Usable chemical energy on earth begins as light energy, usually solar energy. plants and other autotrophs convert solar energy to chemical energy via the process of photosynthesis. carbon dioxide and water, in the presence of light, are transformed into glucose. the chemical energy is stored in the chemical bonds of glucose and is released during the process of cellular respiration. cellular respiration releases the chemical energy stored in food molecules to produce high-energy atp molecules. macromolecules such as carbohydrates and fats can be used as fuels for the production of atp. all foods contain chemical energy, but the amount of chemical energy is dependent of the type of food. the larger the compound, the more chemical bonds present and the greater amount of available chemical energy. we can rank molecule size, from smallest to largest, as sugar, starch, fat. we refer to the stored chemical energy in foods as calories. a calorie is the amount of energy required to raise the temperature of 1 gram of water 1 degree celsius. when we refer to the calories in food, we are really talking about kilocalories or 1000 calories. biology students “burned” 2 grams of food to heat water in a calorimeter in order to determine which food items contain the most usable chemical energy. 1. pick two food items to burn. 2. hypothesize as to which of your items will contain the most calories. 3. record your data in the data table. when we have completed the lab, we will combine all group data to draw conclusions. sample of student data food sample mass of sample (g) initial water temp (c°) final water temp (c°) saltine cracker 2 22 28 snack chip 2 22 32 analyzing data - for each food item use the equation q = mcδt where • m = mass of the water in grams (we used 100 grams) • c = specific heat of water or 1 cal/go c • δt = the change in temperature in degrees celsius food calories saltine cracker 0.6 snack chip 10 combined class data (seen in bar graph) compare the food energy in calories from burning the chip and the saltine. how can you explain this differences in terms of chemical composition? a) the chip contains more lipids than the saltine. b) the saltine is a carbohydrate; the chip is a lipid. c) the saltine has less protein content than the chip. d) the chip is composed of starch; the saltine of simple sugars.