Separating Mixtures

What is a mixture? When two or more materials or substances are mixed together but do not chemically combine. This means they retain their original properties. This means they can be separated by physical means.

What are some different ways of separating mixtures? Magnetism Hand separation Sifting or sieving Decant Filtration Distillation Evaporation Chromatography

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 nonmagnetic substances

Hand separation Separating the parts of a mixture by hand. Only useful when the particles are large enough to be seen clearly.

Example of hand separation: Using your fork to separate tomatoes, lettuce, cucumber, onions, etc. in your salad.

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.

Decantating

Filtration separates a liquid from a solid Mixture of solid and liquid Stirring rod Filtrate (liquid component of the mixture) Filter paper traps solid Funnel Filtration separates a liquid from a solid Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40

Example of filtration: Using a coffee filter to separate the coffee flavor from the coffee beans.

Mixture (salt, sand, water) filter paper filter funnel Mixture (salt and water)

Distillation Water Vapour Mixture (salt and water) Bunsen burner Water

Distillation is a process of boiling a liquid and condensing and collecting the vapor. The liquid collected is the distillate. The usual purpose of distillation is purification or separation of the components of a mixture. This is possible because the composition of the vapor is usually different from that of liquid mixture from which it is obtained.

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

Evaporation Allowing the liquid to evaporate, leaving the soluble solid behind. Example: heating sugar water. The water evaporates and the sugar crystals are left behind.

Evaporation Water Evaporating dish Mixture (salt and water) Bunsen burner

Setup to heat a solution Ring stand Beaker Wire gauze Ring Bunsen burner Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 42

Chromatography Used to separate dissolved substances in a solution from each other. Mixture Components Separation Stationary Phase Mobile Phase

Example of chromatography: Using chromatography paper to separate ink into it’s original components.

Chromatography Tie-dye t-shirt Black pen ink DNA testing Tomb of Unknown Soldiers Crime scene Paternity testing

Paper Chromatography http://www.moe.gov.sg/edumall/tl/digital_resources/chemistry/images/paper_chromatography.jpg