Chem 106 lab 18 (1)

Calorimetry and Combustion “ Burning Food. Where are my carbs? ” In this lab we seek to learn more about the significance of calorie content in foods and what those values mean as well as where they come from. This topic is significant to us all seeing as everything we consume on a daily basis has such different amounts of calories and it is valuable to know what those values actually mean. The process of our bodies digesting food is a reaction and the higher the calories consumed the more energy is required to break down the food and therefore more nutrients are processed into the body. Our bodies require a specific number of calories a day for basic function and survival, however we see foods that are overly calorie dense like fast food are often unhealthy for us because of where those calories are actually coming from. Caloric value can be determined by a bomb calorimeter, which ignites the substance underwater in an oxygen rich container that is sealed. The temperature change of the water caused by the combustion allows us to calculate the number of calories in the food being burned. However caloric content and other information about the reaction can also be determined through calculations. Materials: - Notebook - Lab manual - Excell Part 1 1. In order to find a reaction’s standard enthalpy, we first take the sum of the standard enthalpies of formation of the products. We then must subtract yje standard enthalpies of formation of the reactants. The calculation is as follows: [6(-393.5) + 6(-242)] - [(-1275) + 0] = -3813 + 1275 = - 2538 kj/mol 2. First we calculate the moles of glucose by dividing the given value of 3 grams by 180.156 to get 0.0167. So, we do 0.0167 x -2538 kJ/mol and get -42.38, which we turn into a positive value. We then do 42.38 /4.3 ℃ and get a calorimeter constant of 9.86 kJ/ ℃ Part 2 1. Food sample mass (g) initial T(C) Final T(C) Energy content listed on label Temper ature differen ce Q calimet ers Q combus tion Energy contain ed(kJ/g ) Energy contain ed in calories (cal/oz) (Experi mental) Energy contain ed in calories label (cal/oz) (Theore tical) percent error

oreo cookies 2.41 26.12 30.92 160 Cal per serving (34g) 4.8 47.328 -47.328 19.6381 7427 133.189 5745 133.409 4118 0.164 microwave popcorn 2.29 25.76 29.95 130 Cal per serving (30g) 4.19 41.3134 - 41.3134 18.0407 8603 122.355 8047 133.409 4118 8.29 crunchy cheetos 2.21 25.13 30.49 160 Cal per serving (1oz) 5.36 52.8496 - 52.8496 23.9138 4615 162.187 9382 133.409 4118 21.57 beef jerky 2.23 25.89 29.54 80 Cal per serving (1oz) 3.65 35.989 -35.989 16.1385 6502 109.454 605 133.409 4118 17.96 oil roasted, salted peanuts 2.45 25.64 31.79 170 Cal per serving (1 oz) 6.15 60.639 -60.639 24.7506 1224 167.863 0339 133.409 4118 25.83 2. The sample calculation of energy content for beef jerky is as follows: 9.86 x 3.65 = 35.989 kj, we then divide this value by 2.23 grams and get 16.14 kj/g. Knowing that 1 calorie equals 4.18 kj and that 1 ounce equals 28.3495 grams, we do [16.14 x 28.3495)] x (1cal / 4.18kj) = 109.45 cal/oz 3. We see that the majority of our results are slightly lower than the energy content listed on the label, apart from the crunchy cheetos and the oil roasted salted peanuts which had results higher than that of the label. The percent error calculation for beef jerky is as follows: 109.45 - 133.41 / 133.41 x 100 = 17.96 percent 4. Beef Jerky, Microwave popcorn, Oreo cookies, Crunchy cheetos, Oil roasted salted peanuts. 5. We see that the oil roasted salted peanuts has the highest calorie value of all the food provided. This is because calories are determined by a food ’ s macronutrients. Peanuts are already relatively nutrient dense in protein and fats, but the oil they were roasted in and the salt put on them adds more fat and therefore caloric value. Beef jerky had the lowest caloric value since it is just cured and dried meat which is relatively lean. Our table shows us the values stated on the labels of these foods as well as the values we calculated based on the temperature difference observed and mass recorded. We observed that the foods with the highest caloric content had the largest difference in temperature. This is because of the way calories are measured, a bomb calorimeter is used in order to gain a more accurate and precise value. A bomb calorimeter works by igniting the food in question underwater in a sealed, oxygen rich