Lab Questions 1. Look up the value for the specific heat of water in calories /gC and record it here to at least 3 sig figs 4.186J/9C What units will this yield for q after performing this calculation? Why do the instructions tell you to convert this to Kcal? How to Keals relate to the nutrion facts label on the peanuts? 2. 101.2g of water have a starting temperature of 21.2C. A few peanuts are lit and bumed in the same manner as described in this experiment, and the resulting temperature is 52.3C. What is the energy content in Kcal? 3. For the above question(2), if 2.423g of peanuts are bumed, what is the energy content in Kcal/g. 4. The nutrition facts label states that one serving of peanuts is 148g and contain 828Kcal. What is your experiment calories/serving value for this? What is your percent error? MEASURING THE CALORIC VALUE OF FOOD Theory The caloric value of snack foods is measured using an aluminum can calorimeter. This experiment utilizes the specific heat of water. The heat genenated by combustion (buming) of the snack foods heats water. The temperature change of the water is measured accuratcly and used to deternine the caloric value of the food. Marerials Thermometer, snack foods, aluminum can, ring stand, clamp, wire gauze. Procedure 1. Obtain an aluminum can, weigh, and recond its mass. 2. Add approximately 100ml of tap water to the can, reweigh, and record. the mass. 3. Place the can in the apparatus as demonstrated by the instructor. 4. Place the snack food that you are analyzing on the wire gatze. Weigh the food and wire gaure and record the mass. 5. Place the wire gauze and food in the apparatus as demonstrated by the instnuctor. 6. Measure and record the temperature of the water in the aluminum can. 7. Ignite the food using a Bunsen bumer. Remove the Bunsen bumer as soon as the snack food is buming vigorously. 8. Allow the food sample to bum completely. Record the highest temperature reached by the water in the can. 9. Weigh and record the mass of the wire gauze and any remaining food. Calculations 1. Calculate the mass of the water in the can by subtracting the mass of the can (step 1) from the mass of the water plus can (step 2). 2. Calculate the temperature change of the water in the can by subtracting the initial temperature of the water (step 6) from the temperature of the water after it was heated by the burning food (step 8). 3. Determine the calories released by the food during the combustion process by calculating the heat required to mise the water temperature q=mcTm=massofwater(g)q=heat(calorics)c=specificheatofwaterT=temperaturechangeofwater(C) 4. Convert calories to kcal (dietary calories). 5. Calculate the mass of the food that combusted by subtracting the mass of the gauze after combustion (step 9 ) from the mass of gauze and food before combustion (step 4). 6. Calculate the caloric value of the food by dividing the keal from combustion by the mass of the food in grams. 7. Compare the experimental value with the value found on the nutritional label. 8. Repeat the process for a total of two trials. Do NOT dump the water out of your can
