The laws of thermodynamics govern energy transformations
Energy can change from one form to another and this happens within strict controls known as the Laws of Thermodynamics. The first Law of Thermodynamics states that energy can be neither created nor destroyed. The second Law of Thermodynamics states that entropy (the disorder of a system) will never decrease as isolated systems will tend to thermodynamic equilibrium (objects tend to the same temperature) - the state of maximum entropy. A nice description of the first and second laws can be found at the NASA website: http://www.grc.nasa.gov/WWW/k-12/airplane/thermo2.html.
What do the first and second laws of thermodynamics state?