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Last night I filled a 20 fl oz bottle (http://www.thenibble.com/reviews/main/beverages/soft-drinks/boylans-mash.asp) with lukewarm water from my tap. I filled the bottle pretty much to the brim, capped it, and put it in my freezer.

Today, I took the bottle out, and left it on the table in my far-too-hot room for 10 minutes or so. When I unscrewed the cap, water flew everywhere, like a can of soda that's been shaken up really intensely. What happened? Can anyone explain this?

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Related: physics.stackexchange.com/q/3133/2451 –  Qmechanic Jul 1 '12 at 16:07

3 Answers 3

up vote 13 down vote accepted

Water is an unusual substance in that it expands when it freezes. Evidently this expansion wasn't enough to burst the bottle in your case, but it left the bottle's contents under pressure. After you'd defrosted it for a while there was, presumably, some ice and some water in the bottle. Because the ice was taking up more volume than it did when it was water, the liquid water in the bottle was pressurised. I expect that the bottle's sides were bowed out slightly to accommodate the extra volume. When you unscrewed the cap, the pressure forced the liquid water out of the bottle. Essentially (I would guess) it was being pushed out by the slightly elastic sides of the bottle contracting back to their usual shape.

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water bottles expands because it gets so cold inside and the gas that is in there needs to get out someway so eventually there is so much presure in there that the water bottle gives way

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It was due to the slight expansion of the liquid and the slight contraction of the bottle gained when in the freeze. Normally, when liquids tend to reach their lower fixed point/freezing point they tend to expand which is the opposite of solids. If the bottle was left in the freezer for some time the bottle was going to explode.

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water is the exception, not the rule when it comes to the expansion of liquids near their freezing points. –  Rick Feb 3 at 15:19

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