Task: To make heterogeneous mixture of impure salt and water.
Required accessories: One beaker or glass, spoon, stirrer, impure salt, water and measuring flask.
Procedure: Using a measuring flask take 200 milliliters (different amount may be taken) of water in the well cleaned beaker or glass. Now add 1-2 spoons of impure salt in the water of the beaker and stir gently. Lease the mixture for some time.
Analysis: What do you see? The grains of salt have been dissolved in the water while the heavy dust particles pile up at the bottom of the beaker. On the other hand, the light minute dust particles are floating on the surface of the wafers-that is the dins or impurities are not uniformly distributed in the water, so it is sure that the mixture is a heterogeneous mixture of salt, water and impurities.
How it can be proved by experiment that the impurities (the dust particles) are not distributed uniformly? Dividing the remaining impurities tale several equal portions and vaporizing the entire water from each portion liter as done before and then by measuring the mass of the remaining substances, it will be seen that the different portion have different amount of substances. Now tell, if there is any method to remove eliminate these undissolved impurities.
We can separate these particles from the mixture with the help of a strainer as we separate the tea leafs from the liquor by a tea strainer. Now let us see how pure salt is obtained by separating the impurities; example, dust particles from the saline water by a filter paper.