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QUESTION: Today at work, i took a bottle of water out of the fridge and noted that it was frozen. while opening the bottle, some of the water flowed out. My question is, why does the volume of water in the bottle increase while defrosting as apposed to the volume of water before freezing?

ANSWER: I may need some further clarification on this problem.  Are you saying that as it thawed out the volume increased?  The wording of this question is a little ambiguous.

---------- FOLLOW-UP ----------

QUESTION: My apologies. What i mean is: I filled the bottle with water and put it in the fridge. After it was frozen, i took it out, left it on the sink to defrost, and when i opened it again, some of the water poured out. the volume of the water in the bottle after defrosting was a lot more that when i first put it in the fridge.

Answer
Much more clear, thank you.  That's truly strange, because on the face of it you might expect the expanding ice to stretch the bottle, making it appear upon thawing that the water had actually shrunk instead of expanding.  But perhaps not unexplainable.  Here are scenarios which you can test to find out what happened:
1)  The water was mostly still frozen in the bottle.  Freezing water expands by about 10%, so if it was only partly thawed then mystery solved.
2)  If it was fully thawed then there are two sub-possibilities:
    a)  Something happened to the water, such as absorption of air.  Seems unlikely, since the water is isolated inside the plastic.
    b)  More likely, something happened to the plastic bottle.  Molded plastics like water bottles are funny, they react differently around the freezing point because they have weird patterns of frozen-in stress.  It's hard to say what would happen (plastics is chemistry, not my field) what would happen to a plastic water bottle around the freezing point of water.  The plastic would want to form hydrogen bonds, just like the water.  Maybe even with the water.  But it would also be under stress from the water expanding inside it as it froze.

To truly test if it's the bottle or the water, you need two bottles of water.  Drink or empty one of them.  Pour the contents of another into the first one to make sure that the bottles are relatively uniform.  Cap that bottle and freeze it.  If it does spill, then try to pour the melted ice into the original bottle.  If it was the bottle, it won't fill it all the way.  If it's the water then it will fill it all the way up.

If the situation is that the water was totally thawed but you still had too much to fit in the bottle after it was frozen, you've stumbled on a minor but interesting new phenomenon.  I've never heard of it, but if you can replicate it then a chemist or chemical engineer might be able to help you figure out what happened to the frozen plastic.

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Dr. Stephen O. Nelson

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I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

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Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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