Naked Science Forum
On the Lighter Side => Science Experiments => Topic started by: uanna2341 on 03/03/2013 04:42:53
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Take a milk bottle and fill it with water. Put a drinking straw in it. Fix was round the drinking straw at the top of the bottle and make sure you have an airtight joint so that no air can go in and escape. Can you suck the water out of the bottle? Explain what happens.
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Take a milk bottle and fill it with water. Put a drinking straw in it. Fix was round the drinking straw at the top of the bottle and make sure you have an airtight joint so that no air can go in and escape. Can you suck the water out of the bottle? Explain what happens. :0
You might be able to get a few swallows before the 14.7 lb/sq,in of atmospheric pressure overcomes your ability to retrieve the liquid. However, if you allow air to re-enter the bottle thru the straw between slurps, you will be able to finish it off.
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If the bottle is completely full and the seal is good and inflexible then you can't suck water out. Sucking just produces a partial vacuum so that (normally) air pressure would force the liquid up the straw. By sealing the bottle (and assuming the bottle is made of rigid material, such as glass) then there is no pressure being exerted to force water out. It's possible a very small amount may rise up the straw because of dissolved gases being released.
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The way a barometer works, when the weight of the liquid inside the barometer is equal to the atmospheric pressure, it will actually leave a gap above the liquid, which will consist of both a strong vacuum, and some vapor of the liquid in the bottle.
So, assuming your bottle could withstand the force, with a strong enough vacuum, you could potentially suck the bottle dry, leaving a pure vacuum inside the bottle.
HOWEVER, you may not be able to suck a liquid up a straw (rigid tube) to leave a vacuum below. It may only be possible to suck the liquid out, by inverting the bottle, and using a short drain poking up into the bottle, then connecting the vacuum.
Continuing to suck on a vertical tube, will lower the vapor pressure, and could cause the water in the bottle to boil. This would then be sucked out through your vacuum pump as vapor, to the point where the water in the bottle will disappear. You may need to replenish the heat in the vessel.
Of course, you can't produce the necessary -1 ATM, or -15 PSI vacuum necessary to create the vacuum with your lungs.
Of course, with a plastic bottle that deforms, you can suck the liquid out. Consider juice pouches.
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