AQA Chemistry notes

Summary of core, additional and further material for AQA GCSE Chemistry

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  • Created on: 12-04-11 13:20
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Group 1 ­ Alkaline Earth Metals
Reactions of alkali metals with water
When a group 1 metal reacts with water, a metal hydroxide and hydrogen are
The metal hydroxide then dissolves in water to form an alkaline solution.
potassium + water = potassium hydroxide + hydrogen
2K(s) 2H2O(l) 2KOH(aq) H2 (g)
Reactions of alkali metals with non-metals
When group 1 metals react with non-metals to form an ionic compound, the
metal loses an electron to form a metal ion with a charge of +1.
The products are white solids which dissolve in water to form colourless
Sodium + chlorine = sodium chloride
2Na(s) Cl2 (s) NaCl(aq)
Explanation for the reactivity of Group 1 Elements
They become more reactive as the further down the periods you go, the
further away the outer electrons are from the influence of the nucleus, so an
electron is more easily lost.
The more shells an atom has:
The harder it is for electrons to be gained
The easier it is for electrons to be lost

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Group 7 ­ Halogens
Reactivity decreases down the group
Form diatomic molecules (i.e. F2, Cl2, Br2 etc)
Brittle and crumbly when solid
Poor conductors of heat and electricity
Reactions of Halogens with metals
Halogens react with metals to produce ionic salts.
The halogen gains an electron (forming a halide with charge of -1) from the
metal atom (forming a metal ion with charge +1).
E.g.…read more

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The easier it is for electrons to be lost
The Transition Metals
Found between groups 2 and 3, these metallic elements include iron (Fe),
copper (Cu), platinum (Pt), mercury (Hg), chromium (Cr) and zinc (Zn).
These metals...
Are hard and mechanically strong (except mercury ­liquid)
Have higher densities and melting points (except mercury)
Much less reactive than group 1 metals (do not react vigorously with
oxygen and water)
Form coloured pigments which can be used in pottery pigments (e.g.…read more

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Acids and Alkalis
Some compounds react with water to produce acidic or alkaline aqueous
solutions. On their own, these compounds sometimes do not exhibit any acid or
alkaline characteristics. For these compounds, water must be present for the
substance to act as an acid or base.
All acids dissociate in water (aqueous solution) to form hydrogen ions
An H+ ion is simply a proton.
In water this is hydrated (i.e.…read more

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Sodium hydroxide sodium ions + hydroxide ions
NaOH(aq) Na+(aq) + OH-(aq)
An acid can be defined as a proton donor.
An alkali (or base) can be defined as a proton acceptor.
An acid cannot donate a proton unless there is an appropriate base to
accept it.
Strength of acids and alkalis
Acids and alkalis are classified by the extent of their ionisation in water
(i.e. whether or not the compound dissociates completely into ions).…read more

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Purification of water
Passed through a filter bed to remove solids
Chlorine gas added to kill microorganisms
Passed through a filter of carbon, silver and ion exchange resins to
reduce salt levels.
(Could also be distilled, but this is expensive)
Solubility of compounds
Most ionic compounds are soluble (i.e. copper sulphate, sodium
Most covalent compounds are insoluble (i.e. silicon dioxide), however
some molecular substances are soluble.
Solubility of gases increases when pressure is increased, but increases
when temperature is decreased.…read more

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Joules and Calories
Energy is measured in Joules (J)
It takes 4.2 J of energy to heat up 1g of water by 1°C.
4.2J = a calorie.
Calorimetry is the process of burning substances to measure their
energy content based on the water temperature change they cause.…read more

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Sulfate ions:
Add barium chloride solution and dilute hydrochloric acid.
White barium sulphate will precipitate out.
Barium ion + Sulphate ion = Barium sulphate
2+ 2-
Ba (aq) SO4 (aq) BaSO4(s)
Nitrate ions:
Add aluminium powder and sodium hydroxide solution.
Nitrate ions are reduced to form ammonia (NH3), which turns damp
litmus paper blue.
Chloride, Bromide and Iodide ions (HALIDES)
Add silver nitrate solution and nitric acid.…read more

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Chemical Reactions
Ionic bonds tend to form between groups 2 and 6, and 1
and 7, between metals and non-metals.
Ionic compounds stay together due to strong electrostatic force
between the oppositely charged ions. This force acts equally in all
directions between ions, which is why the ions are held together
so strongly in giant ionic structures. As a result, ionic compounds
have high melting and boiling points (a lot of energy is needed to
overcome the forces of attraction).…read more

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The Haber Process
Nitrogen from air (liquid form is fractionally distilled)
Hydrogen from natural gas
Passed over an iron catalyst at 450C and 200 atmospheres.
Nitrogen + Hydrogen
N2 (g) + 3 H2 (g)
2 NH3 (g)
Exothermic and Endothermic Reactions
In exothermic reactions, energy is given out. If the
temperature is increased, the yield decreases and vice
E.g. combustion, respiration
In endothermic reactions, energy is taken in from the
surroundings. Is the temperature is increased, the yield
E.g.…read more


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