Additional non SI units for pressure used by chemists are atmospheres, which is ATM, millimeters of mercury, which is mmHg, and Torr. Now, these units for pressure have their own pressure value which can be related to one another. Now remember, if you see a purple box, that means you have to memorize it because usually, it's not given to you in terms of a quiz or exam. The pressure values associated with atmospheres, millimeters of mercury, and Torr are 1760 and then 760 again.

The less commonly known ones, pascals, kilopascals, bars, and psi aren't in purple boxes, meaning they're not usually expected to be memorized. They'll be given to you in some way within the question or formula sheet. Now their pressure values are 1.01325×105 kPa. Remember kilo is 103. So, this is 101.325. Bars here is 1.01325. And then finally, if we look at psi, psi is 14.696.

Now, these numbers relate to one another. We said that they're a way to relate to each other. That means that one atmosphere equals 760 millimeters of mercury, or 1.01325 bars equals, 14.696 psi. So these are just ways of them connecting to one another. But again, it's the first three that are going to be the most important. Even though they're non SI units, they're the ones most commonly used by chemists.

So now that we know these different types of pressure values, let's continue onward to an example.