Separation of Mixtures

element

an element is a pure substance that contains one type of atom and cannot be divided into anything. simpler by chemical means

alloy

an alloy is considered a mixture, more specifically a mixture of metals eg. brass, bronze, sterling, steel

compound

a compound is a pure substance consisting of two or more different elements that are chemically combined in fixed proportions

molecules

consist of two or more atoms that are chemically bonded 

• if they are the same: it is a molecule of an element

• if they are different: it is a molecule of a compound

mixture

a mixture consists 2 or more different types of atoms that are physically connected in varying proportions. mixtures can be easily separated by physical means (filtration, evaporation) eg. sand and water

filtration

1. used to operate an insoluble solid from a liquid (suspension)

2. particles the solid are larger than the liquid (that’s the property difference we take advantage of)

3. liquid can pass through tiny holes in the filter paper and after separation is the filtrate

4. the solid is too big to pass through the holes in the filter paper

5. it remains on top of the filter paper and is called the residue

decantation

pouring a liquid of a heavy solid

property difference: one substance is dense and the other is not

evaporation

evaporation is used to separate a soluble solid from a liquid (solution)

1. the solution is heated in an evaporating dish

2. the solvent evaporates

3. the solute remains behind as the residue

property difference: boiling point

simple distillation

is used to separate a soluble solid from a liquid

1. the solution is heated

2. the solvent evaporates and moves into the condenser

3. the vapor condenses in the condenser

4. the condensed solvent is collected as the distillate in a flat bottom flask. the solute remains behind as the residue

property difference: boiling point

fractional distillation

is used to separate fixtures of liquids. that have different boiling points (miscible liquids)

1. the solution is heated to the temperature of the substance with the lowest boiling point

2. the  substance will rise and evaporate first, and vapour will pass through a condenser where they cool and condense, turning into a liquid that will be collected in a beaker

3. all of the substance is evaporated and collected, leaving behind the other components of the mixture

4. when the temperature starts to increase to 100 C heating should be stopped. 

paper chromatography

used to separate substances that are coloured that have different solubilities

a pencil line just be used for this as ink would run into the chromatogram along with the sample

the pencil line must sit above ht level of the solvent so that sample doesn’t diffuse into the solvent

different substances have different solubilities so will travel at different rates

the substance separates, so those substances with higher solubility will travel further than the others

this will show the different components of the ink/ dye

retardation

how much your dye moved compared to the solvent moved

solvent front/ how much your dye moved

should never be above 1