C4, C5, C6 OCR Complete GCSE Revision Notes

Everything you need to know for C4, C5 and C6 for the exam on 28th June.

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  • Created on: 06-06-11 22:37
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Chemistry Revision ­ C4, C5, C6
C4 ­ Chemical Patterns
Atoms:
The nucleus is made of protons (positive) and neutron (negative).
o It makes up the whole mass displayed on the periodic table.
o But size wise it's a small part of the atom.
The electrons move around the nucleus.
o They are negative.
o Arranged in shells.
o Virtually no mass.
o The shells explain the whole of chemistry.
Number of protons always equals the number of electrons.
o So atoms normally have no overall charge.
o Neutrons aren't fixed, but normally similar to the number of protons.
Each element has a different number of protons.
o Elements have different properties because of difference atomic structures.
Balancing Equations:
Atoms aren't lost or made in chemical reactions.
You have to make sure you have the same number of atoms on both sides of the arrow.
State symbols
o (s) ­ Solid
o (l) ­ Liquid
o (g) ­ Gas
o (aq) ­ Dissolved in water
Line Spectrums:
Some elements emit distinctive colours when heated.
o Lithium (Li) produces a red flame.
o Sodium (Na) produces a yellow/orange flame
o Potassium (K) produces a lilac flame.
Each element gives a characteristic line spectrum.
o So spectrums can be used to identify elements.
o New elements like caesium and rubidium have been discovered because of their line
spectrums.
The Periodic Table:
The periodic table puts elements with similar properties together.
o It's in increasing proton order.
o Metals found to the left, non metals to the right.
o Elements with similar properties are in columns.
o Groups go across the top, ignore the transition metals.
o So group 1 (Li, Na, K, Rb, Cs, Fr) react in a similar way. The reactivity increases as you
go down the group.

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But in group 7 it decreases as you go down the group.
o Each new period (row) represents another full shell of electrons.
Electron Shells:
Electron shell rules:
o Electrons occupy shells (sometimes called energy levels).
o Lowest energy levels fill first.
o 1st shell: 2 2nd shell: 8 3rd shell: 8
o Atoms like having a full outer shell. It makes them unreactive.
o Electron arrangement determines chemical properties.
Electrons fill up as you go across the periodic table.…read more

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Chlorine merks bacteria, like other halogens, so it's used in swimming pools.
o As you go down the halogens, they get less reactive, higher melting point and higher
boiling point.
Non-metals with coloured vapours.
o Fluorine is a very reactive, poisonous yellow gas at room temperature.
o Chlorine is a fairly reactive, poisonous dense green gas at room temperature.
o Bromine is a dense red-brown volatile liquid at room temp and forms a red brown
gas.…read more

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Oxidising
o Highly flammable
o Toxic
o Harmful
o Irritant
o Corrosive
Alkali metals are really reactive and combust spontaneously.
o If they meet water vapour the can react ;/
o Never touch with bare hands.
o If you use them, keep everything dry.
Halogen are harmful, chlorine and iodine are very toxic.
o Fluorine is the most reactive halogen; it's too dangerous for use in the lab.
o Liquid bromine is corrosive, so don't touch with skin.…read more

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Covalent Bonding:
Covalent bonds share electrons.
o This way both atoms feel they have a full outer shell.
o The atoms bond due to electrostatic attraction between the positive nuclei and the
negative electrons shared between them.
Hydrogen, H
o Hydrogen need 1 more electron, so 2 H's share their outer electron and they have a
full outer shell.
Carbon Dioxide, CO
o Carbon needs 4 more, oxygen needs 2.
o So two double covalent bonds are formed.…read more

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Metals from Minerals:
Ores contain enough metal to make extraction worthwhile.
o Rocks are made or minerals, which are solid elements and compounds.
o Metal ores are rocks that contain various amounts of minerals from which metals can
be extracted.
More reactive elements are hard to get.
o Most elements are in compound form, so they need to be extracted from their ores
in a chemical reaction.
o More reactive metals, like sodium are harder to extract, so they took longer to
discover.…read more

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Ores are finite resources.
o They'll run out.
o Good because useful production, money, jobs so transport and health services can
be improved.
o But it uses loads on energy, scars in landscape, destroys habitats also noise, dust and
pollution are caused by the traffic increase.
o Deep mines can be dangerous for a long time after it's been abandoned.
Recycling is important.
o Mining and extracting takes energy.
o Recycling uses a small proportion of the energy used to extract a new material.…read more

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An acid is a substance with pH below 7, acidic compounds from aqueous hydrogen
ions H.
o An alkali has a pH more than 7 and it makes aqueous hydroxide ions OH in water.
o When they react they make salt and water. The products are neutral, so its
neutralisation.
o Acid + Alkali Salt + Water
Acids Reacting with Metals:
Acid + Metal Salt + Hydrogen.
o More reactive metals react faster.
o Copper doesn't react at all because it's less reactive that hydrogen.…read more

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Correct size and strength of apparatus and temperature of reaction and
whether you need to use a catalyst.
o Isolating the product:
After the reaction you might need to separate a mixture, evaporation,
filtration, drying ect.
o Purification:
As you isolate the product you're helping to purify it, crystallisation can help
with the process.
o Measuring yield and purity:
Overall success of process. It compares what you should get, with what you
get in practise.
Purity needs to be measured.…read more

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Titrations:
Titrations are carried out using a burette.
o A know volume of alkali in a flask with a few drops of indicator.
o Then add acid drop by drop until it changes colour.
o It's then neutralised.
Solids are weighed out into a titration flask.
o The add a solvent to make a liquid, but the amount depends on the solvent and the
amount of it.
Purity:
Some products need to be very pure.…read more

Comments

Salsabiil Therese

This is not the new syllabus

Sasha Dean

This is brilliant.

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