Separation of mixtures

The separation of mixtures is the method of separating the mixture into its components. The method used depends on the type of mixture and its components. For example, Heterogeneous mixtures can be separated into their respective constituents by simple physical ways like handpicking, sieving, and filtration. Homogeneous mixtures require various separation techniques such as centrifugation, sublimation, and distillation. Several physical and chemical changes may occur in the mixture during these separation processes.

Various Separation Techniques

• Evaporation: When a liquid turns into gas on the application of heat, the process is known as evaporation. This technique may separate a volatile component (solvent) from its non-volatile solute
• Centrifugation: The method is used to separate suspended particles from a liquid

1. The mixture is separated by rotating it at high speed in a centrifuge.
2. Denser particles are forced to the lowest, and lighter particles stay at the top.
3. Following are its applications:
4. Used in diagnostic laboratories for blood and urine tests. 
5. Used in dairies and home to separate butter from cream. 
6. Used in washing machines to squeeze out water from wet clothes.

• A separating funnel is based on the principle that immiscible liquids separate in layers depending on their densities. Following are its applications:

1. To separate a mixture of oil and water.
2. In extracting iron from its ore, the lighter slag is removed from the top, leaving the molten iron at the lowest in the furnace.

• Sublimation: Sublimation is when solid substances are directly converted to the gas state without going through the fluid state. It is used to separate the elements that sublime on heating from the one which does not. Solids that sublime are ammonium chloride, naphthalene, camphor, etc
• Chromatography: It’s the technique used to separate those solutes that dissolve within the same solvent. For example, if we place a drop of ink on a filter paper and immerse it into the water from one end, the water rises, separating the colours. The colour constituent that is more soluble in the water rises quickly, and the colours separate. Chromatography has many practical applications such as
  • This technique was initially used for the separation of colours
  • This technique separates pigments from natural colours and medicines from blood
• Distillation is used to separate components of a mixture containing two miscible liquids that boil without decomposition and have sufficient distinction in their boiling points. When we heat a mixture of liquids, the component with a lower boiling point begins to form vapours collected in a distillation tube. The other component is then separated as it remains in the distillation flask
• Fractional Distillation: It is used to separate a mixture of two or more miscible liquids when the distinction in boiling points is less than 25 K. For instance, the separation of various gases from the air, different factions from petroleum products, etc
• Crystallisation: Crystallisation separates a pure solid as crystals from a solution. It is used to purify solids. For example, the salt we acquire from seawater may include a lot of contaminants. The crystallisation procedure is used to eliminate these contaminants. The crystallisation method performs better than evaporation
• Reverse Osmosis: It is the technique in which solvent molecules move from the solution of higher concentration to the solution of lower concentration separated by a semipermeable membrane when excess pressure is applied to the solution of higher concentration. It is used for the desalination of seawater

Physical and Chemical Changes

• Physical change: The interconversion of states is a physical change because these changes occur without a change in composition and no change in the chemical nature of the substance
• Ice, water and water vapour all look different and display distinct physical properties, but they all are chemically the same
• Chemical change: Chemical change changes the chemical properties of matter, and new substances are obtained. A chemical change is also known as a chemical reaction
• The burning of coal is a chemical change

Conclusion

Most of the time, the chemicals we encounter are not in their purest form. These chemicals are essentially combinations of two or more substances. However, mixtures can take many different forms. As a result, numerous separation procedures are used to separate a combination of components. Physical and chemical changes occur during the separation of mixtures. The primary reason for separation is eliminating all undesirable elements and acquiring valuable components. Separations make use of variations in chemical or physical characteristics. The usual separation and purification methods are distillation, crystallisation, sublimation and chromatography.