Chem+1+Unit+13+Lab


 * Unit 13 Lab Activity **
 * Determining Specific Heat of a Metal **

Chemists identify substances on the basis of their chemical and physical properties. One physical property of a substance is the amount of energy it will absorb per unit of mass. This property can be measured quite accurately and is called //specific heat// (s). Specific heat is the amount of energy measured in joules, needed to raise the temperature of one gram of the substance one Celsius degree. Often applied to metallic elements, specific heat can be used as a basis for comparing energy absorption and transfer. To measure specific heat in the laboratory a //calorimeter// of some kind must be used. A calorimeter is a well-insulated container used in measuring energy changes. The calorimeter is insulated to reduce the loss or gain of energy to or from the surroundings. Energy always flows from an object at a higher temperature to an object 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 surrounding environment. //heat lost = heat gained// In this experiment, you will determine the specific heat of a metal sample. The metal sample will be heated to a high temperature then placed into a calorimeter containing a known quantity of water at a lower temperature. Having measured the mass of the water in the calorimeter, the temperature change of the water (ΔT) and knowing the specific heat of water (4.184 J/g °C) the heat gained by the water (lost by the metal) can be calculated using q=sm∆T.
 * Introduction **


 * Objectives: **
 * Use a calorimeter and make accurate measurements.
 * Calculate the specific heat of an unknown metal.
 * Identify an unknown metal from its specific heat.

1.Fill a large beaker approximately half full of water. Place the beaker of water on a hot plate and turn the hot plate on high. Begin heating the water to the boiling point. 2.Obtain a sample piece of metal and mass it. (mass it a second time just to make sure and use the same scale throughout the lab). 3.Start the Logger Pro program and plug in the LabPro and temperature probe. 4.Obtain a coffee cup calorimeter. Fill the calorimeter with approximately 150 -200 ml of distilled water at room temperature and record the volume to appropriate decimal places. (This water level should be deep enough for the temperature probe to reach it through the lid.) 5.CAREFULLY place the metal sample into the boiling water. Boil at least 5 minutes. 6.While the metal is still in the boiling water bath, measure the temperature of the water carefully with a thermometer and record. //You do not need to start temperature recordings to get this reading.// (It will be assumed that the temperature of the metal is the same as the boiling water.) 7.Place the temperature probe into the calorimeter, through the lid. Place the calorimeter on a magnetic stirrer and turn it on. 8.After the metal has been heating 5 minutes, remove it from the bath with tongs. Start the temperature readings and immediately put the metal into the calorimeter cup so that the metal is covered by the water. Cover the calorimeter with its cover. Turn off the hot plate. 9.Record the highest temperature reached by the water. 10.Remove the calorimeter cover, retrieve and dry the metal. Return metal to its original place. Pour the water down the sink. Rinse and dry the calorimeter cup 11.Repeat the entire procedure with a different metal if time permits.
 * Procedure **


 * Calculations ** : Calculate the specific heat of the metal:

1) Metals have a lower specific heat than that of water how do you know this to be true by what you observed?
 * Questions **

2) Using the list of specific heats of metals, what metal sample did you have?


 * || Trial 1 || Trial 2 ||
 * Volume of water ||  ||   ||
 * Mass of water ||  ||   ||
 * Initial temperature of water ||  ||   ||
 * Mass of metal ||  ||   ||
 * Metal sample # ||  ||   ||
 * Initial temperature of metal ||  ||   ||
 * Final temperature ||  ||   ||
 * Final temperature ||  ||   ||
 * Final temperature ||  ||   ||


 * || // (J/g°C) //  ||
 * Aluminum  ||   0.91   ||
 * Antimony  ||   0.21   ||
 * Beryllium  ||   1.83   ||
 * Bismuth  ||   0.13   ||
 * Carbon Steel  ||   0.49   ||
 * Cast Iron  ||   0.46   ||
 * Chromium  ||   0.46   ||
 * Cobalt  ||   0.42   ||
 * Copper  ||   0.39   ||
 * Gold  ||   0.13   ||
 * Iridium  ||   0.13   ||
 * Iron  ||   0.45   ||
 * Lead  ||   0.13   ||
 * Magnesium  ||   1.05   ||
 * Manganese  ||   0.48   ||
 * Molybdenum  ||   0.25   ||
 * Nickel  ||   0.54   ||
 * Platinum  ||   0.13   ||
 * Potassium  ||   0.75   ||
 * Rhodium  ||   0.24   ||
 * Selenium  ||   0.32   ||
 * Silicon  ||   0.71   ||
 * Silver  ||   0.23   ||
 * Tin  ||   0.21   ||
 * Titanium  ||   0.54   ||
 * Tungsten  ||   0.13   ||
 * Vanadium  ||   0.39   ||
 * Zinc  ||   0.39   ||
 * Zirconium  ||   0.27   ||
 * Wrought Iron  ||   0.50   ||