# Can I suck water out of a full bottle?

If i have a bottle full of water (there's no air in the bottle) with a straw in it and the bottle is sealed completely without any opening except the straw, will i be able to suck water out of the the bottle with the straw?

## 2 Answers

Yes, but only because the water has a vapour pressure greater than zero. If the liquid in the bottle was completely non-volatile then you would not be able to suck it out.

Suppose you reduce the pressure outside the bottle to zero. The water will start to vaporise and form bubbles of vapour that have a pressure greater than zero. These bubbles will expand and push out the water.

With a non-volatile liquid no bubbles of vapour will form and the pressure inside the bottle will be the same as the pressure outside (both zero). That means the liquid will not be expelled from the bottle.

• We should be able to suck a bit of water tough. As we can breath through a snorkel if our chest is not too deep in water (some 40 - 60 cm water column or so). – Alchimista Mar 10 '18 at 10:33
• "With a non-volatile liquid no bubbles of vapour will form and the pressure inside the bottle will be the same as the pressure outside (both zero). That means the liquid will not be expelled from the bottle." Why cannot one use gravity (changing the orientation of the bottle)? – akhmeteli Mar 10 '18 at 11:29

I don't quite see the problem: you can alternate sucking out some water and letting air enter the bottle through the straw. If necessary, you can change the orientation of the bottle at some point to use gravity.

• (1) That doesn't work. The bottle is full and sealed (and presumably cannot be deformed), so changing the volume of water would essentially introduce a vacuum, which you can never do by simple suction. (2) Tilting the bottle no longer qualifies as sucking the water out. – J. Murray Mar 10 '18 at 13:57
• @J.Murray : "Tilting the bottle no longer qualifies as sucking the water out." And why is that? – akhmeteli Mar 10 '18 at 14:58
• It seems self-evident that "sucking" and "pouring" are different, no? – J. Murray Mar 10 '18 at 15:09
• @J.Murray : Not at all. One can tilt the bottle and then suck the water out. – akhmeteli Mar 10 '18 at 15:26
• The issue is that pure suction can not create a vacuum. Introducing gravity to the problem seems unjustifiable, because it changes the nature of the problem. The issue is not whether you can get the water out somehow, but rather whether you can do so purely via suction through a straw. – J. Murray Mar 10 '18 at 15:31