Solutions
Osmosis
The flow of solvent molecules only through a semi permeable membrane is called osmosis.
Osmosis takes place through a membrane called semi permeable membrane (SPM).
Semi permeable membrane is a type of membrane, which appears to be a continuous sheet of film and contain a network of submicroscopic holes or pores. These submicroscopic pores of semi permeable membrane allow the passes of small solvent molecules and do not allow the passes of bigger molecules. For example – water passes through these pores but molecules like solutes in water do not.
Semi permeable membranes can be of animal or vegetable origin. These occur naturally such as pig’s bladder or can be synthetic such as cellophane.
In osmosis flows take place always from higher concentration to the lower concentration. This means flows take place from dilute solution to concentrated solution.
The flow of solvent continues until the equilibrium is attained.
Think a situation, in which water flows from higher level to lower level. Osmosis is a phenomenon just like that of flow of water from higher level to lower level. And water keeps on flowing until both the level become equal, i.e. come at equilibrium.
Example –
When raw mangoes is pickled in brine (salt water), it get shriveled. This happens because the water molecules move out through the cell walls of mango to the brine, this dries the raw mangoes resulting in shriveled into pickles. In this cell wall of mango acts as semi permeable membrane. This happens because of osmosis.
When wilted flower is kept in fresh water, it revives because of passing of water through the cell wall to the flower resulting in revival of flower, this also happens because of osmosis.
A limp carrot, gram, peas, etc. when placed into water becomes firm again. Carrot becomes limp because of water loss into the atmosphere, but when it is placed into water for two to three hours, it soaked water because of osmosis and it gets firm again.
Reference: