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1800 J of heat flows from a very large body at 540 K to a very large body at 270 K.

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

$1800\ \text{J}$ of heat flows from a very large body at $540\ \text{K}$ to a very large body at $270\ \text{K}$ . Find the change of entropy of each body and the total. What would the total be if the heat went from the cold body to the hot one?

Need a reminder? The key ideaShow

Heat $Q$ taken in slowly at a steady temperature $T$ raises the entropy by $\Delta S = \dfrac{Q}{T}$ . Warming from $T_1$ to $T_2$ : $\Delta S = mc\ln\dfrac{T_2}{T_1}$ . A gas at a steady temperature: $\Delta S = nR\ln\dfrac{V_2}{V_1}$ . Entropy depends only on the state, and the total for an isolated system never falls.

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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