Lesson 1.5 - Mixtures
In this lesson:
What is a mixture?
A mixture is made up of two or more elements or compounds.
They are not chemically bonded. No chemical reaction takes place.
Properties of mixtures
A substance's properties do not change when in a mixture.
The mixture has the same properties as the chemicals it contains.
The chemical properties of each substance in the mixture are unchanged.
The above sentences mean the same thing. In an exam, write whichever makes most sense to you.
Seperating mixtures
We can seperate mixtures using one of 5 methods:
Filtration
Simple distillation
Fractional distillation
Crystallisation
Chromatography
These are not chemical reactions, but instead physical processes. No reaction takes place and no new substances are formed.
Filtration
Filtration allows liquid particles to pass through, but not solid particles.
It can be used to remove the solid particles or liquid particles from a substance.
It involves a filter medium, which allows only certain particles to pass through.
Simple distillation
Simple distillation allows substances with higher boiling points to be seperated from those with lower boiling points.
It evaporates substances with lower boiling points, leaving those with higher boiling points in the container.
It then condenses the evaporated substance into a seperate container.
The result is two containers:
One with substances with low boiling points
One with substances with high boiling points
Fractional distillation
Fractional distillation is used to seperate substances with slightly different boiling points.
Often, it is used to seperate liquids from each other.
Because the substances have different boiling points, we can seperate them in a similar way to simple distillation.
However, we can use it more precisely - it can be used to seperate substances with very similar boiling points - as long as they are not identical.
Crystallisation
Crystallisation is where we form solid crystals from a solution.
It is very similar to evaporation.
When the solution boils, some of the liquid evaporates.
This leaves behind a concentrated solution, which then forms crystals.
Chromatography
Chromotography needs two things:
Absorbent paper
A solvent
These two things create a chromatogram.
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