Chapter 3: Separation and Purification

Mixture

a mixture is made up of two or more substances that are not chemically combined together

Pure substance

made up of one single element or compound, and is not mixed with any substances

filtration

• used to separate insoluble solid particles from a liquid

• a filter funnel and a filter paper are usually used

evaporation to dryness

the process of obtaining a soluble solid from a solution by heating the solution until all the water has boiled off

why could the salt obtained from evaporation to dryness be impure?

there might be soluble impurities left together in the solid

crystallisation

the process of obtaining pure solid sample from its solution

which kind of substances cant be obtained by evaporation to dryness

when a substance decomposes on heating or can lose its water of crystallisation

saturated solution

a solution that contains as much dissolved solvent as it can at a given temperature

how to test for saturation

a clean and dry glass rod is dipped and removed from the solution

if small crystals form on the rod when the solution cools, the solution is saturated

a saturated solution is also known as

a solution at its saturation point or crystallisation point

sublimation

used to separate a solid that sublimes from one that does not

simple distillation

used to separate a pure solvent from a solution

purpose of thermometer in simple distillation

measures the boiling point of the substances that is being distilled

purpose of the condenser in simple distillation

condenses the distillate back into liquid state

why does the condenser have cold running water from the bottom to the top

the ensure that the entire jacket is completely filled and this provides a more efficient cooling system

purpose of boiling chips in simple distillation

to ensure smooth boiling

method to separate miscible liquids

a separating funnel

using a separating funnel

used to separate immiscible liquids

methods to separate miscible liquids

fractional distillation or paper chromatography

fractional distillation

used to separate miscible liquids with different boiling points

chromatography

chromatography is the method of separating 2 or more components that dissolve in the same solvent

how does chromatography work

• separation of a substance into its different components depends on the relative solubility of the component

• the more soluble component travels faster and further up the paper than the less soluble components

uses of chromatography

• to separate the components in a sample

• identify the number of components in a sample

• identify the components present in a sample

• determine the purity of a sample

how to determine the purity of a substance

• checking the melting point of a solid

• checking the boiling point of a liquid

• performing chromatography

how do impurities affect the melting and boiling point of substances

• impurities lower the melting point

• impurities increase the boiling point