Download Specific Heat

Introduction to Physical Science
Specific Heat Lab (Inquiry)
2/09
OBJECTIVES:
1.
2.
3.
4.
To understand the nature of specific heat.
To learn what factors affect specific heat.
To use laboratory measurements to calculate the specific heats of several metals.
To use the knowledge gained during this exercise to explain common climatological
phenomena.
INTRODUCTION
Heat is a form of energy for which we use separate units of measurement. The joule, as we have seen, is
used to describe work energy in mechanical systems. One joule of energy is required to raise one
newton of weight one meter high. However, when dealing with heat energy, the calorie is used more
often. The equivalence of the two is:
1 cal = 4.184 J
and, specifically for water, 1 calorie of heat is required to raise 1 gram of water 1° C.
Heat (Q) flows from hotter objects to cooler ones. Three factors affect the amount of heat gained or lost
by a substance:
1. what kind of substance it is (specific value (c) for each substance),
2. how much of the substance is present (mass),
3. the temperature change (ΔT)
The first of these determines one of the physical properties of a material, its ability to hold heat
compared to its temperature. Remember that heat refers to the total amount of kinetic energy of the
molecules in a sample, while temperature refers to the average speed (kinetic energy) of the molecules
in the same sample. Since different materials require different amounts of heat to overcome forces
within themselves (e.g. hydrogen bonds in water) and change temperature, a convenient method of
describing this is called specific heat.
Again, one gram of water, the standard for specific heat, requires 1 calorie of energy to raise its
temperature one degree Celsius. Its specific heat, therefore, is 1, quite a high value as specific heats go.
Some other values for common materials are listed in the table on the next page.
The specific heat (c) of any substance is the amount of heat required to raise one
gram of the substance one degree Celsius.
Specific Heats of Some Common Materials (in cal/g °C)
Ammonia
Water
Ice
Aluminum
Iron
Nickel
1.13
1.00
0.50
0.21
0.11
0.10
Copper
Zinc
Silver
Mercury
Platinum
Lead
0.09
0.09
0.06
0.03
0.03
0.03
MATERIALS & PROCEDURE:
Specific Heat Specimens
Styrofoam cups
Thermometer
Electronic Scale
600 ml Beaker
Hot Plate
Graduated Cylinder
Wire Hook
Determination of Specific Heat:
After looking over the materials available to gather data, develop and use a method
to determine the specific heats of the several different metal cylinders at your
benches.
Given that (in a closed system):
1) heat (Q) lost from one substance equals heat gained by the other, and
2) that the amount of heat gained or lost by the substances is equal to their
mass (m) X specific heat (c) X change in temperature (ΔT),
can you find a way to combine these two ideas into an equation that suggests what
data would need to be collected in order to calculate specific heats of unknown
objects?
You will need to record your data in an orderly, legible fashion, and present it with
an explanation of specific heat and a description of the methods you used to
determine the specific heats of the metal cylinders. Before beginning, decide what
information you will need to make your calculations.
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