The document discusses methods for measuring food energy in calories, specifically through calorimetry experiments involving cheese puffs. It includes a pre-lab problem and provides a detailed procedure for measuring heat energy from burning a cheese puff in water, with calculations for calories per serving. The results indicated differences between measured and labeled caloric content, with potential reasons for inaccuracies noted.

1. FOOD ENERGY
Have you ever counted Calories?
Food energy is measured in Calories (upper case C)
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It takes 1000 calories to make up a Calorie
Example: A standard French fry serving contains 220 Calories of food energy.
How many calories are present?
220 Calories x 1000 cal/Cal. = 220,000 calories
It takes 1 calorie to raise the temperature of 1 g of water 1 °C
Simplified formula may be used: calories = grams of water x (final °C – initial °C)
This is determined by the burning of food under controlled conditions
(CALORIMETRY) using an instrument called a calorimeter.
Pre-lab problem:
1. You want to raise the temperature of 250mL of water from 22 °C to 99 °C. How much
heat energy will be needed?
Use equation calories = grams of water x (final °C – initial °C)
(250 g) x (77) = 19,250 calories = 19.25 Calories

2. EXPERIMENT: CALORIES IN A CHEESE PUFF
Hypothesis: We predict that there are _____fewer_____ Calories in a cheese puff
than the number listed on the nutrition label.
DATA TABLE
½ Cheese
Puff Sample
#1
Mass (g)
Original
1.1
Final
0.6
Change
0.5
Temperature (°C)
Original
Final
28.6
34
Change
5.6
#2
#3
Procedure
1. Obtain ½ a cheese puff. Record it’s mass (ORIGINAL).
2. Pour exactly 100 mL tap water into the aluminum can. Record the temperature of the
water in the can (ORIGINAL).
3. Place the ½ cheese puff on the tab in the bottom can. Indicate with a RED CUP when
ready for a teacher to ignite cheese puff. Immediately place the can filled with 100 mL
of water over the burning puff.
4. Keep the thermometer inside the can, but make sure it is NOT touching the side or
bottom.
5. Allow the puff to burn until it goes out.
6. Record the water’s highest temperature (FINAL).
7. Record the mass of charred puff (FINAL).
CALCULATIONS AND QUESTIONS
Answer these questions on a SEPARATE sheet of paper.
1. Calculate the calories of heat from the burning puff. The 100 mL water has a mass of
100 g (for all practical purposes the density of water is 1 gram/mL) and the specific heat
of water is one calorie/degree Celsius/gram (1 calorie/gram °C = 4.186 joule/gram °C).

3. Use the following equation to make the calculation.
calories = (grams of water) x (temperature change) x (specific heat of water)
calories = (100g) x (34 °C – 28.6 °C) x (1 calorie/gram °C) = 540 calories
2. Divide the calories from question 1 by the change in mass of the puff. This determines
the calories released per gram of puff burned. Record your answer in Kcal or Calories.
540 calories / (1.1 g – 0.6 g) = 1080 calories/g = 1.08 Calories/g
3. Multiply the measured Calories by the number of grams in a serving size, obtained
from nutritional panel.
1.08 Calories/g x (28 g/14 cheese puffs) = 2.16 Calories/cheese puff
4. Compare your Calorie results to the nutritional panel.
150 Calories / 14 cheese puffs = 10.71 Calories/cheese puff > 2.16 Calories/cheese puff
5. Conclusion: There are _____fewer_____ Calories in a cheese puff than the
number listed on the nutrition label.
6. Calculate your percent error.
(actual – measured Calories per serving) x 100 =
actual Calories per serving
(5.36 – 1.08) x 100 = 79.85%
(5.36)
7. Why do you suppose the calculated values for calories per gram are less than the actual
value listed on the nutrition label? What could account for the difference? What are
possible reasons for the inaccuracy?
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Didn’t burn the entire cheese puff- had mass left over
Burning cheese puff could have lost heat to air/surroundings instead of
transferring all heat energy directly to the water filled can
Inaccurate temperature readings
Scaffolded summary of experiment:
The increase in the __temperature__ of the water shows that ___heat energy___ had been
stored in the cheese puff, which was released while it burned. We can look at the change
in ___heat/temperature___ of the water to find out how much ___heat energy___ is
trapped/stored in a cheese puff (the change in enthalpy).