CHEMISTRY LAB: SPECIFIC HEAT OF A METAL
(SPECHEAT.DOC)
Name: _______________________
Date: ________________________
1. Introduction: Specific heat, or specific heat capacity, of materials is a physical
property, defined as the heat energy divided by the product of the mass and temperature
change an object experiences when absorbing or releasing that heat. A simple
calorimeter (a styrofoam cup will do) and some boiling water are all it takes to measure
the specific heat of a material, like a sample of metal. The easiest-to-remember formula
for doing these kinds of things is:
Q = m  c  T
where Q = amount of heat energy, measured in calories, for instance, or Joules
m = mass of the material, measured in grams, for instance, or moles
c = the specific heat (or specific heat capacity) of the material, usually measured
in units of calories / (grams x degrees C.), or Joules / (grams x degree C.)
T = the change in temperature experienced when the heat flowed either in or out
of the material. [Calculated by subtracting the starting and ending temps.]
2. Safety: Use caution to avoid burns from hot metal, hot water, or open flames. Handle
the thermometer gently and leave the triangular roll-guard on it to avoid it rolling into the
sink or onto the floor and breaking. Tie long hair back and watch loose clothing. Wear
goggles when the burner is lighted.
3. Equipment and Materials:
a. From the prep area:
thermometer (red liquid type or electronic probe type)
styrofoam cup and lid
metal sample (lead fishing sinker with string loop to aid in handling)
b. From your lab station equipment drawer:
medium support ring
burner, hose, and spark lighter
wire gauze with ceramic fiber center
buret clamp
beaker tongs (curved, with plastic coated jaws)
c. From your lab station supply cupboard:
100 ml graduated cylinder
250 ml beakers (two of these)
d. At your lab bench:
ringstand
4. Procedure:
a. Set up a ringstand, ring, wire gauze, buret clamp and burner--or hot plate--to
begin boiling about 100 ml of tapwater in a 250 ml beaker. Do not light the burner until
everyone in your group has on their safety goggles. Continue while the water reaches
boiling.
b. Weigh the empty styrofoam cup to the nearest centigram. Record in the data
table below.
c. Add about 40 ml of tapwater. Weigh the cup and the water to the nearest
centigram. Record in the data table below.
d. Place the styrofoam cup with the water in it into the second 250 ml beaker.
The beaker will help to insulate and stabilize the cup. Insert a thermometer through the
hole in the styrofoam lid. Lower the thermometer into the water to get an initial
temperature. Keep a hand on the thermometer so it does not tip over. Use care not to
break the thermometer bulb or poke a hole through the bottom of the cup. Let the
thermometer sit for about a minute to be sure you are getting an honest reading. Record
the starting ("initial") temperature of the water in the calorimeter cup to the nearest tenth
of a degree.
f. Weigh the metal sample (with the string) to the nearest centigram. Record its
mass. (Ignore the weight of the string.)
g. Suspend the metal sample in the middle of the boiling water using the string to
hang it from a buret clamp. Do not allow the metal to touch the bottom of the beaker.
Heat for three minutes in boiling water to ensure thorough heating. Assume the metal
sample reaches the boiling point of water.
h. Check the temperature of the water in the cup just before you perform the next
step. You may revise the starting temperature if needed.
i. Working quickly, remove the metal sample and shake lightly once to remove
water clinging to it and immediately lower it into the water in the styrofoam cup
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calorimeter. Cover and watch the thermometer reading rise until stable. (Is the
thermometer tip all the way down in the water without poking a hole in the bottom of the
cup?) Swirl gently once every 20 seconds or so to ensure the best reading. Don't break
the thermometer against the metal sample. The temperature will change rapidly at first
but give it a full three minutes or more to reach its maximum. When it starts back down
again it is losing heat to the room, so take the highest temperature reached as the final
temperature of both the water and the sample. Use the data table to record this
temperature. Read the thermometer carefully: the change is small and you need
accuracy.
j. Wash your hands and return to your seat to work on your calculations. You
may want to run the experiment again when you discuss your results.
k. If you are satisfied with your results, and after the equipment cools, replace all
materials. Pour out the water. Return the metal sample, the scissors, the styrofoam cup,
lid, and the thermometer to the prep area. Return goggles to the sterilizer cabinet. Clean
up your area with a damp sponge. Wash your hands; lead is a cumulative poison!
5. Data:
mass of empty cup
__________ g
mass of cup with water
__________ g
mass of metal sample
ms = __________ g
initial temperature of water in cup
initial temperature of metal sample in boiling water
__________ C.
100.0
C.
final temperature of water in cup and metal sample __________ C.
6. Calculations:
a. Calculate the weight of the water in the cup only.
mw = __________ g
b. Calculate how much the metal sample changed temperature as it cooled from
100 down to the final temperature.
Ts = ________ C.
c. Calculate how much the water in the cup changed temperature as it heated up
from its starting temperature to the final temperature.
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Tw = ________ C.
d. Calculate the specific heat of the metal sample. Assume the specific heat of
water is 1.0 cal / g  C., and ignore the heat absorbed by the styrofoam, the string, and
the thermometer, or the heat lost to the air. Since the heat lost by the sample was
supposedly all gained by the water when it warmed up, a little algebra gives us:
cs = (mw  Tw) / (ms  Ts)
cs = __________ cal / g  C.
e. Since 1 cal = 4.184 Joules, multiply to obtain your experimentally derived
value for
cs = __________ J / g deg (experimental)
7. Analysis:
a. The accepted value for the specific heat of lead when measured this way is
0.129 J / g  C. Calculate the percent error of the experiment with this formula:
(| experimental - accepted | / accepted ) x 100% = % error
__________ %
b. Describe three sources of error in your experiment.
1) ____________________________________________________
2) ____________________________________________________
3) ____________________________________________________
8. Questions:
a. Calculate calories to Joules:
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23.4 cal x ____________________ = _______________ J
b. What is the specific heat of pure water?
_________ cal / g  C.
c. Answer this question: A hot water bottle contains 1350 g of water at a
temperature of 80 C. How much energy (in kilocalories) will it release as it cools to 25
C.? Show your work.
__________ kcal
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