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Thermal and Statistical Physics

Updated 7 days ago

Education
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Science
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Physics 416 Thermal and Statistical Physics Purdue University Textbook: Thermal Physics by Kittel and Kroemer Lectures follow the text fairly closely, so if you're joining us from iTunes, you might enjoy having a copy handy.

Read more

Physics 416 Thermal and Statistical Physics Purdue University Textbook: Thermal Physics by Kittel and Kroemer Lectures follow the text fairly closely, so if you're joining us from iTunes, you might enjoy having a copy handy.

iTunes Ratings

9 Ratings
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8
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Awesome now you don't need to listen in class

By ifuji - Jan 26 2006
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I'm not even in college yet but this podcast has helped me expand my knowledge of physics and a vast amount of other fields. This podcast was very helpful.

Interesting and surprisingly accessible.

By Will D. - Jan 06 2006
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I have really enjoyed this podcast. The subject is very interesting, and Professor Carlson does an excellent job in explaining the physics behind the laws of thermodynamics. I say this as a person that has not studied any calculus -- I must admit that when the Professor turns to the equations I haven't a clue what's going on -- but the equations are bracketed by very clear explanations and examples. I'm looking forward to the next semester.

iTunes Ratings

9 Ratings
Average Ratings
8
1
0
0
0

Awesome now you don't need to listen in class

By ifuji - Jan 26 2006
Read more
I'm not even in college yet but this podcast has helped me expand my knowledge of physics and a vast amount of other fields. This podcast was very helpful.

Interesting and surprisingly accessible.

By Will D. - Jan 06 2006
Read more
I have really enjoyed this podcast. The subject is very interesting, and Professor Carlson does an excellent job in explaining the physics behind the laws of thermodynamics. I say this as a person that has not studied any calculus -- I must admit that when the Professor turns to the equations I haven't a clue what's going on -- but the equations are bracketed by very clear explanations and examples. I'm looking forward to the next semester.
Cover image of Thermal and Statistical Physics

Thermal and Statistical Physics

Updated 7 days ago

Read more

Physics 416 Thermal and Statistical Physics Purdue University Textbook: Thermal Physics by Kittel and Kroemer Lectures follow the text fairly closely, so if you're joining us from iTunes, you might enjoy having a copy handy.

Rank #1: Lecture 8: Chemical Potential

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Introducing a new thermodynamically conjugate pair of variables: number of particles and chemical potential. Internal and external chemical potential. Voltmeters measure the total chemical potential. Great class brainstorm on internal voltages in your life. How to get a theory named after yourself. Spins in a magnetic field. Why atmospheric pressure falls off with height, hiking in high altitude, and how to solve that deuterated Kool-Aid problem we talked about in Lecture 6. Lead-Acid batteries and your car.

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Aug 21 2006

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Rank #2: Lecture 12: Reversible and Irreversible Expansions

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Now that we've derived absolutely everything about the ideal gas from scratch,
it's time to do something useful with it! We'd like to eventually learn how to use this stuff to build engines and refrigerators. Today we discuss the basic processes (reversible expansions) that are the building blocks of engines and refrigerators.
We also cover Bose condensation at the end of class, and learn why their statistics makes bosons sticky.


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Aug 21 2006

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Rank #3: Lecture 16: Gibbs Free Energy and Chemical Reactions

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We define the Gibbs Free Energy, which is the right energy function to use when you can control temperature, pressure, and particle number. This means chemists like it, because chemical reactions in a lab often take place under these conditions.
We use this to derive the Law of Mass Action, which shows that the relative concentration of reactants depends only on temperature, and apply this to dissociation of the Hydrogen molecule, water, and hydrochloric acid.
We also return to last lecture's discussion of how superconductors repel magnetic fields. Demo: We use liquid nitrogen to cool the high temperature superconductor YBCO
below its superconducting transition temperature, so that it is in the superconducting state, and able to levitate magnets. Class discussions: How not to use a refrigerator to cool your apartment; High temperature superconductors and a small part of what's known about them.

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Aug 21 2006

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Rank #4: Lecture 13: Bose Condensates

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More about Bose condensates. They're really weird -- at the lowest temperature, all bosons flock to the lowest available state, producing a "Bose condensate".
Due to quantum mechanics, this is a remarkably stable state of matter, and is very hard to disturb. In fact, because the chemical potential becomes negative, it costs negative energy to add a new particle to the condensate. (Yes, bosons are "sticky" due to their statistics.) We also show why Bose condensates give rise to superfluidity (and superconductivity if the bosons are charged.) Class demonstration: The Wave (Just like the one in a baseball stadium.) The point is that many-body excitations often have very different character from the constituents. That is, "The Wave" in a crowd is an excitation of the crowd that doesn't look anything like the constituents (individual persons). Class discussions: What are superfluids and superconductors good for? What about the cuprate high temperature superconductors? Since they're ceramics, can you ever make them into wires? Are there higher temperature superconductors? How would room temperature superconductors make your life better?

We also discuss the heat capacity of metals at the end of class. Some of the electrons in a metal are free to flow, and are in a fluid phase of matter that allows us to use the Fermi ideal gas to describe some of their behavior.

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Aug 21 2006

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Rank #5: Lecture 9: Gibbs Factor and Gibbs Sum

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When the system and reservoir can trade particles, you can't use the Boltzmann factor and the partition function anymore. Instead, use the Gibbs factor, and the grand partition function (or Gibbs sum). We introduce these new things, and then apply them to semiconductors, aluminum soft drink cans, and blood.


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Aug 21 2006

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Rank #6: Lecture 17: Introduction to Phase Transitions

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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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Aug 21 2006

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Rank #7: Lecture 18: Van Der Waals and Geckos

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We derive the shape of the phase boundary for solid to gas transitions (sublimation), examples being dry ice (CO2) or ice at low pressure. We derive the van der Waals equation of state, which is an improvement on the ideal gas equation pV=nRT. The ideal gas equation is based on two assumptions: 1. Particles occupy zero volume, and 2. Particles do not interact. Allowing for particles to have a finite size, and also allowing for the fact that at close range, gas particles feel van der Waals attractions, we get the new improved van der Waals equation of state for a gas made of sticky but hard molecules. Van der Waals attractions work because at close range, atoms and molecules notice each other's dipole moments. The dipole moments are due to the fact that at any given instant, the electron cloud is not quite centered on the nucleus of the atom (although it will be centered on average). This instantaneous dipole moment causes atoms in the vicinity to arrange their instantaneous dipoles so as to lower their energy, which causes attraction.
It turns out that geckos can cling to walls and ceilings because of van der Waals attractions. Gecko feet have tiny hairs that split many times to make many very fine tips, giving the hairs a very large total surface area. The fine hairs are able to form many contacts with any surface, and the surface-to-hair contact is adhesive due to van der Waals forces. One gecko foot can support the weight of an entire human.
Video: Sticky gecko feet, and their van der Waals adhesive properties.
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Aug 21 2007

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Rank #8: Lecture 20: Landau Theory of Phase Transitions; Oil, Water, and Alloys

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Now that we know what order parameters are (see last lecture), we'll use the order parameter of a phase to construct the Landau free energy. The Landau free energy depends on the order parameter, and retains all the symmetries of the physical system. It's amazing how much you can get from symmetry, and we're able to see how it is that a ferromagnet can have what's called a continuous phase transition. That is, starting from zero temperature with a saturated magnetization, upon raising the temperature, the magnetization slowly decreases, until it has smoothly (continuously, in fact) gone to zero. This makes it a continous transition. We also show what a first order (discontinuous) phase transition would look like. First order phase transitions can exhibit supercooling and superheating. We also discuss the physics of alloys like bronze, and under what conditions two different materials will mix and form a binary mixture, and under what conditions there will be phase separation into 2 distinct concentrations, as happens with oil and water. A small concentration of impurities is always favorable according to entropy, and will always mix. But larger concentrations may "fall apart" and phase separate.
Class discussions: Lots about supercooling and superheating. More about nonequilibrium behavior like window glass.
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Aug 21 2007

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Rank #9: Lecture 21: Alloys, Mixing, and Phase Separation

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Oil and water -- they don't mix. Or do they? Due to the entropy of mixing, any tiny amount of impurity is highly favored entropically. This means that in general, you can get a small amount of a substance to mix into another. But take that too far, and they no longer mix, but "phase separate" into 2 different concentrations. We discuss this from the following perspectives: energy, entropy, and free energy. Examples: binary alloy with interactions, and a mixture of He3 (fermions) and He4 (bosons).
Class discussion: Can you get oil and water to mix if you heat them in a pressure cooker?

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Aug 21 2007

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Rank #10: Lecture 19: Symmetries, Order Parameters, and the Failure of Reductionism

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We finish the van der Waals equation of state, and use it to illustrate the liquid-gas phase transition. It turns out that at low pressure, the van der Waals equation of state has a wiggle where (dp/pV)>0. Since this would cause an explosion, the system instead undergoes phase separation so that part of the container has liquid, and part has gas in it.

More is different: We discuss the failure of reductionism. Reductionism is the idea that you will learn everything about an object by breaking it into its smallest bits -- like atoms, then electrons and protons, then quarks, then strings. But large collections of particles (like liquids, gases, and solids) have many properties which aren't really due to their constituents per se, but rather are due to larger organizing principles, and the symmetry of the associated phase. Example: All solids are hard, even though they're made out of different substances. So the property "hardness" is not actually caused by the particular form of the potentials for the particular atoms in that solid. Rather, it's due to the symmetry of the regular crystalline structure the atoms take, and is independent of the type of atom.
To illustrate, we discuss several phases of matter, and identify the corresponding "order parameter", which is a measurable quantity that captures the symmetry of the phase.

Visual Aids: Rotini pasta to demonstrate twisted nematic phases. Specimens from my rock collection: quartz, amethyst, hematite, and others to see how all crystals are similar, despite being made from different atoms. The "sameness" manifests itself in the basic property of a solid: being hard. The "differenc" manifests itself in color, and in the shape of the crystals, which reveal the underlying quantum mechanics of how the chemical bonds form from atom to atom. Plus, the return of the squishy crystal to illustrate phonons. 0
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Aug 21 2007

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