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Science Revision (R1+R2), Mixtures ( R2 ) - Coggle Diagram
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Mixtures ( R2 )
Filtration
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Filtration usually involves a circle of filter paper folded to make a cone and placed into a filter funnel.
The filtrate is the liquid which passes through the filter paper and the residue is the solid left on the filter paper.
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Crystallisation
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When a solution is heated, the solvent evaporates and crystals of the solute are left behind.
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Solubility
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Insoluble
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Examples
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Polystyrene is insoluble in water, but soluble in propanone.
Solubility of gas
Solubility measures how much solute can dissolve in a volume of solvent at a specific temperature. For example, sugar has a higher solubility in water than salt. Therefore, more sugar than salt can dissolve in a volume of water at a specific temperature. The solubility of a gas usually decreases when the temperature increases.
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For example, fizzy drinks have lots of carbon dioxide dissolved in them when they are cold. Fizzy drinks warm up quickly in your mouth and release bubbles of carbon dioxide gas.
Chromatography
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These are often coloured substances such as food colourings, inks, dyes or plant pigments.
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On a chromatogram, one spot means that the substance is pure. An impure substance produces two or more spots.
Impurities
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A substance made from more than one element or one compound is impure, meaning it is a mixture.
For example, it is challenging to make pure water. This mineral water contains small amounts of impurities such as sodium and nitrate.
Dissolving
Solution
A solution is made when a substance dissolves into a liquid. The liquid is called the solvent. The substance that has been dissolved is called the solute. A solution can also be called a mixture. When a solid dissolves, it breaks down into smaller particles that spread out through the solvent.
For example, salt dissolves when it is stirred into water. In sea water, the water is the solvent and the salt is the solute.
Solute
A substance which dissolves in a solvent as the solvent breaks up the solute which therefore dissolves it.
For example, Salt, sugar and instant coffee.
Solvent
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For example, water, milk and ethanol.
Pure substances
In chemistry, a pure substance is a single substance made of only one type of element or one type of cmpound.
For example, salt is a pure substance made only of sodium chloride.
Distillation
Distillation is a separation technique used to separate a solvent from a mixture. For example, water can be separated from salt solution by distillation.
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Fixed Boiling Points
A pure substance has a fixed melting point and boiling point, which means they will always melt or boil at exactly the same temperature. For example, the melting point of pure water is 0 °C and its boiling point is 100 °C.
Coloured solutions
When a coloured solid dissolves, it makes a coloured solution, for example, copper sulphate dissolves to makes a blue solution.
Colourless solutions
When a white solid dissolves, it makes a colourless solution, for example, salt or sugar in water.
Saturation
There is a limit to the mass of solute that will dissolve in a particular volume of the solvent. When no more solute dissolves, the solution is saturated.
Evaporation
Evaporation describes the process of a liquid turning into a gas. Evaporation is a slower process than boiling because it occurs at temperatures below the boiling point of the liquid.
Alloys
An alloy is a mixture of two or more elements, where at least one element is a metal. Many alloys are mixtures of two or more metals.
Water
Potable water
Water that is safe for humans to drink is called potable water. Potable water is not pure water because it almost always contains dissolved impurities.
For water to be potable, it must have sufficiently low levels of dissolved salts and microbes. This is because:
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In the UK
Rain provides water with low levels of dissolved substances. In the UK, rain provides sufficient water to meet the needs of the population, although sometimes it needs to be stored and transported. Sometimes during the summer months in some areas of the UK, water reserves run low and hosepipe bans are used to encourage people to conserve water. Most potable water in the UK is produced from naturally occurring fresh water by:
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The methods used for sterilisation include chlorine, ozone and ultraviolet light.
