Question

When the environment is contaminated by a toxic or potentially toxic substance (for example, from a chemical spill or the use of insecticides), the substance tends to disperse. How is this consistent with the second law of thermodynamics? In terms of the second law, which requires the least work: cleaning the environment after it has been contaminated or trying to prevent the contamination before it occurs? Explain.

Short answer

The dispersion of contaminants in the environment is consistent with the Second Law of Thermodynamics, as it increases the overall entropy (disorder) of the system. Preventing contamination before it occurs requires the least work, as it maintains a low-entropy state. In contrast, cleaning the environment after contamination requires more work, as it involves reducing a high-entropy state.

Step-by-step solution

Understanding the Second Law of Thermodynamics

The Second law of thermodynamics states that the total entropy of an isolated system can only increase over time or in best case remain constant. Entropy measures the degree of disorder or randomness in a system. In simpler terms, the second law states that in any spontaneous process, the total entropy of the universe increases.

Relating the Second Law to Dispersion of Contaminants

The process of dispersion of a toxic substance results in the contaminant spreading out and mixing with the environment. This increases the randomness or disorder within the environment, which means that the overall entropy of the system increases. Therefore, the dispersion of contaminants is consistent with the second law of thermodynamics.

Assessing the Work Required for Prevention vs. Cleanup

In order to determine which process requires the least work, we should compare the entropy change associated with both processes. To prevent contamination, actions must be taken that keep the system in a lower-entropy state (i.e., minimizing the level of disorder by keeping the toxic substance separate from the environment). Since preventing contamination would maintain a low-entropy state, it would require less work to be done against the natural tendency of the second law, compared to cleaning up the environment after it has been dispersed. When cleaning the environment after the contamination has occurred, we would have to reduce the high level of entropy by separating the toxic substance from the environment and restore it to the original low entropy state. Achieving this would require more work than preventing the contamination in the first place, as we are working against the natural tendency of the second law, which promotes an increase in entropy.

Conclusion

The dispersion of contaminants in the environment is consistent with the second law of thermodynamics, as it results in an increase in entropy. In terms of the second law, preventing contamination before it occurs requires the least work compared to cleaning the environment after it has been contaminated, since prevention maintains a low-entropy state, while cleanup requires reducing a high-entropy state.