swansont Posted October 9, 2015 Share Posted October 9, 2015 It's also questionable to claim that enthalpy is applicable here, and how much classical thermodynamics would tell you. Link to comment Share on other sites More sharing options...
imatfaal Posted October 12, 2015 Share Posted October 12, 2015 ! Moderator Note Split regarding how life/conscious actions renders examples of entropy invalid split off. If a post has been inadvertently moved or missed let me know by PM Michel Please try to avoid taking threads off at a tangent to explore a personal view of a topic or to ask questions that are not part of the OP. Please do not respond to this moderation. report the post if you think it is unfair. Link to comment Share on other sites More sharing options...
studiot Posted October 12, 2015 Share Posted October 12, 2015 puppypower you may like to look at Mollier diagrams. They plot the relationship between enthalpy and entropy. https://www.google.co.uk/search?hl=en-GB&source=hp&biw=&bih=&q=mollier+diagram&gbv=2&oq=mollier&gs_l=heirloom-hp.1.0.0j0i10j0j0i10l3j0j0i10l2j0.1593.4156.0.6875.7.7.0.0.0.0.219.985.0j6j1.7.0....0...1ac.1.34.heirloom-hp..0.7.985.aV-4v27-bBE Swansont It's also questionable to claim that enthalpy is applicable here, and how much classical thermodynamics would tell you. It is not often explained, but the relationship between entropy and the 'arrow of time' is classical and arises thus. Most equations (note I said equations, there are a few laws but lots of equations) in thermodynamics do not contain time. Time is not a (thermodynamic) state variable. This is also true of the second law that leads to the arrow statement. However thermodynamics is about (thermodynamic) processes and processes are loosely about changes of (thermodynamic) state. Underlying the arrow of time is the assumption that a system cannot be in two (thermodynamic) states at once. So a variable is required that can be used as the independent variable in charting progress of a process. This variable is chosen to be time. So in changing from one defined state to another the second law suggests that entropy is a state variable that can never decrease in value at the end of any such change of state. A (thermodynamic) state is defined as complete set of values of all (thermodynamic) variables, so whatever happens the other variables must adjust to meet this requirement on entropy. So the only permitted changes are those which produce a compatible set of values of state variables for the second state in the process. This is colloquially known as the arrow of time. When you break it down there are several indirect steps to lead to the result. Link to comment Share on other sites More sharing options...
swansont Posted October 12, 2015 Share Posted October 12, 2015 It is not often explained, but the relationship between entropy and the 'arrow of time' is classical and arises thus. What's the enthalpy (or change in enthalpy) of the cup? That's what I was referring to. Link to comment Share on other sites More sharing options...
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