When no more solute can be dissolved in solution at given temperature is called solution a homogeneous B heterogeneous C saturated D unsaturated?

UNSATURATED AND SATURATED SOLUTION

Saturated solution

Activity 2.2:

* Let us again divide the class into four groups – A, B, C, and D.

* Distribute the following samples to each group:

- Few crystals of copper sulphate to group A.

- One spatula full of copper sulphate to group B.

- Chalk powder or wheat flour to group C.

- Few drops of milk or ink to group D.

* Each group should add the given sample in water and stir properly using a glass rod. Are the particles in the mixture visible?

* Direct a beam of light from a torch through the beaker containing the mixture and observe from the front. Was the path of the beam of light visible?

* Leave the mixtures undisturbed for a few minutes (and set up the filtration apparatus in the meantime). Is the mixture stable or do the particles begin to settle after some time?

* Filter the mixture. Is there any residue on the filter paper?

* Discuss the results and form an opinion.

* Groups A and B have got a solution.

* Group C has got a suspension.

* Group D has got a colloidal solution.

Figure 2.1: Filtration

In activity 2.2, we observed that groups A and B obtained different shades of solutions. So, we understand that in a solution the relative proportion of the solute and solvent can be varied. Depending upon the amount of solute present in a solution, it can be called a dilute, concentrated or a saturated solution. Dilute and concentrated are comparative terms. In activity 2.2, the solution obtained by group A is dilute as compared to that obtained by group B.

What would happen if you were to take a saturated solution at a certain temperature and cool it slowly.

Activity 2.3:

* Take approximately 50 mL of water each in two separate beakers.

* Add salt in one beaker and sugar or barium chloride in the second beaker with continuous stirring.

* When no more solute can be dissolved, heat the contents of the beaker to raise the temperature by about 5°C.

* Start adding the solute again.

Is the amount of salt and sugar or barium chloride, that can be dissolved in water at a given temperature, the same?

At any particular temperature, a solution that has dissolved as much solute as it is capable of dissolving, is said to be a saturated solution. In other words, when no more solute can be dissolved in a solution at a given temperature, it is called a saturated solution.

Unsaturated solution

If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.

Source: This topic is taken from NCERT TEXTBOOK

SOLUBILITY

The amount of the solute present in the saturated solution at this temperature is called its solubility. We can infer from the above activity that different substances in a given solvent have different solubilities at the same temperature. The concentration of a solution is the amount (mass or volume) of solute present in a given amount (mass or volume) of solution.

There are various ways of expressing the concentration of a solution, but here we will learn only three methods:

i. Mass by mass percentage

ii. Volume by volume percentage

iii. Mass by volume percentage

Source: This topic is taken from NCERT TEXTBOOK

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