METHODS OF SEPARATION
The process by which mixtures are separated to get pure substances is called separation
A. Separation of solid-solid mixture
1 Hand picking- This method is used when quantity of mixture is small and substance which has to be separated I in the small portion.
Ex. Small stones from grains.
2. Winnowing- This method is used to separate light solids from heavier ones.
Ex. Husk from rice.
3.Sieving- This method is used when the mixture contains different size of substances.
Ex. Large stones from sand.
4.Magnetic separation-this method is used when one of the components of the mixture is iron.
Ex. Iron fillings and sand
5.Stream of water- This method is used for mixtures containing coarse and fine particles.
Ex. Gold from river sand
6.By using solvent- This method is used when one of the solid component is soluble in liquid.
Ex. Sand and salt
7. Sublimation- This method is used when one of the component can evaporate on heating.
Ex. Sand and iodine
B. Separation of solid-liquid mixture
1. Sedimentation and decantation- This method is used for heterogeneous mixtures of solids and liquids where solid component is heavier than liquid.
Ex. Sand from water
2. Loading- This method is used to clean drinking water with the use of alum which makes suspended particles heavier.
Ex. suspended fine impurities from water
3. Filtration- This method is used for heterogeneous mixtures of solids and liquids in which solid component is lighter than the liquid.
Ex. Tea from tea leaves
4. Evaporation- This method is used for separating components of homogeneous mixture in which one component is able to evaporate.
Ex. Salt from sea water.
5. Distillation This method is used for separating to obtain pure liquids. The solution is first heated to form vapours and then condensed back into liquid.
Ex. Tap water is changed into distilled for laboratory purposes.
6. Centrifugation -This method is used for separating solids from liquids where the mixture is homogeneous. The mixture is placed in centrifuge to rotate at a very high speed.
Ex. Cream is separated from milk
C. Separation of liquid-liquid mixture
1.Separating funnel- This method is used for separating immiscible liquids. The mixture is place into separating funnel, the component form two layers the stopper of funnel is opened, the heavier liquid trickles out and collected in a vessel.
Ex. Mixture of oil and water.
2.Distillation This method is used for separating two miscible liquids.it is based on the fact in the difference in the boiling points of these liquids. The liquid which has lower boiling point evaporates first while other remain in the vessel.
Ex. Petrol, diesel and kerosene oil are obtained from crude petroleum oil