Quiz Define a mixture. Define a compound. How many substances do pure substances contain? When two substances are mixed in a mixture, do their properties change? When you are making a solution by dissolving a solid in a liquid, what is the name given to the solid and what’s the name given to the liquid? Is salt water a mixture? Is air a mixture?

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.

Physical and chemical properties A substance will have two types of properties: Physical properties: These properties include how substance look, their boiling or melting point, their density etc. Chemical properties: This property describes how the substance reacts with other substances chemically. Different substances have different physical and chemical properties and we can utilize these properties to help us separate different substances.

What are the different ways of separating mixtures? Solubility Density Magnetism Hand separation Filtration Sifting or sieving Extraction and evaporation Chromatography

Separation by density Different substances can have different density, and by putting them in solutions we can separate them by their densities

Separation by Dissolving Substances may have different solubility, so by place them in solvents such as water we can separate soluble substances from the insoluble (e.g. salt and iron)

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.

Filtration Used when separating a solid substance from a fluid (a liquid or a gas) by passing a mixture through a porous material such as a type of filter. Works by letting the fluid pass through but not the solid. Examples of filters: coffee filter, cloth, oil filter, even sand!

Separating Calcium hydroxide (lime water) mixture Aim: to separate solid calcium hydroxide from water. In your practical groups, grab: 1 retort stand, 1 clamp, 1 glass rod, 2 beakers (one for mixture one for filtrate, and come and collect some mixture off me), a funnel and a piece of filter paper. Set it up as the diagram I will teach you how to fold the filter paper.

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.

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

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

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 Used to separate an insoluble solid (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 Allowing the liquid to evaporate, leaving the soluble solid behind. Example: heating sugar 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. Mixture Components Separation Stationary Phase Mobile Phase

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

In your book Write down each separation technique as we try them, you should be able to do the magnetism one already. e.g. Separating by magnetism: Iron is magnetically active and is attracted by the magnet whereas sand is not, therefore we can separate iron and sand mixture using a magnet bar to suck up all the iron fillings and leave the sand behind. Diagram