Lab 12 Experiment Xii A Specific Heat You May Need To Start With The Group Work Due To Availability Of The Lab Equipme 1 (71.02 KiB) Viewed 41 times
Lab 12 Experiment Xii A Specific Heat You May Need To Start With The Group Work Due To Availability Of The Lab Equipme 2 (43.29 KiB) Viewed 41 times
lab 12 Experiment XII:A - Specific Heat You may need to start with the group work due to availability of the lab equipment When an object of higher temperature is brought into thermal contact with an object of lower temperature, heat will flow from the higher to the lower temperature object until the objects reach a common temperature, at which time there is no longer any exchange of heat. The amount of heat needed to change the temperature of an object is called the heat capacity. Because the heat capacity is proportional to the mass (doubling the mass doubles the amount of heat needed...) we typically use the heat capacity per mas called specific heat When a substance of mass mit absorbs thermal (heat) energy of quantity Q. the temperature change at the substance undergoes is related to Q by 0 = mcAT, where c is the specific heat of the substance. If a system consists of two substances the relation is Q = m,, AT + m2c247. This experiment makes use of this behavior to determine the specific heat of aluminum Energy may be supplied to a system by resistive heating. If a heating device operates at voltage V and current I for a time, the amount of heat energy generated is IVt = Q. The "calorimeter" consists of a resistive heating element embedded in a cylinder of aluminum (AI). The apparatus is thermally insulated from its surroundings. An electric current delivered to the element generates heat in the heating element, causing the temperature of the element to increase and heat energy to flow to the cooler Al cylinder. After a period of time, the current is turned off, and the apparatus is allowed to come to thermal equilibrium. The power supply has two displays, one for VOLTAGE, and one for CURRENT. The VOLTAGE reading can be used, but the CURRENT reading is not precise enough for this experiment. So the power supply is connected to the heating element of the apparatus by way of an AMMETER, which measures the current delivered to the heating element The temperature probe connects to the LabPro interface and the LoggerPro software monitors the temperature. A box in the lower left corner displays the temperature reading in real time. It is important that the number displayed have at least 2 decimal places. If you need to adjust the number of digits in the display, use either the Data menu or right-click to find Column Options; then select the data title and make the change in the "Displayed Precision" box. XII:A-1 Specific Heat
Activity 1 1. Set the computer to record data for up to 1000s by clicking the Clock icon to the left of the START icon) and record the initial temperature Ti. 2. With the power supply off, disconnect a wire from the power supply so only one wire is connected to the power supply 3. Turn the CURRENT knob on the power supply fully clockwise. 4. Turn on the power supply and then turn the VOLTAGE knob to set the voltage reading to about 5 V. Record the voltage V reading below 5. Click the green START icon to begin taking data and leave it running It is important that the time intervalt over which power is delivered to the heating element is accurate. A timer is provided to perform this measurement 6. Connect the second wire to the power supply to allow electric current to flow to the heating element and at the same time start the timer. Record the current I below. 7. After about 2 minutes (120 s) simultaneously disconnect one wire and stop the timer. Record the time I below. 8. Wait while the temperature of the aluminum and heating element reach a steady temperature (about 10 minutes). Record the final temperature T. Given data: mai - 445 g meet-220/C Measured data: I= T T- V- Find the specific heat of aluminum ca Date: Instructor Initials: XII:A-2 Specific Heat
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