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When I think of something shrinking, I would intuitively think it decreases in entropy as there is less movement. E.g. if a gas was to reduce in volume, there would be less movement of the particles and hence less entropy.

How about for as solid?

I have read if polyethene shrinks, it INCREASES in entropy.

Why is this the case?

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    $\begingroup$ As polyethene shrinks, it doesn't necessarily reduce in volume, to begin with. $\endgroup$ – Ivan Neretin Dec 21 '17 at 20:13
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    $\begingroup$ Sorry, could you please elaborate? Doesn't shrink imply a decrease in volume? $\endgroup$ – K-Feldspar Dec 21 '17 at 20:15
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    $\begingroup$ It shrinks in one direction and expands in the others. $\endgroup$ – Ivan Neretin Dec 21 '17 at 20:30
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When stretched, the polymer chains elongate and are held taut. This means there are more crosslinks and fewer opportunities for internal degrees of freedom (movement). A relaxed polymer is not held taut and therefore can freely move, having more degrees of freedom, and an associated increase in entropy.

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