Reddit mentions of Thermodynamics

Read this book.
http://www.amazon.com/Thermodynamics-Enrico-Fermi/dp/1607962381

It's very short and introduces all the fundamental principles of thermodynamics.

The first two laws:
dU = dQ - dW. The change in energy of a system is equal to the amount of heat you put in (dQ) minus the amount of work the system does on its environment (dW).

Clausius statement for the second law:
"Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time." Basically a cooler object cannot spontaneously warm a hotter object (cooler and hotter described by something called temperature).

Then you have PV = nRT for an ideal gas, and W = integral P * dV.
S = entropy = integral dQ/T, and you can prove that entropy is a description of the state of a system using basic properties of differential equations (basically, if you take a closed integral of dQ/T, you'll get 0).

Also if you had a physics test coming up, wouldn't your physics classes have taught it? Or are you talking about some sort of standardized test? If it's the latter, you're better off getting a practice book and chugging away. I know at least for the physics SAT subject tests, the thermodynamics you need is not thermodynamics in the classical sense, but more about heat transfer and the like.

There's a reason whole semesters are devoted to thermodynamics and kinetic theory; it's a very broad topic.

If you're serious, start here for understanding Energy. Then something much more light weight about Oil

Then you can read light edutainment like The Prize with more gain.