MadSci Network: General Biology |
Brandon: This is a really good question, and we are excited to see that you are thinking about the effect of external environment on a process (decomposition) from a thermodynamic perspective. There are really two major answers to your question, the first is on the thermodynamics of decomposition, and the second, is on specifically what you did to shift this process. The short answer is that decomposition is a complex process, which is predominately biochemical in nature, not a strict thermodynamic decomposition of complex molecules into simpler ones. As such, it has virtually thousands of individual chemical reactions that occur, some with positive free energy, some with negative, which are coupled to others. Overall, though the process of decomposition is exothermic, a large portion of the chemical energy is converted to heat. Also, the activity that occurs is not at equilibrium, but rather steady-state. There is a lot of chemical energy in tissue, and organisms such as fungi and bacteria are consuming that during decomposition, which is where the heat (exothermic) comes from. The problem arises when you are changing the system to measure the effect on this exo/endothermic activity. As I see it, there are two ways in which you could accomplish this, A.) by reducing the temperature of the environment, or B.) coupling the decomposition to a chemically endothermic reaction, like you did with Ammonium Nitrate/H2O. The issue here is that changes in the rate of decomposition are primarily dictated by the biological activity of the saprophytes, not simply thermodynamics. Reducing the temperature will slow the growth of these organisms, inhibiting decomposition from a general thermodynamic slow-down, not so specific to exothermic inhibition. This is exactly why we refrigerate and freeze food, to prevent spoilage. Using ammonium nitrate as a proxy for endothermic activity is clever, but unfortunately in this case, you will likely see effects due to the nitrate itself. Nitrate chemicals have been used for centuries as preservatives, because they have antimicrobial and antifungal activity. Just check the ingredient list on any lunch meat, salami, sausage, bacon, etc. Sodium, or potassium nitrate/nitrate is often used in the curing process to retard growth. I hope this helps your quest. I think with this information, you might be able to reformulate your question (hypothesis) and still extract useful data from the work you have done.
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