Two teaspoons of salt are added to a glass of water which is then stirred until no more salt grains can be seen. two more teaspoons are added and stirring is continued, but the salt grains are still evident in the glass and settle to the bottom. after the addition of the last two teaspoons of salt the solution is nonpolar polar saturated unsaturated

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After the addition of the last two teaspoons of salt, the solution is saturated

A solution is saturated when it has the highest amount of solute (in this case the salt) that the solvent (in this case the water) can dissolve at that pressure and temperature. 

Visually, a saturated solution can be detected when the adding of more solute results in the settling of solute grains (in this case salt) at the bottom of the container, because the solvent couldn't dissolve them at that pressure and temperature. That's why we can say that the solution is saturated.

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Particle exchange energy though elastic collision , hope this .