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Name: rbusch
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Before 1993


Question:
One of the laws of thermodynamics states that things become less ordered over time. If that is true, then why do crystals form? Since crystals represent an orderly arrangement of atoms, does the formation of crystals somehow violate the laws of thermodynamics? It seems that most of the Earth's rocks should be made up of glass rather than crystals, if things are supposed to become less ordered as time goes by.



Replies:
Thermodynamics says that any CLOSED system will increase its entropy over time. However, the earth is not a closed system! We are constantly receiving tons of energy from the sun. So there are plenty of ways for systems to become more ordered in the earth. Crystals typically are formed when particular elements or simple compounds in the earth are cooled very very slowly from initially molten states. Speaking from a molecular perspective, substances go into various forms driven by two factors; they would like to increase the entropy AND lower the energy. Crystals are low- entropy states, but they are also very low-energy states, and these two aspects generally compete against each other (there are many exceptions, but this is a decent crude generalization). To sum: only CLOSED SYSTEMS are guaranteed to increase their entropy over time, and minerals which crystallize in the earth are not closed systems. The earth itself is an OPEN system.

Robert Topper



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