Names___________________________________ Date____________________ Period____________
Chemistry Lab: Determining the Amount of Energy in Food
Objectives:


To determine the amount of energy in a Cheeto.
To calculate the percent error in the experiment and evaluate
the sources of the error.
Introduction:
All living systems require energy. Humans get their energy from the
food that we eat. All food contains energy. The amount that it contains depends on the type of the
food it is and the organic compounds it contains. In biology, energy is usually measured in calories. A
calorie is the amount of heat energy needed to raise the temperature of one gram of water by one
degree Celsius. The amount of energy found in food is measured in kilocalories (symbolized by C or
called Calories).
1 Calorie = 1 kcal = 1000 calories
So if a candy bar says it has 180 Calories, it really means that it has 180,000 calories. A calorimeter is
used to determine the amount of calories found in food.
In this lab, you will burn a sample of food (Cheeto) with a known mass. You will construct a simple
calorimeter from a soda can. The calorimeter will contain 50mL (equal to 50 grams assuming the
density of water to be 1g/mL) and will hang the calorimeter above the food sample. The temperature of
the water will be recorded before and after the sample is burned (to calculate ∆T).
The specific heat of water is 1 cal/goC, so you can use the specific heat formula: Q = m * Cp * ∆T to find
the amount of energy absorbed by the water. Theoretically, this will also be the same amount of energy
released by burning the food, although in practice, some energy will be lost to the environment.
Remember that you will need to convert calories to Calories by dividing by 1000.
Procedure:
Obviously, holding a burning sample in your hand would be a bad idea. Likewise, burning the sample on
the ring stand directly would also result in a mess. Therefore, a sample holder is necessary.
1. Obtain a needle and a cork stopper/CHEETO DEATH MACHINE!
2. Obtain a ring stand, a small iron ring, an aluminum can, watch glass, a thermometer, and a
100mL graduated cylinder.
3. Assemble as shown:
4. Measure 50mL of water and add to the soda can.
5. Put the thermometer into the soda can but do not let it rest on the bottom of the can. You may
wish to use a piece of tape to secure the probe to the optional stir rod or can tab to keep it
suspended. After about 30 seconds, the temperature should stabilize. Record your initial
temperature.
Part 3: The Cheeto Flaming
1. Now it is time to burn your cheeto! After you have recorded the initial temperature of
your calorimeter water, find the mass of your cheeto using a balance. Record this value.
2. Using your holder, position the cheeto on the holder securely.
3. Using a kitchen match, light your cheeto. Quickly remove the match and extinguish with
water as soon as the cheeto begins to burn.
NOTE: Hot oil may leak from the cheeto, so be sure the watch glass is in position to
catch any excess grease. If you burn yourself, rinse the affected area with cold water
and notify your instructor immediately.
4. Record the temperature after the cheeto burns.
5. Replace the water and repeat three times for each crunchy and puffy cheeto. Fill in the
tables below as you go.
CRUNCHY CHEETO:
Trial
1
Initial Temperature H2O (oC)
Initial Mass (g):
Final Temperature H2O (oC)
2
3
Average
PUFFY CHEETO:
Trial
1
Initial Mass (g):
Initial Temperature H2O (oC)
Final Temperature H2O (oC)
2
3
Averages
Conclusion Questions
1. Using the formula for specific heat, calculate the number of calories in each sample using the
average (so you only have to do two calculations).
CRUNCHY CHEETO:
(show calculation calories or Q here) – use mass, specific heat, and temperature change for water
calories
(kilo)Calories
(kilo)Calories/Gram of CHEETO
PUFFY CHEETO:
(show calculation calories or Q here) – use mass, specific heat, and temperature change for water
calories
(kilo)Calories
(kilo)Calories/Gram of CHEETO
2. Which snack variety contained the greatest number of Calories per gram?
3. According to the bag, Crunchy Cheetos have __________________ Calories/gram.
Puffy Cheetos have __________________ Calories/gram.
4. Based on your averages calculated and your values for #3, calculate your percent error for
Calorie content.
% Error for Crunchy Cheetos
% Error for Puffy Cheetos
5. Do you feel your percent error is acceptable? Why or why not?
6. Fats and oils used to fry crunchy cheese curls are high in lipids. What foods might you
investigate to determine their calorie content for carbohydrates? Proteins?
7. Oil drips from the crunchy cheese curl as it burns. How will this error affect the (a) number of
kilocalories and (b) number of kilocalories/gram? Your answer should clearly state whether the
calculated value will increase, decrease or remain the same. Mathematically justify your
answer.