triple science c3 chemistry revision notes aqa gcse

made these notes for my aqa chemistry gcse

doesnt include everything but was a great help

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  • Created on: 26-05-10 17:14
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Periodic table
he put them in order of atomic weights and noticed that every 8th element had similar
properties so he put them into groups
problems: he didn't leave gaps for unknown elements and he mixed metal and non-metals
together, also some didn't fit pattern.
he put them in atomic weights also and then left gaps so that only elements in same group
would have similar properties.
This meant that unknown elements properties could be predicted.
problems: he also mixed metals and non-metals
Modern period table
Neutrons, electrons and protons discovered.
Arranged in atomic number and in terms of electronic structure, elements in same group
have the same number of electrons in outer shell
reactivity: the higher the energy level, the more likely electron is lost, and less likely to gain.
Alkali metals (group one)
They have a low density
React with water to form OH- an alkaline solution
React with non-metals to form 1+ ions (they lose outer shell electron)
They produce hydrogen gas with water
More reactive/lower melting an boiling point as you go down
For example lithium, sodium, potassium.
Halogens (group seven)
Both ionic and covalent bonding, form 1- ions with metals (gain outer shell electron) and
molecular compounds with non-metals
Less reactive/lower melting and boiling point as you go down
Have coloured vapours
For example chlorine, bromine, iodine
Transition metals (between groups 2 and 3)
Not very reactive with things such as water and oxygen
Hard and dense
High melting points
Form coloured compounds
Useful as catalysts
Third energy level can hold up to 18 electrons once 4th holds 2 electrons

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Many transition elements have ions with different charges
Acids and alkali's
Said that when mixed with water all acids ionise and produce H+ and alkali's form OH-
opposition: there were exceptions for example ammonia gas, subatomic particles weren't
discovered so no charged ions, he was only a student and people didn't think molecules split.…read more

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Making carbonated water fizzy drinks have a lot of carbonated water which is carbon dioxide
dissolved in water under high pressure. When pressure released CO2 bubbles out. Oxygen in
water Dissolved oxygen is essential for aquatic life. If the temperature of the water
increases, the amount of oxygen that is dissolved decreases. Pollution can lower this also.
Chlorine in water used to sterolise water and kill bacteria
Hard water = water that contains calcium and magnesium ions, usually when water comes
into contact with rocks.…read more

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Energy is needed to break bonds
Energy is released when forming bonds
Exothermic reaction
Negative energy change
Energy released from forming bonds is
more than energy needed to break
Positive energy change
The energy needed to break
bonds is bigger than energy released
from making.…read more


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