Techniques to Separate Matter!!!

How can we separate Matter? There are many ways to separate matter: Hand separation Gravity separation Filtration Evaporation Distillation Solvent extraction Recrystallization Chromatography

Hand Separation: The mixture can be separated by picking one compound out by your hand, a sieve, or a magnet. Eg. Panning for gold – you use a sieve to separate out small pieces from big pieces, and then pick out gold pieces from the rest of the stuff. Eg #2: Magnets are used during recycling operations to separate iron from mixtures of plastic, aluminum and copper.

Gravity Separation Used to separate solids from a mixture based on different densities. ( the more dense compounds sink down to the bottom , and less dense remain at the top). We can use a mechanical shaker, but more commonly we use a CENTRIFUGE which whirls a test-tube around at extremely high speeds forcing the dense solids to go the bottom ( the precipitate) and the low density stuff to remain at the top.

Filtration Used for Separating Liquids from visible solids with filter paper. ( This is no help in trying to separate salt from salt water – the salt is already dissolved – you can’t see it!) You pour the substance into a funnel with filter paper – the liquid moves through the the paper and is called the filtrate , but the solids (called the residue) are trapped on the paper.

Evaporation Allowing the liquid in a Solid/liquid solution to evaporate(or be boiled away) leaving behind the solid that you couldn’t see before! ( the liquid has to have a lower boiling point than the solid) Eg. Salt water evaporation is used in the commercial production of salt on several sea coasts.

Recrystallization Kind of like Evaporation, but you use this method when you have solids in liquid solution where the solid portion consists mostly of the desired material, and only has small amounts of one or more other solids mixed in. You load your solid solution into a suitable solvent until it is saturated (no more solid can be dissolved). Then let the mixture evaporate, but not completely. Some of the solids comes out as crystals (they are an extremely pure form of the desired solid), and are plucked out by hand separation, or filtration.

Distillation Used to separate a LIQUID in LIQUID solution, by heating it in a distillation set-up. The liquid with the lowest boiling point boils first and turns into a gas which rises to the top of the flask. The hot gas is collected in a cooled condenser off to the side of the flask, and the cooler temp. causes the gas to turn back into a liquid, and drop out into a beaker.

Paper or Thin Layer Chromatography Used to separate SMALL amounts of Solid in Liquid solutions containing 2 or more dissolved solids which are colored, or can react to produce colors.

The solids that have a greater tendency to stick to the sheet, don’t travel very far upward, but those solids with a higher tendency to dissolve in the solvent, travel almost as fast as the upward flowing solvent front. After drying the sheet, you can cut off the different sections containing each solid, and then dissolve them out of the paper with solvent. When the solvent evaporates, the solid should be left in its pure form. Eg. Separating different dyes from one another.

Solvent Extraction: Use when trying to separate a solid from a mechanical mixture of solids, or separating a liquid or solid from a liquid solution. MISCIBLE – mutually soluble in each other ( mix well) IMMISCIBLE – NOT mutually soluble in eachother ( don’t mix – like oil and water) This method uses a liquid that dissolves one or more of the solids/liquids present (miscible) but leaves others undissolved (immiscible). Ie. Add water to a sugar sand mixture – so that the sugar dissolves in the water, we can then filter out the sand, and evaporate it the leftover sugar water. VIOLA = we’ve got the sugar by itself!!

Ie. Dye mixed in with an oily substance. When you add the solvent(ie.water) that is miscible with one of the components in the substance(dye), and is immiscible with the other (oil)… They will both stay liquids, and will be visibly separate from the other liquids, and can be drained off from the container (Separatory Funnel). Eg. Separating oils from a solution

Measured value – Accepted value x 100 When we get to Labs... How will you know how “well” you did in your labs if you are asked to separate out a substance from a mixture?? (Ie. Is the substance still mixed with other stuff … did you lose a bunch because you weren’t careful!?) Percent Error = How much error you made as a % Measured value – Accepted value x 100 Accepted value

Practise Time! Hebden Pg.58-59 #45, 46, 47, 53, 54, 57, 58