Thermal and Statistical Physics

Lecture 17: Introduction to Phase Transitions

Aug. 20, 2006

We finish discussing chemical reactions, including how fast they progress, and what a catalyst can do for you. Then we begin a new topic: phases of matter and phase transitions between them. You've heard of solid, liquid, and gas, but did you know about the other phases of matter? Other phases include liquid crystals (of which there are many types). Also, electrons inside of a solid have their own phase transitions.
For example, metals carry current when the electrons inside flow -- that's a liquid phase of electrons. Refrigerator magnets are in a different electronic phase -- there, electrons execute tiny current loops around individual atoms, forming nanosize magnets. When they all align, the phase is called a "ferromagnet", and can be used to post notes to your refrigerator. We also discuss how you can go from liquid to gas and never encounter a phase transition! This is because liquid and gas aren't all that different to begin with. Class discussions: liquid crystal screens, melting snow, and what you really see when water boils.

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