Physics of paper absorbing Water -- Doesn't this decrease Entropy?

  • #1
casparov
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Summary: doesn't this decrease entropy ?

Cellulose is known for its hydrophilic quality, which can be explained from the polarity of its hydroxyl groups.

We all know water can overcome the force of gravity through a piece of paper you put in the water.
Correct me if I'm wrong but this is a combination of adhesive + cohesive forces > gravity.

Why is it favorable for the water to form hydrogen bonds with the cellulose, why favorable to maximize those bonds? Is it because of higher electronegativity of the hydroxyls than the water molecules in the liquid?

How does it bring the system into a lower energy state?

Doesn't it also decrease entropy ? Or only in a very local way, because water found some air pockets inside the paper, therefore increasing the degrees of freedom ?

and more general how does hydrogen bonding rhyme with 2nd law of thermodynamics ?
 

Answers and Replies

  • #2
Demystifier
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How does it bring the system into a lower energy state?

Doesn't it also decrease entropy ?
Energy is conserved, hence closed systems do not evolve into lower energy states. Instead, they evolve into lower potential energy states. Why? Because lower potential energy means higher kinetic energy (because total energy is conserved), and kinetic energy can take the form of thermal motion, which means higher temperature and hence higher entropy.
 
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