# How can i explain how water’s entropy can decrease when it freezes without violating the second law of thermodynamics? specifically, what happens to the entropy of its surroundings?

##### 1 Answer

Ok, this is complicated....

I would say that when water freezes it get to a more ordered configuration (solid in a crystalline form); so consider that, among others, Entropy

The problem is the mathematical part to describe this decrease...

You need (in order to evaluate Entropy) of a **Reversible** process. I would use an isothermal process that takes reversibly (Veeeeeeeery slowly and infinitesimally) your water through the freezing process.

Take a certain amount of water and consider the heat

The change in Entropy will be:

Hope it helps! :-)