Methods of Separating Mixtures PDF

Methods Separating Mixtures What is a mixture? When two or more materials or substances are mixed together but do not chemically combine. T his m e ans t he y r e t ain their original properties. T his means t hey can be separated by physical means.  What are the different ways of...

Methods Separating Mixtures What is a mixture? When two or more materials or substances are mixed together but do not chemically combine. T his m e ans t he y r e t ain their original properties. T his means t hey can be separated by physical means.  What are the different ways of separating mixtures? Magnetism Hand separation Filtration Sifting or sieving Extraction and evaporation Chromatography Distillation Centrifugation Decantation  Magnetism If one component of the mixture has magnetic properties, you could use a magnet to separate the mixture. Iron, nickel, and cobalt are all materials that are magnetic. Not all metals are magnetic: gold, silver, and aluminum are examples of metals that are not magnetic. Example of magnetism Using a magnet to separate nails from wood chips. Hand separation Separating the parts of a mixture by hand. Only useful when the particles are large enough to be seen clearly. Useful for: separating parts of a salad. Example of hand separation: Using your fork to separate tomatoes, lettuce, cucumber, onions, etc. in your salad.  Filtration U se d w he n se p a ra t i ng a so l i d substance from a fluid (a liquid or a gas) by passing a mixture through a porous material such as a type of filter. W o rk s b y l e t t i ng t h e f lu i d p a s s through but not the solid. Examples of f il ters: coffee f il ter, cloth, oil filter, even sand! Example of filtration: Using a coffee filter to separate the coffee flavor from the coffee beans. Filtrate - a liquid which has passed through a filter.  Sifting or sieving Used to separate a dry mixture which contains substances of different sizes by passing it through a sieve, a device containing tiny holes.  Example of sifting/sieving: Using a sieve to separate sand from pebbles. Extraction U se d to se parat e an i nso l ubl e so l i d (something that doesn’t dissolve in a liquid) from a soluble solid (something that DOES dissolve in a liquid). Done by adding a solvent (liquid that does the dissolving) to the mixture. Then pouring the liquid through a filter. Example of extraction With a mixture of sugar and sand, pouring water in the mixture which causes the sugar to dissolve. Then pouring the solution through a filter, causing the sand to separate from the sugar water.  Evaporation A l l o w i ng t h e l i q u i d t o ev apo rat e , l e av i ng t he soluble solid behind. E x a m pl e : h e a t i n g s u ga r water. The water evaporates and the sugar crystals are left behind. Example of using extraction and evaporation together: Using water to dissolve sugar, then letting the water evaporate, leaving the sugar behind.  Chromatography Used to separate dissolved substances in a solution from each other. The method used in separating complex mixtures. Paper chromatography makes use of a s h e e t o f s p e c i a l g ra d e f il t e r p a p e r a s absorbent. Suppose you want to find out the food color (dye) used in the cake's icing, the principle involved depends upon the dyes' solubility in a solvent. Chromatography Stationary Phase Separation Mobile Phase Mixture Components Example of chromatography: Using chromatography paper to separate ink into it’s original components.  Distillation Distillation is the process of separating c o m p o n e n t s o f a m i x t u re b a s e d o n different boiling points. Examples of uses of distillation include purif ication of alcohol, desalination, crude oil ref ining, and making liquef ie d gases from air. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 42  Distillation Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.  Distillation To separate a mixture of liquids, the liquid can be heated to force components, which have different boiling points, into the gas phase. The gas is then condensed back i n to l i q u i d f o r m a n d c o l l e c t e d. Repeating the process on the collected liquid to improve the purity o f th e p r o d u c t i s c al l e d d o u b l e distillation. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 42  A Distillation Apparatus thermometer liquid with a solid dissolved in it condenser tube distilling flask receiving pure hose connected to flask liquid cold water faucet Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 282 Cooling water out Run hose into sink Cooling water in Connect hose to cold water tap  The solution is boiled, and steam is driven off. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 39  Salt remains after all water is boiled off. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 39  No chemical change occurs when salt water is distilled. Distillation (physical method) Salt Saltwater solution Pure water (homogeneous mixture) Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40  Separation of a sand-saltwater mixture. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40  Centrifugation Is a technique used for the separation of particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed. T he p ar t ic le s are susp e nd e d in a liq uid medium and placed in a centrifuge tube. The tube is then placed in a rotor and spun at a define speed. Separation through sedimentation could be d o n e n a t u r a l l y w i t h t h e e a r t h g r a v i t y, nevertheless, it would take ages. Centrifugation is making that natural process much faster.  Centrifugation Rotation of the rotor about a central axis generates a centrifugal force upon the particles in the suspension. Which factors have an influence on centrifugation : Density of both samples and solution Temperature/viscosity Distance of particles displacement Rotation speed  Centrifugation Spin sample very rapidly: AFTER Before denser materials go to bottom (outside) Separate blood into serum and plasma Serum (clear) Serum Plasma (contains red blood Blood cells ‘RBCs’) Check for anemia (lack of iron) RBC’s A B C Decantation D e c a n t a t i o n i s t h e p ro c e s s o f separation of liquid from solid and other immiscible (non-mixing) liquids, by removing the liquid layer at the top from the layer of solid or liquid below. The process can be carried out by tilting the mixture after pouring out the top layer. - End -