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Unit 2

Mixtures and pure substances

• A mixture is a substance that is not chemically joined together
• A pure substance has a sharp boiling point
• A pure substance has no other substance mixed with it
• Mixtures are easier to separate
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Compounds

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• Caption: compound particles
• Compound particles are chemically joined together
• A compound has different properties to its elements
• To split a compound you need to do a chemical reaction

Solutions

• You add sugar to water, then stir it. The sugar is the solute after it dissolves in the water, the solvent
• The mass of one litre of water is 1000g
• The mass of a solution made by dissolving sugar+ water's mass is 20g, so 1020g

Solubility

• A saturated solution is a solution that a solute cannot dissolve in the solvent anymore.
• A saturated solution contains the maximum mass of a substance that will dissolve
• Every substance has its own solubility in 100g of water at 20*C
• Some substances are insoluble like chalk and sand.
• The higher the temperature the greater mass of the substance that dissolves.

Filtration

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• One way of filtrating is through filter paper, filter paper has tiny holes and water goes through it because the particles are smaller than the paper ones The tiny holes are called the filtrate The residue is the bit that cannot get past theses tiny holes

Distillation

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• Distillation is the process that uses evaporation and condensation to obtain the solvent from the solution Distillation only works with two substances with different boiling points
• This is how it works:
• Water in the solution boils
• The steam leaves the solution
• The steam travels through the condenser, and cools down
• The steam condenses into a liquid
• Liquid water drips into the beaker

Chromatography

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• Chromatography is used to find out which dyes are used in ink.
• How it works is that the water moves up the paper As it passes the spot of ink, the dye dissolves and the ink moves upwards. Some dyes move faster than others, so they separate This makes a chromatogram