Problem 12 - Chemistry An Atoms First Approach

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.

Step-by-Step Solution

Answer

The dispersion of toxic substances in the environment is consistent with the second law of thermodynamics, as it results in an increase in entropy due to the spreading out of the contaminants. Preventing contamination before it occurs requires less work compared to cleaning the environment after contamination, as reversing the increased entropy associated with contamination would require a significant amount of work.

Step 1: Understand the second law of thermodynamics

The second law of thermodynamics states that the entropy of an isolated system always increases or remains constant but never decreases. Entropy is a measure of the randomness or disorder of a system. In simple terms, it means that energy tends to spread out or disperse from areas of high concentration to areas of low concentration until equilibrium is reached.

Step 2: Explain how dispersion of contaminants is consistent with the second law

When a toxic substance is introduced into an environment, it starts dispersing due to the natural tendency of energy to spread out and reach equilibrium. This process increases the entropy of the system (the environment), which is consistent with the second law of thermodynamics. The toxic substance becomes more diluted and less concentrated in the process, making it more challenging to clean and address the contamination.

Step 3: Compare cleaning the environment after contamination vs. preventing contamination

In terms of the second law of thermodynamics, preventing contamination before it occurs requires less work than cleaning the environment after contamination. This is because, once the contaminants are dispersed, the entropy of the environment has increased, and restoring it to its original state (removing the contaminants and reducing the entropy) would require a significant amount of work. In contrast, preventing the contamination in the first place does not increase the entropy of the environment and thus requires less work to maintain the initial state. In conclusion, the dispersion of contaminants in the environment is consistent with the second law of thermodynamics as the process increases the system's entropy. Preventing contamination before it occurs requires less work than cleaning the environment after the contamination has taken place, mainly because restoring the environment to its original state would involve decreasing its entropy, which contradicts the second law.