Science question : Does the viscosity......

......of water change in relation to it's temperature :Quad: ?

 

Yes, when the temperature falls below 0 degC

 

It's bound to, but by how much I couldn't say. This website looks trustworthy:

http://www.grow.arizona.edu/water/waterscience/viscositytemperature.shtml

 

:grrr:

Sorry, from 0 to 100 degrees (whilst it is still a liquid) :shame: !

 

Hi Voodoo,

Yes it does. As the temperature decreses the viscosity increases.

Viscosity is the internal ressistance to flow. This is one reason why certain animals & plants don't sink to the bottom. This viscosity helps to suspend them in the water.


SCIDB

 

Just One Of them things that happened to crOss yOur mind yeah?

Try it! Take sOme ice Out the freezer and place in pan. Start tO heat and as sOOn as it reaches it's liquid state put yOur finger in! Keep MOving yOur finger abOut as the temp' increases and using a therMOmeter keep nOte Of hOw it becOmes MOre difficult tO MOve yOur finger the clOser the temp' gets tO 100*

 

Are you sure about that? Surely changes in viscosity would affect how fast they sank rather than if they sank?

 

well he did say "one reason" and "helps"

I'd imagine the flapping of flippers would help too

 

I know , just not sure it would? I'm actually not quite sure of the situation SCIDB was describing. Insects that walk over the water surface do so because of surface tension effects I believe, but I'm guessing he was thinking of something else?

Especially by the plants

 

Hi Martin C,

I'm talking about tiny micro plants & animals eg tiny plankton. As the temps drops the water will have more resistance which will slow down any movement. These items will be small enough to be effect be this.

I wasn't talking about surface tension or big animals & big plants.

SCIDB

 

Surface tension eh? would that be a naim owner being trated to some real kit Umm, maybe this is the same effect that causes you to be able to float a needle of the 'surface skin' of a beaker of water then?.
Generaly as the temperature of a liquid increases so does the vicioscity index.
For example, take a multigrade oil of say 10/40, it's a low 10 when the engine is cold, allowing the oil to flow 'freer around the engine ading lubication at it's most vunrable period, and increasing in viscoscity, as the internal temperature increases to the final weight of the stated index, thus increasing protection for a hotter engine. Wm

 

This doesn't sound right WM. The viscosity generally decreases as temp increases. The multigrade oils were specially developed to have the characteristics you described to stop it's molecular structure from breaking up due to high temps and from becoming too "solid" at low temps.

Take a look at this url:-
http://palimpsest.stanford.edu/don/dt/dt3713.html

I'm sure there are others that discuss the subject but this is the first one I came across.

Sorry, just noticed MartinC's post, he quoted a better url.

 

Have I got arse about face Dev? sorry right effect, wrong discription doh! long day, hence why Ford mundanes have to use a 5w or even a 0 w/30 as the hydraulic tappet tolerenices were so tight, that the 10w just didn't get round the galleries and caused premature top end ware.
You would have thought I'd got that simple one right, especialy as I used to run a race team Motol best oil I've ever used stunning stuff. Wm

 

I think WM has it almost right wrt oils.

Bigger numbers mean more viscous. Higher temperatures mean less viscous. A multigrade acts like its first number when cold and its second when hot. A hot 50 is less viscous than a cold 20, but rather more viscous than a hot 20, IYSWIM...

FWIW the answer to the OP question is 'yes'.... The oddity about water is that it expands when it freezes.

Paul

 

A strange fact about water is that it's at its densest at 4 deg C. Don't know why. The fact that it expands when it freezes is also odd.

Water is not as boring as it would seem.

Michael.

 

You're probably thinking of negatively thixotropic things like tomato sauce, which will pour slowly bbut go stiffer if you shake them suddenly. Also a mixture of corn starch in water can behave this way - you can stir slowly with a teaspoon so that it looks like milk, but if you suddenly jerk the spoon upwards, you can lift the glass and contents off the table. I used to keep a jamjar of this mixture at work for this very demonstration. An ordinarily thixotropic example is that emulsion paint that is a gel in the can but spreads on smoothly with a brush.

 

Am I right in believing glass is actualy a liquid (at room temp)? It's just so viscous that it hardly* MOves!

*If you look at some old windows the bottom can be thicker than the top!

 

No, I'm afraid the thing about glass flow in old windows is a myth. A little googling on 'glass flow old' reveals more than enough.

 

I'm pretty sure it's not a myth. Glass is fundamentally a liquid. Old windows are thicker at the bottom (not the top MO) because over time the glass has flowed down.

I'll need to dig up some links. I remember seeing a BBC Horizon or something documentary about it.

Michael.

 

That's right - 4 degrees. And between 4 and 0 is when it expands isn't it?

Water's the only thing (I think!) that can be both liquid, solid and gas...