 As I told you about bonds, bonds are strong. We're talking about hundreds of kilocalories per mole. Unfortunately, that's something we're gonna need to come back to repeatedly in this class. How do we count energies? Well, we're gonna occasionally gonna use kilojoules, we're occasionally gonna use kilocalories, but it turns out that inside one molecule, these more energies would be absurdly small. They would be 10 to the power of minus 25 or something. And something tells me that you don't wanna use numbers that small because it gets obnoxious. So instead, we tend to measure energies in terms of kilojoules per mole. That is, instead of measuring the energy in one bond, I measure the energy that would be stored in Avogadro's numbers bonds. And the reason why we've adapted that is that that leads to very nice numbers. You can talk about the energy for bond might be 200 kilocalories per mole or something. 200 is an easy number to work with and I can't forget about all those exponentials. And that is so common that sadly, as chemists, we occasionally, we might occasionally be a bit sloppy and say that the energy is 200 kcal. And when I say 200 kcal, you should just take it for granted that I actually mean 200 kcal per mole. There is no way we would have absolute energy that would be 200 kcal inside a molecule. So why do we use kilojoules and kcal? There is an SI standard for this and that would be the kilojou. The problem is that standards are great so people tend to develop their own. And if you look at this all over the world, in particular in the US, people still tend to use kcal, even in parts of Asia. In Europe, kilojoules are more common, but the sad part, both of these number systems are around and you need to be aware of both of them. There are very few, I don't think there is anything in this class that's gonna depend on the exact 4.184 conversion factor between them. But you need to account for this factor of four. For instance, if I ask you about the energy of a hydrogen bond, if you make a factor of four error, that's probably large enough that you might not get that right on the exam. So in summary, I would suggest that you look up these numbers. You're gonna need to think about kilojoules, kilojoules per mole, kcal, and kcal per mole. So try to look up either for bonds if you want to or the other interactions are gonna talk about and get the rough idea what are the orders of magnitudes of the various energies you have and see if you can get a gut feeling about which ones of these are high and which ones are low. I will tell you a little bit about it in some of these short video recordings about the different types of interactions.