We're going to introduce now a few variables that we'll be using
as we go forward with our discussion of thermodynamics.
One of those which we preferred to a few times,
is the heat added to a system
or the thermal energy added to a system.
The units of heat or thermal energy are joules,
and we represent this thermal energy with the letter Q,
and we'll be using a capital letter Q.
And again, the units of this energy that added are joules,
but we have to be careful with our terminology
because often we say heat
and we think that that's the same thing as temperature.
Because in every day sort of colloquial language we talk about the heat of something
or the temperature of something.
And we often use those words interchangeably.
So we really need to be careful
especially right of this point before we get started to understand
that when we say heat,
we're referring to the thermal energy
or the energy from the thermal action of your material,
not to the temperature of your material.
So these two quantities,
the heat and the temperature will be related
but they're very different.
And again, the energy units for the heat are units of energy or joules.
We also have other unit of energy,
this heat energy which is often used on a medical context or a food context or a metabolic context
Which is the calorie,
Which is abbreviated with the letter cal for calorie.
A calorie is simply also a unit energy
so we can ask how many joules as a calorie,
and that calorie is 4.2 joules.
The confusing thing here or potentially confusing thing,
is that we often speak instead in terms of thousands of calories or kilocalories,
because a calorie is such a small unit of energy.
When were talking about this kilocalories or thousands of calories,
we possibly confusingly
just write it as a capital CAL.
So we have to be very careful when we are looking at the units of calories as they're written on the page
because if you see a lowercase c
that is a typical calorie or 4.2 joules,
Whereas if you see in uppercase C
for CAL or calories with a capital C
that is a kilocalorie,
which would be one thousand times the 4.2 joules.
So this is a very brief lecture, just an introduction to our topic of thermodynamics.
Some of the basic laws that we'll be employing,
some of the basic variables that will be trying to measure.
So now these given variables and these laws,
we're going to see how these variables work together
in the system as it changes
and interacts with other systems, and we'll do that next time.
Thanks for listening.