SM0486
Is a form of energy?
Is the total kinetic energy of moving molecules (a name applied to the kinetic
energy possessed by the moving molecules of a body)?
Let's examine the list of
possible answers in sequence to see if any of them or a combination of them agrees
with your concepts of the nature of heat and what heat consists of.
(1) Heat and expansion.
While the word "expansion" identifies one of the
effects heat produces in metals, it is not a satisfactory answer for the original
question of "What is heat?"
We hope that you chose one or more of the other
answers. If you didn't, choose one before we proceed.
(2) Heat and friction.
You know that the moving parts of the engine of
your car generate heat because of friction.
In some instances, the intensity of
heat is such that the resulting expansion of metals prevents the movement of some
parts. Although the preceding statements are true, the original question has not
been answered; you have only chosen one method whereby heat is generated.
(3) Heat and compression.
When a gas is compressed, the space between
individual molecules is decreased. The decrease in space between molecules results
in an increase in the activities of the molecules involved.
The increase in the
activities of the molecules results in an increase in the kinetic energy of the gas
compressed. All of the statements concerning an increase in heat (kinetic energy)
by means of compression are true; but have we answered the original question on the
nature of heat?
Partially, yes.
We say partially because the use of the
expression "kinetic energy" in parentheses following heat indicates that heat is
kinetic energy.
(4) Heat is an invisible weightless fluid called caloric. At one time heat
was considered to be the caloric just described. With the development of the laws
of the conservation of energy, the idea that caloric (heat) could be increased or
decreased as a separate entity (a quantity existing independent of other
quantities) was disproved.
The increase or decrease in the quantity of heat is
always accompanied by the transformation of one form of energy to another. Another
failure; we still haven't given a satisfactory answer to the original question.
This one isn't even partly true.
(5) Heat is electricity. If heat is electricity, then electricity is heat.
Well, technically no. You already know that electrons which constitute electrical
currents are forced through resistances by an EMF (electromotive force).
The
movement of these electrical particles creates an increase in the activity (kinetic
energy) of the particles concerned and a subsequent increase in the quantity of
heat on the electrical conductor.
This means that electricity can be used to
produce heat, but we can't say that they are the same.
(6) Heat as a form of energy.
This statement is acceptable as a general
definition for heat, but it should be combined with the last state-
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