Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc. To helpthemunderstandwhy dissolutionis • studentsthedifference Review with between • Potassium heatfrom absorbs its chloride • Teaching Tips rules. to alllaboratory observe Remind students precautions. Review allsafety Safety Information water distilled to sit Allow about2Lof • orlabstationsin materials Prepare setsof • Install theDataMate onthegraph- program • Advance Preparation one 45-minute classperiod Time Requirements mic processes inprogress andanalyze data. culators to exothermic observe andendother- cal- usegraphing Studentswill perature probe. three minutes usingtheCBL2unitandatem- collect temperature will They datafor water. that occur aschemical compounds dissolve in measure temperature changesStudents will Purpose Name Date Class chemically. It isnotchanged the saltwould remain. thewater were to evaporate, If taste thesalt. canstill they dissolvethey saltinwater, remind themthatwhen a physical process, process. isaphysical This asolidinwater. of solving beinvestigating will they thedis- In thislab, chemical processes andphysical processes. process. isanexothermic calciumchloride of Thedissolution process. is anendothermic potassiumchloride dissolutionof Therefore, itdissolves when surroundings inwater. overnight atroom temperature. complete thelab. advance to helpinsure thatstudentseasily ing calculators. 13 13 Preparation Teacher Endothermic andExothermicProcesses • Ammonium nitrate (NH Ammonium nitrate • Lumps orchunks work better thanfine- • Have studentsresearch to findoutabout • everyday activi- Have studentsmake alistof • Have studentsresearch to findouthow cal- • Have happen studentshypothesize whatwill • Extensions • The solutionmay The become saturated and • alsocanbesubstituted chloride Sodium for • when thewater inthebeaker isstirred. it dissolves inapproximately 15–25seconds but Granulated materialworks, to dissolve. take material becausethey granulated longer n,adseflf ftheseproducts. lifeof andshelf ing, packag- methodsof chemicals used, of types Studentscanfindthedifferent cold packs. items andmake amaster list. their The classcancompile allof processes. andexothermicties thatuseendothermic peratures drop below freezing. isusedwhenoutdoorcium chloride tem- hypotheses. todents to theexperiment test perform their Allow stu- water. decreasing theamount of solidor increasing theamountof try they if h ekr thesolutionisprobably saturated. the beaker, dents seeundissolved solidsinthebottom of stu- If notdissolve. will additional material temperaturesmaller change. however itproduces a potassium chloride, water. cold packsoften and useammoniumnitrate Small firstaid the fumesnearbeaker. Caution studentsnotto intentionally inhale may occur whenitismixed water. with mildammoniaodor a potassium chloride, isusedinstead ammoniumnitrate of If will. thanKCl pergram energy larger amountof release It a will process. an endothermic to potassiumchloride demonstrate instead of 4 NO 3 ) may beused Lab 13 75 76 4. 3. 2. 1. Pre-Lab Answers Exothermic processes are common andthe • Name Date Class Teacher Preparation heat. processAn endothermic isonethatabsorbs heat. An exothermic process isonethatreleases dissolving. and state, changing shape, changing physical change are Possible examples of composition stays thesame. asubstance changes butits or appearance of A physical change isoneinwhich theform stunts inthemovies. researching how pyrotechnics are usedfor Somestudentsmay beinterested in class. research andpresent to theirreport the Studentscanpickaprocess to use them. that activities class cangenerate alonglistof Lab 13 (continued) exothermic processes are below. shown and bothendothermic of Sample graphs Dissolving ofCaCl Dissolving ofKCLinwater 2 in water

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Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc. determine which type of heat energy transfer istakingplace. transfer heatenergy of determine which type you collect In isreleased dataandsearch will thisactivity orabsorbed? heatenergy forcluesto if Will theseprocesses • Processes heatare called thatabsorb from thesurroundings. energy Processes are thatrelease called heatenergy into thesurroundings. releases dissolving heatenergy In some cases, substance thatisdissolving. the water into moleculesbreak positive apart of andnegative andsurround theparticles parts The asubstance isaphysical change. of thedissolving achemical change, of canbeasign energy Name Date Class 4. 3. 2. 1. Pre-Lab Wash your handsbefore leaving thelaboratory. any ordrink materials usedinthelab.• eat, nottaste, Do • Report any spillsto your teacher. • Always andalabapron. goggles wear safety • Safety Precautions What happenswhenCaCl • What You’llInvestigate Endothermic andExothermicProcesses changes? produce temperature water? and KCl are addedto achange in Although occurs. usually change a inenergy When asubstance dissolves inwater, What process? isanendothermic What isanexothermic process? physical change? What are examples of What isaphysical change? 13 13 Probeware Activity 2 over time. Graph ing theprocess. temperature thatoccurs dur- Calculate added to water. perature whensubstances are Measure Goals temperature changes the change intem- exothermic any change inwater . In other cases, dissolving absorbs heat absorbs dissolving In othercases, . endothermic. 5.0g potassium chloride (KCl)5.0g potassiumchloride 5.0g calcium chloride (CaCl 5.0g calciumchloride waterdistilled rod stirring glass plastic spoon 100-mL beaker 400-mL beaker probe temperature DataMate program link cable calculator TI graphing CBL 2orLabPro unit Materials (room temperature) How canyou tell Lab 13 Lab 13 2 49 ) 77 78 Lab 13 50 4. 3. 2. 1. Part B:CollectingData Figure 1 2. 1. Part A:PreparingtheCBLSystem Procedure Name Date Class Temperature probe 100-mL beaker 400-mL beaker Probeware 13 Activity seconds. becollected for180 Datawill into thewater. isemptied thepotassiumchloride sure allof Make tothe potassiumchloride thewater. carefully add after datacollection hasbegun, About five seconds thedatacollection. begin select calculator, On thegraphing dish. weighing paperorina weighing onapiecechloride of potassium Use abalance to measure 5.0gof Place thetemperature probe inthewater. the 400-mLbeaker. room-temperature water to Add 100mLof manually. onhowinstructions to setuptheprobe The to turn page to reset theprogram. not, If automatically. temperature probe shouldberecognized Press Turn DataMate. onthecalculator andstart theCBL 2unit. probe into channel 1of in shown as Set upthecalculator andCBL2unit, Lab 13 CLEAR Figure 1. Plug thetemperature (continued) vi START for to 7. 6. 5. 4. 3. 2. 1. Part C:ExaminingtheData 2. 1. Cleanup andDisposal 6. 5. hnyuaefnse,pes Select . TO MAINSCREEN. RETURN press When you are finished, parts Rinse your beaker thoroughly andrepeat the Record thesetemperatures in solid dissolved. the perature—the temperature after allof temperature andwhich istheendingtem- theseisthestarting Determine which of to selectthispoint. and maximum temperatures reached. Your display calculator will theminimum Press reached. the to of selectthebeginning to selectthelasttemperature datapoint Use arrow key theright temperature graph. Press Select Select Follow thedirections onthescreen. Return to themainscreen by pressing time onthe temperature onthe time with temperature versus of display agraph will thecalculator After 180seconds have lapsed, dissolve.help thepotassiumchloride water inthebeaker forabout20seconds to gentlystirthe Using rod, stirring aglass graph inyour graph ENTER ENTER on the following page. on thefollowing by your teacher andanswer thequestions Clean andreturn allequipmentasdirected unit. connect thetemperature probe andCBL2 calculator anddis- thegraphing Turn off Data Table. B STATISTICS. ANALYZE. .Select . ENTER and C x ai.Sketch andlabelthis -axis. EUNT ANSCREEN. MAIN TO RETURN Science Journal. sn fcalciumchloride. using 5gof ENTER hnyuaefnse,press When you are finished, y ENTER -axis and Select QUIT.

Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc. Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc. 4. 3. 2. Name Date Class 1. Conclude andApply DissolvingofKClandCaCl Data Table: Probeware 13 Activity no additional cooling will beobserved. cooling will no additional Teacher Note: thewaterbec When extension. possiblycoo coolmore, The waterwill water. added to thesameamount of asmuch twice was potassiumchloride beif inferwhattheresult might From your results, dissolved. completely Thetemperature of wasdissolving. solid the thewaterchangedrapidly when temperature The of vary. answerswill Student atfirstandthenleveled off. changed rapidly thewater Suggest apossibleexplanation forwhy thetemperature of Look atyour graphs. process. inwaterisanexothermic dissolving chloride calcium process while inwaterisanendothermic Potassium dissolving chloride Which process andwhich isexothermic? isendothermic thewater. temperature of change)thanthestarting (positive shouldbewarmer solution chloride and thecalcium change) (negative shouldbecooler solution potassiumchloride The resultsStudent may vary. ture changes different? Record your results inthe from theendingtemperature. Calculate thetemperature temperature change for each thestarting substance by subtracting usac °)(C °)Process (°C) (°C) (°C) Substance Potassium Calcium chloride chloride (CaCl (KCl) 2 ) eprtr eprtr hneType of Change Temperature Temperature trigEdn Temperature Ending Starting 50 01 51 Exothermic Endothermic +5.12 –5.70 30.16 19.61 25.04 25.31 (continued) igtiea uh Students couldtestthisasan asmuch. ling twice the water leveled off when the solid was thesolid when off the waterleveled 2 omes saturated with the substance being dissolved dissolved thesubstancebeing omes saturated with Data Table. How are thesetempera- Lab 13 51 Lab 13 79