WHY does the 2nd law of Thermodynamics work?

  • Thread starter Pjoseph
  • Start date
  • #1
1
0

Main Question or Discussion Point

Dear All

Can't get my head around this.

Entropy of the universe (system+surroundings) always increases.
But why?
G = H - TS
G = Energy available for work
H = Enthalpy of reaction
How can the energy available be greater than the enthalpy of the reaction?
There must be some input from the 'rearrangement' of the molecules?
Ok I can accept that.
When S is positive for a chemical reaction there is more energy from the work than H dictates.
How can it come from a a reaction becoming more disordered?
This requires breaking bonds eg. Solid to liquid which REQUIRES energy. Logically more disordering reactions should be less spontaneous due to the additional energy required to break up the ordered molecules.

Thereby making it more difficult to break things up than to put them together.
Please Help
 

Answers and Replies

  • #2
336
0
Welcome Pjosheph.
This requires breaking bonds eg. Solid to liquid which REQUIRES energy. Logically more disordering reactions should be less spontaneous due to the additional energy required to break up the ordered molecules.
Thereby making it more difficult to break things up than to put them together.
Please Help
One must keep a 'tally' of the total energy & entropy properly. Consider what happens when you put a cube of ice on a hot pan -both kept inside a sealed box. Does the ice melt spontaneously? Also, does the entropy decrease as the volume decreases upto 4 C?
 

Related Threads for: WHY does the 2nd law of Thermodynamics work?

  • Last Post
Replies
9
Views
2K
Replies
18
Views
7K
Replies
27
Views
11K
Replies
9
Views
2K
Replies
6
Views
3K
  • Last Post
Replies
11
Views
2K
  • Last Post
Replies
9
Views
3K
  • Last Post
Replies
12
Views
2K
Top