If heating things up causes them to expand, how come clothes shrink when putting them through the wash?

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If heating things up causes them to expand, how come clothes shrink when putting them through the wash?

In: Chemistry

Fibres cling together when shrinkage occurs. The temperature is not the culprit. Agitation is more often the cause.

Heat only make molecule wiggle faster which can expand certain material, especially fluid, but it doesn’t mean that expansion is always what will happen. For example, Ice expand even if it’s cold because of the crystalline structure that it formed.

In the case of your clothes, they are usually make of fibers that are stretch during the manufacturing of textile. When you wash them with hot water, this release the tension of the stretching and the fibers get back into their natural form, which is shorter.

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