Energy Content of Foods Your Name Lab Partners: Period: January 28, 2013
Background Information: Heat is energy that transfers from one object to another because of a temperature difference between the objects. Heat is measured in a calorimeter and the units for heat are joules or calories. The calorimeter uses the Law of Conservation of Energy which states that energy is never created or destroyed but is transferred between objects. Temperature is a measure of the average kinetic energy of the particles an object which is different that the heat which is all the energy in the object. Temperature can be used to calculate heat by looking at the change in temperature. Energy can be calculated using the formula: Q = mc T. In the formula, Q = the energy in joules or calories, m = the mass in grams, c = specific heat and T = the change in temperature which is the final temperature minus the initial temperature. The specific heat for water = 1 calorie/gram C. Purpose: The purpose of this lab was to determine the energy content of different foods. Hypothesis: If different foods are burned, then their energy content can be found, because the energy will be transferred to the water in the calorimeter because of the Law of Conservation of Energy. Materials: Safety goggles Food samples Food holder Can Calorimeter Ring Stand Ring Clamp Water Graduated Cylinder Balance Matches Thermometer Diagram of lab setup:
Procedures: 1. Get and put on safety goggles. 2. Measure water (approximately 50 ml) and put in can calorimeter. 3. Measure temperature of water. 4. Get food sample and put in food holder. 5. Measure mass of food and food holder. 6. Light food on fire and put close to bottom of can. 7. Wait for food to burn completely. 8. Measure temperature of water. 9. Measure mass of remaining food and food holder. 10. Empty water from can and throw away food remains. 11. Repeat steps 2-10 for remaining 3 foods. Safety Considerations: 1. Wear safety goggles at all times. 2. Long hair should be tied back. 3. Close-toed shoes should be worn. Data: Marshmallow Peanut Potato Chip Popcorn Initial mass of food and holder in grams Final mass of burned food and holder in grams Starting water temperature in C Final water temperature in C 28.2 g 18.5 g 19.1 g 18.1 g 25.2 g 18.0 g 18.4 g 18.0 g 21.9 C 22.8 C 23.7 C 25.2 C 27.1 C 37.6 C 37.3 C 26.7 C
Calculations: Marshmallow Peanut Potato Chip Popcorn Calculated mass of water in grams 5.2 C 50.0 g 50.0 g 50.0 g Calculated T in C 5.2 C 14.8 C 13.6 C 1.5 C Calculated heat energy gained by water in J Q = mc T Calculated mass of food burned in grams Calculated energy content per gram of food (J/g) 1086.8 J 3093.2 J 2842.4 J 313.5 J 3.0 g 0.5 g 0.7 g 0.1 g 362.3 J/g 6186.4 J/g 4060.6 J/g 3135.0 J/g Calculations for Marshmallow 50.0 g x 4.184 J/g C x 5.2 C = 1068.8 J 1068.8 J / 3.0 g = 362.3 J/g Calculations for Peanut 50.0 g x 4.184 J/g C x 14.8 C = 3093.2 J 3093.2 J / 0.5 g = 6186.4 J/g Calculations for Potato Chip 50.0 g x 4.184 J/g C x 13.6 C = 2842.4 J 2842.4 J / 0.7 g = 4060.6 J/g
Calculations for Popcorn 50.0 g x 4.184 J/g C x 1.5 C = 313.5 J 313.5 J / 0.1 g = 3135.0 J/g Data Analysis The food with the highest energy content per gram was the peanut. The food with the lowest energy content per gram was the marshmallow. 1. One possible source of error in this lab was that energy was lost to the air because the food wasn t directly next to the can. Another area where error could have occurred was in the measuring of the temperature because it was hard to read the thermometer and the temperature dropped a lot when it was taken out of the can. 2. The calorimeter makes use of the law of conservation of energy because it measures the amount of heat transferred to the water in the can from the burning food. 3. Looking at the data from the peanuts and potato chip (high fat) compared to the marshmallow and popcorn (high sugar), high fat food contains more energy than high sugar food. 4. In this experiment, the peanut had the highest energy content. This makes sense because the peanut burned the longest and had the highest fat content. High fat foods have a higher energy content.
5. The peanut had 6186.4 J/g. (6186.4 J/g) x (50 g) x (1/4.184 cal/j) x (1 Cal/1000 cal) = 73.93 Calories Conclusion The hypothesis for this lab was that if different foods are burned, then their energy content could be found, because the energy will be transferred to the water in the calorimeter because of the Law of Conservation of Energy. This hypothesis was supported because when the food burned the temperature of the water increased. The lab was related to the study of energy because we measured the change in temperature using the calorimeter and used the heat calculation to determine the heat energy. The data showed that high fat foods have more energy than high sugar foods which was expected. The food with the highest energy content per gram was the peanut at 6186.4 J/g. The food with the lowest energy content per gram was the marshmallow at 362.3 J/g. This information could be used to help choose foods when more or less calories are needed and to help choose more healthy foods. This information could also be used if heat was needed and food was the only thing available to burn.