Dr. W. Pezzaglia
Las Positas College
Physics 2A Lab, Fall 2012
Lab #11b Specific Heat
Page 1
2012Oct29
Lab 11b: Specific Heat & Heat Capacity
I. Theory:
Two experiments. The first we measure the latent heat of water. The second, the specific
heats of some metals.
A. Latent Heat of Fusion:
The latent heat of fusion is defined:
Q  mL
where “m” is the mass, and “L” latent heat of fusion (the amount of heat required to melt one
unit mass of the substance). The heat of fusion of water is 79.52 cal/gm or 333.55 kJ/kg.
Sometimes we would rather measure it in terms of moles of a substance instead of mass, in
which case its called a “molar latent heat”.
B. Specific Heat
The amount of heat Q required to raise the temperature by T of an object is called its “heat
capacity”. It is defined,
C
Q
T
It is an extrinsic quantity, i.e. if you have twice as much substance, it takes twice as much heat
to raise the temperature. Therefore it is more useful to define the intrinsic “specific heat” which
is the heat capacity per unit mass,
c
1 Q
m T
Sometimes we would rather measure it in terms of moles of a substance instead of mass, in
which case its called a “molar specific heat”.
Some Specific Heats
==========================================
Metal
Specific Heat J/g C
-----------------------------------------Aluminum
0.897 J/g C
Brass
0.377
Copper
0.385
Iron
0.450
Steel
0.49
Lead
0.129
==========================================
C. Heat Units
The original unit of heat was the “calorie”, which was defined to be the specific heat of water.
In other words, it takes 1 calorie to raise 1 gram (1 cc) of water 1C. In SI units, the calorie is
equivalent to 4.186 Joules.
Question 1: Table of Values
(a) Add another column to the table above, and express specific heat in calories per gram
degree Celsius.
(b) Add another column with the atomic (molar) weights of the elements
(c) Add another column and compute the molar specific heat (Joules/mole-degree C)
==================================================================
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Dr. W. Pezzaglia
Las Positas College
Physics 2A Lab, Fall 2012
Lab #11b Specific Heat
Page 2
2012Oct29
II. Experiments:
We shall measure the latent heat of fusion of ice, and then determine the specific heats of 4
different metals.
A. Setup
Both experiments will use a calorimeter, which consists of an inner and outer container (made of
Aluminum). The intervening space is filled with air to somewhat isolate the inner container so
that little heat is lost to the environment by conduction or radiation (i.e. its an “adiabatic”
process). A lid helps prevent loss due to convection.



Measure the mass of the inner container “mc”
Calculate its heat capacity: Cc=(0.897 J/g C) mc
Measure its approximate volume (so you know how much you can fit into it). I gestimate
it to be about 340 mL.
B. Heat of Fusion of Water

Get Ready
o Hot Water: Have some warm water (T>50C) ready. Measure its temperature.
o Ice: Have some ice ready. Measure its temperature (it should be a few degrees
below zero).
o Put your metal container into the ice to get it cold.

Start Experiment
o Quickly put approximately 75 grams of ice (less than 100!) into your inner
container. If possible without melting the ice, measure its mass (i.e. you can
measure the mass of the inner container with ice inside, but do it quickly!).
o Fill container close to full with warm water, using graduated cylinder (i.e. you
must know how much water you added!). Use approximately 150 mL.
o Cover calorimeter.

Equilibrium Measurement
o Insert thermometer and wait for system to reach thermal equilibrium
o Hopefully all the ice has melted. If not, you will have to start over with less ice
and hotter water.
o Measure the final temperature

Final Measurement
o Measure the total amount of final water (in mL, or by weighing).
o Subtract from this the amount of warm water you added to infer the number of
grams of ice that you must have melted.

Analysis
o Calculate the heat needed to raise the Aluminum container from 0C to the final
temperature.
o Calculate the amount of heat needed to raise the melted water from 0C to the
final temperature.
o Calculate the amount of heat provided by the hot water cooling down from the
initial hot temperature to the final temperature.
o From the energy balance, determine how much heat was used in melting the ice.
o Determine then the latent heat of fusion of ice.

Summary
o Question 2: Compare your measured value to the known value. By what
percent are you off?
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Dr. W. Pezzaglia
Las Positas College
Physics 2A Lab, Fall 2012
Lab #11b Specific Heat
Page 3
2012Oct29
C. Specific Heats of Metals
You will measure the specific heats of 4 different metals (Brass, Aluminum, Steel and Lead).

Get Ready
o Hot Water: Have some warm water (T>50C) ready. Measure its temperature
o Measure the mass of your metal sample “ms”
o Put your metal sample into ice and let it cool to 0C.

Start
o
o
o
o





End
o
o
o
o
Pour about 150 mL of warm water into your calorimeter (this is enough to cover
the block completely). You don’t want to use too much water else your
temperature change will be too small.
Let it come to equilibrium with the metal container.
Measure this “initial” warm temperature “Th”
Put in your cold metal block.
Cover and wait until it reaches equilibrium
Measure the final equilibrium temperature of the system “Tc”
Measure the amount of water used (in grams): “mw”
Measure the mass of the empty container (Aluminum or glass?): “mc”
Analysis
o Calculate the heat (in calories) sucked out of the water to lower the hot water
from the initial hot temperature to the final temperature: Qw= mw (Th-Tc)
o Calculate the heat needed to lower the (Aluminum) container of the calorimeter
from the initial hot temperature to the final temperature:
Qc= (0.215 J/gm C) mc (Th-Tc)
o Thus, calculate the amount of heat that was used to heat the block up from 0C
to the final temperature: Qs=Qc+Qw
o Calculate the heat capacity of the block of metal: Cs=Qs/(Th-Tc)
o Calculate the specific heat of the block of metal: cs=Cs/ms
Summary
o Compare your measured value to the known value [i.e. what is your percentage
error: (Measured/True-1)x100%=?]. Report results both in calories and Joules.
Note
o Note: if you got bad results, then its possible that you used too much water, or
the water was not hot enough.
Repeat for more metals
o Now, repeat the experiment for several other types of metal blocks.
o Try to record your data and results in TABULAR FORMAT.
o Question 3: Summarize your results compared to known values.
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