CALORIMETRY
In this lab you will study heat energy as it is transferred between objects. The historical measure of heat energy is the calorie, which is the amount of heat energy that must be added to 1 gram of water at 14.5 oC to raise its temperature by 1 oC.
For the first part of the experiment, you will be investigating the transfer of heat energy from warm water to cool water. Heat lost by the warm water will be gained by the cool water until thermal equilibrium is attained. The amount of heat exchanged depends on the kind of material (water in this case); the amount of material; and the temperatures involved. Heat energy is given the symbol Q. The heat gained of lost is defined by:
where M is the mass of the object, c is its specific heat capacity (1 cal/g oC for water), and DT is the change in temperature of the object.
In the second part of the experiment, you will measure the specific heat of a metallic object by investigating how the object effects the temperature of a known amount of water.
Start a beaker of water heating. We will use boiling water to bring our metallic sample for the second part to a known initial temperature. Now you are ready to start the first part of the experiment.
Measure the mass of a stacked pair of dry Styrofoam cups. Add about 100 mL of ROOM TEMPERATURE water to the cups, and again measure the mass. Place your temperature probe into the cup. Open Logger Pro and set the experiment time to be 300 seconds. Start the computer taking temperature data. Using the other pair of cups, get a similar amount of HOT TAP WATER. Quickly, return to your experimental area and carefully pour the hot water into the cup. Use the temperature sensor as a stirring rod and continue to stir the water until the temperature has reached its maximum value and started to drop, or until the 300 seconds is up. Find the change in temperature from the initial room temperature water to the maximum temperature of the mixture. (You will find rescaling your graph and using the Analyze option to be useful.) How much heat was gained by the cold water? How much heat was lost by the hot water? Again measure the mass of the cups containing the water and determine how much hot water was added. Finally, determine the initial temperature of the hot tap water. Print your graph to include in your notebook.
Once the water that you are heating starts to boil, suspend the 200 gram mass from a piece of string so that it is fully immersed. Allow the water to boil for AT LEAST 5 Minutes. In the meantime, empty your cups and put about 100 grams of room temperature water in a stacked pair. Use the mercury thermometer to measure the temperature of the boiling water. Be sure to keep the thermometer away from the walls or bottom of the beaker. We have all been taught that water boils at 100 oC. Did you MEASURE the temperature of the boiling water to be EXACTLY 100 oC? If not, why do you think that your temperature might have been different?
Place your temperature probe in the cup of room temperature water and allow it to come to equilibrium. Start the computer taking data and quickly and CAREFULLY bring the mass over to your cup by means of the string. Move your temperature probe to the side of the cup and immerse the mass in your water. Gently lift and lower your mass while taking care that it does not touch the temperature probe. Continue until the temperature starts to decline or until the 300 seconds is up. Print your graph. Again analyze your data and determine the heat capacity of your mass. What material do you think the mass is made of? What do you think could be done to make the experiment more accurate?