PracticePacket:Energy Regents Chemistry: Dr. Mintz PracticePacket Chapter4:Energy http://mintzchemistry.weebly.com 116
Energy Objectives Define energy. Demonstrate the difference between endothermic and exothermic reactions in terms of energy. Describe how heat is transferred. Chemistry 200 Video Lesson 4.1 What is Energy? Energy is the ability to do work or produce heat 1.)Potential Energy positional/stored Chemical Potential Energy Energy stored in a substance because of it s composition chemical bonds) 2.)Kinetic Energy - motion Three Forms of Energy 1. Chemical 2. Thermal 3. electromagnetic Chemical Reactions Energy Some reactions release energy i.e. Combustion of propane) o These are called Exothermic reactions o Freezing of water Some reactions absorb/require energy i.e. photosynthesis) o These are called Endothermic Reactions o Boiling of water Exothermic Reactions 117
Potassium Permanganate and Glycerine Endothermic Reactions Barium hydroxide and Ammonium chloride Heat Transfer Heat can only be measured when it is transferred from one piece of matter to another. o Calorimeter tool that measures heat units Joules) Calorimeter Tool used to measure heat transfer 118
Temperature vs. Heat Chemistry 200 Video Lesson 4.2 Objective: How are temperature heat different? How do we convert between Celsius Kelvin? I. Heat A. the transfer of energy from a body of high temp. to a body of low temp. B. Unit --> calories or joules II. Temperature A. the measure of average K.E. of the particles in a substance. how hot or cold it is) B. Units are in Celsius C) or in Kelvin K) III. Heat vs. Temperature How is Heat different than Temperature? ex: What is the temp. of 1000g ice? 0 C 1g ice? 0 C What would require more energy to be melted, 1000g ice or 1g ice? III. Kelvin A. K = C + 273 ex 1 : 35 C = K K = 35 C + 273 = 308K ex 2 : 225K = C C = K - 273 225-273 = -48 C 119
B. Absolute Zero -273 C or 0 K 1. Freezing point of H 2 O = 0 C, molecules are still moving slowlyvibrating) still have K.E. 2. At absolute zero, the molecules have no K.E. NO MOVEMENT AT ALL!! Specific Heat Capacity Chemistry 200 Video Lesson 4.3 Objective: How do we calculate energy gained or lost using specific heat capacity? I. Specific Heat Capacity of a substance) A. amount of heat required to raise 1g of that substance 1 C B. different substances have different composition, therefore each have a different specific heat **specific heat of H 2 O = 4.18J/g C or J/gK** REFERENCE TABLE B) 120
II.Calculating Heat To determine heat absorbed or released in a reaction, we use the following formula: q = heatin Joules) q = mc T m = mass of the substance C = specific heat of the substance if H 2 O, look to Ref. Table B) T = Temp initial - Temp final will always be +) ex 1 : How many Joules are absorbed when 50.0g of H 2 O are heated from 30.2 C to 58.6 C? q =? **Identify known unknown values always!!! Remember UNITS and SIG FIGS!!!!)** m = 50.0g C H2O = 4.18J/g C Ref. Table B) T = 58.6 C - 30.2 C q = mc T q = 50.0g)4.18 J )28.4 C) g C q = 5935.6J q = 5940 J SIG FIGS) = 28.4 C ex 2 : When 25.0g of H 2 O are cooled from 20.0 C to 10.0 C, what is the number of Joules of heat energy released? **Identify known unknown values always!!! Remember UNITS and SIG FIGS!!!!)** q =? m = 25.0g C H2O = 4.18J/g C Ref. Table B) T = 20.0 C - 10.0 C = 10.0 C q = mc T q = 25.0g)4.18 J )10.0 C) g C q = 1045J q = 1050J SIG FIGS) Heat of Fusion Objective: How do we use heat of fusion H F ) to calculate the energy required to melt or freeze a substance? Chemistry 200 Video Lesson 4.4 121
Heat of Fusion melting) - the amount of heat energy per unit mass needed to convert a solid to liquid fusion) or released in liquid to a solid freezing) q = mh F q = heat in Joules) m = mass of substance H F = heat of fusion = 334J/g Ref. Table B :) **How come H F only has J/g specific heat of H 2 O 4.18J/g C) also has C or K?** ex 1 : How much heat energy is needed to melt 5.76g of ice at its melting point? **Identify known unknown values always!!! Remember UNITS and SIG FIGS!!!!)** q =? q=mh F m = 5.76g q= 5.76g)334 J ) g H F = 334J/g q = 1923.84 J q = 1920 J SIG FIGS) ex 2 : If 20.0g of a substance are completely melted at its melting point 3444J are absorbed, what is the heat of fusion H F ) of this substance? **Identify known unknown values always!!! Remember UNITS and SIG FIGS!!!!)** q = 3444J q=mh F 3444J = 20.0gH m = 20.0g F ) 3444J H F =? = H F 20.0g H F = 172.2J/g H F = 172J/g Sig Figs) Heat of Vaporization Video Lesson 4.5 Objectives Use the heat of vaporization H v ) to calculate the energy required to vaporize or condense a substance. 122
Heat of Vaporization Vaporization o Phase change Liquid to vapor gas) Amount of heat needed to convert a liquid into a gas at constant pressure and temperature or condense a gas to liquid) TABLE s B T constants for water) o q = mh v Heat taken away Heat added Same amount of Heat H vw = 2260 J/g Example #1 How much heat is required to vaporize 15.0 grams of water at 100.0 0 C? q = mh v H fw = 334 J/g q = 15.0 g)2260 J/g) q = 33900 J Example #2 How much energy is required to vaporize 10.00 grams of water at its boiling point? q = mh v q = 10.0 g)2260 J/g) q = 22600 J 123
Name Amazing Ice Melt Blocks ENGAGE Guiding Question: Which block A or B) will melt the ice the faster? Figure 1. EXPLORE Demonstration/ Phenomenon: Record your observations as a piece of ice is placed onto each block. Block Observations/ Evidence A B Model/EXPLAIN: Make a labeled model of the experimental set-up at the beginning, right when the ice cubes were placed on the blocks. 124
Questions/ELABORATE: 1. Which block felt warmer? Label it A. Which block felt colder? 2. Write ice melted fast under the proper block in your drawing. 3. Write ice melted slow under the proper block in your drawing. 4. In your own words, explain why the ice melted at different rates. 5. Imagine a new version of this experiment with a frying pan and a plastic food container; predict which will melt the ice cube faster? 125
PracticePacket:Energy http://mintzchemistry.weebly.com VideoLesson1:Energy Definition Characteristics/Facts Examples Non>examples Definition Characteristics/Facts Examples Non>examples Exothermic Endothermic 126
PracticePacket:Energy HeatTransfer All substances are made up of small particles, which can be atoms or molecules that are constantlymoving.thefasterthemoleculesaremoving,themoreenergytheyhave.the totalenergyofmotionintheparticlesofasubstanceiscalledthermalenergy. Temperatureistheaverageamountofenergyofmotionineachparticleofasubstance.It isameasureofhowhotorcoldasubstanceis. Athermometerisathinglasstubewithabulbononeendthatcontainsaliquid, usuallymercuryorcoloredalcohol.thermometersworkbecauseliquidsexpandwhenthey areheatedandcontractwhentheyarecooled.temperatureismeasuredinunitscalled degrees.onthecelsiusscale,thefreezingpointofpurewateris0 Candtheboilingpointof purewateris100 C.OntheKelvinscale,thefreezingpointofpurewateris273Kandthe boilingpointis373k. 1. TheLatinwordcalormeans heat, andmetercomesfromthegreekwordmeaning to measure. Whatdoyouthinkacalorimeterdoes? 2. Wherehaveyouheardthewordcaloriebefore?Whatdoyouthinkacalorieis? Acalorimeterisaninsulatedcontainerfilledwithaliquid,usuallywater.Whenahotobject isplacedinthecalorimeter,heatenergyistransferredfromtheobjecttothewaterandthe water heats up. The temperature change of the water is recorded and by using a simple mathequation,theamountofheattransferredcanbecalculated. Apieceofgoldat100 0 Cisplacedinasimplecalorimeter. Thestartingtemperatureofthewateris30 0 C. 1. Drawanarrowonthediagramtorepresentthe directionofheatflow. 2. Thetemperatureofthewaterwillincreaseor decrease? 3. Namethe3formsofenergy http://mintzchemistry.weebly.com 127
PracticePacket:Energy Exothermicandendothermicreactions Decidewhethereachofthesereactionsisexothermicorendothermic: a) Whentwochemicalsmixtheirtemperaturerises: b) Asolidburnsbrightlyandreleasesheat,lightandsound: c) Whentwochemicalsaremixedtheirtemperaturedrops: d) Twochemicalswillonlyreactifyouheatthemcontinually: e) Plantstakeinlightenergyforphotosynthesis: MultipleChoice 1. Whatoccurswhen35Zgramaluminumcubeat100 o Cisplacedin90.Gramsof waterat25 O Cinaninsulatedcup? 1) Heatistransferredfromthealuminumtothewaterandthetemperatureof thewaterdecreases. 2) Heatistransferredfromthealuminumtothewaterandthetemperatureof thewaterincreases. 3) Heatistransferredfromthewatertothealuminumandthetemperatureof thewaterdecreases. 4) Heatistransferredfromthewatertothealuminumandthetemperatureof thewaterincreases. 2. Whichtypeofenergyisassociatedwiththerandommotionofparticlesina sampleofgas? 1) Chemicalenergy 2) Electromagneticenergy http://mintzchemistry.weebly.com 3) Nuclearenergy 4) Thermalenergy 3. Giventhebalancedequationrepresentingareaction: 2H2Ol)+energy!2H2g)+O2g) Whatoccursasaresultofthisreaction? 1) Thereactionisexothermicandenergywasabsorbed 2) Thereactionisexothermicandenergywasrelease 3) Thereactionisendothermicandenergywasabsorbed 4) Thereactionisendothermicandenergywasreleased 4. Whichunitisusedtoexpresstheenergyabsorbedorreleasedduringa chemicalreaction? 1) Kelvin 2) Joule 128 3) Volt 4) Torr
PracticePacket:Energy 5. Whichphasechangeisexothermic? 1) H2Os)!H2Og) 2) CO2s)!CO2l) 6. Whichoftheseprocessesisalwaysexothermic? 1) evaporation 2) insulation http://mintzchemistry.weebly.com 3) H2Sg)!H2Sl) 4) NH3l)!NH3g) 3) combustion 4) Melting 7. Whenammoniumchloridedissolvesinwaterthetemperaturefalls.Thetypeof energychangeisdescribedas? 1) exothermic 3) endothermic 2) activated 4) adecomposition 8. Thechemicalchangewhenafuelburnscanbedescribedas? 1) precipitation 2) anexothermicreaction VideoLesson2:Heatvs.Temperature ConvertthefollowingtemperaturestoCelsius C)orKelvinK) 1. Z200ºC! K 2. 275K! C 3. Z40ºC! K 4. 150ºC! K 5. 445K! C 6. 0K! C 3) areversiblereaction 4) anendothermicreaction MultipleChoice 1. Whichstatementdefinesthetemperatureofasampleofmatter? 1) Temperatureisthemeasureofthetotalelectromagneticenergyofthe particles. 2) Temperatureisthemeasureofthetotalthermalenergyoftheparticles. 3) Temperatureisthemeasureoftheaveragepotentialenergyoftheparticles. 4) Temperatureisthemeasureoftheaveragekineticenergyoftheparticles. 2. AtwhichtemperaturewouldatomsofaHeg)samplehavethegreatestaverage kineticenergy? 1) 25 C 2) 37 C 129 7. 23ºC! K 8. Z100ºC! K 9. Z196ºC! K 10. 77K! C 11. 3.2x10 2 K! C 12. 45K! C 3) 273K 4) 298K
PracticePacket:Energy 3. Theaveragekineticenergyofwatermoleculesincreaseswhen 1. H2Os)changestoH2Ol)at0 C 2. H2Ol)changestoH2Os)at0 C 3. H2Ol)at10 CchangestoH2Ol)at20 C 4. H2Ol)at20 CchangestoH2Ol)at10 C 4. WhichgraphbestshowstherelationshipbetweenKelvintemperatureand averagekineticenergy? 5. Atwhichtemperaturewouldthemoleculesofaonegramsampleofwaterhave thelowestaveragekineticenergy? 1. 5 C 2. Z100 C 3. 5K 4. 100K VideoLesson3:SpecificHeatCapacity 1. HowmanyJoulesareabsorbedwhen4.0gofH2Oisheatedfrom12 Cto39 C? 2. AsampleofH2Oat17 Chas250Joulesofheatadded.Thetemperaturethenrisesto 33 C.WhatisthemassoftheH2Osample? http://mintzchemistry.weebly.com 130
PracticePacket:Energy 3. HowmanyJoulesofenergyisrequiredtoheat12gofH2Ofrom24 Cto52 C? AlsocalculatehowmanykiloJoules? 4. 655Joulesisaddedto12.0gofH2Oat16 C.Whatisthefinaltemperatureofthe H2Osample? 5. Anunknownsampleofmetalhasamassof24.5g.Theadditionof350Joulescauses themetalsampletoincreaseintemperatureby12 C.Calculatethespecificheat capacityoftheunknownmetal. 6. A12.4gsampleofH2Ohas300Joulesofheatenergyremoved.Ifthefinal temperatureoftheh2owas12 C,whatwastheinitialtemperatureoftheH2O? VideoLesson4:HeatofFusion 1. Howmuchheatisneededtomelt35.0goficeat0ºC?Expressyouranswerin kilojoules. 2. Calculatetheheatenergyrequiredinjoules,tomelt5.00x10 2 gramsoficeat0.0 C. http://mintzchemistry.weebly.com 131
PracticePacket:Energy 3. HowmanyJoulesofheatisrequiredtomelt42goficeat0 CtoH2Oatthesame temperature? 4. Whatisthemassofwaterthatreleases65,247Jwhenitfreezes? 5. Calculatetheheatoffusionforasubstancethatrequires1253joulestomeltandhas amassof19.9g.isthissubstancewater?explain. VideoLesson5:HeatofVaporization 1. Howmuchenergyisrequiredtovaporize10.00gramsofwateratitsboilingpoint? 2. Theheatofvaporizationofaliquidis1,340J/g.Whatistheminimumnumberof Joulesneededtochange45.0gramsofliquidvaporattheboilingpoint? 3. Whatisthetotalnumberofkilojoulesrequiredtocompletelyboil100.00gofwater at100 0 C? 4. At1atmofpressure,25.0gofacompoundatitsnormalboilingpointareconverted toagasbytheadditionof34,400j.whatistheheatofvaporizationforthis compound? 5. Howmanyjoulesofenergyarerequiredtovaporize423gofwaterat100 o Cand1 atm? http://mintzchemistry.weebly.com 132
PracticePacket:Energy UsingtheHeatFormulas 1. A5.00Zgramsampleofwaterisheatedsothatitstemperatureincreasesfrom10.0 o C to15.0 o C.Whatisthetotalamountofenergyabsorbedbythewater? 2. When20.0gramsofasubstancearecompletelymeltedatitsmeltingpoint,3444J areabsorbed.whatistheheatoffusionforthissubstance? 3. Whatwouldbethetemperaturechangeif3.0gramofwaterabsorbed15Joulesof heat? 4. Whatisthespecificheatofsilverifa93.9gsamplecoolsform215.0 0 Cto196.0 0 C withthelossof428jofenergy? 5. Whatisthenumberofkilojoulesofheatneededtochange15goficetowatera0 o C? 6. Inquestion5,isheatbeingabsorbedorreleased?Isthisprocessendothermicor exothermic? 7. Whatisthetotalnumberofkilojoulesrequiredtocompletelyboil200.00gofwater at100 0 C? http://mintzchemistry.weebly.com 133
PracticePacket:Energy 8. If100.0Jareaddedto20.0gofwaterat30.0 o C,whatwillbethefinaltemperature ofthewater? 9. At1atmofpressure,25.0gofacompoundatitsnormalboilingpointareconverted toagasbytheadditionof34,400j.whatistheheatofvaporizationforthis compound? 10. Thetemperatureofasampleofwaterintheliquidphaseisraised30.0 o Cbythe additionof3762j.whatisthemassofthewater? http://mintzchemistry.weebly.com 134
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