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Chromatography: Used to separate mixtures of liquid/gases in dissolved substances. We can use chromatography to separate and identify different coloured components in dyes/inks. The more soluble the dye, the further it travels.

Important tips: The starting line must be drawn in pencil as pencil markings are insoluble in most solvent. If it is drawn in pen. the dyes in the pen ink will separate and move up together with the spots. Every spot on the starting line must be small to ensure that the sample does not spread widely, interfering with the spots beside it. The solvent level must be kept below the starting line at all times so that the spots will not be dissolved into the solvent.

Advantages of chromatography: Only requires a small amount of mixture and gives quick results.

Uses of chromatography: It tests for purity in many substances, it is also widely used in the testing of food dyes to identify prohibited chemicals in used the production of food, it also detects drugs, sugars, chemicals in the urine of athletes.

Magnetic Separation:

Used to separate magnetic objects from non magnetic objects (solid-solid mixture). It removes iron from scrap metals in incineration plants and removes magnetic splinters from wounds.

Filtration:

Used to separate insoluble solids from the liquid in a solid-liquid mixture. The insoluble solids will be trapped in the filter paper as residue. The liquid that flows out is filtrate. Filtration can also be used to separate large particles from smaller particles.

Evaporation to Dryness:

Used to separate soluble solid particles from a liquid in a solid-liquid mixture. The solvent evaporates leaving behind the dissolved solids as residue. Evaporation to Dryness is only suitable for solids that do not decompose upon heating (e.g. table salt). Evaporation to Dryness is not suitable for solids that decompose upon heating (e.g. sugar, copper 2 sulfate crystals)

Crystallization:

Used to separate soluble solids (that decompose upon heating) from liquid in a solid-liquid mixture . We heat the solution to dryness when we are sure that the substance would not decompose upon heating. If it does, we evaporate most of the water. This forms a saturated solution. When the solution cools, it forms crystals. Water bath is used when the liquid/mixture you are heating is flammable. Advantage of Water Bath: The temperature of heating is constant at the boiling point of water. Disadvantage of Water Bath: The temperature of heating cannot exceed the boiling point of water.

Distillation:

Used to separate pure solvent (liquid) from a solution in a soluble solid-liquid mixture. The boiling chips ensure smooth boiling. The hot vapor enters the condenser to be cooled and condensed. (Why must the bulb of the thermometer be placed at the entrance of the condenser? : To measure the temperature of the hot vapor)

Fractional Distillation:

Mixture is separated based on its different boiling points. The liquid with the lower boiling point will be distilled and collected first. Use of fractionating column: to provide a large surface area for vapors which have not reached its boiling points to condense on, these liquids will then flow back into the mixture again until it reaches its boiling points.

Separating Funnel:

Used to separate liquid mixtures that are immiscible in an immiscible liquid-liquid mixture. The denser liquid (bottom liquid) will drain off first.