The chemical energy stored in the peanut was released and converted into heat energy. The heat energy raised the temperature of the water in the small can.
Try a couple of other experiments using different kinds of peanuts or other kinds of nuts.
- Raw peanuts
- Dry roasted peanuts
- Vacuum-packed peanuts
- Freeze-dried peanuts
- Try cashew nuts, Brazil nuts, pecans, walnuts or other kinds
of nuts. (Do they contain more energy than the peanut? Why or why not?)
You might want to try more than one peanut. You'll need extra needles. Use four or five
peanuts to heat the water. Is the temperature four or five times higher?
Energy is measured in a unit called the Btu, which stands for British thermal unit. A Btu
is the amount of heat required to raise the temperature of one pound of water by one degree
math, you can figure out how many Btu are in the one peanut. (The plural or Btu is still
Btu, not Btus.)
First you'll need to find out how heavy 1/2 cup of water is. Use a small scale and weigh
the small can with nothing in it. Then weigh the can with 1/2 cup of water in it. That
will tell you how much the water weighs.
Then, knowing how hot the water was, how
many degrees its temperature was raised,
you can figure out roughly how many Btu
are in the peanut. (PLEASE
NOTE: This will be
an approximate figure because the
entire peanut will not be completely burned...there
is still some chemical energy left inside
the partially burned peanut. In order to
measure the heat energy exactly, you would
need to use a sophisticated piece of machinery
called a "calorimeter".)
For example: If the water weighed four ounces (1/4 of a pound), one Btu would
raise the water temperature 4 degrees Fahrenheit. So, if your water temperature
increased by 10 degrees (70 degrees at room temperature to 80 degrees), 10 divided by 4
would mean the peanut contained approximately 2.5 Btu. This is only an example of the math and will
not be the same as your calculations.
One Btu equals approximately:
- One blue-tip kitchen match
- 0.252 kilogram Calories (food calories)
1000 Btu equal approximately:
- One average candy bar (252 kilogram Calories)
- One hour of bicycling
- 4/5 of a peanut butter and jelly sandwich
You may see Btu defined as 252 calories.
These are International Table calories
which are equal to 1000 of the "Calories"
or "kilocalories" we use for measuring food