CHM 101/102
Calorimetry
General Chemistry 101/102
Laboratory Manual
University of North Carolina at Wilmington
Laboratory Manual
CHM 101/102
Calorimetry
•
Purpose
 To learn techniques for measuring changes in
thermal energy (heat) in substances.
 To examine the relationship between the specific
heat capacity of a metal and its atomic weight.
•
Safety and Waste Management
 Exercise care when handling objects that have
been heated.
 Remove the stopper from the test tube when
heating your metal sample (never heat a closed
system!)
 Dry your metal sample before returning it.
Laboratory Manual
CHM 101/102
Calorimetry
•
Background
 The thermal energy (q) transferred when an object
is heated or cooled can be calculated from the
following equation:
(1)
heat transferred
(in joules)
Laboratory Manual
q = s x g x DT
specific heat
capacity of
substance
(J/gºC)
mass of
substance
(in grams)
temperature
change (in ºC)
CHM 101/102
Calorimetry
•
Background
 When two objects such as hot metal and cold
water are brought into contact, the heat lost by the
hotter object is equal to the heat gained by the
cooler object.
(2)
qwater = - qmetal
The minus sign is necessary since heat loss
is an exothermic process (q is negative)
while heat gain is an endothermic process (q
is positive).
Laboratory Manual
CHM 101/102
Calorimetry
•
Background
 Substituting Eqn (1) into Eqn (2) leads to an
equation that allows us to calculate the specific
heat capacity of a metal by making a few simple
temperature measurements.
(3)
swater x gwater x DTwater = - smetal x gmetal x DTmetal
Rearranging Eqn (3) leads to:
(4)
smetal =
Laboratory Manual
- swater x gwater x DTwater
gmetal x DTmetal
CHM 101/102
Calorimetry
•
Procedure
 Determine the mass of your assigned metal by
emptying the metal onto a paper towel and
weighing the empty test tube with its stopper.
Return the metal to the test tube and weigh the
test tube with its stopper again.
 Place the test tube in a beaker of boiling water for
10 minutes. Be careful not to allow any water to
splash inside the test tube. The metal must
remain dry.
Laboratory Manual
CHM 101/102
Calorimetry
•
Procedure
 While the metal is heating, weigh
two nested styrofoam cups (coffee
cup calorimeter).
 Add about 40 mL of water to
the inner cup and weigh the
setup again. Determine the
mass of water in the calorimeter.
 Measure and record the temperature of the water
in the calorimeter.
Laboratory Manual
CHM 101/102
Calorimetry
•
Procedure
 Remove the test tube from the boiling water and
quickly empty the contents into the calorimeter.
 Stir the contents of the calorimeter and record the
highest temperature reached. Be sure the
temperature probe is not touching the metal when
you make your temperature measurements.
Laboratory Manual
CHM 101/102
power connector and
serial/USB connector
USB connector on computer
temperature probe connected to
the Microlab unit
Laboratory Manual
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CHM 101/102
1
graph area
3
data table
Laboratory Manual
live data