CBSE Class 9 Answered

(a). A solution in which no more solute can be dissolved at that temperature is called a saturated solution while a solution in which more quantity of solute can be dissolved without raising its temperature is called an unsaturated solution.

To test the saturation or unsaturation of a solution, more solute may be added to the solution. If that solute gets dissolved in the solution then the solution will be unsaturated.

To test whether a given solution is saturated or not, add some more solute to the solution and try to dissolve it by stirring. If solute does not dissolve in the given solution, then it will be a saturated solution.

(b). Take some water in a beaker and heat it slowly with the help of burner. Now, start adding sodium chloride salt to the hot water with a spoon and stir it with a glass rod continuously so that sodium chloride goes on dissolving in water. Take the temperature of water up to 25^oC and then keeping this temperature constant, go on adding sodium chloride till no more sodium chloride dissolves in it and some undissolved crystals will be left at the bottom. The contents of the beaker are now filtered and the clear solution obtained is the saturated solution of sodium chloride at 25^oC.

If the temperature is lowered from 25^oC to 10^oC, then some of the crystals of sodium chloride will separate out from the solution in the form of solute crystals.

OR

(a) Solution like X are known as unsaturated solution.

(b) Solution like Y are known as saturated solution.

(c) If solution Y at 30^oC is cool down to 10^oC by keeping the beaker in crushed ice, then some of the dissolved solid will separate out from the solution and settle at the bottom of the beaker as crystals. This is because the solubility of solid decreases on cooling.

(d) Solubility is the term used to denote the amount of solid dissolved in 100 grams of water in a solution.