Chemistry GCSE C2 Revision Unit 2

Complete study notes for AQA chemistry C2 (Unit 2) revision - got me an A* so it should help you!! :)

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Chemistry Revision Unit 2:
Structure & bonding
Nucleus ­ made up of positive protons and no charge neutrons. Is surrounded by negative
electrons ­ same number of protons and electrons P=E
Same number of protons as atomic number
Electrons are arranged in energy shells ­ either represented as dot & cross diagrams or
numbers
Isotope: Atoms of the same element that has different numbers of neutrons
Ions are formed when atoms lose or gain electrons.
Atoms that lose electrons become positively charged ions. Atoms that gain electrons become
negatively charged ions.
Giant covalent ­ intermolecular forces are weak in comparison with covalent bonds, so when
melting, it's the intermolecular forces that will break.
­ In Diamond, each carbon atom forms four covalent bonds with other carbon atoms in
the lattice so it's very strong.
­ In Graphite, each carbon atom bonds to three others, forming layers, which can slide
over each other. One electron from each carbon atom is delocalised, enabling it to
conduct heat and electricity
Giant Atoms closely Metals e.g. Na, Fe, Atoms are held in a close High melting Conducts Hard but
Metallic packed Cu and other alloys packed lattice by the and boiling electricity malleable
electrostatic attraction of points
positive ions and free
electrons
Giant Large A few non-metals Lots of atoms are joined by High melting Do not Hard but
Covalent molecules. and non-metal strong covalent bonds to and boiling conduct brittle
(macrom Thousands or compounds e.g. H, make a 3D lattice or a very points, strong electricity
olecules) billions of Cl2, O2, CH4, HCl, NH3, long thin molecule. Formed bonds (except
atoms H2O by sharing electrons, so both Graphite)
atoms have a full outer shell.
Simple Small Most non-metals Atoms held in small Low melting Do not Soft when
Molecula molecules and non-metal molecules by strong covalent and boiling conduct solid
r containing a compounds bonds. The bonds between points, v. strong electricity
few atoms the molecules are weak. covalent bonds
Electrons are shared. but v. weak
between
molecules
Giant Ions Metal or non-metal Positive and negative ions High melting Conducts Hard but
Ionic compounds e.g. Na, are held by the strong and boiling electricity brittle
Cl2 electrostatic forces of points when
attraction between melted or
oppositely charged ions dissolved
acting in different directions in water
Giant Covalent structures
Diamond:

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Very rigid ­ hard, strong
Graphite:
3 covalent bonds per atom
Layers that are free to slide over each other ­ slippery, soft
Weak intermolecular forces between layers
Conducts heat & electricity because of free electrons
Silicon Dioxide:
(Silica) ­ what sand is made of
A grain of sand is one giant structure of oxygen and silicon
How structure influences the properties and uses of substances
Pure metal: Layers that can slide over each other and so can be bent and shaped.…read more

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Metal alloy ­ ½ nickel, ½ titanium
Bend & twist it ­ if you heat it, it will return to a remembered shape
Used for glasses frames, dental braces
Nanoparticles ­
Include fullerenes: molecules of carbon, arranged in hexagonal rings, hollow balls
Can be used for: stronger & lighter building materials, sensors, catalysts, deodorant &
sun tan cream, tiny electric circuits
Atomic structure, analysis and quantitative chemistry
Relative formula mass: Ar or Mr ­ one mole of that substance
Number of moles = Mass in…read more

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Place food sample in a cup with a few drops of solvent to extract the colour
2. Put sports of coloured solution on a pencil baseline on filter paper
3. Roll up the sheet and put it in a beaker with some solvent
4. The solvent seeps up the paper, taking dyes with it & spots form in different places.…read more

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Reusable Not used up in Catalysts can They stop working
reactions so you can become poisoned so you have to keep
use them over and by impurities your reaction very
over ­ reduces clean.
costs
Rate of reaction = Amount of reactant used or amount of product formed/ time741
How to measure rate of reaction:
1.Precipitation: the product is a precipitate which clouds the solution ­ result is
subjective, different people may not agree over the exact point when the mark
disappears
2.…read more

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H+ + OH- H2O
Titration: acid + soluble base
Filtration: acid + insoluble base
Metal & filter: acid + metal
Precipitation: soluble salt + soluble salt insoluble salt
Soluble Insoluble
Na, K & NH4OH (ammonium) salts
Na, K & NH4OH carbonates Most carbonates
Na, K & NH4OH hydroxides Most hydroxides
All nitrates
Most sulphates Pb (lead) & Ba (barium) sulphates
Most chlorides, bromides & iodides Pb & Ag (silver): bromide, iodide & chloride
Making soluble salts using a metal or an insoluble base:
1) Add…read more

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At the Cathode, if metals ions and H+ ions are present, the metal ions will stay in the solution
if it's more reactive than the Hydrogen.
THE MORE REACTIVE IONS WILL STAY IN THE SOLUTION ­ the more reactive an element, the
keener it is to stay as ions.
At the Anode, if OH- ions and halide ions are present then molecules of chlorine, bromine or
Iodine will be formed. If no halide is present, Oxygen will be formed.…read more

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Magnesium chloride Hydrogen Chlorine
Silver nitrate Silver Oxygen
Sulphuric acid Hydrogen Oxygen
Hydrochloric acid Hydrogen Oxygen…read more

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