College Chem I 2045C Specific Heat of a Metal-SL. Objective: In this lab, you will use calorimetry to determine the specific heat of a metal.

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1 Student Name Partner s Name Date College Chem I 2045C Specific Heat of a Metal-SL Objective: In this lab, you will use calorimetry to determine the specific heat of a metal. Materials: Metal Sample Bunsen Burner 18 mm x 150 mm Test Tube 400 ml Beaker Ring Stand and Support Thermometer Clamps Calorimeter Boileezers Graduated Cylinder Test Tube Holder Glass Rod Wire Gauze Background: When a substance is heated, the temperature increases. This coincides with the atoms of the substance increased motion, including diffusional motion and vibrational motion. The more heat that is added per gram of substance, the greater the temperature change. The relationship between the amount of heat added, the mass of the substance, and the temperature change the substance undergoes is known as the specific heat. Specific Heat is given by the following equation: Specific Heat = (Joules/g C) Energy Change in Joules (Mass in grams) (Temperature Change in Celsius) Specific heat is defined in words as the amount of energy needed to raise the temperature of 1 gram of substance 1 C. The specific heats of substances vary, and therefore this quantity can be used to identify substances. The measurement of heat changes is called calorimetry. In this lab, calorimetry will be used to determine the specific heat of an unknown metal. This will be done using a coffee cup calorimeter containing water. A calorimeter is insulated so as to minimize any loss of energy to the surroundings. Therefore, when a heated piece of metal is placed into the calorimeter, all the energy should be accounted for. In other words, the energy released from the metal should be gained by the water, with no loss to the surroundings. This is based on the Law of Conservation of Energy, which states that energy is neither created nor destroyed. In 1

2 actual fact, the calorimeter has its own specific heat, and a small amount of heat will be lost in heating up the calorimeter. However, this loss is small, and we will assume no heat loss to the calorimeter. Therefore: Energy Released by the Metal = Energy Gained by the Water Pre-Lab: If a heated piece of metal is placed into a calorimeter containing water at room temperature, where does the metal s heat go? Procedure: 1. Weigh the unknown metal as precisely as possible. 2. Obtain a calorimeter. Weigh it as precisely as possible. Using the graduated cylinder, fill the calorimeter with about 40 ml (or just enough to cover the metal) of distilled water at room temperature. Reweigh the calorimeter, and record the weight. 3. Place the unknown metal sample into the 18 x 150 mm test tube. 4. Set up a water bath using a 400 ml beaker. Fill the beaker about halfway with water and add several Boileasers. 5. Add a clamp to the ring stand. The clamp will hold the test tube in the water bath. You want the test tube to set down far enough in the water bath, so that the metal sample is completely covered by the water of the water bath, but you do not want it far enough in that the water may boil over into the test tube. The metal sample needs to remain dry in the test tube. (See Photo Below) 6. Place the test tube into the water bath. Heat with a Bunsen burner until the water is boiling. Continue heating 10 minutes. 2

3 7. Measure the temperature of the boiling water. This is assumed to be the initial temperature of the metal sample. It may be necessary to replenish the water in the beaker, as it should not be allowed to boil to dryness or below the level of the metal sample. [Temperature of Boiling Water = Initial Temperature of Metal] 8. Measure the temperature of the water in the calorimeter. This is the initial temperature of the water. [Temperature of Water in Calorimeter = Initial Temperature of Water] 9. Immediately remove the test tube from the water bath using the test tube holder. Carefully transfer the metal sample into the calorimeter by sliding it out. Use a glass rod to guide it, if necessary. Begin monitoring the rising temperature of the water in the calorimeter. Measure and record the highest temperature of the water prior to removing the metal. Be careful not to allow any water from the outside of the test tube to enter the calorimeter. Do not allow any water from the calorimeter to splatter out either. 10. Repeat steps 1-9 for Trial Perform the necessary calculations. Once you have determined the identity of your sample based on your calculations, show your instructor. 12. Clean-up your lab area. Return all equipment and supplies to the correct areas. Do no throw away the calorimeters. Allow them to dry on the bench on paper towels. 13. You may not leave lab until the instructor signs you out. Data: Mass of Calorimeter (g) Trial 1 Trial 2 Mass of Calorimeter and Water (g) Mass of Water (g) Mass of Metal Sample (g) Temperature of Boiling Water (also Initial Temperature of Metal C) Initial Temperature of Water in Calorimeter Highest Temperature of Water in Calorimeter ( C) 3

4 Calculation Information: 1. You will need to determine the change in temperature for both the metal and the water in the calorimeter. 2. You will need to calculate the energy change of the water in order to calculate the specific heat of the metal. Specific heat of water = J/g C Energy Change of Water = (Mass of Water) (Specific Heat of Water) (Temperature Change of Water in Calorimeter) The Energy Change in the Water = Energy Gained by the Water As it Absorbs the Heat of the Metal Since the energy gained by the water is equal to the energy released by the metal, Energy Change in Water = Energy Released by Metal Knowing the Energy Released by the Metal, you can determine the Specific Heat of the Metal according to the following equation: Specific Heat of Metal = Energy Released by Metal in Joules (Mass of Metal in g) (Temperature Change of Metal in C) Results: Temperature Change of Metal ( C) Temperature Change of Water ( C) Energy Released by Metal (Also Change in Water) (cal) Specific Heat of Metal (cal/g C) Trial 1 Trial 2 1. Determine the Average Specific Heat of the Metal using the data from Trial 1 and Trial 2. Average Specific Heat 2. Determine the Density of the Metal using the determined Average Specific Heat and the table on Specific Heats and Densities. Density of Metal 4

5 3. Determine the Volume of the Metal using the Density and the Mass you determined. Volume of Metal 4. Identity of Your Metal Sample Instructor s Initials: 5