A little better summary:
The total amount of
energy in the universe is
constant, energy cannot be created nor destoryed, it can merely be
changed from one form to another. And if
Einstein is correct, then this also means that
matter can neither be created nor destroyed. Basically, we
got what we got, and that's all we're
gonna get.
In equation form:
DE = Q + W
Change in Energy = Heat Energy entering/leaving the system + Work Energy done by/on the system
There are many ways to
phrase this... My favorite way to think of it is that in any
transfer of energy from one form to anther (for example, electrical to
mechanical energy),
useful energy is lost. Basically, you can't get out
more than you put in, and you can't
even get out what you put in.
The second law also states that the entropy (randomness) of a system will always increase, and it's impossible to decrease entropy without work. Basically, heat and energy tend to migrate from areas of higher concentration to areas of lower concentration, and it requires work to get it to go the other way.
This states that the
entropy of a system will approach a
constant value as the temperature
decreases, and that the entropy of a pure
crystal will be zero at a certain temperature (
absolute zero).
The Zeroth Law of thermodynamics
Not a true law, but a
derivation of the second law. This states that if two systems are in
equilibrium with a third system, then they must be in equilibruim with each other. For example, if two
containers of
water are at the same
temperature as a third, they must both be at the
same temperature.