in order to talk about temperature we should probably first Define it temperature is the average kinetic energy of a group of particles temperature is the average kinetic energy of a group of particles there is a lot to unpack believe it or not in this definition of temperature first and foremost the word kinetic energy what is kinetic energy I am so glad you asked kinetic energy is the energy of motion and the classic Newtonian definition of kinetic energy is2 mass times the velocity [Music] squared so we have mass and mass is always in kilograms we have velocity and velocity is m/ second so 1 half the mass times the velocity squared is your definition of kinetic energy so in order for something to have kinetic energy it has to have speed in other words motion and it has to have mass and since temperature is the average kinetic energy of a group of particles in order for something to have a temperature it has to have mass and it has to have motion or a velocity to it if it doesn't have mass mass and it doesn't have motion you can't take its temperature so that's one important aspect of that definition but wait there's more and I'm not talking the amazing ginso knife I'm talking the word average the word average is anything but average when you have an average does everybody have the same amount does everybody have exactly that average value no particularly for a large group you get that normalized distribution that we lovingly refer to as a bell curve so if we have a group of particles at an average temperature most of the particles are going to have the temperature close to that average however some are going to have a great deal more of energy and some are going to have significantly less why does water evaporate water boils at 100 degrees celsus so why does a cup of water disappear in our kitchen at 75 degrees Fahrenheit why because even though most of the particles may be at 75° Fahrenheit some of them are going to have enough kinetic energy to enter that gas phase so that average concept is going to be something that we're going to hearken back to throughout the course of this semester and next semester both of these two key aspects of temperature are going to come really important to us as the semester goes on another important thing I'm going to point out real quickly is heat heat is any form of energy that flows from high temperature to low temperatures heat is energy that flows from high temperatures to low temperatures and it can be any form of energy whether it's kinetic energy whether it's electromagnetic radiation any energy that is transferred as a result of differences and temperature is referred to as heat heat is an actual quantity measured in units of jewels as opposed to temperature which is an average easiest way to explain the difference we've all seen that one guy at a party right he lights a match holds his hand over it and goes look at my hand I'm not burning it well that match actually Burns at a temperature that's several hundred degrees hotter than a wooden fire however what happens if you're standing in the middle of a bonfire you're doing a Jon of Arc impersonation right despite the fact that that bonfire is at a lower temperature than the idiot with a match so why is one person not being burned and the other person being turned into um a human steak quantity of heat right the match puts off a very low quantity of heat whereas that bonfire even though it's at a lower temperature puts off a large quantity of heat Heat versus temperature now we said that heat has units of jewels what are our units for temperature complicated story there are several attempts by us as humans to measure temperature tempature or to describe temperature we're going to look at three of them the first is the Fahrenheit scale the only reason we're using the Fahrenheit scale as some of you are going to be engineers and because it's what we use in our everyday life now this is a terribly random scale this random scale has water freezing at 32 degrees Fahrenheit and boiling at 212 Fahrenheits so that the difference between your boiling point and your freeezing point of water is 180° totally random for scientists who are most often working in the aquous environment because we're usually working around life systems and ignoring all metaphysical aspects we're walking talking aquous Solutions so the Celsius scale was developed and it's water focused it defines itself on water it sets it zero as the freezing point of water water and it sets its boiling point of water at 100° and therefore divides the difference between the boiling and freezing point of one of water at 100 degrees CSUS so couple observations here first the freezing point of water is totally different second what if about the size of their degrees the distance it takes 100° to cover on the Celsius scale it takes nearly twice as many degrees 180 to cover on the Fahrenheit scale so a Fahrenheit degree is not equal to a Celsius degree matter of fact the Celsius degree is nearly 1.8 times larger than the Fahrenheit degree I should write that a little bit backwards right um a degrees Celsius is equal to 1.8 degrees F if we were to do a graph of the two what we're going to find is we're going to find our Fahrenheit with a much steeper slope than our degrees Celsius so they're going to have much different slopes another thing that's going to be different is their intercepts going to be different so going from Fahrenheit to degrees Celsius is going to be a challenge instead of just some simple addition or some simple multiplication we're going to have to adjust forther difference in degree size or their slope and their difference in intercept so to go from Fahrenheit to Celsius your temperature in Celsius is equal to your temperature in fahrenheit minus 32 divided by 9 multiplied by five your temperature in Fahrenheit is going to be 9 FS times your temperature in celsius plus 32 if you're not a fraction person I can rewrite them for you in decimal form I however like those fractions just to rewrite this exact same thing but with decimals Fahrenheit minus 32 divided by 1.8 temperature in Fahrenheit equals 1.8 times your degrees Celsius plus 32 order of operations is really important here really super important everybody write down feet by the way or you're when you go from Fahrenheit to Celsius you have to do that subtraction step first when you go from Celsius to Fahrenheit however you do your multiplication first keep your order of operation straight the number one mistake I see on exams with these formulas is people not doing the order of operations right you have to know these formulas you're going to be using them time and time and time again for the rest of your life if you're in this class now both the Celsius scale and the fen height scale had fundamental problems and that fundamental problem comes from the definition of temperature temperature we said requires mass and motion so when you have zero motion you should have zero temperature and vice versa when you have zero temperature you shouldn't be seeing any motion or you shouldn't be seeing any Mass one of the two right because of our definition of temperature well at 0 degrees Celsius the freezing point of water do we see motion yeah we've been outside lots of times at Z de degre C we've played in the snow we can move so obviously molecular motion exists and motion exists at 0 degrees C same for 0 degrees Fahrenheit we've had days in Kentucky that have been -12 Fahrenheit where we've all gone outside and had to take out the trash so both these scales have a huge problem because according to our definition of temperature we shouldn't be having any motion possible that's where the Kelvin scale came in the Kelvin scale took the Celsius scale's slope made a line parallel to the Celsius scale but move the intercept of the line so that the intersection of kinetic energy and temperature was at zero so that when you had zero molecular motion you had zero temperature this zero on the Kelvin scale where you have zero kinetic energy is referred to as absolute zero it's the coldest temperature possible somebody asked well what happens if they discover a temperature colder than absolute zero you can't if ever they have an experiment that suggest there should be a temperature colder than absolute zero they redefine absolute Z Z they say oh this new temperature is absolute zero absolute zero is by definition the coldest temperature possible and it serves as the zero for your Kelvin scale because we are measuring against absolute zero for the Kelvin scale there are no degrees because we're not saying it's so many degrees from water or so many degrees from a different standard it's an absolute difference from absolute zero so for the Kelvin scale whenever we give our temperatures on the Kelvin scale we would just say 100 Kelvin we wouldn't say 100 degrees Kelvin we would just say 100 Kelvin or 313 Kelvin we wouldn't say degrees Kelvin like we would degrees Fahrenheit or degrees Celsius absolute zero on the Kelvin scale is zero Kelvin you have to be okay remembering that you have to be okay remembering that make sure you try the salad bar I'll be here all week hey everybody write down salad bar um the Kelvin scale's line is parallel to that of the Celsius scale and the Kelvin scale is basically an intercept correction on the Celsius scale a Kelvin is the same size as a degrees Celsius so since we're just correcting for The Intercept converting from Kelvin to degrees Celsius is really easy your temperature in Kelvin is equal to your temperature in degrees celsius plus 273.15 you're responsible for knowing these three formulas you're going to be using them for the rest of your life because your Kelvin scale is the only temperature scale with the zero in the correct place is the only temperature scale that we can use mathematically in scientific laws we try using one of the other two temperature scales and things will get messed up because the zero is in the wrong location so whatever temperature you're given in the laboratory you're going to have to wind up going to Kelvin so you have to know all these temperature conversion formulas off the top of your head real quickly let's run through a example here I have 93.2 Kelvin and I want to know how many degrees celsus that's equal to well my temperature in Kelvin is equal to my temperature in celsius plus 273.15 so to get my temperature in celsius I'd have to rearrange right so I'd have to subtract 273 from both sides so my temperature in Celsius is my Kelvin temperature minus 273.15 so my temperature in celsius would be 93.2 Kelvin minus 273.15 or a negative 179 95 degrees CS or a negative 180 degrees C significant figures in temperature conversions I am so glad you asked because I noticed that a lot of you noticed I used that subscript five to note it was um insignificant why is that well my friend forgive me I'm incapable of walking and talking at the same time and I'm incapable of writing and talking at the same time when performing a temperature conversion the number of decimals in your answer should be the same as your initial temperature when performing a temperature conversion the number of decimals in your answer should be the same as in your initial temperature here we had one decimal place in our initial temperature so we should only have one decimal place here that having been said we could report our answer as whoops this isn't the right way to report it then just based on the rule I gave you is it all right so there's my temperature in celsius to get to my temperature in fahrenheit I'm going to have to do that funfilled conversion where my temperature in Fahrenheit is 9 fths my temperature of Celsius plus 32 so 95s times a - 179.99 plus 32 and that's going to give me a -2 91 9 degrees Fahrenheit and that's how you do a temperature convergent chemistry is easy life is hard everybody write down Ray bradbear because we can't talk temper talk temperature without talking about one of the greatest works of literature of all time Fahrenheit 4 um 51 or is it 453 look it up it's by R Bradberry totally awesome best read you'll ever have