Calculating Calories Lab

“Calculating Calories” Experimental Question: How much energy is stored in each gram of different food samples? Introduction: Every animal maintains its life processes by consuming complex molecules that store energy. The processes plants and animals we eat as foods contain varying amounts of proteins, carbohydrates, and fats. Though, carbohydrates are the main source of fuel for organisms and cells, lipids and proteins can be broken down to release energy when the body does not have any carbohydrates available. In our bodies the lipid, carbohydrates and proteins are broken down physically and chemically before their energy can be released and used by cells. Cells release energy through the process of cellular respiration. Similar to the chemical reactions the body use to release energy, burning pieces of food releases the chemical energy stored in molecular bonds is released as heat and light. The heat can be measured in units called calories. A calorie is the amount of heat (energy) required to increase the temperature of one gram of water by 1°C. This process is the basis of the technique of calorimetry. The more calories a food contains, the more heat is gives off when burned. Foods high in calories will release large amounts of energy. Hypothesis: You will have access to marshmallows, sunflower seeds and cheese puffs. Each of these foods contains varying amounts of protein, carbohydrates, sugar, and fat. Hypothesize or predict which food will contain the most energy or calories per gram. Also predict which molecule, carbohydrates, lipids and proteins store the most energy in a single gram. You may want to refer to the nutrition facts of each food posted in the conclusion questions to aid in your prediction. CAUTION!!!!!! Use the scoopula, tweezers, or dissecting needle to handle burnt samples. Procedure 1. Set up your calorimeter as shown by your instructor and pictured to the right. 2. Fill up a graduated cylinder to exactly 100 ml or milliliters. 3. Pour the water in the pop can. Be sure not to spill!! 4. Insert the thermometer into the pop can and secure all clamps. 5. Choose a food sample and measure its initial mass and record in the data table. 6. Take an initial temperature reading of the water in the can and record it in the data table. 7. Place the food sample on its stand and get your instructor to set it on fire. If the sample falls off the stand, start over immediately. 8. Record the temperature of the water at its maximum after the sample stops burning. Usually the temperature will continue to rise shortly after the flame goes out. 9. As soon as the sample has cooled, use the tweezers/needle/scoopula to lift the burned remains onto the balance. Take a final sunflower seeds mass and record in the data table. 10. Repeat steps 5-9 for the remaining food samples. Data and Calculations Food Sample Initial Mass (g) Final Mass (g) Change in Mass (g) Beginning Ending Water Water Temp ° C Temp ° C Temperature Calories Change ° C Per Gram Kilocalories Per Gram 1. Use the following equation to calculate the caloric content of each food sample. Enter your calculation in the appropriate column and row of your data table. Calories/gram = (Mass H2O × ∆H2O temp. × 1.0 calorie/g/°C) / ∆Mass Food Sample  ∆H2O temp. (°Celsius) = change in water temperature = initial H2O temp - final H2O temp  ∆Mass Food Sample = change in food sample mass = initial food mass – final food mass  Mass (grams)  1 milliliter (ml) of water = 1 gram (g)  1000 calories = 1 kilocalorie 2. Construct a graph that represents your data and helps answer your experimental question. Conclusions 1. Looking at our data, and the nutrition facts below, can you determine if proteins, carbohydrates, or fats have the most energy stored in their chemical bonds? Food % Mass of Protein % Mass of Carbs. % Mass of Lipids Cheese Puffs 7 57 36 Sunflower Seeds 21 21 48 Marshmallow 0 92 0 Beef Jerky 53 12 3 2. List any possible sources of experimental error. 3. List the independent and dependent variables. Extension 1. Use the nutrition facts below to calculate the actual calories per gram of each food sample. a. Compare the calories per gram from the nutrition facts to the experimentally determined kilocalories per gram. (Note: the calories on food labels are actually kilocalories but the kiloprefix is dropped by convention) Food Serving Size (g) Total Calories Calories per gram Cheese Puffs 28 150 ? Sunflower Seeds 29 160 ? Marshmallow 30 100 ? Beef Jerky 35 100 ? b. Calculate the percent error of your experimental results using the given equation. c. Propose an explanation between the actual calories per gram for each food and the kilocalories per gram of each food determined by your experiment. 2. Since marshmallows only contain carbohydrates we can easily find the energy stored in each gram of carbohydrate. Examine the marshmallow nutrition facts and divide the total number of calories by the total carbohydrate value to find how much energy each gram of carbohydrate stores. “Nutrition Facts for One Serving” Food Total Calories Protein (g) Lipids (g) Carbs. (g) Calories From Fat Cheese Puffs 150 90 2 10 13 Marshmallow 100 0 0 0 24 3. Use the information above to calculate the actual amount of calories stored in each gram of lipids. 4. Based on your answers from the last two questions and the nutrition facts to calculate the number of calories stored in every gram of protein. 5. Create a mathematical expression that would allow you calculate the total calories in any food based on the number of grams of proteins, lipids and carbohydrates found in the food.