this presentation explains about a simple practical which can be used to find the specific heat capacity of a given solid. The presentation also explains about some special definitions that have to be used when considering about the specific heat capacity of a substance.
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Finding the specific heat capacity of a solid
1. FINDING THE SPECIFIC
HEAT CAPACITY OF A
SOLID
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3. The specific heat is the amount of heat per unit
mass required to raise the temperature by one
degree Celsius.
So, if the mass of the object whose specific heat
capacity is calculated is m, the specific heat
capacity is c, then the heat needed to raise the
temperature of the system by θ is
Q = mcθ
SPECIFIC HEAT CAPACITY
OF A SOLID
5. Let the
mass of calorimeter + stirer = m1 ,
mass of calorimeter + stirer + water = m2,
initial temperature of the calorimeter = θ1 ,
Total mass of the objects = m3 ,
initial temperature of the objects = θ2 and
Final temperature of the system = θ
THEORY/PRINCIPLE
6. Furthermore let’s take the specific heat capacity of the
calorimeter to be C, that of the water to be CW and that
of the objects to be C0.
Assuming that the heat loss to the environment as
negligible,
Heat emitted by the objects = Heat gained by (water +
calorimeter)
Therefore,
m3C0(θ2 – θ ) = { m1C + (m2 – m1)CW}{θ – θ1}
Thus,
C0 = [{ m1C + (m2 – m1)CW}{θ – θ1}] / [m3 (θ2 – θ ) ]
By this relationship we can find the specific heat
capacity of the objects.
7. 1. Measure the weight of the calorimeter and the
stirer.
2. Pour water to the calorimeter so that water fills
about ⅓ of the calorimeter’s volume.
3. Measure the total weight of the objects to be
about thrice the weight of the total volume of
water
4. Heat the objects using a Nicholson’s heater and
record their initial temperature.
5. Introduce the objects to the calorimeter + water
system and stir the objects.
6. Record the final temperature of the system
METHOD
8. 1. Transfer of heat to the environment during the
experiment poses diffculties for the successful
completion of the experiment. This can be
minimized by,
(i) To prevent heat loss from conduction,
the calorimeter should be covered with heat
insulators
(ii) To prevent heat loss from convection
and vaporization, the calorimeter should be closed
with an insulating lid
(iii) To prevent heat loss from radiation, the
calorimeter surface should be polished.
IMPORTANT POINTS
9. 2. For the quick transmission of heat from the
objects to water, small pieces of the objects should
be used instead of large pieces.
3. The action of a Nicholson heater is as follows:
To
calorimeter
Case which can
be lifted to free
the objects
Thermometer
Water
The objects
Heat
Water
Introduce the objects to
the heater. Then water is
introduced to the heater
through the upper inlet.
Then heat the system.
Observe the temperature
change while heating. Do
not let the temperature go
past 100° C as when
introduced to water, some
water particles may
evaporate. Then lift the
stop case and free the
objects towards the
calorimeter.