 2000 Paper I- 8 > 4. (d) Each year the amount ofcarbon dioxide in the atmosphere is increased by billions of tons. (i) Suggest a possi'ole effect on the mean temperature of the Earth. (ii) Suggest two methods to reduce the amount ofcarbon dioxide in the atmosphere. (2 marks) lvJ. electric heater has two settings : 'Low' and 'High'. The power output ofthe heater is 1400 W at the 'Low' setting and 2200 Wat the 'High' setting. The heater is used to cook an egg. The egg is first put into apot contaming 1 kg ofwater and the heater is operated at the 'High' setting. (See the above figure.) The temperature of the wate.r is recorded every 30 s and th e following results are obtained: --- Ti!lle tis 0 30 60 90 120 150 180 210 240 5. <BI(CE 1992 :Paperl-4 > T 0/ °C 27 32 44 57 69 81 92 98 100 A student uses the experimental set-up shown in the below figure To power supply to :find the specific heat cap.acity of a metal. The cylindrical metal (a) Using a scale ofl cm to 5 °C and 1 cmto 15 s,plotagraphof 0 agaiasttongrapbpaper. (4marks) block is heatedby an .immetsion heater of UDknown power. �t}:t�:'}1:X� The following results are obtained: Mass oflhetal block 1 kg Initial temperature ofmetal block "' 29°C Cyl:indri¢al metal block �;;{}<JBftf?:f· ° Final temperature ofmetal block 41 C Energy supplied by the heater 12300 J (a) Describe, with the help of a diagram, amcthodto measure the energy supplied by the heater. (4,,,_) (b) Calco.late the specific heat capacity of the metal. (c) The value obtained in (b) is found to be higher than the actual specific heat capacity of the metal Suggest a reason for this andexplain your answer briefly. {3 marks) (d) Suggest TWO improvements on the set-up to increase the accuracy ofthe experiment. :):i:j:J: (e) Is the above method suitable for finding the specific heat capacity of wood? Explain briefly. -++' +.+ DSE Physics - Section A : Question PA-BGl-Q/08 DSE Physics - Section A : Question PA-HGl-Q/07 HG1 : Temperature, Heat & Internal Energy HGl : Temperature, Heat & Internal Energy 7. {b) (i) Plot a graph ofE agai.nstm in the following figure. A scale of 1 cm to 0.5 kJ and 0. 025 kg is used. 6. (b) (i) Findtheenergysuppliedbytbeheaterfrom t = O to t '= 240s. (2 m,,ks) (Ii) Fmd the energy absorbed by the water from t""O to t=240 s. (Note: Specific heat capacity of water - 4200 Jkg""1 0C-l .) (2m,,ks) (iii) State two reasons to account for the difference between your answers in (i) and (Ii). (c) After the water boils., the heater is turned to the 'Ulw' setting and the water still boils afterwards. A student argues that this will lengthen the time required to cook the egg. Do you agree? Explain your answer. (3 marks) (d) lfless water is used in the above cooking process, on the graph in (a), draw the graph of &against tyou expect to obtain. (2nmk,) 7. <HKCE 2008 Paper 1-4> A student pezfo;rms an experiment with the setup in the below Figure to measure the specific heat capacity of a IiquidX The joul.emete:r in the figure is used to measure energy consumed by the immersion heater. joulemeter thennommr (ii) Using the graph plotted in (b)(i), find the specific heat capacity of liquidX. (3 m,,ks) to power supply input well :lns'\llated container liquu!X The increase in the reading of the joulemeter (E) for an increase of temperature of 10° C for different mass (m) ofliquidXis (Iii) Estimate the heat absorbed by the apparatus. (1 mark) recorded in the Table below. E/kJ 1.6 2.9 4.1 53 m/kg 0.05 0.10 0.15 0.20 (iv) If the experiment is repeated with liquid Y with a smaller specific heat capacity than liquid X and the increase in (a) State the importance of using a "well insulated" container in fue experiment temperature is also 10°C, sketch a graph ofE against m you would expect to obtain in the above figw-e, and label it asL. (2rnarks) DSE Physics - Section A : Question PA-HGl-Q/10 DSE Physics - Section A : Question PA-HGl-Q /09 HGl: Temperature, Heat & Intemal.Energy I HGl : Temperature, Heat & Internal Energy 9. <BKDSE2013PaperIB-1> Part B : HKDSE examination questions storage tank 8. < HKDSE Sample Paper m - 9 > Flgwel The Figure above shows a microwave oven. Mazy wants to conduct an experiment to estimate the useful output power of the A solar water heater shown in Figure 1 is installed on the rooftop of a house. During the day, the heater heats up 1.5 m3- of oven. She is provided with the apparatus and material shown in the Figure below. water to 80° C. At, night, the hot water in the storage tank is circulated to the radiators (see Figure 2) in different rooms of the house to keep the rooms wann. ,,_, Given : density ofwater= 1000 kg m- 3 specific heat capacity of water= 4200 J kg"l 0C-1 (a) Given that 15% of the energy is lost during the transfer of water, how much heat can be released from the system to the (a) Describe how Mary should conduct the experiment. Specify all measurements that Mary has to take. State EITHER rooms when the water temperature drops to 60"C ? (3 marks) one precaution taken OR one assumption made when conducting this experiment. Write down an equation for calculating the useful output power. (5 marks) (b) Given that during night time the radiators maintain an average output power of 4.5 kW, how long can the radiators :maintain this average power until the water temperature in the system drops to 60 °C ? Give your answer in hours. (2""'"") (b) The value obtained by Mary is found to be smaller than the specified power of the oven. Suggest one possible reason to account for this difference. (1 mark) (c) The rate of heat released by the solar water heating system during the time period calcu1ated in (b) is in fact not constant and gradually drops. Explain why this is so. (1 mark) (c) Explain whether increasing the mass ofwater used in the experiment would improve the accuracy of the experiment (J=rl<) DSE Physics - Section A : Question PA-HGl-Q/12 DSE Physics - Section A : Question PA-HGl-Q/11 HG 1 : Temperature, Heat & Jntemal Energy HGl : Temperature, Heat & Jntemal Energy 11. <.RKDSE 2015 Paper IB-1 > 10. < IIKDSE 2014 Paper m -1 > A metallic resistance theonometer is cahOrated at standard atmospheric pressure for the melting point of ice and the steam temperature/ °C point ofboiling "Water. The dotted calibration line in the figure below represents how the resistance of the thenno:ineter varies with temperature if a linear resistanc�temperature relationship is assumed. The solid curve shows how the resistance of the thermometer actwJ.ly varies with temperature. The deviation of the curve from linearity has been exaggerated in the figure. To power resistance "'!'Ply --- --- metallic resistance ___.___________,.____..,.. temperature/ °C -20 20 40 60 80 JOO 120 (a) (i) Using the resistances at the cahDration points tabulated below, calculate the expected resistance at 60 °C if the time /min resistance varies linearly with temperature. (2 marks) The above figure shows an experimental set-up to find the specific heat capacity of a metal. The metal block is wrapped by insulatingmaterial. A heater is connected to a power supply. It is switched on when the temperature of the metal block is temperature / "C resistance/ n 20°c and then switched offwhen the temperature reaches 43 °C. The graph shows the variation of the temperature of the metal blo ck with time. 0 102.00 (a) Use the graph to find the duration time that the heater is switched on. (I =kl 100 140.51 (b) After the heater is switched off; the temperature of the metal block continues to rise for a while. Explain why. (1 mark) (c) Given: mass o fthemetal block= 0.80kg; heater voltage = 12 V; heaterCWTent=4.0A. (ii) Now if the resistance of the resistance thennometer is the value found in (a) (i), is the actual temperature higher than. lower than or equal to 60"C? (1 mark) (i) By considering the maximum temperature rise o f the metal block, calculate the specific heat capacity of the metal as found from the experiment. (2 i:narks) (b) In an experiment to detennine the specific heat capacity of water c,.., Peter used this cahOrated resistance thermometer to measure the temperature of water being heated from 0 °C to 60"C. Heating was stopped when this thermometer's resistance reached the value found in (a) (i). Assuming negligible heat exchange with the surroundings:, no error in (ii) Would your result be the same, higher, or lower than the actual value of the specific heat capacity of the metal ? measurl:tig the energy supplied and the mass ofwater, explain whether the experimental value of c., found is higher than, Explrun . (2maw) lower than or the same as the actual value. (2 mmks) (d) This method is not suitable for measuring the specific heat capacity of a glass block. Explain. (1 marlc) DSE Physics-SectiorA :Question PA-HGl-Q/14 DSE Physics-SectiorA :Question PA-HGl -QI 13 HG 1 : Tffi!)i,rature, Heat & IntemaJEnergy HG 1 :Tffil'.llIB1:ure; Heat & IntemalEnergy 13. <HIDSE 2017PaperlB-l> 12 < HKDSE 2016 Paper lB-1> c Read 1i:e folloril:g x:assage ah::ut .n1 thenrmeter and azl.SllleI'. 1i:e � 1lBt fulla The foll.o,m:g ei:perinmta1 iia'rs a:e ll[O'lided tr� 1re � rest OJP:city ofbrooze o!,, abrmze ,${:iEre' of mass 0.80 kg hung wi1h a thnHi a: room ·teiiera:lllre· 'J; o The teqeratute·, of sil � with d!ptb_ and ibis infCl1oatioo. is iq:ortant t> :fmers aD.i �. To DE:aSUre s:il � a: d:¢hs � ti 1re grc(md, smm. 1te btlb of a 1:henoctooter , is b:lrie::1 :in 1re ru Tlie stem of 1h a JDl.ystynre ClP' � 0. 50 kg of IIErler a!: room �tute 'Io 1iErlro etei' is hintoo·:!i:reasy :rarlirg Figure 1a is a s:iielEatic diagram and Figure lb shows a Jinto of a ID a water l:si:h mintairm at 80 · C t' . ...,.. atl,aro,,eter l tellp::rature � A, ,i& lali �i,)';,11.1 \lll,l'§:lj_F a. a-1 (a) Descril:e 1i:e prccedures of 1i:e �t and stile TWO � �- t:, 1:e ta<aJ. Write down an Figure 1 e:ie,ticn :fir fmiing /:'\! Slil Given: :;prific b:st Oll,lcity of water= 4200 Jkg-1 ·c-:1 tll mrts) Oil For � gnster 1hn 30 CD, a sifd. pi:i:e is drivm into 1re sil '(Fitv,:ri �; and a � the:ranneter wit a Jlt)'il:di\'e g1¥ c:ase is lCJl!leted in!o 'Ire sbel pi:i:e (Figure ai). The btlb of 1re therll:cmrter is embed ed in� ax {Pip' _ 3:i). To red 11'.e � 1l:e thenoc:meter is liflai wt of 1ie se1. pii:e by JJJ,llirg 1i:e dain ,roundsmfuce protective Slil glass case cham Figure 2 ,' tbern,omete,c bulb embedded lD.para:fljnwax (b) The valoo of o. fcmi in 1te �- in® is IC11ler"· fun 1i:e ailJal '\o'Blm.. &,ipJain_ (a) A.s shown in Figure lb 1i:e rulb of 11:e sil �ter is vezy 1::1:JJ;: compared ti 1m:e of common il:euDictexs. Sq;igest a reas:o :li:r 1bis dsig:i. 0 mark) DSE Physics - Section A : Question Solution PA-HGl-QS/01 DSE Physics - Section A : Question PA-HGl-Q/15 HGl : Temperature, Heat & Internal Energy HGl : TOO\PCfature, Heat & Internal Energy BXBAA's Marking Scheme is pmpan,a. for the :mas:kcr&' tcfe:reince. It should not be regarded as a set ofmodel an&wen. Students and teachers who are not involved in the ma:rkmg process are advised to intetpret the Marking Scheme wi1h care. 13. (b) On a certain moming, the air temperature is 15°C. An observer takes a measurement of the soil temperature at 1 m deep . The thcnnometer ICading is 20°C. It is given that the mass of the paraffin wax enclosing the thennometer bulb is Question Solution O.D15 kg, and the specific heat capacity ofparaffin wax.is 2.9 x 103 Jkg"" 1 0c-,I. (i) Calculate the energy loss of the paraffin wax. as it cools down to the air temperature. (2=ks) I. (a) After switching oft; the heater is still.hot. [!] Energy continues to transfer to the liquid. UJ After a 'While, heat is lost to the SUtTouru:Iings, thus tempetature drops. [I] (b) Mmcimlltllincreaseintemperature = 86-32 [I] = s4°c [!] (ti) It is known that the paraffin wax enclosing the bulb of the thennometer gains or loses energy at a constant rate of 0.5 J s�t, estimate the time taken for the paraffin wax to reach the airtctnperature a:fier the tbemwmeter is lifted out of the soil. (2 m arks) (o) E = mc/':..T [I] (83no - 74050) = (0.2) c (54) [2] :. C""900J kg-10c-1 [I] (d) ffigho, [!] (iii)· If there is no paraffin wax enclosing the bulb ofthe thermometer, explain.how the thennozneterreading as recorded by the observer is affected. (2 marks) More energy is required to raise the same temperature of the liquid. [2] (e) Sm,llo, [I] More energy is lost to surroundings [2] 2. (a) <heater.immersed in water> [I] < heater connected to power supply > [I] < therroometer immersed in water> [I] (b) (i) Heat transferred to water : E = 40x60x10 ""'240001 Increase in temperature : b.T = 53.2-25.1 ""28.1°C [I] By E=mc!J.T [I] (24000) = {0.2) C (28.1) ;, C = 4270 Jkg'°1 0C-l [I] 14 <HKDSE2019PaperlB-l> (ii) A student used the following method to find the heater's operating power P: remove the heater from tbe container and record the temperature of fue 16 kg of soup after IO minutes. It is. found that the (•) AniuSlllatedcontainerofnegligibte 11,stcapscity- u kgofteaara leo1!>...-ofoO•C. temperature has dropped 9 °C Estimate P< (3 marks) (i) What ma,s of i<e at 0 'C ,mould be add,d to tho tea so that lb, :liD!II temp"""""' of ibe mi>tUre is low=d to 10 'C ? Assume tharthe specific boat oopaoity oftoo is tho same as that of-or. (3 made,} Given:,;,e<ifu:latentheat of fusion of i<e~3.34 x lo' l kg1 (iii) If the student repeats the measurement after another l 0 minutes, would the corresponding temperature specific heat capacity of water= 4200 J kg-1 0C-1 drop be larger than. equal to or smaller than 9 °C '? Explain. (2 mnrks) (ii) Snggest OIU moclification to tliis bag 1hat would enhance its ability to koep things s!a'cd inm� at a . lowt<mperature. {1 mark} 15. <HKDSE2020PaperlB-l > In a restaurant. 'wontons ·rn soup• is prepared by putting S pieces of cooked wonton at 4 °C into a. bowl with 0.60 kg of soup at temperature% 'C. Given: average mass of each piece of wanton = 0.02 kg specific heat capacity of wonton = 3300 J kg-1 0c 1 - k specific heat capacity of soup = 4200 J g - 1 0c- 1 (a) Find the final temperature of the mixture. Assume that the heat capacity of the bowl and the heat loss to the surroundings are negligible. (2 marks) -(b) The soup in (a) is taken from a metallic container of heat capacity 2000 J 0C-1 containing 16 kg of soup niaintained at 96·°C by an immersion heater. (i) Why does that energy hove to be supplied by the heater to keep the soup et 96 'C 7 (I mark) . DSE Pbysics - Section A : Question Solution PA-HGl-QS/03 DSE Physics - Section A : Question Solution PA-HGl-QS/02 HGl : Temperature, Heat & Internal Energy HG1 : Temperature, Heat & Internal Energy 3. (c) (i) (Il) E =mct..T 2. (b) (ii) Energy absorbed by the polystyrene cup is small since its heat capacity is small. [l] = (1.6)x(4200)x (100-20) [!] Energy lost to the surroundings is small since polystyrene is a poor conductor ofheat [!] = 5376001 [!] (iii) To ensure that the temperature of water is unifonn. [ 1] (ii) (D There is heat lost to SU1TOunding air. [!] (o) ti @ Some heat is used to heat up the kettle. [l] [l] (d) © Water can be used as coolant in motor car. [!] @ Water causes the temperature ofthe sea to change much more slowly than that ofthe land. -- -- ---- Thus the coastal areas have relatively cooler summer and warm.er winters than inland areas. - --- - The- heater is connected to the power supplytbrough ajoulemeter. [!] 4. (a) The energy given to the h.eater Eis found by recording the initial and final readings of the joulemeter. [l] Temperature/"C The time taken tis found by a stop-.watch.. [!] The power output of the heater is found by p = !!.... [!] 3. (a) It means that the energy needed to increase the temperature of 1 kg of water [!] 4-0 through l "C is 4200 J. [!] (b) Joulertieter Power supply [!] 30 Heater W,re, Thermometer Polysl;Yrene cup (b) Put known mass of water, m, into a polysty.rene cup and then put the heater and thermometer into the water. [IJ 20 12 15 18 The heater is then connected to the power supply through a joulemeter and the energy E given out from the heater is recorded. [I] < Correct scales > [!] < Conect labelled axes with units> [!] The increase of temperature t:.T is recorded by using the thennometer. [l] < Correct points for the curve of flask A> [!] The specific heat capacity of water is then found by c = _,!__ [l] < Correct points for the cwve of flask B > [!] m·l:,.T < 2 smooth curves fitted to the points> [!] (c) (i) (I) E =Pt (b) The rate of heat lost by the gas to the surroundings [!] = (1000) X (14 X 60) [l] is just e!F,Utl to the rate of heat absorption from the sun. [!] = 840000] [!] DSE Pbymcs - Section A : Question Solution PA-HGl-QS/05 DSE Physics - Section A : Question Solution PA-HGl-QS/04 HGl : Temperature, Heat & Internal Energy HGl : Temperature, Heat & Internal Energy 5. (e) No. [I] 4. ( c) Temp.mture rise offlaskA = 48.8- 28.0 = 20.SQ C [I] Woodis apoor conductor ofbeat. (OR Wood is not a good conductor of beat.) [I] Energy absorbed by carbon dioxide in flask A = m c /::.T The wood cannothave \lilllonn teoiperature throughoutthe wood. Ul = (Q. 00196) X (640) X (20.8) [I] (OR Different parts ofthe wood would have different temperatures . [I] = 26.1 J UJ Energy absorbed by air :in flask B = (0.00125) x {740) x (46.0 - 28.0) = 16. 7 J [I] 6. (a) :. FlaskAabsOibsmoreenergy [I] (d) 10 (d) (i) Temperature rises. [I] (ii) © Plant more trees. [I] OR Stop deforestation. [l] @ Any ONE of the followings : [I] * Use less fossil fuels. * Use alternate sourc:es of energy. * Save electricity. * Use less private cars. 5. (a) Connect ajoule'metertotbe beater from the power supply. (I] Measure the initial and final readings of the joulemcter. [I] The difference of the readings is the energy supplied by the heater. [l] 4 f :;::::;-1:::::=:::::::ropower Jo-alenlclet supply [I] Heater 3 {b) By E=mcbT [I] 2 (12300) = (l)c(41-29) [I] (c) There is heat lost to surroundings, [I] so the energy supplied by the heater is greater than the actual energy absorbed by the metal. [2] OR 0 ti' 3 6 12 21 There is heat lost to surroundings, [I] <Labelled axes with units > [I] so the temperature rise ofthe block is smaller than that if all the energy supplied is absorbed by the metal. [2] <Conect scales > [I] < Cotrect points plotted> (d) <D SUJTound the metal block with insulating material. Ul Ul <Conect curve> [I] @ Put some oil in the holes to ensure good thennal contact between the heater, thermometer and the meta.L [I] DSE Physics - Section A : Question Sohltion PA-HGI-QS/07 DSE Physics - Section A : Question Solution PA-HGI-QS/06 HG1 : Temperature, Heat & Internal Energy HGl : Temperature, Heat & Internal Energy 7. (b) (i) <Twoaxeslabelledwithcorrectunits> [I ] 6. (b) (i) E=Pxt = 2200x240 [!] < Correct scales used > [I] 528000] [1] <Points correctly plotted> VJ (ii) E = mc/J.T = (I)x(4200)x(l00-27) VJ <Best fitted line drlt-Hn > [I] 306600 J [1] (ii) Slopeofthestraightline"' {S.3-0 . )x!& ""24500 4 [!] (iii) Aay TWO of the following: [2] 0.20 * Some energy is lost to the surrounding. ByE=mclT+Eopp [I] * Some energy is absorbed by the egg. : .E=c6.T·m+Eopp (compa:redwithy = mx+c) * Some energy is absorbed by the pot : . slope = ct{!' (c) No, the time would not be lengthened. [!] (24500) = , (JO) & the temperature of water remains at 1oo•c, [!] c "" 2450 Jkg-1 0C'1 <accept 2300 to 2600 Jkg"" 0c-1 > [I] 1 the rate of energy absorbed by the egg remains unchanged. [!] (iii) Heat absorbed by the apparatus = y-intercept (d) <Tb.ecw:vehasasteeperslope than (a)> [!] "' OAkJ <accept 0.2 to 0.6kJ> [I] < The curve reaches 100°C eveotnally> [!] (iv)< Binney-intercept> [!] <Straight line with slope smaller as c is smaller, slope = c l::,.T> [I] 7. (a) To reduce the heat lost to the SlllTOundings. [!] (b) (;J E!kJ 8. (a) Pat the thermometer into the vvatel:to measm:e its initial temperature Ti. [!] Put the beaker of water into the oven andtllnl on the oven. [1] 5 Use the stop watch to reccrd thefune of heating t. [1] Take out the beaker ofwater from the oven. Put the thennometer into the water to measure its final temperature T2. 4 Precautions/ assu.m.ptions : (]',JJ.y ONE of the followings) [!] * Do not use the thermometer to stir the water. * The heat capacity ofthe beaker is negligible compared with that of water. 3 * The heat lost to the sm:roundings is negligible. * The energy given out by the microwaves is completely absorbed by the water . 2 <Use a sfurerto well stir the water is not acceptable, as no stirrer is provided> Outputpower = (0.2)xcx(1;-1;) [I] where c is the specific heat capacity of water (b) Some energyis absorbed by the beak.et. OR Some energy is lost to the surrounding rot. [!] (c) The percentage of energy Jost would be smaller iflarger quantity of water were used. [1] ..:·•·::i�:!:- :i--Ff-:� : o . m/kg This measure would improve the accuracy ofthe experiment 0 0.05 0.10 0.15 0.20 DSE Physics - Section A : Question Solution PA-HGl-QS/09 DSE Physics - Section A : Question Solution PA-HGl-QS/08 HGl : Temperature, Heat & Inrernal Energy HG1 : Temperature, Heat & Internal. Energy 12. (a) Put the sphere into the waterbath for a few minutes. [l] 9. (a) m = pV= l000xl.5 = 1500kg [l] Transferthe sphere into thepolystyl'ene cup of water. [l] t Measure the fuial temperature Tr of he water with a thermometer. E"' mc!::.T x(l-15%) [l] [l] = (1500) (4200) (80 - 60) X (1 - 15%) By (0.80) x Cb x (80- Tr) = (0.50) x (4200) x (Tr - To) [l] =1.07x108J [l] .•. Cb = 2625 X r,-fo 80-T r (b) E•Pt PreCSlltions: * (1.07 X 10s:i = (4.5 X 103) t [l] Dry the sphere withthe towel quickly beforeputting it into the cup. * [I] .·. t"" 23778s = 6.60b.ow <accept6. 61homs> [l] Stir the water to ensure uniform tempeuture ofwater. [l] (c) The rate ofbeat transfer drops as the water temperature drops. [l] (b) Any ONE of the followings: [1] OR * Some heatis lostduringthe transfer * The rate of heat traru,fer d:rops as the temperature difference drops. [l] Some heatis lost duringthe dzying ofthe sphete * Some beatis lostto the aI)paratus (thernromcter, stirrer or cup) * The temperatw:e ofthe sphere is still higher than Tr when this final temperature is measured 10. (a) Time= Sminutes <accept300s> [l] Thus, the temperaturerise of water m the cup is lower than it shouldbe. [l] (b) When the heateris switch off, its temperature is still higher thatt the metal [l] (c) (i) P =VI"" (12)(4.0) = 48W [l] 13. (a) Alargebulb increases the sensitivity ofthe ther.mOllleter. [l] By Pt=mc!::,.T .-. (48)(5, 60) • (0.80), (45 • 20) (b) (i) E = mc4T ;. c=720Jkg-l<>C'l [l] - (0.015) X (2.9 X 103) X (20-15 ) [l] = 217.5 J <accept 218 J> [l] (ii) The calculated value is higher than the actual value. [l] (u) ByE=Pt Since energy is lost to the surroundings. OR Some energy is absorbed by the heater and the thermotneter. [1] •·. (217S) • (05) t OR [l] Not all the energy supplied by the heater goes to the metal. [l] :. t=435s <accept436s> [l] d () Glass is not a good conductor ofheat OR The heat conductivity of glass is poor. [l] (lll) The thermometer would cool down quickly when it is in direct contact with the cooler air. [l] The temperature reading wouldbe less than the actual soil temperature. [l] ll. , ( i) R-R, 0-0 ( ) [l] Ri oo-Ri =ioo:o R-102.00 60 140.51-102.00 - 100 :. R = 125.1060 <accepredl25.11O OR 1250 > [l] (:UJ Actual temperature is lower than 60°C. [l) (b) Since the actual temperature is lower than 60 °C when beaing t stops, [I] OR The energy supplied is actually lower than it should be, [l] thus, the experimental value of c.,, is lower than the actual value. ( c.., = �) [I] m-U 14 <HKDSE20!9Paper!B-1 > (c)" (z) '(1) ·a Hong Kong Diploma of Secondary Education Examination '"'' (c) ,, (z) "8 '"" (s)" (1) ·a Physics - Compulsory part (�1.f-.:gfl?J'") '"'' (z),, (1) -v Section A-Heat and Gases ("?.!!i:f,, li'fi..�) 11mfJO .rot3ttPUO::i rood 'B si: � gguods :itf.L (£) 1. Temperature,Heatandintemalenergy($;.li, �>loRlf.) �qJO �1?!PtU po oil e si: �ftlM filfop:=dd!l£M. :)tU, (z) 2. TransferProcesses (�-��a) �qJo l01::ltt{lll� .rood \l S! �!'llM �:; p:idd!trM. mt.I. (I) ! 3. Change of State (i!H!f;Jtt�) 1, uo.mtuou..qd SftP JoJ suo� 4. General Gas Law ( f-l&$i.i'lt.it.W:) l)\OJSSOd � Slu:ro:tOl'ElS itJ!M.OflOJ � JO t{:l:t(tA -u;IA(l tm tIJ: profBq S!- lJ'. ®t{A\ lfltll lDtl s:iop � :llp 3P!SU! tlllml0--0::l� � 5. Kinetic Theory (-;)-.:f�fhtt) i�� Jl"ti Section B - Force and Motion ( fJ ;fa i!:th) 1. PositionandMovement(-ii!.l.;fo�th) - 2 Newton's Laws ( 4�,t.W:) '�11 !i,1l �:)! I,., 3. MomentofForce (ht!.) ';f�I 4. Work,EnergyandPower(1'piJ, flt-!l::fl'-"h�) ' tli 5. Momentum (fhit) 6. l:'rojectileMotion(:J.\Ul>l.th) , �;Buods 7. Circular Motion ( 00 Jlil lUJJ) �qqnq.xret.=li1¥>1-:llJliM-�p�d!t[1,1. 8. Gravitation C 5111) -� 'I?Jo .i�s ;i:p SA\ot{S tt.q:iq ttnmleyp aqi Section C- Wave Motion (i§..1rh) 1. WavePropagation (ilt�4!l�) < 6 -ll .1adllcl LOO't 'Jtl})]l > '£ 2. WavePhenomena(iltililJL.t..) 3. Reflectionand.Refrattion ofLight (if.111.i..M.&A!i"M) (£)" (Z) X1) ·a 4. Lenses (;t;,t) Arao (E) '1'J (z:) ·;:, 5. Wave Nature ofLight (,t.�/b..11;.'j;l'-�) '"'' Cs)" (1) ·a 6. Sound(�-fr) Arao (z) 78 (1) ·v Section D - Electricity and Magnetism ( 'Ul.; if,, -oii.:) ·uoµ'8fPe.Ilq ssor � sa�p:;u SUUM- SS'l!p! :irqnop :itti lF.);)MlQq lllt\TI'J'eA :lllJ. (£) 1. Electrostatics (M-f!:�) ·uoµ:iMuo:i ptre u�:mpuo:> Aq ssor +� so:inp� i'ilddoµ; '(Io::> :iqi Ct) 2. Electric Circuits ( 1l!:Jt3.) ·sso1�:i:mp:1101-.Cw"flll p:iilJ!l?d :m B pmi rI =-ey:rns =tLL (1) 3. Dottiestic Electricity(�,%- ffl 'Qt) l, i:iazw::i o:re n�t:l.S iey.-.ouoJ :itp JO tp!tlh\ -� SS'I!� OJ\ii tp� ){S'l!IJ llln'Mllto. 'll w.oqs :i�-g: ;qi 4. MagneticField (.T#:4-) 5. Electromagnetic Induction ('lt.T#:�4) 6. Alternating Current (�:ilii.it) ""'""'A (.'i:iOejltlS Section E - Radioactivity and Nuclear Energy (-$:.Af "11. t.,.:f,, ;I#;: »t) "''"'™ 1. Radiation and.Radioactivity (tUt;fti:Jli:.AHI!.$.) 'ff'A'"'l• 2. AtolllicModel(Ji.:ff/\�) 3. Nuclear Energy (.i,l1$) P!flb:l+Oll 1-1dd01,S)IJO:l Physics- Elective part (;!if�;i-) < C,-II.Rdllcl900t ;iOJIH> •t Elective 1 - .Astronomy and Sp ace Science (;;__ :SC.-!f!::to-:AA:.7-.¾'I-*) '"'° 1. The ul:liverse as seen in dif'femlt scales (;f !5l '.!l: r,IJ:tlli Tti9 ':f 'iii Mtt.) '"'° 2. Astronomythroughhistory(;tSC.!!p.l(.Jif"kl�) (cl" (1) ·a 3. Orbital :motions undet gravity ( j: iJ r ti9 �il.lU/J) Cz)" (1) ·8 4. Starsandtheuniverse('ill.>lo*'iii) Al"' (cl ·a '"" (z) -v Elective 2 - Atomic World (;f.-f-1!!: 1f..) UO!l-en,at (£) 1. Rutherl'ord'satomicmodel C.!li%:1£J!.:f.»t'!t!) uowi:u.uoo (i ) 2 Photoelectric effect (if. 1ti;t.!t) uo�uo:i Ct) 3. Bohr's atomicmodelofhydrogen (3&'..ffl ti!J .m.,,f.,=t-;flt�) l, S�Ol.mS :lttl Ol owiod l)lp 4. Particles or waves ($..:f ;.\it.) 5. Probing into nano scale (;'l�il'l*1!!:.\'I-) � mo.g lSOI l8lomi JO� :itp.�p:11 dpq UoJ :iq:i. mr., Sntr.ml � Ag "J:OJ 'llltlpl!Utt\fl: l1l!t{s Ml p:;dd"eJM. Olt?ladioq '8 s&Olf,l qdruj'OJ.Olf.d ,;nu. Elective 3- Energy and Use ofEnergy (t!si::falti!f.{{;J-fVil) 1. Electricity at hOJD.e ( If.,% Jll 11!:) <1. ·n.Rde,1 soot :O)IH> ·1 2. Energy efficiency in building (���11tilf.ttt.ll1-) 3. Energy efficiency in transportation (ll.#r"lti!Jtt.l!t-:!tl:41) suop.sanb nop.t?1Z!l,UWr.l a:)}lB: v1-mc1. 4. Non-renewable energy sources ( ;f of .jlj.!!..f!t!!j) 5. Renewable energy sources (of.jlj.i_/lti"lf.) I io1w-z::m-va Elective 4-Medical Physics ( l-,$-4hJ!.,$-) SQS� lllJSUllll : ZDH 1. Making sense ofthe eye (Ult<f.11,1;\ 'if) 2. Makingsenseoftheear(lf-1(.Jll\'lf) ·;:yw : V UOf)OQS · S<l!SAlld HSO 3. Medical imagingusing non-ionizing radiation (�f 11!:�ff.Mfl,!}!,-!$-fl!!p.) ' 4. Medical imagingusing ionizing radiation ( 11:1\ltffrM-U-$-!$,f#..!:J',-) 4. <HKCE2008Paperll-9> DSE Physics - Section A : M.C. HG2 : Transfer Processes PA-HG2-M/02 Ii 7. A. elemrons. DSE Physics - Section A : M.C. HG2 : Transfer Processes A metal spoon is put into a bowl of hot soup. Whenit is taken out of the soup, it cools by emitting PA-HGZ-M/03 11 B. infra-red radiation. aluminium.heat sink C. visible light. D. ultra-violetmdiation. •• J.n winter, when we sit on a metal chair, we feel cold continuously . What is the reason behind ? A Metal has a small specific heat capacity. The above figure shw.rs the aluminium heat sink of an audio amplifier which is used to transfer heat a:m.y from th components inside the amplifier. Which ofthe following statements about the heat sink is/are correct ? B. Metal is a good reflector ofheat. (I) Theheat sinkis made of aluminium so that it can transfer heat away faster by conduction. C. Metal is a good radiator ofheat (2) The heat sink is silverin colour so 1:bat it can transfer heat away faster by r.idiation. D. Metal is a good conductor ofheat. (3) The beat sinkhas a fin-like design to .increase the surface area so that it can transfer heat away faster by conducti toah-. 9. Which of the followings are related to the process cf convection? A. (2)only (I) Some birds use hot air cw:tents to gain height B. (3) only (2) At day time, breezes move from. sea to land C. (I) & (2) only (3) Atnigh.t time, breezes move from land to sea. D. (I) & (3) only A. (I) & (2) only B. 0) & (3) only 5. <BKCE2011Paperll-12> C. (2) & (3) only h D . (!), (2) & (3) T e figure below shows a solar cooker . Which of the following statetllents about its design is incorrect? 10. Which of the following processes does not involve the movement of molecules? A conduction B. convection C. radiation D. diffusion 11. Which of the following animals is the best emitter ofinfra-red radiation from their bodies? A a white cat B. ablackdog potQ C . a brown horse D. aredfox A. BoardP should be shiny to reflect suclight into the cooker. B. PotQ sholll.d be paintedin blackto increase the heat absorption. : 12. Anange the followjng materials from the poorest conductor to the best conductorin order. C. Case R should be made of metal to enhance heat transfer. (I) ah- D. The glass cover can reduce heat loss by convection. (2) copper (3) vacuum (4) _, A. (!), (3), (2), (4) B . (!), (3), (4), (2) Part B : Supplemental exercise c . (3), (1), (2),( 4) D. (3), (1),(4), (2) 6. The diagram shows an experiment that demonstrates convection takingplace in water. What happeru to the waterto cause the convection ? 13. The radiatots on motor cars are painted black What is the reason behind? A. The water expands and its density decreases. A It will not get dirty easily. B. The watet expands and its density incr�. B. Black surface is a good emitter of heat C. The water contracts and its density decreases. C. Black surf.ace is a good conductor of heat. D. The water contracts and its density in�ases. h"'t D. Black surface is more beautiful. 14. DSE PhYsics - Section A : M.C. HG2 : Transfer Processes Which of the followin g isNOT an. application ofthe poor conductor ofheat 'I PA-HG2-M/04 i :21. DSE Physics - Section A : M.C. HG2 : Transfer Processes PA-HG2-M/051 A. wooden handles of fryingp ans B. fur ofthe animals C. cooling fins of be cngin.e radiators t '''"""''"'--� D. double glazing of windows � "'ldvratocin.......,_ 15. Which of the following correctl y describes shiny surfaces co.ncemin g infra-red radiation 'I The above iigu:r e shows a simple solar beater. What type of material should be used for the pipe to give the hottest water A. They arc good absorbers and good emitters. from the heater ? B . They are good absotbers butpoor- emitters. A. Plastic painted white C. Th ey are poor absorbers and poor emitters. B. Plastic painted black D. They are poor absorbers but good emitters. C . Copper painted white D. Copper painted black 16. Ametal rod and a rubber rod are at the same tem perature. When they are held in the hand, the metal rod "feels" colder than 22. Nonnall y, the conduction of heat through a sub.staDce depends on its state. Which of the fulloWUlg correctly ananges the the rubberrod. The best explanation for this observation should be three states from the poorest conductor to the best conductor? A. metal has a hi gher melting point than rubber . A. gas li quid solid B. metalhas a lower specific heat ca pacitythan rubber . B. solid gas liquid C. metalis abetter conductor ofheat than rubber. C. gas solid liquid D. liquid gas solid D. metal is a better al:Jsorber ofbeat than rubber. 23. When a match is placed near the flame of a Bunsen burner as sho wn, it is found 17. Which ofthe followin g correctly describes dull Sl.lifaces concerning illfta-redradiation 'I that the match does not ignite. Whlchofthe following is the best reason? A. They are good absorbers and good emitters. A. The temperature of the flame is not high enough. B. They aie good absotbers but poor emitters. B. A.iris not a good conductor of beat. C. They are poor absorbers andp oor emitters. C. There is no convection current near the flame. D. They are poor absorbers but good emitters. D. There is no radiation from the flame. In a bot summer day , Peter wears white shirt and black trousers. When be stands under the sun, be feels that his feet are 18. Abowl ofhot soup is placed in air. Which ofthe followin g transfer processes would carry a:wa y the energy from the soup tc hotter than his back. Which of the following is the possible reason ? cool it down? A. The white shirt emits less infra-red radiation than the black trousers. (1) conduction B. The white sllirt emits more infra-red :radiation than the black trousers. (2 ) convection C. The Vl'hite shirt absorbs less infra-red tadiation than the black trousers. (3) """""' D. The white shirt absorbs D10re infra-red radiation than the black trousen. A. ( I) & (2) o,Jy B. (I ) &(3) only C. (2) & (3 ) onfy 25. In the diagtam shown, a piece of metal gauze is used to keep the ice at the D. (I ), (2) & (3) bottom of the test tube. The upper part ofthe test tube is then heated unti1 the water boils. However, the ice still exlsts at the bottom. Which of the followings are the possible reru.ons ? 19 . h Whfob ofthe following substances is thebest conductor of eat ? (1 ) Water is not a good conductor ofheat. A.-= (2) Convection. can hanily be set up between boiling water and ice. B. air (3) The metal gauze prevents beat from concfuctingto the ice. C. water A. (I) & (2) omy D . iron B. (I) & (3) only C. (2) & (3) on ly D. (I), (2) & (3) 20. Which ofthe following process can beatbe transferred in a vacuum ? (1) conduction 26. A vacuum can prevent beat transfer by (2) convection (1) conduction (2) convection (3) -.. (3) radiation A. (1) only A. (1) only B. (2) onfy B. (2) onl y (3 ) onl y C. C. (3 ) only D. (2) & (3) onl y D . (1)&(2)only DSE Physics - Section A : M. C. PA-HG2-M/06 DSE Physics - Section A : M. C . PA-HG2-M/071 HG2 : Transfer Processes HG2 : Transfer Processes 27 Questions 31 and 32: The followingfigm:eshows t1:te design of the top of a house . ( . silvc cy Slldace In avacuumflask. 1:he :inridewalls have silvery su.t:face The mainptup0se of this design. is to reduce heat transterby . A. conduction only. 31 What material should be used to cover the roof ofthe house in order to kee p the house cooler in a hot day under the Sun ? . B. tadia.t:ion o.nly . A. a layer of red brick C coruJ.uctlon and convection only. B. a layer of dark soil . D convectionandradiation only. . C alayer ofblack paint . D alayerofwhitepaint . 28. 32. Fibre is used to separate the roof and the ceiling. Row mayiibre help to prevent heat from passing 1hrough the ceiliJlg ? A. Fibre allo-ws air to pass thrmigheasily. B. Fibre traps air. C. Fibre is cold. D. Fibre is light in colour. Billy wants to set up a C-Ollvec:tion current .inside the water in ametal tank. Which of the following methods can achieve this t (1) Heat hewateratA . Which of the following correctly explait1s the main reason for the heat to be transferred in the process of conveclion? 33 . (2) Cool thewater atA. A. The heat is carried away by infra-red radiation. (3) CoolthewateratB. B. The process ls achieved due to the temperature difference in a solid . A. (!) only C. The process is achieved due to the density difference in a fluid. B. (2) only D. The process is achieved due to the VI1'ntion ofmoleccles. C . (3) only D. (!) & (2) only 34. In the design of a solar heater, the panels are painted black in colour. What is the reason behind? 29. A beaker of waterisheated by a flill:lle placed at the bottom. Which diagram below best shows the convection currents ? A. To ntake the panel become good conductor. A. B. C n B. To allow convection to take place. \t/ C:J C. To improve the absmption of infra-red radiation. D. To improve the emission ofmfra.-redradiation. I 35. white metal plate electric heater black metal plate 30. htawaterheating system, the hot water from the heater flows to the tap tbxough wat.:r pipes. However heat is lost during the , flowing process. Which oftb.e followingstatements are correct conceming the flowing process ? Two identical metal plates, one painted with white colour and the other painted with black ct>lour, are placed at equal. (1) Heatis lost through the walls ofthe pipes by conduction. distances from a radiant heater as shown. After some time, 'Mlich metal plate absotbs more energy and which metal plate emits more energy ? (2) Heat is lostthrough the SU!rouruling air by convection. Metal plate that absorbs more energy Metal plate that emits more energy (3) Heat is lost to the SUttoundingby radiation. A. white white A. (I) & (2) only B. (!) & (3) only B. wlute b!,cl< c. (2) & (3) only C. brack .aute D. (!), (2) & (3) b!rl b1"cl< D. DSE Physics - Section A : M.C. PA-HG2-M/08 DSE Physics - Section A : M.C. PA-HG2-M/09 HG2 : Transfer Processes HG2 : Transfer Processes Part C: HKDSE examination questions 139. <HKDSE2016PaperIA-1> Some icy cold liquid is kept cold inside a vacuum flask. Which statements are correct? 36. <BKDSE Sample PaperIA-1 > (1) The flask's co_rk stopper reduces heat gain from the surroundings. (2) The silver coating on the inner surfuce of the glass wall is a good reflector of infra-red. (3) The vacuum between the double glass walls reduces heat gain by radiation. A. (!) & (2) only B. (1) & (3) only C. (2) & (3) only D. (!), (2) & (3) 40. <HKDSE 2019 Paper IA-1> Cynthia places a carpet on a tile floor. After a while, she stands in bare feet with one foot on the tile floor and the o on the carpet as shown. She feels that the tile floor is colder ·than the carpet Which of the following best explains thi phenomenon? A. The tile is a better insulil.tor ofheatthan the CMpet. a The ti.le is at a lower temperature than the carpet. C. The specific heat capacity of the tile is smaller than that of the carpet. D. Energy transfers.from Cynthia's foot to·the tile·at a greater rate than thilt'to the caJpet. 37. < IIKDSE 2014 Paper IA-1 > 41 <HKDSE 2020 PaperIA-1> Temperature sensors P, Q, Rands ed cubic water tank- A heater is installed at the centre ofa fully �ft. right and bottOm surfaces ofthe tank. the top, e are fixed at the respective centres of Two idetttical scoops of ice-cream are 11'ansferred from a refrigerator into paper cup X and vacuum flask Y shown above. Under room temperature, the riDle required for the ice"cream in the containers to melt completely is tx and ty respectively. What is the expected result and explanation? A. tx > tv as ·the vacuum flask reduces beat loss to the surroundings. B. tx > tv as the vacuum flask retains ·the heat C. tv > tx as the vacuum flask keeps things cold by releasing beat into the -surroundings. After the heater is swt'tched on for 2 short dur:ation. which pair of sensors below would indicate the ta,gcst tempe,atwc difimncc ? D. ty > -tx as the vacuum flask reduces the ·rate of heat gain from the sunoundings. A. QandR B. RandS 38. < BKDSE 2015PaperIA -1 > C. QandS A driver parks his ·car ·outdoor under the $U11. After parking. he switches off the engine of the car. Two hours later when he D, PandR gets back into the car, he feels that ·the inside of the car is far hotter than outside. The best explanation is A. the cats engine is still generating heatder t he engille has been switched oft B. 1he car's metal parts absorb Infra-red radiation at a faster rate than the surroundings. C. the glass windows ofthe car trap infra-red radiation and a greenhouse effect results. D. the sw:rounding air is a good i:nmtlatot ofheat wbich reduces heat loss by conduction. DSE Physics - Section A : M.C. Solution PA-HG2-MS/0l DSE Physics - Section A : M.C. Solution PA-HG2-MS/02 HG2 : Transfer Processes HG2 : Transfer Processes HKEAA's Marking Scheme is prepa= fo1' the marker..' Iefen:nce. It should not be regarded as a set of model answe.r Students and teachers who are not involved in the mazking _process ate advised to mezpzet the Mamng Scheme with c.u, 4. D ✓ (!) Aluminium is a good conductor, it can conduct heat away faster. M.C. Answers Silver in colour transfers heat away by radiation slower, not faster. (2) I. B 11. B 21. D 31. D 41. D ✓ (3) Fm-like design can increase the surface area for faster conduction ofheat. 2. A 12. D 22. A 32. B 5. C 3. B 13. B 23. B 33. C ✓ A. Board P should be shiny to reflect sunlight into the cooker, so that more solar energy can enter the case. 4. D 14. C 24. C 34. C ✓ B. Pot Q should be palllted in black to increase the heat absorption, since black surface is good absorber. 5. C 15. C 25. A 35. D c. Case R should be made ofinsulator to reduce heat lost to the surroundings. ✓ D. The glass cover can reduce heat loss by convection, as hot air cannot escape from the case. 6. A 16. C 26. D 36. D 7. B 17. A 27. B 37. D 6. A When water is heated, it expands and density decreases. 8. D 18. D 28. B 38. C Thus it rises to the top to foxm the convection current. 9. D 19. D 29. D 39. A 10. C 20. C 30. D 40. D 7, B All hot or warm objects would emit heat by radiation which is infra-red radiation. M.C. Solution 8. D 1. B Since metal is a good conductor ofheat, it conducts heat continuously from our body to make us feel cold. • (!) A1wninium is a good conductor ; '9. D heat lost by conduction cannot be reduced. To reduce heat lost by conduction, the potato should be wrapped with an insulated foil ✓ (I) Some birds make use ofthe rise of hot air currents to gain heigbt and reach the upper sky. The air currents are due to convection in air. (2) Convection outside the wrapped potato can still talce place after wrapping with aluminium foil. ✓ (2) At day time, the land is hotter than the sea. To reduce heat lost by convection, the potato should be placed inside an insulated box. Air above the land rises and breezes move from the sea to the land to fom:i convection cwrent. ✓ (3) Shiny surl'ace of the aluminium foil is poor emitter oftacliation, ✓ (3) At night tim.e, the sea is hotter than the land. thus heat lost is reduced. Air above the sea rises and breezes move from the land to the sea to fonn convection cw:nml 2. A C ✓ (I) Silvery can reduce heat loss by ra<liation since silvery swface is a poor emitter ofradiation. Radiation is the transfer of energy by infra-red radiation which can travel in vacuum, ✓ (2) Cork is a poor conductor and reduces beat loss by conduction. thus it does not involve any molecular motion. The stopper prevents hot air rises up and reduces heat loss by convection. (3) Vacuum can reduce heat loss by conduction and convection but not radiation, . 11. B as heat radiation can transfer though vacuum. Black colour surface is the best etnitter ofradi.ati.on. 3. B 12 . D ✓ Vacuum does not conduct heat, therefore it is the poorest. (!) Since the whipped egg white is a poor conductor, heat can hardly transfer from the top to the ice-cremn. Air is a gas which is poor conductor. (2) The egg white is white in colour, it should be a poor radiator, and radiation is not a factor here. Water is a liquid which does not conduct heat well, but the conduction is bettei: than air. ✓ (3) Since the cake is a poor conductor, heat can hardly transfer from the bottom to the ice-cream. Copper is a solid which is the best conductor. DSE Physics - Section A : M.C. Solution PA-BG2-MS/03 DSE Physics - Section A : M.C. Solution PA-BG2-MS/04 HG2 : Transfer Processes HG2 : Transfer Processes 13. B A Black roface is a good emitter of radiation, thus heat can be emitted quickly. Gas is the poorest conductor Solid is the best conductor among the three states of substances. 14. C ✓ A Wood is a poor conductor. 23. B It is used so that heat cannot conduct well to the handles from the hot pans. Since air is not a good conductor, heat cannot be conducted weU to the match. ✓ B. The furofthe anillla1s traps air and is poor conductor ofheat. Thus the temperature of the match is not high enough to be ignited. They prevent heat1ost from the bodies ofanimals to the surrounding air. c. Cooling fins ofthe engine radiators are rnadc ofgood conductors to condl.Ict away beatqcickly. 24. C ✓ D. Double glazing 'Window contains mt between two sheets of glass. Since the white shirt is a poor absorber oftadiation, It can reduce heat flow across the 'Window by conduction. it absorbs less heat tban the black trousers which is a good absorber of radiation.. 15. C 25. A Shlny $Url'a.ces are both poor absorber and poor emitter ofinfra�red radiation. ✓ (1) As water is a not a good conductor ofheat, heat is not easy to conduct from the top to bottom of tube. ✓ (2) Since the hot water is at the top and ice at bottom, convection <:w:rent can hardly be set up between them. 16. C (3) Metal gauze is a good conductor. It does not prevent heat to be conducted. Since I'l1etal. is a better conductor ofheat, it conducts heat quickly away frOill the hand, thus the hand feelscold. 26. D 17. A ✓ (1) Conduction requires a medium to transfer heat. Thus, there is no conduction. in. vacuum. Dull surfaces are both good �orber and good emitter of infra�redradiation. ✓ (2) Convection. reqUires a fluid to 'lr.UlSfcr heat. Thus, there is no convection in vacuum. D (3) Radiation can take place in vacuum. ✓ (1 ) Heat is conducted away from the bowl to the surrounding air. 27. B ✓ (2) Above the soup,convection CUirents foan to carry away the energyfrotn the St1up. Silvery surfuces are poor emitter ofradiation.. ✓ (3) The soup emits infra�red radiation to lose energy. 19. D 1 28. B Iron is metal, all meta.ls are good conductors, thus iron is the best conductor ofheat among the given substances. (1) Ifthe water at A is heated, the bot water has no place to rise to foIIll convection eunents. ✓ (2) If the water at A is cooled, the cold water sinks to formconvection currents. 20. C (3) Ifthe water at Biscooled, the cold water has no place to sink to forlll convectioncunents. (1) Conduction requires a medium (solid, liquid or gas) to transter heat. (2) Convection requires a fluid (liquid or gas) to fonn a convection current : 29. D ✓ (3) Radiation transfer heat by infra-red radiation which can travel through vacuum. The bot water rises to the top and then flows to the sides of the beaker 1D form convection currents. 21. D 30. D Copper is a good conductor. ✓ (1) Some heat is lost by conduction through the walls ofthe pipes. It should be used so that heat can conduct well from the pipe into the water. ✓ Since the temperature ofthe pipe should be higher than the room temperature, (2) Black surface is a good absorber of radiation.. air around the pipe is heated and rises to form convection currents. The surface should be painted black to absorb more h� by radiation. ✓ (3) All warm objects would emit heat by radiation. DSE Physics - Section A : M.C. Solution PA-HG2-MS/05 DSE Physics - Section A : M.C. Solution PA-HG2-MS/06 HG2 : Transfer Processes HG2 : Transfer Processes 31. D :39_ A 'White colour surfaces are poor absorbers of radiation. ✓ The cock stopper is a poor conductor, it can reduce heat gain from the surrounding air by conduction. The stopper can reduce heat gain.from the SlllToundings by convection. 32. B ✓ (2) The silver coat:illg is a good reflector of infra-red and thus reduce heat gain by radiation. Fibre traps air to become apoor conductor ofheat (3) Vacuum cannot reduce heat gain by radiation, it can only reduce heat gain by conduction and convection. 33. C For convection.current to be formed, the fluid must have different densities at different temperatures so that hot fluid rises and cold fluid sinks. 34. C The panels ofa solarheateris painted black since black surface is good absorber, it can absorb more heat by radiation. 35. D Black surl'acesareboth good absorber and good emitter ofradiatfon.. 36. D A. The tile is a better conductor ofheat than the cazpet, not better insulator. B. Both the tile and the carpet are at the same temperatunt ofthe surroundings. c. For a fixed amount of energy transfer and same mass, SD:1aller value of specific heat capacity would cause greater rise of temperature. Butinthis case, the energy is transferred from the foot continuously with different rate. ✓ D. Since the tile is abetter conductor than the carpet, heat is transfened from the foot to the tile at a greater rate-than that to the caipet; thus the tile floor is felt colder. 37. D The vac:mun flask Ytakeslcngertitne for the ice-cream to melt completely since the vacuum flask can reduce theheat transferwith the mmounding.s, thus reduce the rate ofheat gajn from the surroundings. 38. C A. The car's engine would stop giving out heat when the engine has been cooled down aftersome time when the engine has been switched off. B. The car's metal parts absorb infra-red radiation would only cause the metal body of the car hot, but not the temperature inside the car. ✓ c. Infra-red radiation from the Sun can pass through the window to heat up the air inside the cru:, but the infra-red :radiation inside the C2J cannot pass through the window and is trapped inside. Th.is is the greenhouse effect D. Heatis trapped inside the car by greenhouse effect Heat loss by conduction is not the main reason. DSE Physics - Section A : Question PA-HG2- Q / 01 DSE Physics - Section A : Question PA-HG2-Q I 02 HG2 : Transfer Processes HG2 : Transfer Processes The following list of formulae may be found useful : 1. (c) State ONE design in the vacuum flask shown in Figure 2 that helps to reduce heat loss by radiation. (1 nwk) Energy transfer during beating or cooling E== mc/lT Part A : HKCE examination questions (d) Can a i:henrull flask also store cold liquids and keep them cold for a period oftitne? Explaill your answer. (2 mad<s) 1. <BKCE2007Paperl-3> Read the following passage about thenna1 flasks and answer the questions that follow. Working principles ofthttmal ihsks Therznal flasks are used to store hot liquids and can keep them warm for a period of time. Insulating by foam and insulating by vacuum are two common ways of making thennal flasks. 2. <HKCE2010Paperl-3> For a themlal flask applying insulation by foam. a layer of foam is used to Wiap the container (see Figure 1). Both the Des<:ribe how to use the apparatus as shown in the Figutc below to conduct an experiment to demonstrate the convection of foam and the air trapped inside the foam are poor conductors of heat Also, the air mside the foam is broken into many air current. (4 marks) tiny bubbles, which reduce convection of air inside the foam. Heat transfer through foam is therefore pretty slow. For a thermal flask applying insulation by vacuum, there is a vacuumbetween the double glass walls of the container (see Figure 2). The heat insulation of VllC\l1llll is better than that of foam. Furthennore, the inner surface of walls of the glass container is painted silvezy to reduce beat transfer. As glass is fragile, the glass container is protected by an outer case with an insulated support. �- ii a lighted joss stick(�) with smoke double-wall silvered glass fomn I hot liquid """"'"" _,rt Fl"""l Figure2- a lighter a glass with upper part separated by a cardboard (see schematic diagram) (a) Explain how the fuaI!I reduces heatb:ansferby conduction and convection. (b) Explain why the heatittsulation ofvacuum between the double glass walls is better than that of foam. PartB : Supplemental exercise DSE Physics - Section A : Question HG2 : Transfer Processes PA-HG2-Q/03 !I 1• · (b) DSE Physics - Section A : Question HG2 : Transfer Processes When watffl"flows through the pipe in the solar beater at a rate of0 . (Specific heat capacity of water = 4200 Jkg' 0C-1 ) 1 01 PA-HG2-Q/04 kg r1, its temperature rises by 7°C . 11 . 3. (i) Find the power supplied by the heater . (3 marks) (ii) If the rate of flow ofwatet were reduced to 0 04 . kg mht- 1, find the increase in tcn:Jperature. Briefly con:unent on The above figure shows a vacuwn flaskused for keeping hot liquids warm. yanr answer. (4 marks) (a) What is the use of the stopper placed at the top ofthe flask? (b) Whydo the inside walls of the flaskhave silvery surfaces ? (2 marl<,) (c) Why is the space between the ion.erwall and outer wall vacuum ? 5. hotwaterout +-=If:::========'°', " I cold water in--+ =lfC========-:c:/ hotwateront- The above figure shows a solar paae1 used to heat water. (a) State the process bywhlch energy is transfetred lagging (i) from the sun to the outside of the pipe in the solar panel; (1 m,,k) (h) from the outside of the pipe to the watednside it. (1 m,ui<) The figureabove shows a simple solar heater. (a) (i) Why should the innerwall ofthe heater and sudace of the pipe be blackened? (2marl<s) (b) The following is a list ofmaterials which are proposed to be used as the pipe material that cotttains the water. "polished copper, glass, white plastic, black plastic, black-painted copper'' (ll) The heater is covered by a sheet ofglass. Give one reason for tlris. (1 m,ui<J Suggest the IllOst suitable material fur the pipe. Give two reasons to support your choice. (3 matlcs) (iii) Suggest one material suitable for the lagging. (1 m,ui<) DSE Physics - Section A : Question Solution PA-HG2-QS/01 DSE Physics - Section A : Question Solution PA-HG2- QS/02 HG2 : Transfer Processes HG2 : Transfer Processes BKBAA's Matk:ing Scheme is piepatCd fur the markers' teference. It should not be :,:egarded as a set of model answei Students and teacbm's who are not involved in the :m:a:ddng process are advised to inte:r:PLet the Marking Scheme with cm ;4, (b) (ii) Inlnrimrte,heatsuppliedbytheheater =Pt= (294)(1 x60) = 17640J [!] By E=mcAT Question Solution .-. (17640) = (0.04)(4200) LIT [!] 1. (a) Foam is a poor conductor of heat [!] ;. !::,T = 105°C [l] This is impossible because water would boil at l00"C. [!] The small air bubbles inside the foam reduce the air convection. [!] (b) Vacuum does not have air, thus no corufuction ofheat. [!] VatuUm. does not have air, thus no air convection. [l] [!] 5. (a) (i) radiation (c) The vacuum flaskhas silvery surface t o reduce radiation. [!] (:iJ.) conduction [!] (d) Yes! [l] [!] (b) The most suitable material is black-painted copper. Since the thennal flask can reduce heat transfer, the liquid can be kept cold for a period oftime. [!] Black surface is a good absorber of radiation, thus more solar energy can be absorbed. [!] Copper is a good conductor, thusheat can be conducted well from the pipe to the water. [!] 2. Put the candle in the glass and light up the candle with the lighter. [!] Put the lighted joss stick inside the other side of the glass. [!] Observe the movement of the smoke. [l] The smoke from the joss stick moves through the bottom of the separator and rises on the side of the candle. [1) 3. (a) To reduce heat lost by convection [!] and conduction. [!] (b) To reduce heat lost by radiation. [!] since silvery surface is a poor emitter of radiation. [!] (c) To reduceheat lost by conduction [!] and convection. [!] 4. (a) (i) To ensure IIl3Ximum amount ofheat absorbed [l] since blackened �e is a good absorber of infra-red radiation. [!] (tl) To prevent cooling by convection. [l] OR To trap heat by greenhouse effect. [!] (:Ill} AnyONE ofthefollowings: <OR any other suitableinsula.tor> [!] * cotton wool * foam * polystyrene (b) (i) By Pt=mc!::,.T [!] P (1) = (0.01) x (4200) x (7) [!] :. P=294W [!] Hong Kong Diploma of Secondary Education Examination Physics - Compulsory part (;t.•*<Jl<l-) Section A -Heat and Gases (-Mi,:fl'I.UU I DSE Physics - Section A : M.C. HG3 : Change of State PA-HG3-M/01 II 1. Temperature, Heat and Internal energy (ill.&: , #.:'fl' pg AG) 2. Transfer Processes (#.:#$,1!,U) The following list of formulae may be found useful: 3. CbangeofStat.e(mS&�at!!) 4. General Gas Law ( ·i:H&.ffi.tt�#) Energy transfer during heatitlg or cooling E= mc/:J.T 5. KineticTheozy (13-"T'il1/Jtll-) Section B -Force and Motion (iJ:fl'��) Energy transfer during change of state 1. Position and Movement (1nJ:Jflf$Jli]) 2. Newton's Laws (4-tJUt#:) 3. MomentofForce (:}];&.) 4. Work, Energy and Power (#.W , �½'fl':,;&$) Part A : HK:CE examination questions 5. Momentum (fni!:) _.,.,.,. 6. Projectile Motion (/A!fti[:fh) 1. < HKCE 1980 Paper Il-14 > 7. Ci:rcalarMotion (00��1h) 8. Gravitation ( �/ h) Section C - Wave Motion (ut�) 1. WavePropagation(iltl'$$.:!1!) A 2. WavePhenomena(it1h.JJ1.,t.) 3. Reflection and Refraction ofLight(j\;,1¥.1.81.M .&.#M) 4. Lenses (.i!n!:) B ------------ 5. Wave Nature ofLight (.itttilt:fh#,li_) 6. Sound(*i-) Section D - Electricity and Magnetism ( it:fl'"lt) 1. Electrostatics (if"'ttf,-) Two liquids A and B are cooled in air. TheJr cooling curves are shown. If A and B have the same mass, which of the 2. Electric Circlllts (1l!:$) folfowing &atements is/are true? 3. DomesticElectricity(\f;:JkJ!l'II!:) 4. MagneticField(.!:itJf) (I) A bas a higher freezing point than B. 5. Electromagnetic Induction ('t"it�.&O (2) A has a greater specific latent heat offusion tbanB. 6. Alternating Current (::E.mi.'t) (3) Liquid A has a greater specific heat capacity than liquidB. Section E- Radioactivity and Nuclear Energy (�JJt�!.;fu'ftilf.) A. (3) only 1. Radiation and Radioactivity (tHtift>.:tt..fflJ'lt..) B. (1)&(2)on!y 2. Atomic Model (�T.m-fil) C. (2) &(3) only 3. NuclearEnergy(;/t�) D, (!), (2) & (3) Physics - Elective part ( J! *<JI 11-) 2. < BKCE 1981 Paper II - 10 > Elective 1 -Astronomy and Space Science (XSC.-f::f<iottR.#4!-) L The universe seen in different scales (;;i:: /al Si: r.,ffiJ.iT/ru q: 'iii iliitt.) A liquid placed inside an insulated vessel is kept boiling by a heating coil immersed in it When the power supplied to the coil is 42 W, the liquid boils away at a rate of l o-4 kg s- • What is the specific latent heat of vaporization of theliquid ? 1 2. Astronomy through hist.ory(;};.,X,$iY:i-i'-Al�) 3. Orbital motions under gravity( :i:/JTiY:l-t.liiti!t.i) A. 42 x 103 Jkg-1 4. Stars and the universe ('1!.Jtift>q='ili) B. 21 X 1Q4 Jkg-1 Elective 2-Atomic World (,W,..filt.ff..) C. 42 X 104 Jkg-1 1. Rutherford's atomic model C..t�-li/,li T'fJt'!l!) 2. Photoelectric effect (�11::!!Ui) D. 21 x 105 Jkg-1 3. Bohr'satomicmodelofhydrogen (JJtlli iY:,j_J,JH·��) 4. Particles orwiwes ($.!r.T�ilt) 5. Probing into nano scale (4-ilbi,/si!t-$-) 3. < HKCE 1981 Paper Il- 13 > Elective 3 - Energy and Use of Energy (HE :l:!f"�aii.�-fitffl) 0.10 g ofsteatn at 100°C is mixed with 0.10 g of ice at 0°C. No heat is lost to the surroundings. Which of the following I.Electricity at home(�� JI! 11!;) descn"bes the final mixture ? 2. Energy efficiency in building (Jttitlru a!sil!itt.lf!-) Given : specific heat capacity of water = 42 kJ kg-1 0C-1 3. Energy efficiency in transportation (i!#*l\<J�i!Utlfl) specific latent heat of ice= 336 kJ 1cg-1 4. Non-renewable energy sources (;;i::oJ".i§.:i�ii.) specific latent heat of steam = 2260 kJ kg-1 5. Renewable energy sources(oJ"-Pi-:i�l!f-) A. A :mixture ofwater and steam at 100°C Elective 4 -:- Medical Physics ( -1-*t/h .1£*) B. Water at 0°C I. Makingsenseoftheeye(����) 2. M:ak:i:ngsenseoftheear(.Jf�jl,'t) C. Waterat 50"C 3. Medical imaging using non-ionizing radiation (�� '!lt#.t.Htfl-,f,;11.Hf.,f,) D. Wateratl00°C 4. Medic al imaging using ionizing radiation (11!;.ttffiM§,f,M-®.$) I DSE Physics - Section A : M.C. HG3 : Change of State PA-HG3-M/0211 DSE Physics - Section A : M.C. HG3 : Change of State PA-HG3-M/03 -=• 4. < HKCE 1982 Paper 11-10 > 7. < HKCE 1984Paper II - 11> Temperature/ "C 80 A 70 B C 20'C D 60L-----��------�------------>-Time/s A solid substance of mass 2 kg and specific heat capacity 1000 J kl( 1 0C-1 is heated unifoarily by a constant heat source. The temperature-time graph of the substance is shown in the graph. Assuming that no beat is l ost, find from the A cooling curve for liquid naphthalene is shown above. °From the graph, which of the following statement(s) is/are true ? graph the specific latent heat of fusion ofthe substance. (1) The melting point of naphthalene is around 70 C. A. 1000Jkg""1 (2) In the periodBC, only liquid naphthalene is present B. 20000Jkg-1 (3) In the period BC, no energy is given by naphthalene to the surroundings. A. (l)only C. 30000 Jkg"1 B. (1) & (2 ) only D. 50000 Jkg-1 C. (1) & (3) only D. (2) &(3) only 5. < BKCE 1982Paper ll- 22 > 8. < HKCE 1984 Paper n-10 > The following data s� the thennal.properties of four substances P, Q, Rand S: If an immersion heater takes l0 minutes to bring a cup of water to its boiling point 100°C from the room tetnperature of20°C, what will be the tune t2ken for the boiling water to vaporize completely 7 Subrtanc, p Q R s (Specific heat capacity ofwater= 4.2 kJ kg-1 0C-1 ; specific latent heat of steam "" 2268 kJ kg-1• ) A. 33.75minutes Melting point 40K 98K 114K 270K B. 54.00 minutes C . 67.so minutes Boiling point 280K 880K 180K 370K D. 75.40 minutes Average specific heat capacity in J kg"1 oe-1 800 1200 226 40 9. <BKCE 1985 Paperil-13 > Heat is needed to keep water boiling because energy is required to Specific latent heat of fusion in J kg-1 2x10" 11 X 10 4 5 X 10" 33 X 10 4 (1) increase the potential energy of the water molecules. 1 4 (2) increase the kinetic energy ofthe water molecules. Specific latent heat of vaporization in J kg" 30 X 10 34 X 10 4 40 X 104 230 X 104 (3) increase the average speed ofthe water molecules. A. (I) only When the temperature of each substance is increased from 250 K to 400 K, which one will absorb the greatest amount B. (1) & (2) only ofenergy? C. (1) &(3) only D. (2) & (3) only A p B. Q 10. <BKCE1986Paperil-21> C. R D. S 6. <BK.CE 1983PaperII-15 > Itis given that: the specific latent heat of fusion of ice= 3.3 x 1QS J kg-1 the specific latent heat of vaporization of water= 2.3 x 106 J Icg-1 If 1 kg of ice at 0° C and 1 kg of steam at 100°C are mixed in a well insulated vessel, the result will be A. a mixture of ice and ice.cold water. The graph shows the cooling curve ofliquid naphthalene. In which region has naphthalene completely solidilied? B. a mixture of steam and boiling wmer. A p C. water at 0°C. B. Q C. R D. water at 50° C. D. S DSE Physics - Section A : M.C. PA-HG3-M/04 DSE Physics - Section A : M.C. PA-HG3-M/051 HG3 : Change of State HG3 : Change of State 11. <HKCEI987PaperII-26> IS. <BKCE 1990 Paper II- 22> 0 Arrange the following in ascending order. E1 = EncrgyrequiredtomeltlkgoficeatO OC E2 = Energy required to raise the temperature of I kg of copper by 1 °C E3 = Energyrequiredtovaporize l kg of water at 100°C £4 = Energy required to raise the temperature of 1 kg ofwater by 1 °C A E2<1h < E1<E3 B. lh.<E4<B3<E1 ,�-------- A 20 Wheater is used tomelt a solid. A graph oft�e 0agamst time tis plotted as shown above. ffa heater of 40 W C. B3<E1<E4 < E2 is used, which graph (using the same scale) would be ob-tamed? D. &.<Ez<E3 < E1 A 0 B. 0 12. < BKCE 1988 Paper II-11 > Five different solids, each ofma.ss 1 kg, are heated by identical immersion heaters for IO minutes. The following graphs ,8_/� show their heating curves. AsSDIOingno loss in heat, which solid has the greatest specific latent heat of fusion? A T"""""""' a Temperature C. D. 0 0 o�----� ,-. time/min 10 10 c. Temperatu:re D. 16. <HKCE 1991Paper II- 18 > Temperature "'------ '-titne!min 1, 13. <BKCE1989Paperll-18> heater cruiliedice A 400 W electric heater is used to heat 0.4 kg of a solid The graph shows the temperature against time of the substance. The figure shows an experiment to determine the specific latent heat of fusion of ice. The result obtained is lower than the The specific latent heat of fusion of the substance is one expected. The main reason could be that A. 64kJkg-1 A. thereis heat gain from the SUiroUndmgs. B. l60kJkg-1 B. there is heat loss to the surroundings. C. 400kJkg- 1 C. there is some water remairungin the funnel, not falling into the beaker. D. 500 kJkg-1 D. the temperature ofice is below 0°C. 17. < HKCE 1992 Paper II - 17 > 14. <HKCE1990Paperll-21> """' T · w=•w�dp,-rupp1y An iI:l:nnen;ion heater is used to heat a cup of water. It takes IO minutes to bring the water from 20"C to its boiling point The apparatus: shown is used to find the specific latent heat of vaporization I00°C. Find the tllnetaken fur the beater to vaporize theboiling water completely. ofwater. Which ofthefollowfug is NOT correct? (Given: specificheatcapacityofwater = 4200 Jkg-1 0C -1 A Cover the beaker with. a lid specific latent heat of vaporization ofwater = 2.268 x 106 J �1.) hmnersion heater B. Use a suitableheater to prevent boiling the water too vigorously. A. 54 :minutes B. 60minutes C. Surround the beaker with some cotton. Eltctranic balance C. 67 .5 minute s D. Repeat the experiment several times and take the mean of the results. D. 77.5minutes
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