CALORIMETRY EXPERIMENT DO NOT WRITE ON LAB PAPER – RECORD IN SCIENCE NOTEBOOK Purpose. People who check nutrition labels to make informed decisions about food often base those decisions on the number of calories per serving. A calorie, like a joule, is a unit of energy. The International System of Units (SI) unit for energy is the joule; however, the calorie is commonly used for a unit of food energy. A calorie is equal to the amount of energy per unit mass required to raise the temperature of 1 g of water by 1° C. One calorie is the equivalent of 4.18 joules. Food calories, as read off a nutrition label, are actually kilocalories (often denoted as Calories with a capital C). There are 1,000 calories in a kilocalorie (or food Calorie). A calorimeter is a piece of equipment designed to measure the energy released or absorbed during a chemical reaction or phase change. Food calorimetry allows us to determine the number of calories per gram of food. In this activity a piece of food is burned and the released energy is used to heat a known quantity of water. The temperature change (∆T) of the water is then used to determine the amount of energy in the food. In this investigation you will demonstrate how energy is transferred and calculate the calories and kilocalories or Calories of various types of foods Hypothesis: Create an “If, then, because” statement making a prediction as to which type of food contains the most energy. Materials. - 50 mL Water - Graduated Cylinder - Soda Can - Stirring Rod - Paper Clip Stand - Lighter - Thermometer Electronic Scale Aluminum Foil Ring Stand with Ring Food (Doritos, Cheetos, Cashew, Marshmallow) Procedures. Part A: Setting Up the Calorimeter & Initial Measurements 1. Fill four soda cans with 50 mL (50 grams) of water each. Each can is labeled with the food to be used. 2. Measure the temperature of the water in your first can using a thermometer and record the initial measurement or Ti in Table A. 3. Slide a stirring rod through the tab of the soda can. 4. Rest the stirring rod on the ring stand with the soda can hanging in the middle of the ring. 5. Place your paper clip stand on top of the aluminum foil. 6. Place your first food on top of the paper clip stand. 7. Measure the aluminum foil, paper clip and food using the electronic scale and record the initial measurement in Table A. This is mi 8. Place the aluminum foil, containing the paper clip and food, on the base of the stand and underneath the soda can. 9. Adjust the ring so that the soda can is right above the food on the stand. Part B: Performing the Experiment & Final Measurements 1. Use the lighter to light your food until has caught on fire. 2. After the food has finished burning, use the thermometer to measure the temperature of the water and record the final measurement or Tf in Table A. 3. Calculate the change in temperature or ΔT and record this in Table A. 4. Pick up the aluminum foil, containing the paper clip and burned food, on the electronic scale, measure the mass and record the final measurement or mf in Table A. 5. Calculate the change in mass or Δm and record this in Table A. 6. Slide the can off your stirring rod, add your second can and repeat the experiment for all four foods. 7. When finished, clean off the soot from all cans using water from the sink and paper towels. Dump out remaining water in the soda cans. Results. This should include 1 table with the measurements for all four food types. Show your math calculations including the appropriate formulas. 1. Calculate the energy (in calories) released by the burning food sample by using the formula below: Q = heat absorbed by water or ΔH m = mass of water (50g) C = specific heat of water (1 cal/g°C) ΔT = change in temperature °C Q= mCΔT 2. Determine the number of kilocalories or food Calories by multiplying your calories from question 1 by 1000. 3. Calculate the energy content of the food in Calories/gram by dividing your Calories from question 2 by your Δm or change in the mass of the food. 4. Calculate the theoretical energy in the food by determining the Calories/gram of each food as given by the nutritional labels of each food. Analysis/Conclusion. Answer the questions located on your syllabus, as well as those below, in paragraph form with complete sentences in preparation for a class discussion. 1. How did your experimental results compare with the energy calculations from the theoretical results? Discuss why there are discrepancies between the energy transfer from food to water in your experiment versus the nutritional label. Discuss how the procedures could be modify to maximize the energy transfer in the lab. 2. By comparing the experimental results of each food, which type of macromolecule leads to the highest amount of energy transfer? In order to do this accurate you should look at the nutritional label of each food. Hint: Carbon-Hydrogen bonds release a great deal of energy. 3. Explain how this experiment relates to a cheetah in the wild that has caught and will consume an antelope.
