Chemistry help regarding 2nd law of thermodynamics?

Question

how is a toxic substance dispersing in our environ ment after an oil spill consistent with the 2nd law of thermodynamics? and...which requires the least work... cleaning environment after it has been contaminated or trying to prevent contamination before it occurs?

Answer 1

Are you using Chemical Principles by Steven Zumdahl? Great book... anyways, dispersal of a substance increases entropy because the amount of order decreases; the substance has a greater volume available to it and therefore more positions. Attempting to clean the environment after contamination requires that we consume the entropy that was generated as the dispersal occured, which necessitates the expenditure of lots of energy as we will need to create even more entropy in the process (total entropy must keep on increasing). Whereas, if we prevent the contamination before it occurs, all that this means is that we don't let the entropy suffer such a drastic increase in the first place, and this requires a lot less energy.

Answer 2

Second law of thermo. states that a system in a nonrandom equilibrium situation is isolated, it will change in time to achieve a random equilibrium state.  

With respect to spills, this simply means that the contaminant eventually disperses until some equilibrium is achieved.

It is much easier to contain a contaminant in its concentrated form (e.g. oil) and prevent its leakage than it is to clean up the mess later.  

Think about it like this, if you step in dog doo, it is much easier to immediately stop and clean off your shoe than it is to clean it off everywhere you walk.....you car floor, your carpets, floors, etc.  Better still, its easier to pay attention where you are walking.