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9 Specifics of Heats of Metals

9 Specifics of Heats of Metals - M6 WSUW 1 ‘ W F 020(Jo/0...

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Unformatted text preview: M6 . WSUW 1 ‘ W F,__. 020 (Jo/0 / A Name New “Mound Section 00\ EXPERIMENT 9 : SPECIFIC HEATS OF METALS g PRE-LABORATORY QUESTIONS 1 The following preparatory questions should be answered before coming to lab. They I E are intended to introduce you to several ideas that are important to aspects of the E : experiment. You must turn in your work to your instructor before you will be : 2 allowed to begin the experiment. : 1. What is the relationship between a) joule and calorie? Tout: is energy Hmswfi Jtor ‘Force and ”3 tr? Calorie {s enemy, meas mmmfi- 5.3m $500,! anal. bod}: Energy, A 1 mt : 4.14541“ b) temperature and heat Temperm'we =- o‘vfismigfi fiif3%© energy bmk : exem— every 2. AB. Dyer supplied 45.9 cal of heat energy to a 156-g piece of aluminum block that was kept at 28.0 °C. What is the final temperature of the aluminum block?. [specific heat of aluminum = 0.89 J/ g °C; 1 cal = 4.184 J ] 45%“ *M—fl‘g‘f = m: =(Ise9, H‘X‘gqF/sDCX—Vznzg’ooq LO» ' ‘ ' \,3‘3°Q : T2 -2_8.0"C T; = 28°C 3. A piece of metal is added to 36.4 g of water that was kept at an initial temperature of the water is 28.2 0C. After equilibration, the temperature of the water and metal is found to be 29.6 0C. What is the heat change in the metal piece? [specific heat of water = 4.184 J/g. C’C] a :(3eiag\(41\8437ye§(1.4m3 A q =zaes.‘ % Cheml4l4-Academic Year 2010/2011 9—1 4. You can burn your hand if you touch the metal handle of a pot on a stove when the water in the pot is still lukewarm. a) Give an explanation for this difference. View? hag a \mer sgeeie-ie heath 4mm anew mere-em Wm “503 Q'aeeee needs \Dw h %%‘§E*§?S“ them the wire? b) Given that the pot ( stainless steel) weighed the same as the water (2100 g), calculate the temperature rise for the water and the pot if 5.5 k] of heat is added to each. [ specific heat of steel = 0.45 J/g °C, and water = 4.184 J/g OC]. HAT . ‘ -— T 55003 t (2100 3\<0 .45 /3 QCX bT$+egg ATMM’CV = 0. $30 C ’5ng r. S. ‘8 “C 5. What is the difference between the Scientist/Engineer ’s calorie and the dietician’s Calorie? The energy released when a food sample is burned ( in a calorimeter) is determined by measuring the mass of water and the increase in the temperature of the water. A chem. 1414 student named L. M. Bondi decided to carry out the experiment in order to determine the Calorie value of a banana. He took a banana that weighed 120 g and burned it in a calorimeter that was filled with 5000. g of water. If the temperature of the water rose by 21.0 °C what is the Calorie value of the banana? [specific heat of water = 1 cal/ g 0C] (show work) q : (\gom%§LlEQi/g Vc>(z‘o® 105. 14le Chem14l4—Academic Year 2010/2011 9—2 A Name Section RESULTS PART ONE: THE DENSITY OF A METAL BY WATER DISPLACEMENT Cheml414-Acadcmic Year 2010/2011 Metal _J Mass Initial volume of water Final volume of water Al \‘L‘TfiAg ZsmL ”52-0 “‘L Cu 51.6“?» i_ 15 ML EZ‘OML Fe ‘30 1% la ng‘y 31.6w}, Unknown 34.75100; (if: WV $1.6m» /\ PART TWO: SPECIFIC HEAT OF METALS BY CALORIMETRY Metal Initial temperature of Initial temperature of Final temperature of |_ 4 metal Lwater metal and sample A1 1036C J zm°c 11°C Cu mg“ i 2L0 °e ’24 . 5°C Fe ma: rub“; 25°C Unknown 193% 20 5°C 22°C L_ L L. SIGN-OUT: All equipment is put away, and the stud t bench is clean and dry. A TA {gas Date 5! &f& 9—7 CALCULATIONS PART ONE: THE DENSITY OF A METAL BY WATER DISPLACEMENT Metal Mlume (ems) Density (chm3) 1 . 1 53.34 A1 EZmL ~ Z‘c‘me =10cm3 1—33- : 2.6 (gs/em? 7.0cm'5 .. 3 ETEHQ CU 322m. ~15ML -7!0CW‘ :: 3, Z 9/0“} _‘, IGGm?‘ . 50.252 Fe EZmL—ZSmL 17.03“": A 2 '21 Z fem: 16;;th Unknown (541703 _ , <3 1°(‘5ML - ZSmLT— 459w} — 7 6’ [05‘1” 4 “fit???" PART TWO: SPECIFIC HEAT OF METALS BY CALORIMETRY Metal AT (metal) AT (water) Specific heat (J/g. 0C)? 27°;- xo3°c 1'1 00 — ZL$°C . “J' 0 A1 : were -_-. 5.5%: U” Ila C 24.6% . my: 7A5“. - Z\.O°c Cu 323,7 gDC: 1-73-5°C : 3.631 O 9, 26°C _. W155 28% - 21.0%. Fe : -"!6°C : 4|Q°g [fiflmown [—22% ~— sozfic 22°C ”205°C “5 -%\°C, : [95°C A84 3/5°Q\Q{)0Q\, (5.5%“? '3 We g‘fi 5WC03\{(A \84 figcfia @5135 °€fl €7.S\‘i%\}{;735 Chem1414-Academic Year 2010/2011 (qu34g)<'[email protected]) : our/QC, 1 0C ‘3 Name Section A POST LABORATORY QUESTIONS 1. a. Of the metals you tested, which one requires the least amount of heat energy to raise its temperature by 1 0C? . 01%an b. Calculate the temperature rise that would occur when 42.6 J of heat is added to each of two metals (silver and platinum) that have identical weight of 25.6 g [Specific heat of silver = 0.23 J/g °C and platinum = 0.13 J/ g 0C] Ag 3 42! (0'5. : 7‘ Z Qt (Mm 1m Pt = _._——————“Z‘°’.T = 139:. 2. a. Use a periodic table to obtain the atomic weights of aluminum, copper, and iron. A A1 zms 97m Cu W1 F6 55. 85 3117on b. The law of Dulong and Petit states that 1 mole of any pure element has the same capacity for absorbing heat. Expressed mathematically, look at P 1;. (Dd-6mm “:2qu (cg/mm) 7K specific; hBOrtCT/S C’Q : QOQS‘l‘QhfiT/mol 'C) Based upon your specific heat results, what is the value for this constant? 51m: 500%. 91‘: 629273 fig flbflfis/rncfi X L"! 3796% A1 ML 2 Cu ‘ m : (93-55%!moi x 0,32 93°C. Fe AIzmgL : Basswmui 1 0‘ ars we 0. The law of Dulong and Petit can also be used to determine the approximate atomic weight of an unknown metal (within i 10%). 131mg: amp” “Wows; $91“ magi-aw?“ x; m mu: “we ““3“ 0 207,00 t CI) 4— 24 T/N\o\ C F: constant (J/mol° C) M .. atomic weight (g/mol) = _ spe01fic heat (J/g° C) ~ 2 .- V g 17' S/mt" E Cheml414-Academic Year 2010/2011 9“9 7 6 g <6 V Using this equation, what is the approximate atomic weight of the unknown metal? 22 %Ql OC» 2. ac Q‘lmm {3,13E—I'3QQ 3. In the calorimetry part of the experiment, we assumed that all of the heat from the metal was absorbed by the water. In reality, small amount of heat was also absorbed by the styrofoam cups, the thermometer, and the environment in general. a. If this heat loss is taken into account, will your value for the specific heats of the metals increase or decrease? equaflm 45.0! 5.1:?‘5513‘5‘ 5T0? desrease b. Will the value for the atomic weight of the unknown increase or decrease? iacmae 4. Comparing your experimental results for the density and atomic weight of the unknown metal to the information in the following table, what is the most probable identity of the unknown metal? Look a): 8m. gem—3&3, u); g: a): Close; Element 9‘? Densit /cm3 Atomic Weig’ ht 1 g/mol) Magnesium 1.7 24.3 Zirconium 6.4 , 91.2 Zinc ' 7. l ' 65 .4 @113 C72) Cadmium 8.6 112.4 Rhenium 21.0 186.2 5. C. L. Burnett weighs a piece of a rock on a balance and finds the mass to be 69.3 grams. He then immerses it into 25.0 mL of water in a 50 mL graduated cylinder. If the level of the water rises to 33.8 mL, what would the density of the rock be? MD$ D: Mm ' 33.8 mL,—26.01:“!- '3 35w“. 6r ‘St‘acmz‘ (451,39, gficm‘v’ Cheml414—Academic Year 2010/2011 ' 9_1 0 ...
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