Cheetos vs. Marshmallows Calorimetry Lab
Name: Date: Purpose The purpose of this experiment is to determine the amount of heat released when Cheetos are burned versus marshmallows.
Introduction: What does it mean to say that we burn food in our bodies? The digestion and metabolism of food converts the chemical constituents of food to carbon dioxide and water. This is the same overall reaction that occurs when organic molecules—such as carbohydrates, proteins, and fats —are burned in the presence of oxygen. The reaction of an organic compound with oxygen to produce carbon dioxide, water and heat is called a combustion reaction. The chemical equation for the most important reaction in our metabolism, the combustion of glucose, is shown in Equation 1.
C6H12O6 + 6O2 6CO2 + 6H2O + heat Equation 1
With in our bodies, the energy released by the combustion of food molecules is converted to heat energy (to maintain our constant body temperature), mechanical energy (to move our muscles), and electrical energy (for nerve transmission). The total amount of energy released by the digestion and metabolism of a particular food is referred to as its caloric content and is expressed in units of nutritional Calories (note the uppercase C). The caloric content of most prepared foods is listed on their nutritional information labels.
Nutritionists and food scientists measure the caloric content of food by burning the food in a special device called a calorimeter. Calorimetry is the measurement of the amount of heat energy produced in a reaction. Calorimetry experiments are carried out by measuring the temperature change in water that is in contact with or surrounds the reactants products. (The reactants products together are referred to as the system, the water as the surroundings.)
Safety Wear safety glasses when performing this or any lab that uses chemicals, heat or glassware. Care should be taken when handling or placing food onto the pin point. Allow the food sample to cool before touching or discarding it. Use a glass stirring rod to stir the liquid; never stir with a thermometer. Students should not be allowed to eat the snack foods once they are brought into the lab. This lab should be performed in a well-ventilated room.
1 Cheetos vs. Marshmallows Calorimetry Lab
Materials Each group Communal (teacher monitored) lab aprons Cheetos eye protection Marshmellows 1 – watch glass 2 - Balances 1 – 50mL graduated cylinder 30 - Paperclips 1 – butane lighter Thermometer and clamp Ring stand with ring Empty soda can
Experimental Procedure: 1. Form a paperclip into a stand for food (see instructor’s demo stand) 2. Carefully insert stand into a single cheeto. Set aside. 3. Insert paperclips into soft-drink can as shown in illustration 4. Assemble the ring stand and ring. The clamp should be 12 inches above the watch glass. 5. Place 50 mL of water in the empty soda can and clamp the pop can into the clamp. The bottom of the pop can should be 2 inches above the food stand. 6. Attach the thermometer to the ring stand with the clamp. Thermometer bulb should NOT rest on the bottom of the can, but is in the water within the can. Record temperature of the water in the data table. 7. Obtain 2 Cheetos. Find the mass of each of the samples to the nearest 0.1 g (one decimal place), and record its mass in the DATA TABLE. 8. Place the cheeto on its stand under the can as shown in the illustration. Adjust height of the ring so that the bottom of the can is about an inch from the top of the cheeto. 9. Lift the can of water up and light the cheeto with the lighter. Place the can back on the ring stand over the flame. CAUTION: be careful not to burn yourself! a. Relight it immediately if it goes out before all of the food is burnt to a black crisp. 10. After the food sample is completely burned, measure the temperature of the water again to the nearest 0.5 degrees C, and record in the DATA TABLE as final water temperature. Be sure to watch the thermometer carefully, to catch the highest temperature reached. 11. Find the mass of the sample remaining to the nearest 0.01 g and record in the DATA TABLE as mass of sample after burning (ash weight). 12. Repeat procedure for another Cheeto sample. You should have 2 trials of Cheetos 13. Repeat the calorimetry experiment two more times using marshmallows instead. Record the new data in Table 2.
2 Cheetos vs. Marshmallows Calorimetry Lab
Data:
Table 1 – Cheetos Data Initial Final Change in Cheeto Mass before Mass after Change in Temperature Temperature Temperature Sample burning (g) burning (g) Mass (g) (°C) (°C) (°C)
Trial 1
Trial 2
Table 2 – Marshmallow Data Initial Final Change in Marshmallow Mass before Mass after Change in Temperature Temperature Temperature Sample burning (g) burning (g) Mass (g) (°C) (°C) (°C)
Trial 1
Trial 2
Calculations: 3 Cheetos vs. Marshmallows Calorimetry Lab
1. Calculate the amount of energy transferred to the can in terms of thermal energy a. Use Q = mcΔt b. To estimate the calories in the food sample you will need the mass of the water you heated. The 50.0 mL of water you used is 50.0 g.
2. Calculate the amount of energy transferred to the can in terms of calories. Use Q = mcΔt a. To estimate the calories in the food sample you will need the mass of the water you heated. The 50.0 mL of water you used is 50.0 g. b. specific heat of water is 1 cal/goC c. Then, convert to kcal (1 nutritional calorie) calories Kcal(kilocalories) = 1000
Cheeto:
Marshmallow:
3. Calculate the number of nutritional calories (Kilocalories) per gram of cheeto. a. Take the kcal answer from #1 & 2 and divide by the number of grams of Cheetos or marshmallows used.
Cheeto:
Marshmallow:
4 Cheetos vs. Marshmallows Calorimetry Lab
4. Examine the Nutritional Value Information found on the last page for the Cheetos food sample. Use this information to determine the “accepted value” for the nutritional calorie content per gram of snack food. What is the percent error for your experiment? *Repeat this for the marshmallow* Accepted - Experimental Percent Error = ´100% Accepted
5. Which of the food had a lower percent error? Why do you think that this food was more accurate than the one with the higher percent error? BE SPECIFIC
6. Give 2 examples of how you could improve the accuracy of this experiment.
5 Cheetos vs. Marshmallows Calorimetry Lab
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