Page 85 - ICSE Chemistry 6

A solu on is said to be saturated when it cannot dissolve any more of the solute at a par cular temperature.
A solu on is said to be unsaturated when it can dissolve more of the solute at a par cular temperature.
A solu on is said to be supersaturated when it contains more solute than can be dissolved in the solvent
under normal condi ons.
Let’s perform Ac vity 4.10 to prepare a saturated solu on of salt and water.

Activity 4.10

Aim: To prepare a saturated solu on of salt and water

Materials required: A beaker, some water, a spoon, some salt
Procedure
• Take some water in a beaker.

• Add a teaspoon of salt to it and s r it.
• Con nue adding salt ll no more salt can be dissolved in it.
Observa on: A er a point salt stops dissolving in water.

Conclusion: The solu on, so obtained, in which no more salt can be dissolved at this par cular temperature
is a saturated salt solu on.

The forma on of a solu on is a physical change. Molecules of the solute and the solvent remain the same
in a solu on. It is easy to get back the solute and the solvent in their original form from the solu on. Let’s
perform Ac vity 4.11 to observe how salt can be separated from a salt solu on.

Activity 4.11

Aim: To separate salt from salt solu on by evapora ng ll the water dries

Materials required: A beaker, some water, a spoon, some salt, an evapora ng dish, a burnerner
Procedure
• Take some water in a beaker and add two teaspoons of salt to it.

• S r the contents of the beaker. You will get a salt solu on.
• Transfer this salt solu on to an evapora ng dish.

• Now heat the dish over the fl ame of a burner.
• Observe what happens a er 15–20 minutes.
Observa on: You will observe that a er some me water starts boiling and turning into water vapour.
If the vapour coming out of the solu on are allowed to condense, then we can obtain the solvent. A er
some more me, a stage will come when no more water is le in the evapora ng dish and only salt is
present at the bo om of the beaker.

Conclusion: This way, salt (solute) can be separated from salt solu on.

From Ac vity 4.11, we can conclude that a solvent can be obtained from a solu on by the process of
dis lla on, while a solute can be obtained by evapora ng the solu on ll it dries.

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