I t ' 4 ti. t ti. IQ:::: mass x heat of fusion (or heat of vaporization) I HEAT AND ITS MEASUREMENT. t t. t f I I I. Name

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1 HEAT AND TS MEASUREMENT Name a (or energy) can be measured in unis of calories or joules. When here is a,,,,,,nperaure change (AT), hea (Q) can be calculaed using his formula: During a phase change, we use his formula: Solve he following problems. Q = mass x L\ T x specific hea capaciy (L\T = Final Temp - niial Temp) Q:::: mass x hea of fusion (or hea of vaporizaion) 1. How many joules of hea are given off when 5.0 g of waer cool from 75 C o 25 C? (Specific hea of waer = 4.18 j/g C) 2. How many calories are given off by he waer in Problem l?. (Specific hea of waer = 1.0 cal/g C). 3. How many joules does i ake o mel 35 g of ice a 0 C? (hea of fusion = 333 j/g) 4. How many calories are given off when 85 g of seam condense o liquid waer? (hea of vaporizaion = cal/g) 5. How many joules of hea are necessary o raise he emperaure of 25 g of waer from l 0 C o 60 C? 6. How many calories are given off when 50 g of waer a 0 freezes?,..-...\ (hea of fusion = cal/g) Chemisry F nsrucional Fair, nc. - 4 i i e -e f

2 : FREEZNG AND BOLNG.-ONT GRAPH. \ 25 () 0 15 :l e (J) 0. E (J) 5 b Energy Answer he following quesions using he char above. 1. Wha is he freezing poin of he subsance? --...,...- : 2. Wha is he boiling poin of he subsance?,.-.\\ Name d 3. Wha is he meling poin of he subsance?... r\., Wha leer represens he range where he solid is being warmed? 5; Wha leer represens he range where he liquid. ls being warmed? 6. Wha leer represens he range where he vapor s being warmed? 7. Wha leer represens he meling of he solid? 8. Wha leer represens he vaporizaion of he liquid? 9. Wha leer(s) shows a change in poenial energy? l 0. Wha leer(s) shows a change n kineic energy? Wha leer represens condensaion? 12. Wha leer represens crysallizaion? Chemisry F8766 nsrucional Fair, nc.

3 x _ &.&.... U.LL"V Y "3 " V.lJ.U &::>UUi:>l111\.ij ma w over a 30 minues period. The subsance absorbed hea a a consan rae of > 100 calories/minue over he enire 30 minue period. The graph shows he 30 minue divided ino five ime inervals (labeled,,, V, and V) D- Heaing Curve 1SO l.-- :...-- / / / 60 l / / B M 20 M nmo (mfnues) V v 1 Which phase or phases are presen during nerval, and wha is happening o he subsance during his inerval? 2. Which phase or phases are presen during nerval, and wha is happening o he subsance during his inerval? 3. Which phase or phases are presen duringlrlerval, and wha is happening o he subsance during his inerval? 4. Which phase or phases are presen during nerval V, and wha is happening o he subsance during his inerval? 5. Which phase or phases are presen during nerval V, and wha is happening o he subsance during his inerval? 6. During which inerval or inervals does.he kineic energy of he subsance remain he same hroughou he inerval or inervals?,. 7. A wha ime during he 30 minue heaing period is he kineic energy of he sample greaes? 8. Wha is he meling poin? The boiling poin? 9. How many calories of hea mus he sample of he subsance absorb o vaporize he enire sample a he boiling poin of he subsance? qz_,, ,, ::=::..-

4 ,., Quesions refer o he Cooling Curve for a subsance in he gaseous phase ha was cooled during a 24 minue period. The subsance gave off hea a a consan rae of 40 calories/minue during he enire ime. The 24 minue period has been divided ino five ime inernals, labeled,,, V, andv. i ao... i Cooling Curve \ \ --r " 10. n which inerval or inervals are here wo phases presen? 11. Wha is he boiling poin of he subsance? 12. During which inerval or inervals is all of he subsance a gas? Par of he subsance a gas? 13. During inerval V, wha is happens o he kineic energy of he molecules of he subsance? 14. During inerval V, wha happens o he poenial energy of he molecules of he subsance? 15. s he change ha akes place during inerval V endohermic or exohermic? Explain. Calorimery 16. f 50.0 g of waer is heaed from 30.0 C o 40.0 C, how many joules of hea are absorbed? 17. f 4.00 g of waer absorbs 335 joules of hea, how many degrees Celsius does he emperaure of he waer rise? 18. How many grams of ice a 0.0 C will mel o waer a 0.0 C if he ice absorbed 30,096 J?

5 ....:.i Chemisry: Calorimery Problems 1 Solve he following problems. As always, include work and show he unis o ensure full credi. 1. A 445 g sample of ice a -58 C is heaed unil is emperaure reaches -29 C. Find he change in hea conen of he sysem. 2. A 152 g sample of ice a -37 C is heaed unil i urns ino liquid waer a 0 C. Find he change in hea conen of he sysem. 3. A 218 g sample of seam a 121 C is cooled o ice a-14 C. Find he change in hea conen of he sysem f 161 g of waer a 85 C is cooled o ice a 0 C, find he change in hea conen of he sysem. 5. A 79 g sample of waer a 21 C is heaed unil i becomes seam wih a emperaure of 143 C. Find he change in hea conen of he sysem. 6. f a 348 g sample of seam a 127 C is cooled o 103 C, find he change in hea conen of he sysem...: 7. n going from ice a -34 C o seam a 138 C, a sample of waer absorbs 1.41 x 10 5 J. Find he mass of he sample.

6 -. Find he energy change of he sysem required o change g of ice a -15 C o ice a -63 C g of waer a 4 C o waer a 88 C g of seam a 150 C o seam a 112 C g of waer a 0 C o ice a 0 C g of waer a 100 c o seam a 100 C g of ice a -13 C o waer a 58 C.! ll. r / ;.?. l g of seam a 100 C o ice a 0 C g of seam a 118 C o waer a 100 C g of waer a 43 C o seam a 140 C. i i! g of ice a -38 C o seam a 160 C.