Dear Dierdre (a sad child)

Dear Dierdre (a sad child), this is Lord Kelvin writing to you about my law of thermodynamics. The second law of thermodynamics states that it is impossible to devise a cyclically operating thermal engine, the sole effect of which is to absorb energy in the form of heat from a single thermal reservoir and to deliver an equivalent amount of work. In simple terms, this means when energy changes from one form to another, or when matter moves freely, chaos in a closed system increases. Differences in temperature, pressure, and density tend to even out after a while. Take a look at the attached diagram for more help understanding.

-Lord Kelvin