# GCSE Atomic Structure and the Periodic Table

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Elements
Periodic Table shows us the elements, 118 Elements, In an Element, all the atoms are the same
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Compounds
They contain 2 or more different elements chemically combined in a fixed proportion- They usually have totally different elements to the properties they're made from- To separate back into its elements, we need to use chemical reactions to do so
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Mixtures
They have different elements or compounds not chemically combined together - To separate them, we need to use physical separation techniques (Crystallisation/Filtration/Distillation/Chromatography)
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Molecules
A molecule has any elements- even the same elements-chemically combined together
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Physical Separation techniques
They are used to separate mixtures, cannot be used to separate elements in a compound
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What is filtration?
used to separate an insoluble solid from a liquid,
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Filtration process:
Pour mixture into filter paper, liquid passes through the tiny pores in the filter paper- solid material can't pass through the filter paper so it is trapped. so our liquid is separated from our solid
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What is crystallisation?
Crystallisation is used to separate a soluble solid from a liquid
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Crystallisation process:
If we leave the solution for a couple of days, then the liquid will evaporate. This will leave behind crystals of solid sodium chloride. To make crystallization happen faster, we can gently heat the solution to evaporate the liquid
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We have to be careful that the heating does not affect the chemical trying to crystallize-e.g certain chemicals will break down if we heat them. Sometimes better to just leave the solution
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## Other cards in this set

### Card 2

#### Front

They contain 2 or more different elements chemically combined in a fixed proportion- They usually have totally different elements to the properties they're made from- To separate back into its elements, we need to use chemical reactions to do so

Compounds

### Card 3

#### Front

They have different elements or compounds not chemically combined together - To separate them, we need to use physical separation techniques (Crystallisation/Filtration/Distillation/Chromatography)

### Card 4

#### Front

A molecule has any elements- even the same elements-chemically combined together

### Card 5

#### Front

They are used to separate mixtures, cannot be used to separate elements in a compound