Osmosis is the movement of water across a partially permeable membrane from a region of high solvent potential to an area of low solvent potential, up a solute concentration gradient. It is a physical process in which a solvent moves, without input of energy, across a semi permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Osmosis can also be defined as the net movement of water molecules through a selectively permeable membrane, from an area of higher water potential, to an area of lower water potential.

Answered by Vikas Mor , an ibibo Citizen, at 4:00 PM on October 12, 2008

A particular website I referred to defines Osmosis as follows-
“Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.”

That is, the semi permeable membrane could be a thin layer of skin, or sponge or even cloth. It allows only nothing except water or gas to pass through.For example when we put dry sponge into water, the concentration of liquid is more in the bucket than in the sponge.So the sponge collects water.After the sponge is full of water, it will not take in any more.
So it means that there will be no water movement..By the same process, if you keep a wet sponge on a dry surface, the sponge will begin to lose water and make the place it had been placed quite wet and full of water .By the process of osmosis, the water has flowed from the sponge to the dry surface ie from a high concentration level to a low concentration level.

Answered by Vida Writer , an ibibo Master, at 4:31 PM on October 04, 2008

well, Although osmosis is a familiar phenomenon, and of pivotal importance in natural systems, it is seldom explained how it might work on the molecular level (if treated at all in physics text books). The standard treatment of osmosis in thermodynamics employs the concept of the chemical potential and does not give any clues how the process "really" works. On the other hand one may also encounter conflicting qualitative and molecular explanations of osmosis. We use the case of osmosis in the present paper to elucidate different ways to "explain" and "understand" physical phenomena. The role of qualitative understanding of physical phenomena is emphasized. However, as the case of osmosis demonstrates, there may be a big gap between the abstract macroscopic theory and molecular conceptions of the mechanism.

1. Semi-permeable membranes are very thin layers of material (cell membranes are semi-permeable) which allow some things to pass through them but prevent other things from passing through.

Cell membranes will allow small molecules like Oxygen, water, Carbon Dioxide, Ammonia, Glucose, amino-acids, etc. to pass through. Cell membranes will not allow larger molecules like Sucrose, Starch, protein, etc. to pass through.
2. A region of high concentration of water is either a very dilute solution of something like sucrose or pure water. In each case there is a lot of water: there is a high concentration of water.

Some teachers use the definition which starts "Osmosis is the passage of water from a dilute solution to a......" this means exactly the same as the definition I have given.
3. A region of low concentration of water is a concentrated solution of something like sucrose. In this case there is much less water.

So you could use the definition "Osmosis is the passage of water from a dilute solution through a semi-permeable membrane to a more concentrated solution.

Answered by Satya ~ , an ibibo Master, at 8:42 AM on October 01, 2008

Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.

The definition contains three important statements:

1. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.

2. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.

3. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.

It does not matter too much which order you put these statements in. Nor does it matter if you write the definition as one sentence or three sentences. All that matters in your exam is that you make all three points when you explain what osmosis is.

Answered by Yogeshwar , an ibibo Specialist, at 5:47 PM on September 29, 2008

Osmosis quite simply is the physical process by which a liquid from a weaker medium is drawn through a semi-permeable membrane into a stronger liquid medium. So what does this mean and how does this relate to boat hull damage?

The simple answer is probably not a lot! Contradicting earlier theories, the damage from “osmosis” is not caused by excessive water permeation. There are absolutely no osmotic forces involved as the gelcoat is an absorbing material which can never act as an osmotic membrane! Instead it is the process of hydrolysis, which creates the water soluble corrosive products which in turn create the familiar cavities. (Hydrolysis is the general term given to the reaction of any material with water, for example organic compounds like polyester resin, itself the main constituent of GRP laminates.)

Once the cavities have formed, then excess water will enter giving rise to high moisture readings. This process may normally be slow, but the presence of free acids or alkalis will greatly accelerate it.

The first point to note is that it is the phthallic acid, formed in the process of hydrolysis of polyester resin, which causes the chain reaction and subsequent laminate damage, not the water! The acid forms as water insoluble crystals and cannot be washed out of the laminate as claimed by some. Even after years of hard-standing and weekly washes, the acid will remain in the capillaries and cavities, fixed in styrene and glycol. However, water will react with PVA binders in the laminate, reducing them to acetic acid. It is this that gives the strong smell of vinegar when blisters are burst. Even so, it must be noted that the laminate can become severely damaged before any warning blisters appear.

Osmosis blisters are not only a cosmetic problem. They are the visible sign that the hydrolysis of the polyester has affected at least one laminate layer.By the time the first blister shows, hydrolysed alkali products will have reduced the bond between fibre-glass and polyester deep in the laminate below the water line! This in turn, will have caused a 20-30% loss of structural strength which no “dry and shield” treatment can restore. Without a proper treatment large parts of the laminate layers will sooner or later have larger areas of polyester hydrolysed with only soft wet fibreglass left.

Answered by Alok , an ibibo Master, at 12:50 PM on September 27, 2008

Well

Osmosis quite simply is the physical process by which a liquid from a weaker medium is drawn through a semi-permeable membrane into a stronger liquid medium. So what does this mean and how does this relate to boat hull damage?

The simple answer is probably not a lot! Contradicting earlier theories, the damage from “osmosis” is not caused by excessive water permeation. There are absolutely no osmotic forces involved as the gelcoat is an absorbing material which can never act as an osmotic membrane! Instead it is the process of hydrolysis, which creates the water soluble corrosive products which in turn create the familiar cavities. (Hydrolysis is the general term given to the reaction of any material with water, for example organic compounds like polyester resin, itself the main constituent of GRP laminates.)

Once the cavities have formed, then excess water will enter giving rise to high moisture readings. This process may normally be slow, but the presence of free acids or alkalis will greatly accelerate it.

The first point to note is that it is the phthallic acid, formed in the process of hydrolysis of polyester resin, which causes the chain reaction and subsequent laminate damage, not the water! The acid forms as water insoluble crystals and cannot be washed out of the laminate as claimed by some. Even after years of hard-standing and weekly washes, the acid will remain in the capillaries and cavities, fixed in styrene and glycol. However, water will react with PVA binders in the laminate, reducing them to acetic acid. It is this that gives the strong smell of vinegar when blisters are burst. Even so, it must be noted that the laminate can become severely damaged before any warning blisters appear.

Osmosis blisters are not only a cosmetic problem. They are the visible sign that the hydrolysis of the polyester has affected at least one laminate layer.By the time the first blister shows, hydrolysed alkali products will have reduced the bond between fibre-glass and polyester deep in the laminate below the water line! This in turn, will have caused a 20-30% loss of structural strength which no “dry and shield” treatment can restore. Without a proper treatment large parts of the laminate layers will sooner or later have larger areas of polyester hydrolysed with only soft wet fibreglass left.

Studies of hundreds of larger hulls with heavy woven roving mats in the laminate have been undertaken. All were found to have numerous sites inside each roving layer and direct evidence of de-laminations deep in the bulk caused by degrees of severe hydrolysis. Significantly most hulls showed no telltale blisters at all!

For further information on “Osmosis” and its chemistry, we do recommend you visit www.osmosisinfo.com and read what Bengt Blomberg has to say. You will be able to buy a copy of his book from that site, which is one of the most comprehensive (and controversial!) on the subject. The comments above are drawn from his text.

And for more information visit the source site:

http://www.hotvac.com/osmo sis/default.aspx

Answered by Dinesh , an ibibo Master, at 12:41 PM on September 27, 2008

osmosis is opposite of diffusion..

diffusion means flowing of substance from more concentration to less concentration..

so osmosis means flowing of substance from less concentration to higher..
it is possible with the help of semipermeable membrane..
therefore in osmosis definitely an membrane is involved

Answered by Alok Rathi , an ibibo Citizen, at 8:50 AM on September 27, 2008

Osmosis is the movement of water molecules (or other liquids) from an area of high concentration (high pressure) to an area of low concentration (low pressure).

If a cell was in a high solute solution and the cell it's self was a low solute solution, the liquid in the cell would leave the cell and it would shrivel. This is a hypertonic solution.

If a cell was in a low solute and the cell it's self was a high solute, the liquid would go into the cell which would cause it to expand and possibly explode. This is a hypotonic solution.

Hope this helps.

Answered by Mohd Saqib , an ibibo Master, at 1:28 AM on September 27, 2008

Osmosis is the diffusion of a solvent (frequently water) through a semi-permeable membrane, from a solution of low solute concentration (high water potential) to a solution with high solute concentration (low water potential), up a solute concentration gradient.[1] It is a physical process in which a solvent moves, without input of energy, across a semi-permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations.[2] Osmosis releases energy, and can be made to do work, as when a growing tree-root splits a stone.

Shot of a computer simulation of the process of osmosis

Net movement of solvent is from the less-concentrated (hypotonic) to the more-concentrated (hypertonic) solution, which tends to reduce the difference in concentrations. This effect can be countered by increasing the pressure of the hypertonic solution, with respect to the hypotonic. The osmotic pressure is defined to be the pressure required to maintain an equilibrium, with no net movement of solvent. Osmotic pressure is a colligative property, meaning that the property depends on the molar concentration of the solute but not on its identity.

Osmosis is important in biological systems as many biological membranes are semipermeable. In general, these membranes are impermeable to organic solutes with large molecules, such as polysaccharides, while permeable to water and small, uncharged solutes. Permeability may depend on solubility properties, charge, or chemistry as well as solute size. Water molecules travel through the plasma cell wall, tonoplast (vacuole) or protoplast in two ways, either by diffusing across the phospholipid bilayer directly, or via aquaporins (small transmembrane proteins similar to those in facilitated diffusion and in creating ion channels). Osmosis provides the primary means by which water is transported into and out of cells. The turgor pressure of a cell is largely maintained by osmosis, across the cell membrane, between the cell interior and its relatively hypotonic environment

Answered by sanjay , an ibibo Guru, at 11:40 PM on September 26, 2008

The diffusion of liquids through a membrane until they are mixed is called osmosis. Similarly the process by which people or ideas influence each other gradually or subtly is also called OSMOSIS.

Answered by Anveshi , an ibibo Citizen, at 11:32 PM on September 26, 2008