2 replies to this topic

[sri]

It is often said that Entropy of the universe is always increasing.
By definition, change in Entropy is defined as dS=dQ/T and the units are
KJ/Kg Deg C. The units of Heat Capacity are also the same. Then does it
imply that Entropy & Heat Capacity are similar terms?
If the Entropy of universe is always increasing, then does it imply that
Heat Capacities of substances increase with time scale?

[Adriaan]

In the technical sense entropy is a STATE, an energy level if you will. Heat capacity is just THAT; a capacity. That they have the same units is immaterial, basically (its like saying that because an apple = fruit and a pear = fruit that an apple = a pear).

The entropy of the universe, however, can not be taken in this technical sense; what the persons saying it mean is that the universe becomes less ordered over time.

If we take it as given that the universe expands AND that the universe is an absolutely closed system then one could argue that the universe is becoming MORE ordered; the universe mostly consists of nearly nothing (both in the sense of interstellar space, though that is not absolutely empty, and in the sense of the submolecular because an atom is a core and a cloud of electrons' possible positions with mostly NOTHING in between) the total density will decrease so there will be more NOTHING. In the end the universe will be so big that there will be next to nothing in it, and nothing is very nicely ordered.

In a mathematical sense; anything but infinity (the total energy / mass in the universe) divided by infinity (the size the universe will have in time) equals zero. So we might as well say that the entropy level of the universe is zero

[sri]

Thanks for the explanation. I could also glance through some literature which i would like to add.
Specific entropy is defined as dS=dQ/T where 'T' is Absolute Temerature in Deg K. Mean Absolute Temperature has to be taken.
For example to calculate Specific entropy of water at 0 Deg C, (Specific heat of water at 0 Deg C = 4.18 Kj/Kg Deg C) then Specific entropy = 4.18/273.5 = 0.015 KJ/Kg Deg K.