SC2 - Methods of Separating and Purifying Substances ✓

The composition: • Cannot be changed by physical means • Is the same in all parts of a piece of the substance

• A mixture contains multiple elements/compounds that aren’t chamically joined together. • The composition cannot be changed and so it isnt a pure substance.

• Instead of straight lines there will be curves. • This is because there are multiple different elements which will have different melting points.

Using a filter to trap larger insoluble substances from a mixture.

• When a solution is evapourated, meaning that the solvent turns to gas leaving behin dthe solute which forms crystals. • The size of these crystals depend on the time the crystallisation takes • (Longer time taken = larger crystals)

• A saturated solution is a solution in which a solvent contains the highest amount of dissolved solute as possible. • This limit can be increased by increasing the temperature.

• Identifying and evaluating the hazards and considering ways of reducing the risk of harmful effects. • In crystallisation this would be indentifying: • The solution can spit: wearing eye protection and removing from the bunsen burner before the solution is completely evapourated • You can get burnt from the bunsen burner: keep your hands away from the flames at all times

• A method of speration that involves having a piece of paper with dots of ink slightly dipped in the water (so that the water doesnt reach the pencil line that the ink is one). • The solvent is called the mobile phase and the paper contains the stationary phase. • If an ink moves less up the page it is less attracted to the stationary phase. • Different inks have different levels of attraction to the stationary phase and so will get sperated out at different distances.

Rƒ = Distance travelled by spot ÷ Total distance travelled by solvent

• Distinguishing between pure/impure substances • Identifying substances by comparing their chromotogram with known substances • Identifying substances by calculating their Rƒ value

The separation of a liquid from its dissloved solids, by evapourating it and condensing the gas formed.

They have to have boiling points that are at least 25° C apart.

• A side-arm flask on a tripod over a bunsen burner. • It contains the solution and anti-bumping granules to help the liquid boil more smoothly. • A thermometer is connected to the top. • A delivery tube, leading to a conical flask, is surrounded with a cooling jacket (condenser) which takes cold water in from the bottom and puts it out at the top. • The conical flask is in a bath of ice water. • The bunsen burner is ona heat resistant mat.

• Paper chromotography • Simple distillation

It takes up too much energy.

Tap water contains small amounts of dissolved salts and minerals which may react and alter the resuslts

• First, it is screened with a seive to get rid of large objects such as leaves and twigs • It is then sent to a sedimentation tank where small particles will settle out at the bottom • The water is then filtered through layers of sand and gravel • Finally it is treated with chlorine to kill microbes