(b) The atomic number of copper is 29. In its. normal state two electrons are in the first shell,

Transcription

1 Caper 7 Review, pages Knowledge 1. (c) 2. (b) 3. (d) 4. (a) 5. (c) 6. (a) 7. (a) 8. (c) 9. (d) 10. (b) 11. False. Te mass number is equal o e number of proons and neurons in an aom. 12. True 13. True 14. True 15. True 16. True 17. True 18. False. CANDU reacors use enriced uranium as fuel. 19. False. Nuclear fusion is e nuclear reacion a powers e sars. 20. (a) (iii) (b) (i) (c) (iv) (d) (v) (e) (ii) (f) (vi) 21. Te paricle in an aom a does no ave carge is e neuron. 22. A posiron is a paricle wi a posiive carge and e same mass as an elecron. 23. Te law of conservaion of mass-energy saes a mass can ransform ino energy and energy can ransform ino mass. Te oal amoun of mass-energy in a sysem remains consan. 24. Te binding energy of e dauger nuclei is greaer an a of e paren nucleus, making i more sable. Undersanding 25. (a) Te aomic number of beryllium is 4. In is normal sae, wo elecrons are in e firs sell and wo are in e second sell = 4. Two sells are occupied. (b) Te aomic number of copper is 29. In is normal sae, wo elecrons are in e firs sell, eig are in e second sell, 18 are in e ird sell, and one is in e four sell = 29. Four sells are occupied. (c) Te aomic number of argon is 18. In is normal sae wo elecrons are in e firs sell, eig are in e second sell, and eig are in e ird sell = 18. Tree sells are occupied. 26. (a) Poassium-43 as 19 proons. (b) Poassium-43 as 19 elecrons. (c) = 24 Poassium-43 as 24 neurons. (d) 27. (a) Te elemen wi 20 proons is calcium = 44. Calcium s mass number is 44. (b) Te elemen wi 17 proons is clorine = 37 Clorine s mass number is (a) Radioisoopes emi radiaion a can be deeced and convered ino an image. Paiens are injeced wi a small amoun of a radioisoope, suc as ecneium-99m. Tecnicians en compare e radiaion paerns in e organs of e unealy paien o e paerns in ealy organs. Radioisoopes are able o sow paerns in bo ard and sof issue, unlike X-rays, wic can only sow paerns in ard issue. (b) Answers may vary. Sample answer: In cancer reamens, rapidly dividing cells are bombarded wi radiaion. Tese cells absorb e radiaion and are unable o coninue dividing. 29. Answers may vary. Sample answer: Radioisoopes wi sor alf-lives are used for medical esing because ey emi a large amoun of radiaion quickly as ey decay. Tis ensures a e medical devices ave enoug radiaion o perform e ess. Radioisoopes wi long alflives will no emi enoug radiaion for e medical devices o work properly. Copyrig 2011 Nelson Educaion Ld. Caper 7: Nuclear Energy and Sociey 7-2

2 30. Answers may vary. Sample answers: (a) Cemical reacions involve forces beween molecules, suc as covalen forces and van der Waals forces. Some cemical reacions are endoermic and oers are exoermic. Te reacans and producs are all elemens or compounds. Nuclear reacions involve srong nuclear forces (in fusion) and repulsive elecrosaic forces (in fission) among paricles wiin e nucleus of an aom. Nuclear reacions may require energy o begin, bu are usually exoermic, usually resuling in muc more energy being released an in any cemical reacion. Te producs may include subaomic paricles and energy. In e reacion, mass is ofen convered ino energy. (b) Elecrons ave negaive carges and proons ave posiive carges. Opposie elecrosaic carges arac eac oer. Tis is ow e posiively carged nucleus of an aom olds e elecrons and keeps em from drifing away. Elecrosaic forces also cause proons in a nucleus o repel one anoer. Srong nuclear forces ac o keep e proons and neurons in an aom s nucleus eld igly ogeer. In a sable nucleus, elecrosaic forces and srong nuclear forces balance eac oer. (c) Wen oo many proons are added o a eavy aom s nucleus, e elecrosaic forces causing em o repel one anoer become so srong a ey can overcome e srong nuclear forces and e nucleus can disinegrae. 31. (a) Elecron capure. An elecron is being absorbed by a nucleus. Te proon a e elecron combines wi o form a neuron mus be on e opposie side of e nucleus, since we canno see a new neuron in e produc. (b) Bea-posiive decay. A proon as canged ino a neuron and a posiron, wic is being emied o e rig. (c) Gamma decay. Te number of proons and neurons remains uncanged in e produc, bu a poon is being emied. 32. (a) Te cemical formula for gold-198 is 198 Au Au! Hg e Te new elemen is mercury-198. (b) Te cemical formula for iron-53 is Fe Fe! Mn e Te new elemen is manganese-53. (c) Te cemical formula for argon-37 is Ar Ar! Cl e Te new elemen is clorine (a) Gamma decay occurs afer alpa or bea decay, wen e dauger nucleus is in a igenergy sae. A ig-energy gamma ray, or poon, is emied, and e nucleus reurns o a lowerenergy sae. (b) Te number of proons, neurons, and elecrons in e aom remain e same, so gamma decay is no a ransmuaion. (c) Using elium as an example, e general equaion for gamma decay is 3 2 He *! 3 2 He Te aserisk means a e paren nucleus is in a ig-energy sae. 34. (a) Tis is alpa decay. An aom of elium is emied. (b) Tis is elecron capure. An elecron is absorbed and joins wi a proon o form a neuron. (c) Tis is bea-negaive decay. A neuron as decayed ino a proon and an elecron (d) Tis is bea-posiive decay. A proon as canged ino a neuron and a posiron. 35. (a) Mass of poassium-42 (mg) Mass of calcium-42 (mg) Toal mass (mg) Time () (b) Te numbers in e las column demonsrae e law of conservaion of mass (and energy). 36. (a) Given: = 320 mg; = 7.2 s; = 11 s Required: A A = Soluion: A =! = 320 mg 1 $ = mg 11 s 7.2 s A = 110 mg Saemen: Tere will be 110 mg of nirogen-16 remaining afer 11 s. Copyrig 2011 Nelson Educaion Ld. Caper 7: Nuclear Energy and Sociey 7-3

3 (b) Given: A = 132 mg; = 8.51 min; = 15.0 min Required: A = A = Soluion: A = 132 mg = = mg 15.0 min 8.51 min = 448 mg Saemen: Te iniial mass of e iron-53 sample was 448 g. 37. (a) Given: m Be-9 = u; m p = u; m n = u; m e = u; c 2 = 930 MeV/u Required: mass defec ( m); binding energy (E) m Be-9 Soluion: Te symbol for beryllium-9 is 4 9 Be. m Be-9 = 4( u) + 5( u) + 4( u) u!m = u = ( u) 930 MeV % $ u ' = MeV E = 58.1 MeV Saemen: Te mass defec of beryllium-9 is u, and e binding energy is 58.1 MeV. (b) Given: m O-16 = u; m p = u; m n = u; m e = u; c 2 = 930 MeV/u Required: mass defec ( m); binding energy (E) m O-16 Soluion: Te symbol for oxygen-16 is 16 8 O. m O-16 = 8( u) + 8( u) + 8( u) u!m = u = ( u) 930 MeV % $ u ' = MeV E = 123 MeV Saemen: Te mass defec of oxygen-16 is u, and e binding energy is 123 MeV. 38. (a) Mass-energy equivalence means a mass can ransform ino energy, and energy can ransform ino mass. Te energy of an objec a res is equal o is mass muliplied by e speed of lig squared. Te oal amoun of mass-energy in an isolaed sysem remains consan. (b) Mass defec describes e difference beween e oal mass of all e proons, neurons, and elecrons in an aom, and e mass of e aom iself. (c) Mass-energy equivalence is a cause of e mass defec. Te mass of e aom iself is less an e sum of e masses of is pars because some of e mass of e aom s componens as been convered o energy. Tis binding energy olds e nucleus ogeer. 39. Answers may vary. Sample answer: In nuclear fission, e nuclei of aoms break apar, releasing e binding energy a eld e nuclei ogeer. Nuclear fission is iniiaed by a neuron bombarding a radioacive nucleus wi energy. Te nucleus breaks apar, creaing wo dauger nuclei and releasing some of is binding energy and free neurons. If ere is more fuel available, ese neurons can cause oer nuclei in e fuel o break apar, and release more energy and more neurons. Tis is e beginning of a cain reacion. Te amoun of energy released by e firs nucleus is small, bu in e cain reacion uge amouns of energy can be released. Te amoun of nuclear fuel required for a cain reacion o occur is called e criical mass. Afer e cain reacion begins, i is self-susaining as long as ere is fuel available. 40. (a) Anoer erm for e core of a nuclear reacor is e calandria. Te calandria conains fuel rods, conrol rods, and eavy waer. Fission occurs in e core. Copyrig 2011 Nelson Educaion Ld. Caper 7: Nuclear Energy and Sociey 7-4

4 (b) Heavy waer circulaes roug e calandria and absorbs ermal energy from e nuclear fission reacion. Te waer is used o boil normal waer, producing seam. Tis seam drives a urbine, convering ermal energy o mecanical energy, en o elecrical energy. (c) To conrol e reacion rae, cadmium rods are insered ino e calandria ey absorb neurons and slow e reacion. Heavy waer also slows e neurons and elps conrol e reacion. In a CANDU reacor e cadmium rods are suspended over e calandria by magnes. If e elecriciy supply malfuncions, e magneic field will sop and e rods will drop ino e calandria, suing down e reacion. (d) Maerials a sield e reacor core are cosen o provide proecion from radiaion. In addiion, employees wear badges a conain poograpic film, wic sows e amoun of radiaion ey ave come ino conac wi. Nuclear wase mus be sored in sielded conainers for undreds of years unil i no longer poses a azard. 41. (a) Answers may vary. Sample answer: Nuclear fission reacions usually occur wi eavy nuclei. Nuclear fusion reacions usually occur wi liger nuclei. Bo of ese reacions resul in nuclei closer o e middle of e range, wic are e mos sable. For is reason, bo fission and fusion reacions are exoermic. Nuclear fusion reacions do absorb energy a firs, o overcome e elecrosaic forces a separae em, bu once e nuclei fuse, e reacions are srongly exoermic. (b) Wile fission produces more energy per aom of fuel, e fuel used for fission as significanly less mass, so fusion produces more energy per uni of mass. 42. (a) Te Sun s energy is produced by nuclear fusion. I is difficul o creae conrolled fusion in a lab because i is difficul o produce ig enoug emperaures and pressures o creae e amoun of kineic energy needed o iniiae e reacion. (b) Srong magneic fields sow some promise for conaining nuclear fusion in a reacor. In a magneic confinemen reacor, deuerium and riium would be placed in e reacor and eaed unil ey canged o plasma e four sae of maer. Tis plasma would be conained by magneic fields. On e Sun, fusion can occur because of exremely ig emperaures and graviaional forces. Neier e ig emperaures nor e ig graviaional forces of e Sun are pracical for reacors on Ear. 43. Nuclear radiaion as been used o serilize male insecs, prevening reproducion. Screwworms and sese fly populaions ave been conrolled is way, using wa is known as e serile insec ecnique. Wile is allows us o conrol pess wiou using cemical pesicides, i does resul in some risk of exposure o nuclear radiaion by e people wo work wi i. I also resuls in an organism being eliminaed from e ecosysem, wic may ave serious consequences a do no become eviden for several years. Analysis and Applicaion 44. (a) Fluorine-19 sould ave nine proons, no eig. (b) Silicon-28 sould ave 14 elecrons, no 12. (c) Calcium-44 sould ave 24 neurons, no 20, and 20 elecrons, no 19. Te elecrons in e firs sell sould be in e sandard locaion. Copyrig 2011 Nelson Educaion Ld. Caper 7: Nuclear Energy and Sociey 7-5

5 45. (a) Answers may vary. Sample answer: Wen a aom undergoes alpa decay, is nucleus emis an alpa paricle. An alpa paricle is a elium nucleus, wic is wo proons and wo neurons. Te dauger nucleus will ave an aomic number a is wo less an e paren aom s aomic number and an aomic mass a is four less an e paren aom s aomic mass. (b) Torium-232 as an aomic number of 90. Te dauger aom will ave an aomic number of a is wo less = 88 Radium as an aomic number of 88, so radium- 228 is produced. Te reacion equaion is T! Ra He. (c) Te more massive an aom s nucleus, e more proons i as. Te more proons in a nucleus, e sronger e negaive elecrosaic force beween e proons is, and e more a negaive force couneracs e srong force a olds e nucleus ogeer. For is reason, elemens wi nuclei a are massive, suc as orium, are no very sable. Wen an alpa paricle is emied, e nucleus becomes less massive and more sable. Energy is released. Elemens wi large nuclei are e mos likely o undergo alpa decay. 46. (a) Answers may vary. Sample answer: Bea-negaive decay occurs wen a nucleus conains oo many neurons and e srong force becomes muc greaer an e aom s elecrosaic force. To elp balance e forces, one neuron decays and forms one proon and one elecron. Te elecron, called a bea paricle, is emied from e nucleus. In bea-negaive decay, e aomic number of e dauger aom is one greaer an a of e paren aom, and e mass number remains e same. (b) Answers may vary. Sample answer: In bea-posiive decay, a proon canges ino a neuron and a posiron. Te aomic number of e dauger aom is one less an a of e paren aom. Te mass number remains uncanged. An isoope wi more proons an neurons could ave elecrosaic forces greaer an e srong force olding e nucleus ogeer. Tis isoope would undergo bea-posiive decay o acieve a beer balance beween e srong force and elecrosaic forces. (c) Elecron capure also addresses imbalances beween e srong and elecrosaic forces, and is considered a form of bea decay. In elecron capure, a nucleus wi srong elecrosaic forces absorbs an elecron. Tis elecron combines wi a proon o form a neuron. Te mass number of e dauger aom is uncanged, bu e aomic number decreases by one. (d) (i) Te isoope P would likely undergo alpa decay since i is a eavy elemen. I could also undergo bea-posiive decay since i as more neurons an proons, and e srong force could be sronger an e elecrosaic force, causing a neuron o decay. (ii) For Ne, bea-posiive decay or elecron capure would mos likely occur. Tis isoope as more proons an neurons, so e elecrosaic force would be sronger, causing a proon o decay. (iii) For I, bea-negaive decay would mos likely occur. Tis isoope as more neurons an proons, and e srong force could be sronger an e elecrosaic force, causing a neuron o decay. (iv) For U, alpa decay would mos likely occur. Tis isoope as a very large nucleus and alpa decay would reduce e mass number by four. 47. (a) Nuclear fission reacions need one neuron o iniiae em. Te correc equaion is U n! Ba Kr + 3( 1 0 n). (b) Given: m Ba-142 = u; m Kr-91 = u; m U-235 = u; m n = u; c 2 = 930 MeV/u Required: E!m = m U-235 m Ba m Kr m n ( ) Soluion:!m = m U-235 ( m Ba m Kr m n ) = u [ u u + 2( u)]!m = u = ( u) 930 MeV % $ u ' = MeV E = 140 MeV Saemen: Te energy released in is fission reacion is 140 MeV. Copyrig 2011 Nelson Educaion Ld. Caper 7: Nuclear Energy and Sociey 7-6

6 48. Given: 4( 1 1 H)! 4 2 He + 2 ( 0 +1 e) + energy; m H = u; m He = u; m e = u; c 2 = 930 MeV/u Required: E!m = 4m H ( m He + 2m e ) Soluion:!m = 4m H ( m He + 2m e ) = 4( u) [ u + 2( u)]!m = u E = mc 2! = (0.276 u) 930 MeV $ u % = MeV E = 26 MeV Saemen: Te ne energy released in e overall proon-proon cain fusion reacion is 26 MeV. Evaluaion 49. Answers may vary. Sample answer: I predic a gamma rays, or poons, will penerae e fares because ey ave ig energy and no mass. Alpa paricles ave a ig mass, so i akes more work o move em and ey will penerae e leas. Bea paricles ave an inermediae mass and will be able o penerae a moderae disance. 50. Answers may vary. Sample answer: I would measure e mass a leas wice, record e ime inerval beween mass measuremens, and calculae e alf-life using e following equaion: A! A = or = 1 $. I would begin by finding e mass. If ere was a cange from e saed mass, I would measure again in a few seconds o calculae e alf-life. If ere was no cange, I would measure again a increasing inervals, for example, 1 min, 10 min, 1, 10, 4 days, 10 days, 50 days, and so on, unil I observed a significan cange in e mass. I would en use e mos recen inerval o calculae e alf-life. I would repea e experimen o make sure my resuls were reliable, and sore e sample carefully beween measuremens o proec i from breakage, moisure, and dus. 51. Answers may vary. (a) Sudens answers sould include a discussion of e environmenal effecs of nuclear and fossil fuels, sorage and ransporaion of nuclear fuels and nuclear wases, safey of operaing veicles a use nuclear fuels, nuclear submarines, and poenial coss of nuclear fuels and e veicles a use em. (b) Sample answer: No, I do no ink a we are likely o use nuclear ecnology for space ravel. Newon s ird law is wa makes spacecraf move in space. By ejecing fuel a exremely ig speed wen i is burned an equal and opposie force puses e spacecraf. Tis could no work wi nuclear ecnology because ere is noing being pused or pulled. I may ea up a large mass of waer and ejec i a exremely ig speeds, bu is sill requires e spacecraf o conain a bulky fuel supply a mus be refilled. Nuclear ecnology may be used o generae elecriciy for space saions or spacecraf bu would no be used for propulsion. Reflec on Your Learning 52. Answers may vary. (a) Sudens concep maps sould relae informaion abou isoopes suc as mass number, aomic number, and sabiliy; elemens of radioaciviy suc as ypes of radioacive decay, mass-energy equivalence, energy oupu, fission and fusion; and applicaions suc as fission and fusion reacors, medicine, pes conrol, as well as social and environmenal issues. (b) Sudens essays sould explain ow energy is creaed from mass in a nuclear reacion, ypes of nuclear reacions a ypically occur in sars, and ow e reacions are mainained and conrolled. 53. Answers may vary. Sudens answers sould include relevan facual informaion o confirm or refue eac percepion. Researc 54. Answers may vary. Sudens answers sould describe e life and acievemens of Marie Curie. Se was e firs female o win a Nobel prize, wic se and er usband sared wi Becquerel for eir work on radioaciviy. Se is also e only woman o win wo Nobel prizes. Her work was largely involved wi e sudy of radium. Te uni of radioaciviy, e curie, is named afer er. Se died a e age of 67 from anemia caused by overexposure o radiaion. Copyrig 2011 Nelson Educaion Ld. Caper 7: Nuclear Energy and Sociey 7-7

7 55. Answers may vary. Sudens answers sould describe Canada s nuclear power indusry, ow muc wase is produced, and ow i is managed. Canada produces more radioacive wase per person an any oer counry. We are second in overall nuclear wase producion afer e Unied Saes. bu are expeced o surpass em someime soon. Canada s nuclear wase is kep in sorage sies deep underground. Researc is ongoing o improve sorage safey and o deermine leng of sorage necessary. 56. Answers may vary. Sudens answers sould describe ow smoke deecors work. Radiaion from americium is used o ionize e air in a small region, wic creaes a small amoun of elecrical curren. Wen is curren is disruped by smoke, sensors inside e deecor cause e alarm o go off. 57. Answers may vary. Sudens answers sould describe radon gas, were i comes from, and prevenaive measures a are aken. Radon occurs naurally and comes from e ground. I is usually no a problem oudoors, bu can collec inside buildings, causing respiraory problems and cancer. Radon ess can be done relaively inexpensively, and radon levels can be lowered by venilaing e ouse and sealing e basemen. 58. Answers may vary. Answers sould describe inerial confinemen fusion ecniques, specifically ose a involve lasers. Fusion compounds are firs isolaed and en exremely powerful lasers are used o provide e necessary ea and energy o a very localized area o creae fusion. Tis ecnology creaes a lo of plasma in e process, wic as recenly been sown o be muc less of a problem an previously oug. Europe as several ig-power laser faciliies eier buil or planned. 59. Answers may vary. Answers sould explain a neurinos are a naural produc from many nuclear reacions, specifically ose from e Sun and all sars. Approximaely neurinos per square cenimere i Ear from e Sun eac second. Tey are massless and ave no carge. Neurinos can pass roug millions of kilomeres of lead, bu remain unnoiced by umans and pose no eal risks wasoever. 60. (a) Te ani-paricles of proons and neurons are ani-proons and ani-neurons, respecively. (b) Scieniss do no know wey ere is so lile ani-maer in e universe. An amoun equal o e amoun of maer was originally creaed, bu i is no in evidence oday. (c) Wen a paricle and an ani-paricle mee, ey cancel eac oer ou, or anniilae eac oer. Teir mass is convered ino energy. (d) Given: m P = u; c 2 = 930 MeV/u + m -p!m = 2m p E = 2m p c 2 Soluion: E = 2m p c 2! = 2( u) 930 MeV $ u % E = 1870 MeV E = 1900 MeV Saemen: Wen a ydrogen nucleus and an aniydrogen nucleus mee, 1900 MeV of energy would be given off. Copyrig 2011 Nelson Educaion Ld. Caper 7: Nuclear Energy and Sociey 7-8