Heat and temperature are two concepts
that are often confused. They are related to each other because they are both
related to the concept of thermal energy, as discussed in lesson
1-6. As you may recall, thermal energy is the energy that a substance possesses
due to the, kinetic energy, or motion of its molecules. Three factors affect the
amount of thermal energy that a substance has:
1) Temperature - Temperature is a measure of the average kinetic
energy of the molecules of a substance. An increase in temperature results in an
increase in the kinetic energy of the molecules and an increase in thermal energy.
It is fair to say that temperature and thermal energy vary directly, but they are not the
same thing.
2) Mass - Mass is a measure of the amount of matter in a
substance, as you recall from lesson 1-3. It makes sense
that a more massive sample will have more thermal energy than a smaller sample, if all
other factors are equal. Imagine the difference in total energy between a spoonful
of boiling water and a vat of boiling water.
3) Specific Heat Capacity - Each material is able to
"hold" a certain amount of thermal energy at a given temperature, due to what we
call its specific heat. Think of the wide range of temperatures that your feet
encounter during a day at the beach. The water may seem cold while the sand feels
quite warm. The wood on the boardwalk may feel comfortable, but the blacktop in the
parking lot is burning hot. Things will heat up at different rates, due, in part, to
their different specific heat values.
So, as you see, temperature is one of the
factors that affects the thermal energy of a substance. What is heat? Heat is
the transfer of thermal energy from a hotter to a colder object. What we think of as
"cold" is really the absence of heat. An object with at a higher
temperature can release more heat than the same object at a lower temperature, but
temperature is only one of the factors that affect the amount of heat an object can
transfer.
The factors that affect the amount of heat are
the same as the factors that affect thermal energy, for reasons that should now be clear
to you. Thermal energy is only measurable as heat, during heat transfer. The
amount of heat transferred can be found according to the following formula:
amount of heat transferred = mass x change
in temperature x specific heat
It is important to note that the symbols
that are used for the formula will vary from textbook to textbook, but the values
that they represent never change. One way to write the heat transfer formula is
shown below:
q = m(DT)Cp
Where q = heat transferred, DT = the
change in temperature and Cp = the specific heat.
This formula will be used in a later lesson,
but you should begin to understand the concept now. Going back to our earlier
example, picture a spoonful of 100.0 oC water and a vat filled with water, also
at 100.0 oC. Which would you rather have spilled on you? The water
in the vat can transfer much more heat, despite the fact that its temperature is no higher
that the water in the spoon. This should help you understand that heat and
temperature are not the same thing at all.
Now, be sure to check out the worksheets
and the online
quizzes!
