Separating Mixtures


Mixtures can be divided into two types. Heterogeneous and Homogeneous Mixtures.



1) Heterogeneous Mixtures. This type of mixture is also called a mechanical mixture. In a mechanical mixture, We can see that one substance is different from the other in the mixture because it has different properties.( colour, shape, size, magnetic.)

    We can separate the different parts in a heterogeneous mixture fairly easily because the substances in the mixture have different properties.


There are different ways to separate the substances in a mixture.

  A) Mechanical sorting- This involves separating the particles based on their properties. Some examples are:

--Magnetism- removing iron filing from sand using a magnet.

-- size- separating the raisins from the bran flakes in a bowl of cereal.

--flotation -- separate wood from metal or pepper from sand.

  B) Filtration-- This is a common way to remove solid particles from a mixture with water or air. Filtration also uses the property of size to separate the substances. For example we use a coffee filter to separate the coffee grounds from the coffee solution or a colander( strainer) to separate spaghetti from the water.


2) Homogeneous Mixtures

A homogeneous mixture is a solution. The solute and solvent look the same so they are hard to separate. There are several ways we can separate solutions


    A) Evaporation

We can use a change of state to separate the solute from the solvent. During evaporation or boiling only pure water will change state. If we evaporate salt water, then the water changes to water vapor and we are left with the salt. Another example is boiling maple tree sap to get rid of the water to make maple syrup.

    B) Distillation

We can use distillation if we want to retain the solvent and the solute. Distillation involves boiling the solution and then cooling the water vapor so that it turns back into a liquid that is collected. The solute is left behind and can also be collected. Distillation involves two changes of state ( evaporation-liquid-gas and condensation- gas-liquid) For example: distillation can be used to make pure water out of salt water.




 C)    Paper Chromatography.This a method for separating mixtures that are colored. If we put a colored solution on filter paper and place the paper in water, the water will diffuse( spread) up the paper and separate out the different colors in the mixture.


D)    Fractional Distillation. Petroleum( crude oil) is a mixture of solids, liquids and gases. Petroleum is sent to a refinery ( Come By Chance) where it is broken into its various parts. Such as:

jet fuel

diesel oil

lubricating oil

tar ( asphalt)

   Fractional distillation is a process that uses the different boiling points of the substances to separate out each one. As the heated petroleum rises it cools and each of the substances changes back to a liquid at a different temperature and are collected in different tanks.