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Energyofpeanut.docx CHEM 121: Energy of a Peanut Lab Name: Partner(s): NOTE: IF YOU ARE ALLERGIC TO NUTS INFORM YOUR LAB INSTRUCTOR You get energy from the foods you eat. That energy derives from chemical reactions -bonds are broken, and new bonds are formed. In this lab you will calculate the chemical energy contained in a peanut and in another snack food using calorimetry. You will burn a peanut and "use" the heat to melt ice in a simple calorimeter. If we ignore heat losses to the air and calorimeter itself: Heat evolved by the reaction - Heat absorbed by the (melting) ice The total heat absorbed by the melting ice can be calculated using the following formula: Heat (enthalpy) = m AH fus Where m is equal to the mass of liquid water produced and AHfus is equal to the heat of fusion for water (80.0 cal/g). Because the density of water is 1.00 g/mL, the volume (mL) of melted water is equal to the mass of the water (g). Since heat is absorbed by the water (ice), the "combustion" of the peanut is exothermic (energy is given off). 1) Obtain an aluminum can. Clamp the can to a ring stand using a large 3-prong clamp. 2) Select a peanut and weigh it. Record the mass in Table 1. 3) Using the special holders, wrap or firmly support your peanut with the wire. 4) Add ice to the can so it is approximately one-third full. 5) Light your peanut using a match or lighter. Move the burning peanut under the can carefully and position it so the top of the flame just touches the bottom of the can. Allow the peanut to burn completely. If the flame goes out and the peanut is not completely burned, relight the peanut 6) After the peanut is burned, some charcoal will remain. Carefully transfer the remaining material to a preweighed piece of paper. Record the mass in Table 1.. 7) Using the clamp holding the can as a handle, carefully pour the liquid water (but no inal from the con into a graduatad aulindar Dlanina a finnal on ton of the amadustad ice) from the can into a graduated cylinder. Placing a furtul on top
of the graduated en van uw a grousaing av pun cylinder will prevent any solid ice from falling into the cylinder. Determine and record the volume of the water in Table 1. 8) Repeat the procedure with another peanut. Record the data in Table 1 (Trial #2). 9) Record the serving size (g) and Calories per serving of the peanuts in Table 1 (These will be the same for both Trials). Table 1: Mass and Volume Data for Peanut Experiment. Trial 1 Peanut #1 Trial 2 Peanut #2 Initial mass of Peanut 0.357 9 0.435 9 Final Mass of Peanut (after burning) 0.040 g 0.048 g Mass of Peanut burned (Initial-Final) 0.3179 0.3879 Volume of water (ml.) 23.0 mL 22.0mL Serving size from label (g) 28 2 Calories per serving from label 160 Cal Table 2: Energy Calculations. DH20 1.00 g/mL so Volume of water (mL) = Mass water (g) Heat mass water (g) x 80.0 cal/g 1 kcal 1000 cal Mass of Water Trial #1 Mass of Water Trial #2 Heat (cal) Trial #1 Heat (cal) Trial #2 Food (nutritional) Cal from peanut Trial #1 Food (nutritional) Cal from peanut Trial #2 Food (nutritional) Cal per gram of burned peanut Trial #1 Food (nutritional) Cal per gram of burned peanut Trial #2 Average Food Calories per gram of two peanuts Calories per gram of peanuts from the package (published value) 1 Cal - 1000 cal
1. Calculate a % difference in your measurement according to: (experimental Cal per g-label Cal per g) label Cal per g % difference - x 100 2. Are your experimental energy values greater than or less than the advertised values? How might you explain the difference? Reflection Questions: 1. What was the purpose of the lab? 2. What two pieces of equipment were used and what were they used for? 3. What did you learn by completing the lab?