 So let's do this one. It says calculate the amount of heat energy in kilojoules that is transferred when 300 grams of water is cooled from 25 degrees Celsius to 3 degrees Celsius. Is the energy being gained or lost by the system? So in this case, hopefully you guys notice that it's asking or in the question it's talking about the mass. So you're looking, hopefully, thinking specific heat capacity. So when you think that, you're going to think q equals mass times heat capacity times delta t. So what do we know? So q is heat. That's what we're looking for. So we don't know that. Do we know that? Yes, 350 grams. The heat capacity, do we know that? Well, the heat capacity you have to be given. It's a number that's specific to the particular substance. If it's water, it's actually 4.18 joules per gram degrees Celsius. You can cancel your units out eventually. And remember also delta t, right? That's a little equation in and of itself, right? It's tf minus ti, do you guys remember that? So tf minus ti. So do we have tf and ti? So tf is what? 3 and ti is 25 degrees Celsius. So notice this is in degree C, and this is in degree C. So we don't have to convert our temperature units. So here we're going to say degrees C minus 25 degrees C. That equals negative 22 degrees C. So now we have delta t. We have C, and we have m, right? And we're looking for q. So all we do is plug each other in. So q equals m, which in this case is 350 grams times C, 4.18 joules per 1 gram times degree C, and delta t is negative 22 degrees C. So it's saying not in joules, but in kilojoules, right? So why don't we just convert to kilojoules right now? So 1,000 joules per 1 kilojoules. So let's cancel, kilojoules. So everybody see that? About 1,000. And this should be to 2 6 bigs. Is that right? Everyone? Is that what you guys got? So I got negative 32 kilojoules is the heat transfer. So I guess then the second question is the energy being gained or lost by the system. What do you guys say? Lost, why? Negative. How else could you know? If you didn't know that, the temperature decreased, right? So since the temperature decreased, right? Molecular motion decreased, so that means the energy of the molecules decreased. So everybody OK with this problem? One question. Uh-huh. Oh, this is great. No question? OK. OK. You sure? I'm sure. OK. Any other questions? OK, cool.