Skill 3.1e-Recognize the significance of absolute zero

The significance of absolute zero is that it permits the development of an absolute temperature scale. According to the kinetic molecular theory, there would be no kinetic energy at a temperature of absolute zero, zero Kelvin (0 K). There would be no movement of molecules. Molecules would be unable to sample different states, so there would also be zero entropy. 

In reality, it is impossible to achieve a temperature of absolute zero, but this temperature may be approached. We also cannot strictly say that all movement would stop because the Heisenberg Uncertainty Principle (See Skill 1.2a) states that the exact position and momentum of particles cannot be found at the same time. At absolute zero, molecules have the least amount of kinetic energy and motion permitted by the laws of physics. However, this level of being strict is mostly important to physicists and often isn t mentioned in high school chemistry where the kinetic molecular theory is applied. 

According to the ideal gas law, PV = nRT, a volume of gas will have zero pressure and a gas at a certain pressure will have zero volume at absolute zero. In reality, gases do not exist at such low temperatures. All gases will liquefy or solidify before approaching absolute zero. 

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