Pure carbon exists is several forms, two of which are...

Name: Problem 59, Chapter 7: Introduction to General, Organic and Biochemistry
Uploaded: 2020-07-07T17:58:08-08:00
Duration: 56 s
Channel: Evey Z
Description: Pure carbon exists is several forms, two of which are diamond and graphite. The conversion of the diamond form to the graphite form is exothermic to a very slight extent. How is it that jewelers can advertise "Diamonds are forever"?

Pure carbon exists is several forms, two of which are diamond and graphite. The conversion of the diamond form to the graphite form is exothermic to a very slight extent. How is it that jewelers can advertise "Diamonds are forever"?

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Key Concepts

Activation Energy Barrier

This is the energy barrier that must be overcome for a chemical reaction or phase transition to occur. Despite the conversion of diamond to graphite being exothermic, the process requires a high activation energy to initiate the change, which means that under typical conditions, the rate of conversion is extremely slow, preserving the diamond structure.

Thermodynamic vs Kinetic Control

This principle distinguishes between the ultimate energy outcome (thermodynamics) and the timescale or pathway of a transformation (kinetics). While thermodynamic considerations reveal that graphite is the favored form of carbon because it is lower in energy, kinetic control—the presence of a significant activation energy barrier—prevents diamonds from immediately converting to graphite, helping explain why they remain stable over long periods.

Metastability

This concept refers to a state that is not the most thermodynamically stable but persists because the system is trapped in a local energy minimum. In the case of diamonds, although converting to graphite would release energy (making graphite the more thermodynamically stable form), the transformation does not occur readily because diamonds are in a metastable state under normal conditions.

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