# Entropy and heat flow

1. Mar 7, 2012

### aaaa202

In my book it says: The bigger entropy of a system, the more heat from the surroundings can enter it. Now, I don't really understand why that is completely. Can anyone explain me? - both in terms of the actual thermodynamic formulas (thermodynamic identity etc.) and in terms of multiplicity?

2. Mar 7, 2012

### Andrew Mason

I don't think that is what your book says, exactly. Perhaps there is a translation problem because what you have written does not really make any sense. It would make sense if the book said that as heat from the surroundings enters the system, the entropy of the system increases. This is because ΔS = ∫dQ/T

You are looking at an open system - one that can interact with its surroundings. In such a system, the amount of heat that can flow into the system depends on the temperature of the surroundings, the temperature of the system and the heat capacities of both the system and surroundings. As net heat flows into the system, the entropy of the system increases. This increase in entropy does not result in more heat entering the system.

AM

3. Mar 7, 2012

### aaaa202

maybe I am interpreting it wrong. It's about the Helmholtz energy, and the book says:

"The helmholtz energy F is the total energy needed to create a system minus the energy you can get for free from an atmosphere at temperature T. This energy is given by TS, where S is the final entropy of the system. THE MORE ENTROPY A SYSTEM HAS THE MORE OF ITS ENERGY CAN ENTER AS HEAT "

What do you get from that? Where am I going wrong? :)

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