Examples of decreased entropy .

Nick666

Could someone please give me some examples of natural non-living processes where entropy decreases locally ?

Now I know all natural processes eventually lead to increased entropy, but from what I've read and understood so far, entropy can be decreased locally.

An example was "water can (locally) flow uphill when it encounters a rock in a rapids" . Any more examples ?

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Refrigeration.

Nick666

You mean with a refrigerator ? I would prefer some examples that dont include man-made stuff, I know about the classic refrigerator or air conditioning example, but I'm having a debate with a creationist, and I dont wanna give him examples that include man-made stuff .

Bill_K

Crystallization.

Evaporation, which cools the remaining liquid.

I like Serena

Homework Helper
An example was "water can (locally) flow uphill when it encounters a rock in a rapids" . Any more examples ?
Actually, this is not a good example of decreasing entropy.
The entropy remains constant here, that is, the kinetic energy is reversibly converted into potential energy.

What you'd be looking for is any system, that looses heat, where the applicable formula is dS ≥ dQ/T.

In the wikipedia example we have a warm room with a glass of melting ice.
The entropy of the glass increases, the entropy of the room decreases, and the entropy of the combined system increases (dS = dQ / 273 K - dQ / 293 K).

Similarly the sun heating up a patch of earth, makes the entropy of the sun decrease, the entropy of the earth increase, and the entropy of the solar system increase.

Put otherwise, any heat source has decreasing entropy. This includes a refrigerator [/edit].

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