WJEC chemistry 2 higher

WJEC Chemistry 2 revision notes higher tier. sorry for any spelling mistakes (:

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Chemistry Mocks Jan 11
Ionic and covalent bonding
Ionic = +'s and ­`s bonded together,
Simple molecular is covalent
Giant covalent- not all joined together
Giant metallic- only +'s and square shaped solid structure.
A radical is a group of atoms that exist in several compounds but does not exist on its own
Polyatomic means containing more than once atom positive ions- cations
Negative ions- anions
Ionic bonding (electrovalent bonding)
The electrons move from one atom to another
Comes about when atoms of some elements obtain full outer shells by losing or gaining electrons, when they react
with other elements
Metals and no metals
Metals have a tendency to lose electrons
An electrovalent or ionic bond is one due to the transfer of one or more electron from one atom to another.
The transfer of electrons from one atom to another results in the formation of positive and negative ions.
The transfer of electrons form one atom to another results ion the formation of positive an negative ions
Electrostatic attractions between ions of positive and negative charged produce crystalline solids.
Compounds formed by transfer of electrons from an atom to another are called ionic compounds.
Particles which have lost electrons are positively charged, particles which have gained electrons are negatively
Soluble in water
High melting point
Composed of giant ionic structures/lattice structures
Usually crystalline solids at room temperature
Conducts electricity when molten or dissolved in water
Have string electrostatic forces of attraction (takes a lot of heat to separate them)]
Made up of ions
Covalent bonding
A covalent bond is formed by their sharing of a pair of electrons between two atoms, each atoms contributes one
electron to the bond,
When non metals join together b sharing electrons the bonding is covalent and molecules are formed
Covalent bonds are not restricted to one element; compounds formed from non metals are also covalent
Insoluble in water
Low melting points
Composed of simple molecules
Usually as, volatile liquid or waxy solid
Can be easily split
Weak electrostatic forces of attraction (low melting point- doesn't take much heat to separate the atoms_
Giant molecular covalent have high boiling and melting points but still don't conduct
Covalent compounds exist as neutral molecules
Giant covalent structures
Some covalent structure exists as giant structure that has high melting points because all the atoms are held together
by strong covalent bonds.
Graphite and diamond are both forms of carbon, but they are allotropes (different physical forms of the same
Each carbon atom is joined by a strong covalent bond to 4 other carbon atoms making a covalent lattice, this is called
giant covalent.
The carbon atoms in layers of graphite are held together by three covalent bonds Carbon has four outer electrons.

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The fourth electron which is not used in bonding becomes part of a sea of free electrons between layers of carbon
Therefore, GRAPHITE CAN CONDUCT ELECTRICITY AND IS DUCTILE (the layers can slide over one another)
The carbon atoms are held together by string electrostatic forces of attraction and therefore have a high boiling
In diamond, all four electrons are involved in covalent bonding therefore it cannot conduct electricity.
Grey black shiny solid
Very soft. Used as lubricant.…read more

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Some made into nitric acid to neutralise the ammonia to nitrates. Some neutralised using sulphuric acid to make
ammonium sulphate
Ammonia solution + sulphuric acid -> ammonium sulphate
2NH3 + H2SO4 -> (NH4)2 SO4
Ammonia solution + nitric acid -> ammonium nitrate
NH3 + HNO3 -> NH4NO3
Fertiliser can encourage the growth of water plants, algae cover surface = eutrophication. Blocks light form the water
plant below surface . they die. bacteria feed on dead plants and use up oxygen. Not enough oxygen for fish.…read more

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During polymerisation, many small molecules called MONOERS join together to make very large polymers.
The double bonds break so the monomers can join on to other monomers
More than pone Ethene = polyethene (chain of Ethene)
Remember the brackets! When showing polymerisation
Addition polymerisation ­ e.g.…read more

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Smart materials
Smart materials is a material whose properties can change depending on their surroundings e.g. light,
Shape memory alloy ­ nickel and titanium ­ nitinol/NiTi ­ regains original shape when heated. Used in
spectacle frames, coffee thermostats.
Shape memory polymer ­ plastic which regain its shape when heated- biodegradable surgical sutures, self
repairing car bodies which recover their shape on heating e.g. bumpers.
Themrochromic paint- changes colour when heated- kettles, testing temperature of children's food, on
radiators, electric ovens.…read more

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The Blast Furnace
Iron is extracted for its ore, haematite, in a blast furnace.…read more

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So, we dissolve the aluminium oxide in cryolite. This brings the melting temp down to 900 C so the
aluminium is cheaper to heat up, so cheaper to produce
The electrolyte has an electrical current which causes the ions to move to the opposite poles.
The oxygen ( is attracted to the anode (positive electrode). Here the 202- loses 4 electrons to Form O2.
oxide ion loses electrons forming oxygen (oxidised)
However, some of the Oxygen reacts with the carbon anode to from co2.…read more

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Coastal locations provide good transport links ­ most of the worlds bauxite arrives by ship from Australia or
Good road links are needed to transport the aluminium throughout the country
Location must be chosen to have as little impact on existing towns and villages and are therefore sited in rural
Most aluminium processing industries are connected to a HEP plant or a Tidal/wave power plant.…read more

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But, in an alloy, a different sized atom disrupts the regular pattern so the ions cant slide past ach other as
easily in an alloy.…read more

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Sodium carbonate (washing soda) can also soften the water
Calcium hydrogen carbonate calcium carbonate + carbon dioxide + water
Permanent hard water
Harness cannot be removed by boiling. The solution contains calcium/magnesium sulphates. Can e softened
by adding sodium carbonate (washing soda0, or by using a ion exchange column e.g. Brita water filter.
Sodium carbonate precipitates the calcium ions as calcium carbonate (displacement reaction). The
precipitates can be trapped and filtered out before they enter the house.…read more


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