Ch13HW - 9:15 (6"ch (futuwpl-turi Questions 27 I...

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Unformatted text preview: 9:15 (6"ch (futuwpl-turi Questions 27 I change. from solids to liquids to gases. At higher temperatures. molecules atoms‘ and even nuclei break apart. There. is a limit to how much internal energy can be removed from an object. and thus there is a lowest possible temperaturefiabsohtte zero. or ’27: o(l——the same as the zero on the Kelvin scale. A substance at absolute. 7ero has the. lowest possible. internal energy. The temperature of a substance does not change while. it undergoes a physical change of state. The energy that is released or gained per gram of material is known as the latent heat. The natural flow ol‘thermal energy is always from hotter objects to colder ones. In the process called conduction, thermal energy is translerred by collisions ber tween particles; in convection the transfer occurs through t he mmrement of the particles; and in radiation the energy is carried by electromagnetic waves. absolute zero: The ltnxest possible temperature; ti K—‘JTSCC, or ilfillal‘. British thermal unit: The amount ol'heat required to raise tlte temperature of 1 pound ol‘ water by lOFA calorie: The amount ol'heal required to raise the temperature 01' 1 gram ol‘ water by l”(?. change of State: The change in a substance between solid and liquid or liquid and gas. conduction: The transl'er ol'thermal energy by the collisions ot the. atoms or molecules within a substance. conductor: A material that allows the easy flow of thermal en- ergy. Metals are Itftltitl conductors. convection: The lransiet oi thermal energy in lltlids by means ol‘cnrrents suth as the rising ol'hot air and the sinking ol'cold air. heat: l'itiergy [lowing due to a dint-retire in temperature. heat capacity: The amount of heat required to raise the tenr per-attire ot'an object by 1°C. insulator: A material that is a poor conductor of thermal en- ergy. Wood and stationary air are good thermal insulators. internal energy: The total microscopic energy of an object. which includes its atomic and molecular translational and rota- tional kinetic energies. Vibrational energy, and the energy stored in the molecular bonds. KEY TERMS latent heat: The amount of heat required to melt (or vapor— ize) l gram ottt substance. The same amount Utilltjllt is released when 1 gram of the satne substance [reeves (or condenses). radiation: The transport ol' energy Via electromagnetic wares. specific heat: The amount of heat required to raise the tem- perature ol'l gram ol'a substance by lgtl. thermal energy: internal energy. thermal Equilibrium: A condition in which there is no net [low ol' thermal energy between two objects. This occurs when the two obiects obtain the same temperature. thermal expansion: The expansion ota material when heated. thermodynamics: The area ol physics that deals with the con- nections between heat and other forms intent-rig}: thermodynamics, first law of: The increase in the internal energy o1 a system is equal to the heat added plus the work (lone on the system. thermodynamics, third law of: Absolute zero may be ap- proached experimentally but can never be reached. thermodynamics, zeroth law of: It objects A and 13 are each in Ihermodynamic equilibrium with object (I. then A and 13 are in thermody‘tnnnic equilibrium with each other. All three ob— jects are at the same temperature. .111 an avalanche, the snow and ice begin at rest at the top ol the mountain and end up at rest at the bottom. What hap- pens to the grm-‘itatiornti potential energy that is lost in this process? 2. What happens to the sound energy l'rom your stereo speakers? 3. What evidence dirl Rtnnliird have that heat was not a lluid? 4. Ruml'ortl concluded that heat cannot be a lluirl. Does this imply that heat does not Ilow? @ How are the totu'epts ol'worlt and heat the same? How are they! tlillerent? 272 Ccsrn: Candtnar'Stune/Gettv 9‘ IO. I2. / (Jim/Mm- 13 Thermal Energy What would you expect to [ind il'you measure the temper— ature ol‘ the water at the top and bottom nl‘ Niagara Falls? Explain your reasoning. It might be argued that the only time you measure the undisturbed temperature of a system is when the reading on the thermometer does not change when it is placed in thermal contact with the system. Use the reroth law to ex- plain why this is so. imagine a uui\'erse where the [cloth la“ ol‘ llrcrrntnlynarn- ics was not valid. \\'ould the concept ol' temperature still make sense in this ttuiyerse? Why or why not? (lould two objects be touching but not be in thermal equi? librium? Explain. ls it possible [or a bucket ol' water in l.os Angeles and a bucket olnatcr in New York (Iity to he irr thermal t'tlllilil)- riurrr? l‘prlaiu. 'y‘r'hy is it incorrect to talk about the llnw ol' temperature li‘om a hot object to a colder object? 021 the inside back cover of this textbook are conversion l'actors between dill'erent units. Why is there no t()11\ er‘sion [actor betweenjoules and kelyin? What is tlte dillerence between heat and temperature? 4. The same amount ol'heat [lows into two diller'ent buckets ls. of water. which are. initially at the same temperature. \'\"ill both buckets necessarily end up at the statue temperature? lixplain, Student 1 claims, "'l'wo buckets of water I‘lltist have the ‘ satire heat it they are at the same temperature.“ Student 2 l6. I7. l8. eotruter'S, “That’s true only il‘ both bttckets contain the same amount old-rater." Which, if either, of these students do you agree with? Explain. How do the internal energies ol‘a cup ol'water and a gallon of water at the saute temperature compare? Under what conditions is the lirst law of therrriodynamics valid? \Not‘k is done on a system without changingI the internal energy ol' the system. Vl’hiclt direction {into or out of the I9. 20. 2!. 22. 23. 24. 25. 26. 28. system) must heat llowduriug this process? Use the lirst lit nl' thertutdeuanrics to justil'y your answer. I low is specitic heat delinch Does it take more thermal energy to raise the lt‘lltpCl'HlllI: ol'h grams ol‘watcr or 5 grams nl‘ ice by ti”(‘.? 1".xplaiu. Liquid X and gas Y have identical specilic heats. “huh ltlll calories of heat raise the temperature ol‘l liter ol ho trid X by the same amount as 1 liter olr‘uas ‘r'? lixplaiu \rrtt reasoning. ()ue kilogram ol'material A at 80%? is brought ilrto the-rum contact with l kilogram nl' material B at 40°C. When lllt materials reach thermal equilibrium. the temperature 1 680(2. Which material. it either. has the greater specilit heat? lixplaitii A hot block olhluurinum is dropped into hilt) grains ol‘ttgt ter at room temperature in a thermally insulated coutauie where it reaches thermal equilibrium. ll' lt)t)t) grains ot wtt let‘ had been used instead. would the amount ot'heat tr ans hated to the water be greater than. equal lot or less titan i was before? Why? A hot block ol aluminum is dropped into Stltl grams o water at room temperature in a ther‘t'nally insulated eon tainertrlrere it reaches thermal equilibrium. ll‘ lllllll gram ol‘ water had been used instead. would the icmperaiurt change ol‘ the water be greater than. equal to, or less that it was below? \\'hy? ‘Why (in climates near the coasts lend to be more tuodet'att than those iii the middle ol'the continent? ‘Why does the coldest part ol' winter or cut tlut int; lalejan may and l-‘ehruary when the shortest day is near lleeem hci'L’l? (liven that the melting and [reeling ternpet .ttut'es nl wile: are identical. what determines whether a mixture o! in and water will freeze or melt? ll‘ you make the mistake ol' retnoyiug ice cubes [rout tbt l'ree/er with wet hands, the ice cubes will stick to your hands. Why does the water on your hands lree/e rather than the ice cubes melt? Photo Associates Why can 2111 iceberg sun'it'e for several weeks [loating in seawater that's above l'reeving? The boiling point for liquid nitrogen at atmospheric pres— sure is 7? li. Is the teml'ierature ol'an open container of liqr uid nitrogen higher. lower. or equal to 77 K? Explain. One hundred grams of ice at [ICC is added to 100 grants of water at Hthtl. The system is kept thermally insulated from its environment. \-\’ill the equilibrium temperature of the 111i.\'tnre be greater than. eqttal to, or less than =l()”(‘.? Ex— plain your reasoning. .-\n ice tube at l)"'(l is placed in a Styroloant cup containing 2t“) grants ol water at lill“('.. When the system reaches ther— mal equilibrium. its temperature is 300C. Was tlte mass of tlte lt‘t‘ cube greater than. equal to. or less than L’Ul] grants? Explain your reasoning. Why is steam at ltltf’C more dangerous than water at ltltfli? A new hqttid is discovered that has the same boiling point and spet'ilit beat as \x‘atet' but a latent heat ofvap<u‘i/uliou ol' ill calories per gram, Assuming that this new liquid is safe to drink. would it be more or less convenient than water [or boiling eggs? Why A system is thermally insulated front its surroundings. is it possible to do work on the system without changing its in: ternal energy? Is it possible to do work on the system with out changing its temperature? Explain. In Vl'ashington, 1).(,Z,. tlte weather report sometimes states that the temperature is 9531: and the humidity is 95%. Why does the high humidity make it so utu'omi'ortable? Use a microscopic model to explain how a metal rod trans— ports thermal energy from the hot end to the cold end. Why would putting a ruler on a tiled bathroom floor tnake it feel less chilly to bare feet? Rank the following,r materials in terms of their insulat— ing capabilities: static air, glass, polyurethane foam. and concrete. Which of the following is the best thermal conductor: fiber— glass. stainless steel, wood. or silver? 4|. 42. 43. 44. 45. 46. 47. 48. 49. 50. (inure/111ml Questions 273 If the temperature is find” and the wind is blowing at ‘10 mph. the equivalent wind chill letttpt‘t'alnre is 2401“. Will a glass ol water freeze in lllis situation? Explain vour reasoning. You hear on the morning weather report that the outside temperature is 75°F with a wind—chill equivalent telnperm ture of filial“. You know that your old car. which is parked outsidtu \vill ttot start if the temperature of the battery drops below lt'r'l“. Will your car start this morning? Why or why not? The respective thertnal conductivities of iron and stainless steel are 79 me '°(? and [-1 \Wm - “(3. Use these data to ex— plain tvhy you need to use potholders for pots with iron handles but not for pots with stainless steel handles. Why might a cook pttl large aluminum nails in potatoes be— fore bakin‘er them? In northern climates drivers often encounter signs that read “BRIDGE FREEZE}; BEFORE R( );\l)\‘l.-".-\Y." Why does this occur? You have just made yourself a hot cup of coffee and are about to add the cream. which is at room temperature. Suddenly the phone rings and you have to leave the room for a while. ls it better to add the cream to the eoll‘ee before you leave or after you get batk il‘you want your eoll‘ee as hot as possible? Why? When pilots fly under clouds. they often experience a dott‘ndralt. Vl'hy is this? :7 1: It is midal'ternoon and you are canoeing down a river that empties into a large lake. You are having a hard time mak- ing progress because ofa stiff wind in your face. is this sits nation likely to get better or worse as the Sun sets? Explain. A black car and a white car are parked next to each other on a sunny day. The surface ol' the black car gets much hot- ter than the surface ol the white car. Which mode ofenergy transport is responsible for this dillerence? Earth satellites orbit Earth in a very good vacuum. Would you expect these satellites to cool oil when they enter Earth’s shadow? Explain. 274 (Jim/1m- 13 Thermal Energy 5|. A Thermos bottle is usuaily constructed 1111111 two nested glass (ontainers with :1 vacuum 1‘11'111'1'1'11 them. as shown in the figure. The walls are usually silVet't'tl as well. How does this construction minimize the loss 111'1111‘1'111al energy? 52. Will :1 Thermos bottle (shown 111 the figure} keep some- 11111115111111 :1swell as it keeps it 11111? Explain. 53. The metal r111 11' on :1 wooden shed 111:1kes noises when :1 cloud passes in front 111‘111e 81111. Why? 54. Why [night :1 glass dish 1:1ke11 1111111 the oven and put into cold water shatter? *55. Suppose 1111' column in an :111'111111ls1114g111ss 111ern1111ne11'1' is not uniform. How would the spacing between the de- grees on ;1\\=ide portion 01' the 11'11'1'111111111111-1' compare with those 011 :1 narrow portion? $5151. When :1 mercury thern'tometer is 111st put into hot water. 1111' level 1_11'111e mereut—y drops slightly before it begins to climb. Wlu'? I. How much heat is required to raise the lentperalure 111' 51l1lg111'11':1ler 11‘11111 211°(i111 511113? 2. 11 the temperature 111‘ 11011 g 111' water drops by .‘"(1, how much heat is released? How 11111111 work is required to push :1 erale with :11111‘1'1' (11‘ 2111) N across :1 [111111' :1 distance 111—1 111? How 111:1111-‘1'alories 111‘ thermal energy does the 1‘1'i1‘lit111 produce? *4. How many calories are released to 1111' surroundings11'111'11 111111101111111 3111111 falls from :1 heing 111' 51] £111 and doesn't bounce? *5. A physics student foolishly wants to lose weight 111' drinking; cold water. 1111c drinks 1 1: (111111) 0113) 111'11'2111’1'111 111°C below body temperature, how many Calories will it take 111 warm the water? 6. A typicaljogger burns up food energy at the rate 111111111111 40 11] per minute. How long would it take to run 1111‘ :1 pit-1'1- 1'11‘1'ake i1'it Contains 401) Calories? )uring :1 process‘ 28] ol'heat are transferred into :1 system! . while the system itself does 12} o1‘work. What is 1111- change 111 the internal energy 01' the system? 3. 1111111 internal energy 111' an ideal g: ' increases by 151) _§ when 2411‘] (11"11'01‘1; are (10111: to compress it, how 111111111 heat is released? 9. It takes 250 cal to raise the temperature 111:1 111et‘allic ring 1'1‘11111 211°C to 30"(‘.. 11‘ the ring 11111111 11111111111191) 11;, what. is 1111: specific heat 01‘ the metal? 10. “it takes 3411111111 to raise the (em perature 111‘ :1 51111—1; statue by 1101 i, wltal is 1111' speeilit' l1e:1l 111‘1111- 111:111-1'ial used 111 111:1ke1111-slalue? :E‘XEERCl-S ES Vartuun S11\'ere(i Questions 51 :111111'12 ll. How111:111y1‘alori1'swill11takeloraisethelemperautreol a 311—53; 3411111 1'11ai11 1111111211"(11o 11111"'(Ti- I2. 1-11111' 11121111 t‘alories 111111111 it take to raise 1111' lentpelaluze 111113111171;ahnnintun11:111111111129211§tol173ii? @Six gralusol liquid X :11 f’15"(i:1|'1'2111111-1l 11135411111111111'1111- uirlYal21H}.'1111's11ee1111‘heal11llir|uithis 21:11 “(7. :11111lltesperilu'111'211111'1111111111'is l ral "13. [11211111112111] ."4li'l ' h 1 ,U ' 1-! 1117111111111 X girt's up two 1111111113 1:1 111111111 1'. 111111 1111' change 111 tenlpelattlre 111'1'111'11 111111111. I4. 111 l‘isert'ise 131.1111ag1111' [11:11 111111111X1'11111111111'sl1111111111111 energy to the other liquid 12 1'311111‘1es'111:1111111‘. 11111111111111 11111111115 would111'1‘e1111111'rl1111121111:111111111111111e111p1'1ar ture?\-\"l1:1l is this equilibrium 11'111111'1‘111111'1'? l5. Eighty grams 111-11':1ler :11 71111: are mixed with an equal 111111111111 111‘ water at 31101! in a e111np1e11'11' insulated 1011' 1:11111'1‘. 1111' 1111a] lt'Inperalure111'1111' water is 5113(1. 21. How much heat is lost by the hot water} b. l'1own1111'11heatis gained 111' the cold water? c. What happens to 1111' total 111111111111 olintet 11:11 eneig' 111‘ the system? :3‘ I 6. 11211011; olwater :11 l1)11°(i are mixed with $111111); 111‘11'ater :11 51W} in :1 completely insulated container. what is 1111: 1111.11 equilibrium te111pe1':.11.111‘e? 17. A kettle containing 3 kg111'waler11:1s_justreae11ed its 1111117 1111;" point. How 11111111 energy, inj11111es_ is required 111111111 / the kettle dry? How much heat would it lake to melt :1 17111111111111 111111" I9. 1111111’is11111111ell:11H1g111111'k111:1111111i1111111,whieliisinir liallr at 211%}. How 111111'11 energy: in 'joules‘ is required 111 ...
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Ch13HW - 9:15 (6&amp;quot;ch (futuwpl-turi Questions 27 I...

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