Which thermodynamics concepts confuse or confused you the most?

In summary: What level in your education were/are you at when encountering these difficulties? And which degree programs are you in? Level and background content definitely influence these things.What level in your education were/are you at when encountering these difficulties? And which degree programs are you in? Level and background content definitely influence these things.I took a thermodynamics course last year and I know which topics confused me (fugacity for example) but I'm curious now in general about things people struggle with.
  • #1
pa5tabear
175
0
I took a thermodynamics course last year and I know which topics confused me (fugacity for example) but I'm curious now in general about things people struggle with.

Please add the time at which it confused you (first time undergraduate class, graduate class, etc), or describe how it was difficult.
 
Science news on Phys.org
  • #2
Entropy was the only thing that confused me. Unfortunately, effectively everything we did was just variants on the second law of thermodynamics ie the first law made sense, the second one was much, much less intuitive.
 
  • #3
Applying thermodynamics to dynamic processes - the confusion is whether to think of the substance as a rarefied gas or as a continuum.

Also non-equilibrium thermodynamics
 
  • #4
Curl said:
Applying thermodynamics to dynamic processes - the confusion is whether to think of the substance as a rarefied gas or as a continuum.

Also non-equilibrium thermodynamics

Jorriss said:
Entropy was the only thing that confused me. Unfortunately, effectively everything we did was just variants on the second law of thermodynamics ie the first law made sense, the second one was much, much less intuitive.

What level in your education were/are you at when encountering these difficulties? And which degree programs are you in? Level and background content definitely influence these things.
 
  • #5
pa5tabear said:
What level in your education were/are you at when encountering these difficulties? And which degree programs are you in? Level and background content definitely influence these things.
I first encountered it in upper division thermodynamics, but without a microscopic basis, I was comfortable with not understanding it entirely. After graduate stat mech, when entropy was still fuzzy, is when I realized it was very complicated.
 
  • #6
I encountered it when thinking about thermodynamics on my own. It is probably impossible to find a course on thermodynamics that poses such questions.
 
  • #7
Entropy, without a doubt. The more I learn about it, the less I understand it. Anybody who thinks that if they learn the thermodynamic definition, the statistical mechanical description, the information theory description, and can solve any problem involving entropy, that they then understand entropy, is, I think, fooling themselves.

There's something really deep going on with entropy. There is no such thing as "before" and "after" in time in any physical law except the second law of thermodynamics, where entropy is defined. Yet we all understand "before" and "after" - our consciousness, our sense of time "flows forward". This is very unscientific, but I just have much the same weird feeling as when studying relativity, how our perception of the distinction between space and time is subjective, not "real" in some sense. In quantum mechanics, what you know about a system is what you choose to know, in some sense. The more you know about one aspect of a system, the less you know about another aspect. Regarding entropy as an information-theoretic concept, entropy is a measure of what you don't know. Classically, the more you know about a system, the less entropy it has. Only in classical physics can you completely "know" a system, and the concept of entropy evaporates, and there is no before or after. But, then, the real world is not classical.

I can calculate the hell out of most problems and get it right. I understand where many legs of the elephant are, but I still can't see the entropy elephant in the living room.
 
  • #8
I once saw a video of Feynman discussing his first thermodynamics class...He said something to the effect he did not understand entropy and he was the brightest guy in the class.

It reminded me of the thermodynamics class I had...I was baffled by entropy and I'm pretty sure so was the person teaching.
 
  • #9
In college as an EE, I used to joke with ME friends: "I'll explain imaginary power to you, if you can make me understand entropy."
 
  • #10
Why do Legendre transforms work, and why do thermodynamic potentials make sense? How does the mathematical structure of derivatives, partial derivatives, total derivatives and differential forms work?
 

1. What is the difference between heat and temperature?

Heat and temperature are often used interchangeably in everyday language, but they have distinct meanings in thermodynamics. Heat refers to the transfer of thermal energy from one object to another, while temperature is a measure of the average kinetic energy of the particles in an object. In other words, heat is the transfer of energy, while temperature is a measure of the amount of energy present.

2. What is the difference between an open and closed system?

An open system is one that can exchange both matter and energy with its surroundings, while a closed system can only exchange energy. In other words, an open system allows for the movement of particles in and out, while a closed system does not.

3. What is the meaning of entropy in thermodynamics?

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it is often referred to as the measure of the unavailable energy in a closed system. It is a fundamental concept in the second law of thermodynamics, which states that entropy in a closed system will always increase over time.

4. What is the difference between an adiabatic and isothermal process?

An adiabatic process is one in which there is no transfer of heat between the system and its surroundings, while an isothermal process is one in which there is no change in temperature. In other words, an adiabatic process does not involve any heat exchange, while an isothermal process maintains a constant temperature.

5. What is the significance of the Carnot cycle?

The Carnot cycle is a theoretical thermodynamic cycle that describes the most efficient way to convert heat into work. It is an important concept in thermodynamics as it sets the upper limit for the efficiency of heat engines. The Carnot cycle also helps to explain the concept of reversible processes and the second law of thermodynamics.

Similar threads

Replies
1
Views
912
Replies
1
Views
790
  • Thermodynamics
Replies
17
Views
1K
Replies
152
Views
4K
Replies
6
Views
609
  • Thermodynamics
Replies
4
Views
3K
Replies
11
Views
1K
  • Set Theory, Logic, Probability, Statistics
Replies
6
Views
1K
  • STEM Academic Advising
Replies
9
Views
2K
Back
Top