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1、Specific Heat of a Metal (35 Pts)Background:Specific heat capacity is the amount of energy, measured in calories or joules, needed to raise the temperature of 1 g of the substance by 1 C. Water was chosen as the standard and assigned a specific heat of 4.184 J/g C. The specific heat capacities of al
2、l other substances are compared to water. The value for DH can be calculated using:DH = (mwater )(T)(4.184 J/g C) To measure specific heat in the laboratory, a calorimeter is used. A calorimeter is a well-insulated container used in measuring energy changes. The calorimeter contains water and is ins
3、ulated to reduce the loss or gain of energy to or from the surroundings. Energy always flows from a substance at a higher temperature to a substance at a lower temperature. The heat gained by the cooler substance equals the heat lost by the warmer substance, if we assume no loss of heat to the air o
4、utside the calorimeter.heat lost by system = heat gained by waterTarget: (5pts)In this experiment, you will determine the specific heat for a given metal. The metal sample will be heated to a high temperature then placed into a coffee cup calorimeter containing a known amount of water. If you can fi
5、nd out how much heat was gained by the water in the calorimeter than you will know how much heat was lost by the metal. Heat lost by the metal, DH metal = - (Heat gained by the water, DH H2O)You will be able to solve for the specific heat capacity of the metal (cmetal) because everything else in the
6、 equation will be measured or known. Prelaboratory AssignmentRead the Introduction and Procedure before you begin. Answer the Pre-laboratory Questions.1. A 22.50-g piece of an unknown metal is heated to 100.C then transferred quickly and without cooling into 100. g of water at 20.0C. The final tempe
7、rature reached by the system is 26.9C.a. Calculate the quantity of heat absorbed by the water. Show all work. (1 pt)b. Determine the quantity of heat lost by the piece of metal. Show all work. (1 pt)c. Calculate the specific heat of the metal in J/g C. Show all work. (1 pt)2. What would be the effec
8、t on the value of the specific heat capacity of water if all temperatures were measured in kelvins (K) rather than degrees Celsius (C)? Explain. (2 pts)Materialsbalance Tap waterFoam cups, 6 oz (2) Metal sample250-mL beaker Thermometer50-mL graduated cylinders Hot plate Safety gogglesLab apronTongsP
9、rocedureCalorimeter ApparatusThe calorimeter used in this experiment is Aluminum and is used to insulate the heat of the room from the water inside. The thermometer should touch the bottom of the inner cup. 1. Fill a 250 mL beaker with about 200 ml of water. Place it on your hot plate or heating app
10、aratus and begin heating the water to boiling.2. Place exactly 50 ml of water in the calorimeter and measure the exact volume. Note and record the temperature and volume in your Data Table.3. Obtain a metal sample. Note and record the mass of the metal sample in your Data Table. Place the metal samp
11、le in the boiling water bath for about 3 minutes. This is to ensure that the temperature of the metal is 100C, the temperature of boiling water. Note: The metal sample is hot. Use tongs to QUICKLY remove your metal sample from the boiling water.4. Quickly and carefully transfer the metal sample at 1
12、00C to the room temperature water in the calorimeter. Quickly place the lid containing the thermometer back on the calorimeter.5. Note and record the highest temperature reached by the contents of the calorimeter.6. Repeat the experiment two more times, starting with fresh, cool water in the calorim
13、eter and a dry sample metal. Data Table: (10 pts)Trial 1Trial 2Trial 3Volume of H2O in your calorimeter ( mL )Mass of H2O in your calorimeter ( g )Initial temp of H2O in your calorimeter (oC )Final temp of H2O in your calorimeter ( oC )T of H2O (Final H2O Initial H2O) ( oC )Mass of metal sample ( g
14、)Initial temp of metal sample (100 C )Final temp of metal sample ( oC )T of metal (Final metal Initial metal) ( oC )Questions and Analysis 1. Calculate the quantity of heat gained by the water, using DH = (mwater )(T)(4.184 J/g C) Report the results of all trials, as well as an average (mean) value.
15、 You need to show your work for all of the trials. (7pts)2. Assume that the quantity of heat lost by the metal is equal to the quantity of heat gained by the water. Use Smetal= DH/ (mmetal )(T) to determine the specific heat, S, of the metal. Be sure you use T for the metal in your calculation. Report the result for each trial, as well as a average/mean value. Show the calculations including set up in all trials. (7 pts)3. Consider the assumption you were asked to make in 2.a. Explain why the assumption is not valid. (1 Pt)b.
