 This one says calculate the change in internal energy for a system that is giving off 25.0 kilojoules of heat and changing from 12.00 liters to 6.00 liters in volume at 1.50 atm of pressure So let's write it down the things that it gives us in the problem. So it says that it's giving off 25 kilojoules of heat. So heat is Q. If it's releasing 25, what's the sign of that? Negative, right? It's going to be negative 25.0 kilojoules and it gives us the initial volume as 12.00 liters and the final volume 6.00 liters. So we can calculate our change in volume as we want it to, right? Which is VF minus EI or 6.00 liters minus 12.00 liters equals negative So this means it's decreasing in size by 6.00 liters. It also gives us the external pressure. So P e x t is 1.50 Okay, so you can go about this a couple of ways. Let's write down the equations. So change in internal energy equals Q plus W. And remember for chemistry, it's Q plus WPB, that Pb is the pressure volume equation. So remember that WPB equals negative P external times the change in volume of the system. So everybody okay with that? Here we go. So when we do this, we've got P external being 1.50 ATM and we've also got our change in volume as negative 6.0 liter ATM. So we're looking for energy units here. Remember, liter ATM are energy units, but we want to convert them to a more manageable unit. And since the other iron kilojoules, we're probably going to put the whole problem in the kilojoules. Okay, so let's do that. So they give us the conversion. This is the conversion that you won't have to remember. Okay? So 1 liter ATM equals 101.3 joules. So liters, ATMs, cancel. But we want to get it into kilojoules. So let's just do that right now. Okay, so in this case, we've got 0.912 kilojoules. So if we were looking at the change in energy here, it's going to be Q plus W. So this is W. This is Q here. Maybe we have 25.0 kilojoules, plus 0.912 kilojoules. So 24.1. There's a change in the internal energy. Are there any questions on that one? Does it make sense to you at least?