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Ch 20: The Second Law of Thermodynamics

Chapter 20, Problem 20

CALC You decide to take a nice hot bath but discover that your thoughtless roommate has used up most of the hot water. You fill the tub with 195 kg of 30.0°C water and attempt to warm it further by pouring in 5.00 kg of boiling water from the stove. (a) Is this a reversible or an irreversible process? Use physical reasoning to explain.

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Welcome back everybody. We are setting up an ice bath for an athlete here and we are told that the way to do it is to fill it up first with cold water. Specifically, we're gonna be adding 100 kg of cold water at a temperature of 10°C. Then on top we are going to add some ice, specifically one kg at a temperature of 0°C. And we are tasked with finding two things. One whether or not this process is reversible or irreversible, irreversible. And then to what is going to be the resulting sign on the change in entropy here. Let's look at our tub again eventually, you know, as as time passes and as time approaches infinity, we're just going to have water inside the tank and there's no way that heat can just spontaneously leave the water so that it is frozen once again. This is not possible. It's just going to stay in its liquid form without any third party assistance. A. K. A. This process is irreversible. Now. For the change in entropy it is known that for an irreversible process, the change or the entropy is going to increase, meaning the change in entropy is going to be positive or the change in entropy is going to be greater than zero. So we labeled this process is irreversible and we deemed that the change in entropy will be positive, leading us to a final answer of C. Thank you all so much for watching. Hope this video helped. We will see you all in the next one