Chemistry 108, Spring 2015 Lab 4: Food Calories Report: You have been hired by a textbook publisher to evaluate the accuracy and feasibility of laboratory experiments for first-year chemistry students. The first lab they send you to evaluate is a lab involving the concepts of heat and energy. Use your results to submit your opinions to the textbook publisher. Is the lab easy to do? Are the results accurate at all (either absolutely, relatively, both, or neither)? What assumptions are made in doing the lab? What are the sources of error (and which errors can be controlled and which cannot)? What, if anything, is the educational merit of the lab? Would you recommend having chemistry students do this lab? Why or why not? Compare results with other students doing this lab and include this in your discussion. Make sure you incorporate all of your observations, data, calculations, and conclusions in an organized manner. Procedure: Part One: Exploring Heat Capacity 1. Obtain a conductometer. 2. Place a small bit of wax in the well of each of the spokes of the conductometer. 3. Place the center of the conductometer in the hottest part of the Bunsen burner flame (the tip of the inner cone). 4. Watch the wax and take note of the order of melting. Record observations. Part Two: Testing the Calorimeter 1. Place 50.0 g of water in a clean soft drink can (this is your calorimeter). Measure the temperature. 2. In a separate beaker, heat 50.0 g of water to around 70°C. Measure the temperature. 3. Using gloves, add the hot water to the calorimeter (soft drink can). 4. Measure the final temperature of the water. Part Three: Measuring the Heat Released From Food 1. Obtain the mass of 100.0 mL of water (measured in a graduated cylinder). 2. Place 100.0 mL of water in a clean soft drink can. Measure the temperature of the water. Do not touch the sides of the can and make sure the thermometer bulb is completely submerged. 3. Put a glass stirring rod through the pull tab of the can. Place the rod on a ring connected to a ring stand so that the can is suspended. 4. Place the food item to be tested on the pin/cork set-up and measure the mass of the set-up with the food item. 5. Light the food item with a match and immediately place it directly under the center of the can. 6. Record the highest temperature that the water reaches. Do not touch the sides of the can and make sure the thermometer bulb is completely submerged. 7. After the food has finished burning, record the mass of the pin/cork set-up with the burned food. 8. Pour the water out of the can and make sure the can is clean. 9. Repeat Steps #2-8 for each food item. Do two trials for each food item.Chemistry 108, Spring 2015 Part Four: Nutrition Labels 1. Look at the nutritional label for each food item. Record the mass of one serving and the Calories it contains for one serving. Data and Calculations: (Show all work!) 1. Include well labeled data for all trials. 2. Calculate the heat released for each trial. (heat = mass of water × 1 cal/g°C × change in temperature of water) 3. Calculate the heat released for 1 g of each food item for each trial. (answer from #2 divided by mass of food burned) 4. Determine the heat released for 1 g of each food item by averaging the two trials in #3. Average Heat Released (cal)/1 g Cashews Marshmallows Cheetos Doritos 5. Calculate the Calories per serving of each food item (using the averaged values). ( )answer from #4 mass of one serving1000×⎛⎞⎜⎟⎝⎠ 6. Calculate the percent error for each food item. answer from #5 - Calories on label% Error = 100Calories on label⎛⎞×⎜⎟⎝⎠ Lab Questions: 1. Include and explain the observations of the conductometer from Part One. 2. What did the results of Part Two of the lab show you? 3. Organize your data and calculations in the table below by ranking which food items (cashews, marshmallows, Cheetos, Doritos) has the most Calories/serving to the least Calories/serving. 4. Are your results accurate in an absolute sense? (In other words, is your percent error low for each food item?) 5. Are your results accurate in a relative sense? (In other words, do you get the correct order from most to least Calories/serving as compared to the food labels?) Food Label Lab Results Most Calories/serving ↓ ↓ Least