 Hello, welcome to my channel. My name is Adrian and today in the understanding thermodynamic series, we are going to look at the property temperature. The outcomes of this video includes an introduction to the concept of temperature. I'm going to have a discussion on the differences between degrees Celsius and Kelvin. We're going to explain how you can convert temperature values between Kelvin and degrees Celsius and we're going to see that temperature is an intensive variable. So when you hold an ice cube, you can feel that it's really cold to the touch, whereas boiling water is really hot. If you touch it, you can do serious damage to your skin. Under degrees Celsius temperature scale, ice is melting at zero degrees Celsius. And the temperature of boiling water at sea level is 100 degrees Celsius. Did you know that at sea level, liquid nitrogen will boil at minus 195.8 degrees Celsius? That is really, really cold. But then the question pops up, what in fact is the coldest temperature that you can get? The lowest possible temperature is minus 273.15 degrees Celsius. In a later video, I will explain why it is not possible to reach this temperature. So when we use temperature in calculations, the equation for the ideal gas law pops up. And here's an example of the ideal gas law as PV equals nRT. Now a question for you, do you use degrees Celsius for T in the gas law? Yes or no? The answer is in fact, no, you don't. If you use a temperature in degrees Celsius and that temperature is zero, then you won't be able to use the ideal gas law. And in order to avoid this problem, we use the temperature and we express it in Kelvin. This is usually done when we multiply or divide with temperature. We always use Kelvin. So be like Drake, use Kelvin when you are multiplying or dividing by temperature. This graph shows the relationship between degrees Celsius and Kelvin. Now if you first look at the dashed line, that is where ice is starting to melt at zero degrees Celsius. And the corresponding temperature in Kelvin is 273.15. If we look at the solid line, that is where water starts to boil. And that is at 100 degrees Celsius. And the corresponding temperature in Kelvin is 373.15. You will see that in order to convert zero degrees Celsius to Kelvin, we add 273.15 to the value of zero. Similarly, for when water is boiling, we add 273.15 to 100 to get 373.15 Kelvin. But the difference in temperatures is still 100. Irrespective, if you are using degrees Celsius or Kelvin. Now let us do a few calculations. Here's two questions. The first one states that liquid nitrogen at sea level boils at minus 905.8 degrees Celsius. And you now need to go and calculate this boiling point of nitrogen in Kelvin. The second question asks you to calculate the temperature in degrees Celsius for a temperature given as 500 Kelvin. Now remember that in order to convert a temperature value in degrees Celsius to Kelvin, we add 273.15 to that value. Pause this video now and have a go at it. So for the first question, we take minus 195.8 degrees Celsius and we add 273.15 to it. And we get a value of 77.35 Kelvin. For the second question, we take 500 Kelvin and we subtract 273 from it. And we get an answer of 227 degrees Celsius. Here's another one. Calculate the temperature difference between the sun's surface temperature of 5500 degrees Celsius and the Earth's average temperature of 14 degrees Celsius. And you need to do this 4 degrees Celsius and Kelvin. So for degrees Celsius, we just take the value of 5500, we subtract 14 from it and we get 5486 degrees Celsius. If we do the same for Kelvin and we convert these two values to Kelvin first and we subtract them from each other, we get the same value of 5486 Kelvin. Why do you think this is the same? Let me know in the comments below. So lastly, the quantity of any material that you're looking at has no effect on its temperature. If you're looking at the temperature of a small droplet hanging from a leaf or you're looking at the temperature of a whole glass full of water, the quantity of the droplet water on the leaf and the quantity of the water in the glass does not affect the temperature. As such, we can say that temperature is an intensive variable. So to summarize what we've just discussed, temperature is used to quantify how cold or hot something is. There are two temperature scales that we discussed here, Celsius and Kelvin. The lowest possible temperature is zero Kelvin. And as such, we can say that Kelvin is called the absolute temperature because you get absolute zero in Kelvin. Kelvin is used for multiplication and division by temperature. And to convert degrees Celsius to Kelvin, you just add 273.15 to your temperature value. To convert Kelvin to degrees Celsius, you subtract 273.15 from the Kelvin value. And the temperature difference between two sets or two bodies is always the same, irrespective if they are expressed in degrees Celsius or in Kelvin. And then lastly, temperature is an intensive variable. As such, it is independent of the quantity of the material. Thank you very much for watching the course notes that these videos are based on is available on my website, odreonsblog.com. And you are welcome to connect with me on Twitter. Twitter handle is at ASVN 90 for any other questions that you might have. Hope you've enjoyed this and I will see you in the next video. Bye.