Additional chemistry help

Breif notes on all of AQA chemistry GCSE additional science

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  • Created by: beno007
  • Created on: 12-09-13 19:26
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Chemistry revision
The Atom
Atoms are made up of 3 sub-atomic particles, which are protons (mass =1, charge=+1, part of the
nucleus) Neutrons (mass=1, charge= neutral, part of the nucleus) and electrons (mass=0, charge =-1,
always in shells) together there are the same number of protons as electrons, meaning that the
overall charge is always neutral. The first shell on the inside holds 2 electrons, and the others can hold
up to 8, which are shown in groups of the periodic table (group 1 has 1 electron in its outer shell etc)
and in columns it shows how many shells there are (Column 4 has 4 shells etc. Compounds are 2 or
more elements chemically bonded, for example carbon dioxide, these are incredibly hard to
separate as they take a lot of energy. Atoms are shown on the periodic table as having a mass
number (protons + neutrons) and the Atomic number (number of protons or electrons)
Isotopes are different types of the same element, and they have the same number of protons but
have different numbers of neutrons, which means that there is a different mass number, but the
same atomic number, so although they are the same chemically, they behave differently. There are
different isotopes of carbon, and hydrogen.
Ionic Bonding
Ionic bonding is the bonding between a non metal and a metal (or alternatively 2 metals) and this is
done by transferring electrons so that all of the outer shells are full. This means though that there are
charges, for example in sodium chloride, the formulas are [2, 8] + and [2, 8, 8] - this means that the
sodium has given up one electron, as it has one in its outer shell, so has gained an overall positive
charge, and also the chlorine has gained that electron, and become an overall negative charge, but
has a full outer shell. Also it is now called chloride instead of chlorine. The charges will then create
electrostatic forces between each other, and then will attract to form a giant lattice, which has quite
a high boiling and melting point as it takes hundreds of degrees of energy to break, and because it
forms blocks that is why there grains of salt, as these are the giant lattices. When molten or dissolved
in a solution, they conduct electricity, because the Ions are now free to move and pass on the energy.
Also the dissolve in water as the water separates them and pulls the charges apart. If you have a
group 2 atom and a group 7 atom you want to combined, the thing to do would be to use one group
2 atom, and 2 group 7, then they would be full outer shells, and would work in the same way. Finally
Group 4 atoms cannot be made into ions, as they don't have enough energy to pass on electrons,
they are formed though covalent bonding.

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Covalent bonding
Covalent bonding is where atoms get a
full outer shell by sharing electrons, and
this is done by two non metals getting
their electrons from there outer shell and
joining with other non metals, and there
can be one pair shared, or multiple
electrons to create double or triple bonds (but not quadruple bonds as there wouldn't be enough
energy to form it, and there can also be multiple atoms, for example in all the alkanes and alkenes.…read more

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Polymers are plastics, and they have very useful properties in industry, and there are 2 main types of
polymers, thermosetting and thermosoftning. Thermosetting polymers hydrocarbon chains have the
structure of rows and interlocked sections, meaning that they can't slide over each other, they also
have strong intermolecular forces holding the chains together making them have a high melting point
and a good hard structure; however they may be more expensive.…read more

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Fe2O3, an experiment has to be done to get an empirical formula.
Masses in reactions= this is where you're given 2 bits of information, and for example if X product
was produced, how much of Y reactant was used, or if X reactant was used, how much of Y product
was produced.…read more

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The Rate of reaction is how quickly a substance fully reacts, and it can be affected by 4 things,
concentration (or pressure), temperature, catalyst and surface area, and I will explain each one of
these areas. The conversion to work out rate of reaction is.…read more

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The next way is to measure the ROR is the change in mass, and what you do is you get 2 reactants,
such as HCL and magnesium strips, and what you do is you put the HCL in a conical flask, and measure
on a scale. Then what you would do is add the magnesium and measure how long it took for the
scales to stop. The quicker it takes the higher the ROR.…read more

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L= liquid
G= gas
Aq= aqueous, dissolved in water
Acids and metals
The main equation for reacting metals with acids is
Acid + Metal = salt + hydrogen
However the reaction only takes place if the metal is more reactive than hydrogen, for example if
you where to try and react HCL with sodium, this would work as sodium's more reactive, however if
you tried to react it with copper, no reaction would take place as copper is less reactive than
hydrogen.…read more

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Ammonium nitrate is mainly used for fertiliser, as it has double nitrogen and therefore gives the plans
more nitrogen, which is used for protein.
Making salts
There are 3 main ways to make salts; the first way to make a soluble salt is through mixing an acid
with a metal or an insoluble base, such as hydrochloric acid and copper oxide.…read more

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Reduction: gain of electrons at the negative electrode (Remember OILRIG (Oxidation is loss,
Reduction is gain)
To show how electrolysis works I will use the example of copper bromide (charges of Cu+2 Br-) these
solutions are molten, so the Ions are free and there are no other ions to displace the copper or
bromide ions. What happens is the negative electrode has a stronger force than the bromide ions, so
will pull the copper towards it.…read more

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Electroplating is when you deposit one metal on another for 2 main reasons, firstly it may be for
decoration, as a bronze cup with electroplated silver is cheaper than a pure silver cup, but they look
the same, also there is the fact of conducting heat and electricity, as electroplating a metal with
copper is cheaper than using pure copper, but just as effective.…read more


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