Some substances have impurities added in them which changes their physical properties. However, these impure substances can be removed. Do you know how to remove impurities? In this lesson, we will be learning about separating solutes from solvents and separating two solids.
There are many different methods for removing impurities.
Filtration
Evaporation to Dryness
Crystallization
Magnetism
Sublimation
Suitable Solvent
Explanation:
Solutes from Solvent:
To separate an insoluble solid from a liquid, we do filtration. The apparatus needed for this is filter paper, filter funnel and a beaker. Some insoluble solutes for liquid are sand, clay and dust etc. To remove dust from water, we will pass the solution through the small pores of filter paper (placed on filter funnel on the beaker). Only the water will be able to pass, sand will be trapped on the filter paper. Filtrate will be pure water and the dust will be the residue. Filtrate is the solvent which passes through the filter paper and residue is the trapped solute on the filter paper. Hence, in this way we will get pure water in the beaker placed under the funnel.
To separate soluble solids from the solvent, we either do the process of crystallization or evaporation to dryness. The problem which arises in evaporation to dryness is that we don't receive the pure results. Evaporation to dryness is the process in which we heat the solution until all the solvent has evaporated and the solute is left behind in the evaporating dish. The solute which is separated through this method is sodium chloride, salt.
For some substances that can not be heated strongly (like sugar) we use the method crystallization. To get pure solid from the solvent we do crystallization. It is the process in which the results received are pure. We first add an excess amount of solute in the solvent. And then filter it. Insoluble impurities are trapped. Then heat the filtrate until the solution becomes saturated. Then leave it to cool down. After this, filter the solution and as a residue impure crystals will be obtained. To make them pure, wash them with cold distilled water. The pure crystals of the substance will be obtained. Saturated solution is obtained when the solute is not dissolved in the solvent and it is present in excess amount. If after removing and cooling the solution on the rod, crystals are seen then it is a saturated solution.
Separating Two Solids:
To separate two solids, in which one is magnetic and the other is not, a person can use a magnet. For example, to separate sulfur from the mixture of sulfur and iron, we can use a magnet. Iron will be attracted to the magnet and sulfur will be left behind.
For separating the solids in which one is soluble in the solvent and the other is insoluble, we are first going to dissolve them in the suitable solvent. Then filter to obtain insoluble solute which will be obtained as a residue and the solution with soluble solute as a filtrate. Crystallize the filtrate to get the soluble solute.
Sublimation is another method of separating those solutes in which one sublimes and the other do not. Sublime means to change solid directly into gas without becoming liquids. For example, for separating iodine and sand, we will sublimate iodine. The wet cloth on the filter funnel will change iodine back into solid. At the funnel, iodine will be obtained and in the dish sand and iodine crystals will be left. To obtain pure sand, wash the residue from the dish with distilled water.
*All pictures are taken from google*
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