The Energy In A Peanut
Abstract: This lab will show how to calculate the energy stored in a peanut by measuring the heat released as the peanut is combusted.
Introduction:
Just about everything has potential energy stored in it. Not all of the stored energy is available to do work, however. A peanut contains stored chemical energy. When eaten, the stored energy ( known to you as Calories) is converted to chemical energy by our bodies so we can do work. We can also use the energy in a peanut to heat a container of water.
The heat gained by the water will be equal to the heat lost by the peanut:
Qlost by peanut = Qgained by water
Qwater = mcDT
where Q = heat gained in Joules
m= mass of water
c = 4.184 J/g·°K
DT = change in temperature of water
Chemical Information: Your table should contain information about the peanut, especially the accepted value for the Calories in peanuts. Be sure to include the serving size with your Calorie value.
Source: this website
Safety: flames will be used; goggles, apron
To prepare at home:
A large metal juice or coffee can
A small metal can (like a soup can) with paper label removed
A can opener
A hammer
A large nail
A metal BBQ skewer (like the kind for kebobs)
OR a length of coat hanger wire
To make your "roaster"
1. Remove the two ends of the large juice can with the can opener. Be careful as the top's and bottom's edge can be sharp!
2. Using the hammer and nail, punch holes around the bottom of the large can. These are air holes that will make the can act like a chimney and will contain the heat energy focussing it on the smaller can.
3. Remove the top end of the small can (if it is not already removed).
4. Using the hammer and nail, punch two holes near the top of the small can exactly opposite each other.
5. Slide the BBQ skewer or length of wire through the holes of the small can.
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Materials:
2-3 unsalted, shelled peanuts
1 cork
1 needle
200 mL water (record mass)
thermometer (we will use the computers)
matches
Wood splint
Procedure:
1. Carefully push the eye of the needle into the smaller end of the cork.
2. Then gently push the pointed end of the needle into a peanut. If you push too hard the peanut will break. If it does, use another peanut. It's also better to have the peanut at a slight angle.
3. Set up the apparatus you constructed at home.
8. Pour 200 mL (measure carefully to get mass by difference and record all MASS data in Data Table) water into the small can.
9. Put the thermometer into the water and record the initial temperatuter.
ure.Alternaqte method: place temperature probe into water and begin recording.
10. Place the cork and peanut on a nonflammable surface. Light the wood splint and use it to light the peanut.
11. As soon as the peanut has caught fire, immediately place the large can around the nut. Balance the skewer holding the small can on the top of the large can.
12. Allow the nut to burn for several minutes or until it goes out.
13. Stir the water with the thermometer and record the temperature again.OR click STOP on the comp |
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Data Table:
Prepare a table to record the values mentioned in the procedure.
Data Analysis:
Use 3-step calculations and conversion factors to find the following. List them in a calculations table.
1. Calculate mass of water used.
2. Calculate the amount of heat gained by the water.
3. Calculate the heat the peanut gave off (in calories)
4. What amount of energy was released per gram of peanut? Record your answer on the board.
5. What is the amount of energy released per pound of peanuts? Record your answer on the board.
6. What is the accepted value you found for the calorie content of peanuts?
7. Calculate the percent error between your experimental value and the accepted value for the energy in a pound of peanuts.
8. Calculate the class average for the calorie content per gram of peanuts.
9. Calculate the energy stored in a pouind of peanuts, using the class average for 1 gram of peanuts.
10. Find the percent error between the class average and the accepted value for the energy in a pound of peanuts.
11. Which value was more accurate, your value or the class average? Explain.
12. Discuss several possible experimental errors, whether or not you believe they happened in your particular experiment or not.
Conclusion:
What was the goal of the experiment? Was it reached?
What was your hypothesis? Was it supported or refuted? Explain.
Summarize any experimental error that took place.
What further investigation might you do? Be specific.
For additional information, check this site:
http://www.members.hoosierlink.com/kerr/pball.htm
