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Dynamic Thermodynamics

A study in static

Thermodynamics is the study of heat. What is heat? That's like temperature, right? Hot and cold and so on. And thermodynamics has something to do with entropy, whatever that is (disorder something something). You might also have heard something about energy loss becoming heat somehow. All this is actually pretty easy if you look at it right. Let's take a closer look, literally.

Main explanations

  • What is heat/energy?
    • Billiard balls
    • Lots of billiard balls
  • What is temperature?
    • Inverse popularity?
  • What is pressure?
    • Relation to volume (piston?)
    • Smattering sound
    • Negative pressure (e.g. a jar)
    • Gravity -> air pressure
  • What is entropy?
    • Color mixing
    • Warm/cold mixing
    • Egg breaking?
  • Arrow of time
    • Messy initially -> run forwards and backwards
    • Divided (ordered) initially -> run forwards and backwards
  • Brownian motion
    • Draw trajectory of one particle
  • Friction
    • Bigger ball collides into sea of small balls
  • Annealing
    • Local energy minima
    • Need heat to randomly find lowest energy state

Small ideas

  • Top of each page: "This page assumes you are familiar with the following concepts (click on them to read more)"

  • We see that Energy is conserved, which should be true for elastic collisions. [Is momentum conserved? Why/why not?]

[If something is in brackets, it is meant as an exercise]

$$\Delta S = S{later} - S\sub{at first}$$ New to math Experienced
Math changes when radio button changes

  • Two cold things coming together become warmer, because of the bond energy released.
  • Warming something up helps it find lower energy state.
    • Hole in the middle of structure does not get filled with T = 0, but with more energy, the particles wiggle loose.
  • Exercises
    • Try to lower the temperature by accelerating individual particles with mouse.
      • Easy with big, few particles, hard with small, many
      • Does expend energy, increase enthropy just to know which way to accelerate them!
    • Which system has the higher enthropy?
    • Make this system have higher/lower enthropy than that one
      • Cannot lower, try as you might
    • Heat conduction: Move heat from here to there
      • as fast as possible?
    • Friction: brake this particle