comes in a variety of forms: light, heat, motion, electricity, and so
forth.The energy stored in food is
measured in units of Calories.A Calorie
is defined as the quantity of heat it takes to raise the temperature of 1 kg of
water 1°C.(Don’t confuse Calories
with calories: 1Calorie = 1000 calories – Tricky!)The energy in food is seen as heat because
the energy is released as heat when food is combusted (or burned).Complete combustion results in the production
of energy, carbon dioxide and water.Look
for evidence of these products during the lab.
In this lab, you will measure the amount of energy in calories
in two types of nuts: peanuts and almonds.The accepted values for these nuts are 5180 calories/gram for peanuts
and 5470 calories/gram for almonds.When
you eat nuts, the energy in the nuts is converted to a useful form, giving your
body the energy it needs.
Throughout this lab, we will have
open flames in the lab.Make sure that
your hair and any loose clothing that you are wearing do not come into contact
with the flames.Wear your safety
goggles at all times during the lab.Make sure that all flames are extinguished properly when you are
finished and are completely cool before you place them in the trash.
Measure the mass (in
grams) of a nut.Record data in
CAREFULLY place the nut on
the tip of the needle (you don’t need to push it on very far).
Measure the mass of an
EMPTY soda can.Add water to the
can until it is half full.Take the
mass again.Record the two masses
in the data chart.You can now
determine the mass of the water by taking the difference of the two
Set up the apparatus as in
the diagram below.When you are
sure that everything is set up properly, record the temperature of the
water very carefully and accurately.Record data in chart.Notify the teacher when you are ready and he or she will light your nut to be
burned.BE VERY CAREFUL WITH THE
THERMOMETER; IT IS VERY DELICATE!!!
Immediately after the nut
is lit, position the exterior can and soda can so that the bottom of the
soda can is about 1 inch above the top of the nut.
Record the highest
temperature reached after the flames go out.Make sure you stir the water gently
to be sure you have an accurate temperature.Record temperature in data table.You can now calculate DT from the two temperatures (before and
Use the heat equation to
solve for the amount of heat given off by the nut (in Joules).Convert Joules to calories by dividing
Divide this number by the
mass of the nut to get the calories/gram for the nut.Compare this value to the accepted value
listed in the 2nd paragraph.
Repeat the procedure two
more times with peanuts and three times with almonds.