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Separation Techniques. Yeo Shi Wen 103. Sublimation. -Used when one of the solid substances can sublime while heating - Examples of sublimed substances are dry ice, iodine crystals, mothballs
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Separation Techniques Yeo Shi Wen 103
Sublimation • -Used when one of the solid substances can sublime while heating • -Examples of sublimed substances are dry ice, iodine crystals, mothballs • -It is used in printing processes that uses heat to transfer dye onto paper or fabric to produce photographic prints
Magnetic Attraction • -Magnets are used to separate magnetic materials from non magnetic ones in a mixture • - The magnetic materials are iron, steel, nickel and cobalt • -For example, iron filings can be separated from sulfur powder in a mixture • -At the scrap yards, a strong electromagnet is used to salvage scrap iron and steel from other junk materials • -In mining, it is used to separate magnetic ores from none-magnetic ores. • - It is used in hospitals to remove iron splinters from patients’ eyes.
Filtration • -It is used to separate an insoluble solid from a liquid • - For example chalk powder from water • -In filtration, the insoluble solid that remains on the filter paper is called the residue. The liquid that passes through the filter paper is called the filtrate • - Examples are sink filter, teabags. Sieve and air-con filter • -It is carried out in the human body as well: The mammalian kidneys carry out filtration to remove unwanted substances from bloodstream, and the nostril hairs filter and remove dust and large suspended particles from the inhaled air. • -Reverse osmosis can be used for desalination
Evaporation • -It is a method used to separate a dissolved solid from a solution by heating the solution to dryness • -This method is used if the dissolved solid is a heat stable substance This means that it will not decompose upon strong heating • -Common salt is obtained through evaporation of seawater • - Evaporation of sweat cools our body down and thus helps our body to maintain a constant body temperature during hot days.
Crystallisation • -It is a method to separate a soluble solid from its solution which is not heat stable. The soluble solid that is not heat stable decomposes on strong heating. • -The process of crystallization is to obtain a soluble salt from a solution • -Crystallisation is an important application in food technology. For example, the table sugar is obtained from sugar beet or sugar cane by crystallization • -It is used in the production of silicon which is the main component of most semiconductor devices including radio, computers, telephones and many other devices.
Chromatography • It is useful to separate and identify small amounts of substances that are dissolved in a solvent, such as dyes in coloured ink. • Chromatography can be used to separate different components in a mixture based on the following principles. • Different compounds in a mixture have a different solubility in a solvent. • The different solubility in a solvent causes them to move at different speeds on the chromatography paper. • The results of the separated components on the chromatography paper is called a chromatogram • In food industries, it is used to analyze the safety levels of food sample and pollutants present in water.
Simple Distillation • -It is used to separate a liquid from a solid-liquid mixture • -For example, pure water can be separated by seawater through distillation • -When a substance is distilled over, the temperature remains constant at the boiling point of the substance. • -Distillate is the liquid collected from the process of distillation • -A gentle blue flame is used to heat up the mixture in the distillation flask • - If the distillate is a volatile liquid, the receiving flask is placed in a container filled with ice water to prevent the distillate from evaporation. A volatile substance is a substance which evaporates easily at room temperature. • -In Singapore, desalinated water is also obtained from seawater using distillation. In this method, seawater is heated until water changes into steam and condenses in a new container. The salt will be left behind and drinking water is produced.
Fractional Distillation • -It is a process used to separate two or more miscible liquids in a mixture. Miscible liquids are liquids which dissolve in each other to form a single layer. • -For example Alcohol can be separated from water in alcoholic drinks • -Fractional distillation is able to separate different liquids in a mixture because they have different boiling points. • -In fractional distillation, a liquid with a lower boiling point will be distilled first • -The fractionating column allows a liquid of higher boiling point to condense and fall back during the distillation of a substance of lower boiling point. This ensures a more efficient separation of different liquids.
