Practical - Data logger: Biology To compare the energy content of different type of food Time: 2 periods Apparatus and equipment ScienceWorkshop Interface Temperature Sensor test tubes balance can, small (for calorimeter) clamp, food holder graduated cylinder, 100 mL stirring rod (2) Chemicals and Consumables cold water food samples (four different foods: peanut, bread, potato chips, animal fat) matches wooden splint Purpose To measure the energy value of food in a home-made colorimeter and the data logger. To compare the energy content of different type of food. Theory All human activity requires “burning” food for energy. You will look for patterns in the amounts of energy released during burning of different foods. When food burns and heats a known quantity of water, the amount of heat given off by the food is theoretically equal to the amount of heat gained by the water: Q m c T where Q is the amount of heat, m is the mass of the water, c is the specific heat of the water, and T is the change in temperature of the water. The specific heat of water is: joule c = 1 calorie = 4.18 gram C gram C Procedure 1. Measure the initial mass of the food sample. 2. Put 10 cm3 of distilled water into the test-tube. 3. Insert a tempterature sensor into the water in the test-tube. Turn on the computer software to record the temperature change against time. 4. Use a tongs to hold the first food sample over a bunsen burner until it catches fire. 5. Transfer the food quickly to the calorimeter. 6. Stir the water as it is heated up. 7. Leave the temperature sensor in the water for at least 45 seconds after the food has stopped burning. Then stir the water until the temperature stops rising. 8. Click the "STOP" button to end data recording. "Run #1" will appear in the Data list in the Experiment Setup window. 9. Measure the final mass of the remains of the food sample and food holder and record the mass in the Data section. 10. Repeat the data recording process for the second food sample. Use a new 50 mL quantity of cold water. After recording data for Sample 2, “Run #2” will appear in the Data list in the Experiment Setup window. Result Energy per unit mass = Q (m c T)/mass of food Food sample Initial weight Final weight Increase in temperature Energy per unit mass (KJ/g) Peanut Bread Potato chips Animal fats Questions 1. Which food had the highest energy content? What is the major composition of this kind of food? 2. Which food had the lowest energy content? What is the major composition of this kind of food? 3. Two of the foods in the experiment have a high fat content (peanuts and animal fat) and two have a high carbohydrate content (bread and potato chips). From your results, what can you conclude about the relative energy content of fats and carbohydrates? 4. Suggest the difficulty of measuring the energy value of butter with this set-up? 5. How can you improve the set up?