09-11-2012, 04:21 PM
Thermodynamics
[attachment=38790]
Entropy
Entropy, S, a measure of how many possible
energy states are occupied by a system.
A hot object placed into a cool container will
cause more of the possible energy states to be
occupied as heat flows from the object to the
container.
The entropy of the combination of the object
and container will increase.
The Third Law of Thermodynamics
The 3rd law of thermodynamics relates solely to
entropy of pure substances.
At 0 K, the entropy of a pure perfect crystalline
substance is 0 J/K.
This means that the energy of the system is
distributed among the fewest possible number of
states.
It also means that, unlike enthalpy or internal
energy, there is an absolute minimum of entropy
(0).
Interpretation of free energy
Maximum work
◦ Reactions can be carried out to do work, such as in
your body to move you.
◦ Most reactions are in a beaker and cannot do work.
◦ If we can carry out the reaction so that no entropy is
produced (reversibly), the free energy is the
maximum amount of useful work.
Free energy is the energy free to do work.
[attachment=38790]
Entropy
Entropy, S, a measure of how many possible
energy states are occupied by a system.
A hot object placed into a cool container will
cause more of the possible energy states to be
occupied as heat flows from the object to the
container.
The entropy of the combination of the object
and container will increase.
The Third Law of Thermodynamics
The 3rd law of thermodynamics relates solely to
entropy of pure substances.
At 0 K, the entropy of a pure perfect crystalline
substance is 0 J/K.
This means that the energy of the system is
distributed among the fewest possible number of
states.
It also means that, unlike enthalpy or internal
energy, there is an absolute minimum of entropy
(0).
Interpretation of free energy
Maximum work
◦ Reactions can be carried out to do work, such as in
your body to move you.
◦ Most reactions are in a beaker and cannot do work.
◦ If we can carry out the reaction so that no entropy is
produced (reversibly), the free energy is the
maximum amount of useful work.
Free energy is the energy free to do work.