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July 7th 2009 17:13
The increase in disorder is evident in our everyday lives. Each day, food is consumed and largely converted into heat, which is a more disordered state than the original food items. In general, it could be argued that all life forms have devised methods of taking ordered resources, such as molecules or food, and converting them into disordered states in order to generate energy. If all processes are moving to a disordered state, how can highly organized states such as crystals or biological cells be created? The answer lies in considering the overall state and not just one part. For example, your bedroom may tend to become very disordered with daily use until you decide to clean it up. While the clothes and other objects in the room may be more ordered, the process of cleaning the room involves the expenditure of energy in the form of heat. Thermodynamics would say that the disorder associated with the heat is greater than the order associated with the folding and stacking of the clothes.
In a sense, the change in order of an object provides a direction for chemical reactions. When a process results in a change from one state to another that occurs in an irreversible way, the process is called spontaneous. Only irreversible changes are spontaneous; truly reversible processes are not. Truly reversible processes do not occur in nature, as it would require all forces to be perfectly balanced with no driving force for the system to move. However, by moving objects very slowly while keeping forces in nearly perfect balance, processes that are very close to reversible can be created. As an example, gas inside a piston expanding under constant pressure inside and outside does not have any net force to drive the expansion, and the piston does not move. By making the imbalance very small, the piston moves, although at a very slow rate. Such a motion would take a considerable amount of time to be completed, but the rate is not under consideration here, only the direction.
Source: Biophysical Chemistry 2008
Source: Biophysical Chemistry 2008
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