Activity 2.3 NCERT Class 9 Science Is Matter Around Us Pure

Activity 2.3 NCERT Class 9 Science Chapter 1 Is Matter Around Us Pure

Brief procedure:

Activity 2.3 asks us to prepare a saturated solution of salt and sugar and check if the temperature increases the solubility.

Observation:

We can dissolve more solute at a higher temperature.

Explanation:

When we add a solute to a liquid, it fits into the voids between the solvent molecule. On adding solute particles, a time comes when the solute molecule occupies all the voids in the solvent. In such condition, there is no more space for additional solute particle. Beyond this solute, the particle does not dissolve and settle at the bottom. We call this the saturation point.

A saturation point of a solvent and a solute is fixed at a particular temperature. For example solubility of sugar in water at room temperature is 200gm/100ml; while at 100°C, it is around 500gm/100ml. When we increase the temperature, size of void increases. As a result, we can dissolve more amount of solute.

Note: The solubility of a substance is characteristic of the solute and the solvent at that temperature. The solubility of common salt does not increase up to the extent as of sugar.

Next: Experiment to demonstrate the separation of a mixture by evaporation, Activity 2.4.

See also: Experiment to demonstrate A homogenous solution does not block the light while a colloidal or suspension block the light, Activity 2.2.

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