5. distillation Distillation involves 2 stages and both are physical state changes. (1) The liquid or solution mixture is boiled to vaporise the most volatile component in the mixture (liquid ==> gas). The ant-bumping granules give a smoother boiling action. (2) The vapour is cooled by cold water in the condenser to condense (gas ==> liquid) it back to a liquid (the distillate) which is collected. This can be used to purify water because the dissolved solids have a much higher boiling point and will not evaporate with the steam, BUT it is too simple a method to separate a mixture of liquids especially if the boiling points are relatively close. 6. crystallization Crystallisation can mean a liquid substance changing to its solid form. However, the term usually means what happens when the liquid from a solution has evaporated to a point beyond the solubility limit. Then solid crystals will 'grow' out of the solution because the solution is too concentrated for all the solid to remain dissolved at that temperature. Crystallisation is often done from a hot concentrated solution, because most substance are more soluble the hotter the liquid. Consequently on cooling a hot concentrated solution, crystals form as the solubility gets less and less. 7. chromatography
11. sublimation Sublimation is the term for when matter undergoes a phase transition directly from a solid to gaseous form, or vapor, without passing through the more common liquid phase between the two. It is a specific case of vaporization. 12. evaporation Evaporation means a liquid changing to a gas or vapour. In separation, its removing the liquid from a solution, usually to leave a solid. It can be done quickly with gentle heating or left out to 'dry up' slowly. The solid will almost certainly be less volatile than the solvent and will remain as a crystalline residue. 13. magnetic separation
Distillation, described above is used to separate miscible liquids that dissolve in each other. If two liquids do NOT mix, they form two separate layers and are known as immiscible liquids (e.g. oil/water). This is illustrated in the diagram on the left, where the lower grey liquid will be more dense than the upper layer of the yellow liquid and shows how you can separate these two liquids using a separating funnel. (particle picture on gas-liquid-solid page) 1. The mixture is put in the separating funnel with the stopper on and the tap closed and the layers left to settle out. 2.The stopper is removed, and the tap is opened so that you can carefully run the lower grey layer off first into a beaker. 3.This leaves behind the upper yellow layer liquid, so separating the two immiscible liquids. Condensation
* cooling a vapor causes components with the highest boiling points to condense as liquids first * examples
* separating steam and air
* separating oxygen and nitrogen in air
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* components in a mixture retain their identities * exploit properties that distinguish the components to separate mixturesSome manufacturers add iron filings to cereal to increase its iron content! The bits of iron will stick to a magnet, but the cereal won't. So you can easily separate the mixture by...