# C4

Science Section C4 OCR Gateway

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## pH scale

Calculated from the concentration of Hydrogen ions in solution.

Universal indicator is only a way of more accurately determining the strength of the acid or alkali.

Acid- pH 0-6, turns red pH 1-3, turns orange pH 4-5, turns yellow pH6 (with universal indicator), turns red with litmus.

Alkali- pH 8-14, turns dark green or blue/green when pH 8-9, turns blue (getting darker) pH 10-14 (with universal indicator), turns blue wit litmus.

Neutral- pH 7, turns green (with universal indicator).

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## General

Allotrope- where the same substance can come in different forms i.e. both graphite found in pencils and diamond are made out of carbon, therefore carbon is an allotrope.

Buckminsterfullerene- also known as buckyballs are made out of hexagonal and pentagonal shaped structures to create a dome shape, these can be stretched to create nanotubes.

Base- a substance that releases hydroxide ions in a solution.

Chemical extraction from plants- Crush plant, add a solvent, then boil it to evaporate the liquid, leaving the chemical for the drug behind.

Atomic Mass- For instance if you had Calcium Hydroxide Ca(OH)2 (<- small 2) and it gave you that Ca=40, O=16, H=1 you would add 40 to 32 (there are two Oxygen so you times 16 by two) this would equal 72, then you add 2 onto that (two Hydrogen so times 1 by two). The answer would be 74.

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Calculate mass of one made from a mass of another- For instance: Calculate the mass of Calcium Chloride, CaCl2 (<- small 2) that can be made from 50g of Calcium Carbonate, CaCO3 (<- small 3). Ca=40, C=12, O=16, H=1,Cl=35.5. Work out amount of Calcium Carbonate: 40 + 12 + 48 (which is 3 x 16) = 100g of Calcium Carbonate. Work out Calcium Chloride: 40 + 70 (which is 35.5 x 2) = 110g. Half each to make 50g of Calcium Carbonate = 55g of Calcium Chloride.

Filtration- Separation of liquids from undissolved particles. Makes it purer.

Sedimentation- Allows small, solid particles to settle.

Chlorination- Kills off bacteria. Makes water purer.

Why diamonds don't conduct electricity- Electrons have no space to move, so there are no free electrons that could bump into eachother causing a reaction.

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