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Author Topic: Capillarity  (Read 8441 times)

Gabriele

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Capillarity
« on: October 07, 2014, 05:56:37 PM »
Hello. If we have a capillary put in water and the first half is in glass and the second in non-stick material and the level of water reach the first half but she would reach the second part too if the capillary was made completely in glass. Now,as i was saying,we put water into the capillary till the top. Will the water flow through the capillary to the base container? Will the level of the water in the capillary move down  till it reach the first half? Thanks.

profitis

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Re: Capillarity
« Reply #1 on: October 07, 2014, 09:05:56 PM »
Can you put this in a diagram for us please

Gabriele

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Re: Capillarity
« Reply #2 on: October 08, 2014, 11:50:06 AM »
Oui,this is the diagramm. In orange anti-stick material,in blue the glass...in light blue the water. If i add water to the upper part of the capillar will the level then decrease? Will the pressure of water do something to system? To decrease a little the level of water?

P.S. I forgot to write that if there weren't the antistick coating the water level would be on the top.

profitis

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Re: Capillarity
« Reply #3 on: October 08, 2014, 08:06:34 PM »
This is really interesting question.I think the level in the tube will stay the same if water flows out bowl.even if level climbs in bowl will stay same level in tube at junction.its the skin tension that makes it so,not the volumes.

profitis

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Re: Capillarity
« Reply #4 on: October 08, 2014, 09:52:36 PM »
Have a look here.the vapour pressure of pure water at top of capillary tube is less than at bottom by exactly weight of column of vapour gas height bottom-top.if we add salt to water its surface tension increase a little,its vapour pressure drop a little,however,its density increase thus at right concentration it will not go as high as it should go.ie.column of water vapour weight will no longer be equivalent to vapour pressure difference.we should get flow of gas vapour from bottom to top perpetuum

Gabriele

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Re: Capillarity
« Reply #5 on: October 09, 2014, 12:47:02 PM »
So you say that if we have a capillar that can hold 10cm of water by capillarity action,we cut it in 2 parts and we let act the weight of the superior half capillar,the level dowsn-t decrease...right?

Where does the weight of the upper column of water go? On the walls of the lower capillar even if the weight acts on the lower column of water? Does the superficial tension drop the weight to the walls of the capillar? What happen is we cut a 99% of the height of the capillar and let the weight acts on re reimanent 1%? It makes me think.... :o

profitis

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Re: Capillarity
« Reply #6 on: October 09, 2014, 02:49:30 PM »
Its like if you stick a capillar underneath bowl instead of top of bowl..water will pass through if weight-pressure-force is sufficient to disengage skin-force at bottom of capillar tube.if it insufficient pressure then some water should remain in bowl ontop?maybe you are right it should be easy to chek experiment like this.

profitis

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Re: Capillarity
« Reply #7 on: October 09, 2014, 02:56:21 PM »
if we take two solutions of equal vapour pressure but different weight solids dissolve in them we will get different heights in capillars.different heights,same vapour pressure,signal for violation of 2nd law thermodynamic.vapour will flow in the heavier: NaCl vs BaCl2(barium chloride)

Gabriele

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Re: Capillarity
« Reply #8 on: October 09, 2014, 06:27:24 PM »
I don't see discrepancy in the behavior with the 2 salts... simply one is heavier so the level of water is lower... where is the discrepancy?

profitis

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Re: Capillarity
« Reply #9 on: October 09, 2014, 08:52:03 PM »
Like this.barium chloride solution is heavier than sodium chloride solution.height A is where it will be,height B is where it should be.the level will differ btween NaCl vs BaCl2 solut at same vapour pressure ontop.water vapour will condense continually ontop,level will remain same.google: surface tension vapour pressure