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Units of Measurement

In science, a unit is a standard numerical value used to quantify a physical quantity. A unit can be defined by a fundamental physical law or empirical observation and can be expressed as a conventional value of a physical quantity or a rationalized additive constant.


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Video Transcript

you didn't specify a measured physical property. It could be a single unit or a combination of units, depending on what we're talking about. Some units are defied by a combination of units for convenience and are widely accepted, like the Newton or morality. So you're enlisted a couple of physical properties that you'll probably encounter throughout your chemistry course, and I won't be covering all of them. But I think these kind of summarize the ones that you will see the most. So the first one I listed is Mass and usually, um, under Mass. You'll encounter things like the mole, which is related to the OB cadres number, which I will cover later. A swell as something like Grams, which is the unit that is often reported in literature when we're talking about reactions and how much of each molecule you're using for your reactions. So grams air, usually abbreviated as a lower case G and the mole is usually ran as mole. So the next thing is energy and energy is an important concept in the aerodynamics, and it's also really important in theoretical chemistry as well. And usually energy will be represented. Skill jewels or some kind of jewels. Um, and sometimes you also see something like TVs or electric bolts for concentration. You'll mostly encounter the morality, which is a mole per earlier, But sometimes you'll also encounter something called morality Um, which is a mole per kilogram. So the next thing is temperature and usually temperature shows up in thermodynamics and is usually in Kelvin because of the units in your equation. Um, you'll also see degree Celsius when you're reading literature, and you come across some kind of synthetic procedure that reports that you have to heat some reaction at some temperature, and that will be usually in degrees Celsius. Desperately, this is usually in mirrors, but sometimes you also see something like Centimeters when you're talking about the path length of a Kibet for volume that's basically length squared, so you'll see something like, you know is cubed Centimeters Cube. Um, also, you'll see the leader, which we have seen in concentration, and one leader is equal to 10 to the negative. Third meter is cute, and if you can't remember that an easy one to remember is that one millimeter is equal to one centimeter cute. For a time, you'll usually see this reported in seconds foreign hours depending on or you're trying to observe. You'll also encounter pressure, which is usually measured in Pascal's or bar, and you'll usually see this. What we're talking about gas is in terms of pressure, volume work, the ideal gas law on things of that sort. Oh, and I forgot. Um, usually, you also see atmospheres, so you'll encounter this unit a lot as well. So the next thing is forced. You may not see this very often. You'll probably Seymour in physics course, but I just wanted to include it to talk about the Newton eso again. I said that sometimes we define new units, um, that are made of a combination of different units. So in the case of a noon, this is actually a kilogram times 1 m over a second squared kilogram from Mass. You know, it's per second squared from acceleration. Um, this is kind of where it's from eso again. Sometimes when we buy formulas, we can create these new units, um, as a kind of a way to understand the relationship between different physical quantities. I want to talk a bit more about common prefixes since you'll see this a lot, too, and you can pretty much find a table of all the prefixes that you'd ever want in your life. But I want to include someone's that you'll see more often. Um, just so you have these in the back of your head, eso won thing. That you'll probably see most often is the Milly, which is turns the negative. Third, he'll probably never often you also see my girl, which is indicated by Mu, which is hence, thinning of six. You will probably see Nano, which is 10 to the negative ninth. You will likely see senti um, like the centimeter, which is tens and they go to and a kilo like tequila jewels, which is 10 to 30. So there are definitely more prefixes, the ones that listed, but these are the ones that you'll probably encounter the most. So, um, it will be useful if you remember these ones right off the bat. And lastly, since we're kind of talking about numbers anyway, I wanted to briefly mentioned the scientific notation and this is essentially a way for you to rewrite numbers so it is more compact, especially really large numbers. Um, as well as very small numbers. So, for example, if you have something like, um, like this 500 1323 if you want around this. So it's three sig figs, 5.1 times. 12345 Um, tens of it. And whether you, right this is, um you're basically multiplying an integer or a number between, um one and 10 by some kind of factor of 10. In this case, I want to multiply this by 100,000. And that should equal mm three. Which, if we rounded it in this manner, would be close to that. But if you wanted to rewrite the whole thing exactly, you would write it out in this manner. So that's one way, um, to write this number. And if you have a really small number instead of really large number say 0.0 3 to 5, you can rewrite this as 3.25 times 10 to the negative 1234 And this makes sense because if you place the decimal at energy point and move across four, you'll end up with the right number. And so this is kind of what scientific notation is or how to write numbers in scientific notation. Um, sometimes you'll be asked to write something in scientific notation, using a certain modestly figs, which we will go over a bit later. And so it is important to understand how scientific notation works, which could be very useful again when you're working with really large numbers or really small numbers.