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Igid
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Please help me in this. Are gel, cream and paste liquids? I'm getting the answer for primary school students. So, please help me explaining in simple way. Thank you!
Igid
Igid
Igid said:Please help me in this. Are gel, cream and paste liquids? I'm getting the answer for primary school students. So, please help me explaining in simple way. Thank you!
Igid
A gel is an apparently solid, jellylike material formed from a colloidal solution. By weight, gels are mostly liquid, yet they behave like solids. An example is gelatin.
from http://en.wikipedia.org/wiki/ColloidWikipedia said:In general, a colloid or colloidal dispersion, is a two-phase system of matter; small droplets or particles of one substance, the dispersed phase, are dispersed in another, continuous phase forming so called phase colloid. Another type of colloid is called molecular colloid and is formed of macromolecules dispersed in a continuous phase (dispersion medium).
Gokul43201 said:A piece of glass, given sufficient time, will flow to fill a container and exert pressure on the side walls. But while some will call glass a liquid, most still like to think of it as a solid.
Aerogel, is much more solid than your typical gooey gel. It shears and it doesn't flow. Also importantly, it is anisotropic over microscopic scales.Nereid said:
This distinction is important for many kinds of gels where you will find that, on setting for long periods, the different components tend to partially separate. But even when invoking the rebuttal based on mixtures, there is sometimes a grey area. The counter-argument often used is that a state can be assigned to a homogeneous mixture but not a heterogeneous one. The grey area : where the crossover happens...GOD__AM said:Freshly mixed concrete appears to be a liquid, but it is made up of stone aggregate, cement, sand, and water. It's a mixture at this point of solids and liquid. If you remove a stone from this concrete you will find it to be very much a solid not liquid. In grade school science I remember discussing adding substances together and determining whether they were mixtures or new substances created through a chemical reaction. I think you can only apply the term solid, liquid, or gas to individual groups of the same molecules. Sure you can have 2 liquids in the same glass but its still a mixture.
Lets say we have a glass filled with marbles and water, what would you consider this a solid or liquid...it's a mixture.
This is a myth that was effectively debunked a couple years ago. The myth was started by someone examining a stained glass window in an old Cathedral in Europe. All the pieces of glass seemed to be thicker at the bottom than the top. The person concluded the glass had flowed over several centuries.Gokul43201 said:A piece of glass, given sufficient time, will flow to fill a container and exert pressure on the side walls. But while some will call glass a liquid, most still like to think of it as a solid.
Here's a good article on the subject of glass.zoobyshoe said:This is a myth that was effectively debunked a couple years ago. The myth was started by someone examining a stained glass window in an old Cathedral in Europe. All the pieces of glass seemed to be thicker at the bottom than the top. The person concluded the glass had flowed over several centuries.
As hexhunter was trying to point out, further examinations of Cathedral stained glass have shown that many windows from the same period have a statistically proper number of pieces that are thicker at the top than the bottom.
All the glass back then was hand blown, and they had no way to regulate the thickness. It is likely that the maker of the window that precipitated this rumor just put all the glass in thick end down for consistancy's sake. They can't find any others like it.
Gokul43201 said:The counter-argument often used is that a state can be assigned to a homogeneous mixture but not a heterogeneous one. The grey area : where the crossover happens...
Hmmm...didn't know this. Interesting !zoobyshoe said:This is a myth that was effectively debunked a couple years ago. ...
Let me rephrase. A heterogeneous mixture need not necessarily have a state assigned to it.GOD__AM said:Ok I had to look up hetrogeneous anyway the description for hetrogeneous mixture gave granite as an example. For homogeneous air is used as an exapmle. Both in this case can be assigned a "state".
But virtually anything you have in reality is a mixture. Show me a pure, isolated element or compound and I'll show you an egg balancing on its tip. By not allowing a 'stat'e to be assigned to a mixture, you are grossly hampering the usefulness it provides to communication.Still if you separate the components (in either mixture) which aren't bound chemically you get individual compounds with individual properties and states. By assigining states to mixtures we are just being incomplete in the description.
Yeah. I used to love telling people that glass was a liquid.Gokul43201 said:Hmmm...didn't know this. Interesting !
Who believed you?zoobyshoe said:Yeah. I used to love telling people that glass was a liquid.
Every zoobie I told.yomamma said:Who believed you?
Check out this site and see if you agree or not.rainbowings said:maybe i m missing the context ... but glass IS a liquid. a very viscous one and one that requires nonequilibrium statistical mechanical description.
Not even in a mere [itex]10^{9}[/itex] centuries ?zoobyshoe said:The main point, I think, is that glass is not going to slowly take the shape of a container, even after centuries.
The glass being referred to there is not just the transparent, SiO2 based molecular network material that we make windows out of - it refers to a whole class of materials that exhibit the specified characteristics.zoobyshoe said:That site is interesting, Gokul. It asserts that glass is another phase in and of itself: solid, liquid, gas, glass.
edit: and plasma. Musn't forget plasma.
Reading about ceramics, and especially glazes, I've run across the information that many things can undergo "vitrification", before, yes. I hadn't ever come across mention of this as one of the "phases", along with solid, liquid, etc. Are there any other "phases" you humans have been keeping secret from the zoobies?Gokul43201 said:The glass being referred to there is not just the transparent, SiO2 based molecular network material that we make windows out of - it refers to a whole class of materials that exhibit the specified characteristics.
Yeah - glass is a glass. We also discussed it a little HERE .Gokul43201 said:The glass being referred to there is not just the transparent, SiO2 based molecular network material that we make windows out of - it refers to a whole class of materials that exhibit the specified characteristics.
That whole thread is interesting, not just the glass part.russ_watters said:Yeah - glass is a glass. We also discussed it a little HERE .
Glasses get a bad deal there. The representation of a glass as merely an amorphous solid is incorrect. Glasses are unlike normal amorphous solids, which can be described by equilibrium statistical mechanics. In such solids, fluctuations in thermodynamic and transport properties are on timescales that are small compared to typical measurement times. This is not true of glasses.russ_watters said:Yeah - glass is a glass. We also discussed it a little HERE .
Do these share "glass" glass' transparency to light?Gokul43201 said:And in addition to "glass" glasses you have spin glasses, Fermi glasses, Bose glasses and metallic glasses (to name a few others).
Not at all. That works only for the "glass"glass.zoobyshoe said:Do these share "glass" glass' transparency to light?
In pondering this, and definitions in general, perhaps we could add something about physical scale? To a bacterium, an aerogel may look something like a cave system (or a multistorey building) does to us; 'microscopic structure' is a purely human convention; 'atomic' or 'molecular' scale would be less arbitrary ... but then, how would you define the solid/liquid distinction at that level? In terms of 'microscopic solid/liquid/gas constituents', what is a tree, or a cell comprised of?Gokul43201 said:Mk, your definitions of a liquid lack any mention of time scales. A piece of glass, given sufficient time, will flow to fill a container and exert pressure on the side walls. But while some will call glass a liquid, most still like to think of it as a solid.