Energy Value for Nuts

Energy Value of Nuts

Problem: How much heat is available from the combustion of peanuts, almonds, and other nuts. Can this heat be measured?

Objective:  When you eat food, your body is actually “combusting” the food.  The fat, protein and carbohydrates react with the oxygen in your body to produce carbon dioxide and water.  You will choose three types of nut to burn and measure the amount of energy released via water being heated by flame.  Unfortunately, we will lost a lot of heat to the surroundings and we also will have to heat the aluminum can as well. 

1. Hypothesis: Predict which nut—peanuts, cashews, almonds, brazil nut or pecans—will furnish the greatest amount of energy per gram. Explain your hypothesis.

2. Data Table:

	Trial #1—type of nut ___________	Trial #2—type of nut _________	Trial #3—type of nut _________
Mass of nut (initial)
Mass of can
Volume of water
Temperature initial of water
Temperature final of water
Mass of leftover nut

3. Determine the change in mass of each nut from before and after combustion.

     Mass of nut (initial) – mass of leftover nut =  mass of nut that combusted

4. Determine the change in temperature of water (and therefore, also the can) before and after combustion.

          Temperature final – Temperature initial = Temperature change

5. Determine the heat absorbed by the water, using the equation Q = s x m x DT

          (specific heat for water is 4.18 J/g×C°)

                                                                                                             

6. Determine the heat absorbed by the can, using the equation Q = s x m x DT

          (specific heat for aluminum is 0.9 J/g×C°)

7. Determine the total heat absorbed by the water and the beaker.

          NOTE: This is also equal to the heat released by the nut.

8. Determine the total heat released per gram of nut.

          Divide by the total heat by the total gram of nut that combusted.

9. Summary Table

	Trial #1—type of nut	Trial #2—type of nut	Trial #3—type of nut
Mass of combusted nut #3
Change in Temperature (DT) #4
Heat absorbed by the water #5
Heat absorbed by the can  #6
Total heat absorbed #7
Total heat released per gram of nut #8

10. Critique the procedure used in this experiment. Do you expect the procedure to give an accurate energy value for the nuts? Explain your answer.