All right, so I want to do a quick video on temperature, because in the heating, ventilating air conditioning and refrigeration trade HVAC, our understanding temperature is huge and one of the problems with temperature is that everybody thinks that they understand it. And so here's the main distinction that I need you to make right off the bat temperature and heat while they are related. They are not explaining the exact same thing so heat we measure in total heat quantity. We measure it in things.

Like I don't know, BTUs would be probably the most common or therms or we can even convert it into watts. There's a lot of different measurements. We can use for total heat content temperatures sort of like measuring miles per hour. If you measure miles per hour of a car that doesn't tell you what type of car it is, it isn't tell you how big it is.

It just tells you how fast it's moving and temperature is a measurement of to be technical. The average molecular velocity within a substance or another way of saying it would be the average kinetic energy within a substance and when we say average, that just means that there are some molecules that are moving faster, some that are moving slower. But if we average out the energy within a substance say a glass of water, that's how we come with temperatures. So if I put a put a thermometer into a glass of water and that glass of water says 80 degrees, that's telling me something about the average molecular velocity.

If I had another cup of water, that was sixty degrees. That would mean that the average molecular velocity in the 80-degree cup of water is higher, meaning the molecules on average are moving faster than the molecules in the 60 degree cup of water, but now, let's use this example of why heat and temperature are different. I could take a swimming pool that was 80 degrees. I could take a glass of water that was 80 degrees.

They both have the same molecular velocity, which means that they have thermal equilibrium. Thermal equilibrium just means that on average, a net you won't move heat energy from one to the other if you were to place them together. So if I took the glass and I kind of like dipped it slightly into the pool that was 80 degrees, heat wouldn't move in between the two. There might be a little bit of heat energy that's transferred, but there would be no net gain or loss.

So they would both just stay 80 degrees because they're at thermal equilibrium, with each other right now. That does not mean, by any stretch of the imagination, that they both have the same amount of heat in them. That'd be crazy. The swimming pool obviously has more heat because it has more stuff, there's more molecules and because there more stuff in the swimming pool, there's overall, more heat content.

So if we were to measure that in BTUs, we would see that the swimming pool had far more BTUs of heat contained in it than the glass of water. Now, a lot of technicians love to be snarky when they're talking about heat and temperature and all this and somebody says, don't don't leave the fridge door, open, you're, gon na let the cold out and they'll say actually ma'am. There is no such thing as cold. Cold is simply the absence of heat, and it is true that we don't measure amounts of cold.

We don't measure quantities of cold. However, we do measure a point of cold and a point of cold that we measure is absolute. Zero absolute zero is the point at which kind of a theoretical point, because we don't achieve it. We can get very close in science, but it's a point at which all molecular velocity all molecular motion stops, and so that is what we call cold or the point of cold.

It's the point where there is no heat right, so by definition, what would it be? But cold, so you can use that as a comeback to somebody who says that there is no such thing as cold. Cold is a point where, as heat doesn't have there's no max, you can keep increasing the temperature for infinity and they just keep moving faster and faster right, at least theoretically speaking. But there is a point at which it stops, and that is sort of our starting point and that's we call absolute zero and so the most useful thing that we do with temperatures is we can compare molecular velocities to each other in order to come up with Which direction will heat move so, for example, when you say you're cold? What are you saying, you're saying that I am uncomfortable because of the amount of heat that's leaving my body, the rate at which heat is leaving. My body is making me uncomfortable, and that happens at lower temperatures.

It doesn't really matter what the thermal mass of the thing is, although it does affect it actually a little bit because of density, for example, if you're in 32 degree, air versus 32 degree, water or 30 degree, water or whatever. Of course, that would have to be ocean water, otherwise we would be ice, but you get the point. If you're, you just fell off of the Titanic into the ocean, you're going to be much colder than if you're in the same temperature, air that was kind of dark, but anyway, water has a greater density of molecules. So therefore, it's going to transfer heat off of your body more quickly, but it doesn't change the fact that 32 degree water one place in 32 degree water at another place as long as they have.

The same makeup is going to transfer heat out of your body at the same rate, and so when we have water, that's warmer, then it's going to transfer heat out of your body, lesser wraiths and water. That is colder, I mean so. Those are that sort of heat transfer thing is what causes us to feel hot or cold, but it starts with it which direction it's moving. So if heat is moving into our body at a rate, that's uncomfortable, that's what we would call it hot or if our body's not dissipating its own heat because we're warm-blooded creatures - and we have our own internal body heat by nature.

We need to dissipate some of it, so we're comfortable in temperatures that are actually lower than our skin surface temperature. I think so anyway. What's the point? The point is we look at temperature because we care about which direction heat is going to move and we can have some understanding of the rate at which it's going to move. So when there's a greater differential in temperatures, heat moves more quickly when two things are the same temperature there within thermal equilibrium.

Now we do also care about the total heat content of things. So again, a BTU is a common term. That's used for measuring the amount of heat in something and a BTU defined is the amount of heat it takes to change the temperature of one pound of water by one degree Fahrenheit. So again, the amount of heat it takes to change the temperature of one pound.

Not a gallon, that's something that people get confused, one pound of water by one degree Fahrenheit. So it's actually about you know a lot of people have tested this. You take a typical match, typical, wouldn't match you. Let it burn! That's the about about the amount of heat that a that a match creates is one BTU, it's pretty small unit of measure, but you can have two things.

You can have your glass eighty degree, glass, 80 degree swimming pool and the swimming pool has far more BTUs of overall heat in it because there's just a lot more water there's a lot more mass there, and so that's the difference between total heat content and temperature. Now, let's talk a little bit about temperature scale, so we talked a little bit about absolute zero and the Fahrenheit scale. That's negative 460 in the Celsius scale, that's negative! 273! I think going off a memory there negative 273 and that's the point at which a three reticle point at which things don't move anymore at the molecular level. There's no more motion molecular Li, so that's sort of our cold pointer our base point, but early on when scientists you know made temperature scales, they sort of made it up, and so the Fahrenheit scale water freezes at 32 and then boils at 212, which defines the Size of the degree, so that shows you how big the degree is it was sort of they use what they had at their disposal and then somebody else came along and said: hey.

I don't want to do this anymore. That's a silly way, so we're gon na make freezing zero and we're gon na make boiling a hundred, and so the Celsius degree is a smaller degree, because there's fewer digits in between 0 and 100, then there is between 32 and 212, eventually long cane, some scientists And they're like this sucks because we're trying to do scientific math and having negative numbers and positive numbers, you know the ability to have negative temperature there's no such thing as negative heat, so it throws off the equations. So they came in and created the Rankine and the Kelvin scale, and so the Kelvin is basically the Celsius version of an absolute zero starting scale and the Rankine is the Fahrenheit version, so they both start at Absolute Zero. They have no negative numbers, so zero is absolute, zero and both of those scales, and then they go up from there.

So if you look at the Rankine scale, because it uses Fahrenheit degree size absolute, zero, zero point on the Rankine scale is going to equal negative 460 on the Fahrenheit scale and then, as it goes up from there, it's gon na match in size of degree and With Celsius again, I think it's, I think it's 273 you're gon na have to check me on that one, not that it really matters, but it starts. That's the zero point with the Kelvin scale Celsius and Kelvin, and then they both go up from there. They gives you a sense of what we're talking about with degrees and why we have to do these. Conversions is because not only do they start at different points, Celsius and Fahrenheit, but they also are different sizes of degree.

There. You go measurement of average molecular velocity, that is, our friend temperature I'll, get you in the next video.