Thermodynamics

The Second Law of Thermodynamics (SLOT) has been bandied about lately so I though I might clarify any misconceptions there might be about it.

One way to state SLOT is that the entropy, or disorder, of the universe is always increasing.
Another version, the Clausius version, states that no process whose sole result is the transfer of heat from a cold object to a hot object can exist.

In thermodynamics, we divide the universe into the system (whose properties we are interested in) and the surroundings. Entropy in the system can decrease as long as there is a bigger increase in the entropy of the surroundings. Mathematically:

dS_universe = dS_system + dS_surroundings (differential form)

If dS_system < 0 (decreasing entropy), then as long as dS_surroundings > -(dS_system), dS_universe > 0 and SLOT is satisfied.

Systems can be defined as open (permitting transfer of mass and energy across system boundary), closed (not permitting transfer of mass, could be allowing transfer of energy), or isolated (no transfer of mass or energy across the system boundary- special case of a closed system).

The entropy of a closed system can only increase. Since the universe is by definition a closed system (isolated, technically), its entropy can only increase. This is because there is nothing outside the universe. However, a cell can decrease its entropy as long as there is a bigger increase in entropy outside the cell. Changes in entropy are often described as changes in free energy, or G. G = H - TS. The "G" stands for Gibbs, after Josiah Gibbs, who described it first. The change in free energy (delta G) of a spontaneous reaction is negative.

This has implications for chemical reactions. Normally, most of the reactions that occur inside a cell do not occur spontaneously (positive delta G). However, a nonspontaneous reaction can occur if it is coupled with a sufficiently large spontaneous reaction ( large negative delta G).

I'm taking thermodynamics in my chemical engineering classes right now, so feel free to ask me any questions.

EDIT: Posted before I finished reading

[Rhinoqulous]

Thanks for the post, Brick. Now we can just point theists here when they start ranting about what they "think" entropy is.

Rhinoq

Thermo is a no-brainer.

[Choobus]

sludge wrote

Thermo is a no-brainer.

There's only one thing worse than sludge and his gay lover slapping each other on the back telling themselves how smart and insightful they are --- sludge and his gay lover slapping each other on the back telling themselves how good they are and how rotton [sic] choobus is. Pathetic. :lol::lol:

Another brick in the wall wrote

The Second Law of Thermodynamics (SLOT) has been bandied about lately so I though I might clarify any misconceptions there might be about it.

One way to state SLOT is that the entropy, or disorder, of the universe is always increasing.
Another version, the Clausius version, states that no process whose sole result is the transfer of heat from a cold object to a hot object can exist.

In thermodynamics, we divide the universe into the system (whose properties we are interested in) and the surroundings. Entropy in the system can decrease as long as there is a bigger increase in the entropy of the surroundings. Mathematically:

dS_universe = dS_system + dS_surroundings (differential form)

If dS_system < 0 (decreasing entropy), then as long as dS_surroundings > -(dS_system), dS_universe > 0 and SLOT is satisfied.

Systems can be defined as open (permitting transfer of mass and energy across system boundary), closed (not permitting transfer of mass, could be allowing transfer of energy), or isolated (no transfer of mass or energy across the system boundary- special case of a closed system).

The entropy of a closed system can only increase. Since the universe is by definition a closed system (isolated, technically), its entropy can only increase. This is because there is nothing outside the universe. However, a cell can decrease its entropy as long as there is a bigger increase in entropy outside the cell. Changes in entropy are often described as changes in free energy, or G. G = H - TS. The "G" stands for Gibbs, after Josiah Gibbs, who described it first. The change in free energy (delta G) of a spontaneous reaction is negative.

This has implications for chemical reactions. Normally, most of the reactions that occur inside a cell do not occur spontaneously (positive delta G). However, a nonspontaneous reaction can occur if it is coupled with a sufficiently large spontaneous reaction ( large negative delta G).

I'm taking thermodynamics in my chemical engineering classes right now, so feel free to ask me any questions.

Huh? :(

Think of it this way: I put an ice cube in a metal box. The box and the ice cube are the system and the system is closed. The ice cube melts and as it melts, it goes from a more ordered state (solid) to a less ordered state (liquid). If I put the box in a freezer, the water will refreeze. The entropy of the water goes down, but only because the freezer creates more disorder (in the form of heat) in the surroundings. You can't transfer heat from a cold object to a hot object without performing work.

sludge wrote

Thermo is a no-brainer.

Actually, thermo (and statistical mechanics) use an eight-dimensional Jacobian determinant to link the various terms together. If your brain can handle that, run amok. Otherwise there's smoke coming from your anal sphincter.

[calpurnpiso]

Another brick in the wall wrote

Think of it this way: I put an ice cube in a metal box. The box and the ice cube are the system and the system is closed. The ice cube melts and as it melts, it goes from a more ordered state (solid) to a less ordered state (liquid). If I put the box in a freezer, the water will refreeze. The entropy of the water goes down, but only because the freezer creates more disorder (in the form of heat) in the surroundings. You can't transfer heat from a cold object to a hot object without performing work.

Gratias tibi ago ( thanks) for the lesson, which the Christ-psychotics will never be able to understand...:)

calpurnpiso wrote

Gratias tibi ago ( thanks) for the lesson, which the Christ-psychotics will never be able to understand...:)

Actually, the Christ-psychotics will never be willing to understand because they are afraid of knowledge. If anything is shown to be a threat to their understanding of the world they turn a deaf ear and then actively try to exterminate that knowledge--hence, ID.

Another brick in the wall wrote

Think of it this way: I put an ice cube in a metal box. The box and the ice cube are the system and the system is closed. The ice cube melts and as it melts, it goes from a more ordered state (solid) to a less ordered state (liquid). If I put the box in a freezer, the water will refreeze. The entropy of the water goes down, but only because the freezer creates more disorder (in the form of heat) in the surroundings. You can't transfer heat from a cold object to a hot object without performing work.

Interesting, no doubt. I have a Bachelor's in English and American Literature with a minor in History, so you guys went way above my head. :(:(

Would you like to know about Shakespeare or James Joyce? :rolleyes:

But seriously, where would a slow-witted (in science) lit. man start out if interested in said subject?

Daniel wrote

But seriously, where would a slow-witted (in science) lit. man start out if interested in said subject?

www.google.com

But you can cut your teeth on this if you'd like.

EDIT: P.S. I have a BFA in Jesus-H-Christ-on-a-popsicle-stick-mutherfucking Theatre fer cryin' out loud. If you can read Joyce, that article won't be over your head.

schemanista wrote

www.google.com

But you can cut your teeth on this if you'd like.

EDIT: P.S. I have a BFA in Jesus-H-Christ-on-a-popsicle-stick-mutherfucking Theatre fer cryin' out loud. If you can read Joyce, that article won't be over your head.

Thank you. I'll exagmine for my factification.

What is the argument from theists using thermodynamics? I don't think I've heard it yet.

It's a creationist argument. They say evolution is impossible because it involves a decrease in disorder. Of course, living things are not closed systems, so order can arise in them.