Full Chemistry IGCSE Revision Notes

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R ATES OF REACTION
The rate of a chemical reaction is determined by HOW FAST a reaction occurs (this is the rate of
reaction):
T YPES OF REACTION :
VERY FAST ­ an explosion e.g. dynamite
FAST ­ group 1 metals + water
SLOW ­ zinc + acid
VERY SLOW ­ rusting
F ACTORS AFFECTING RATE :
TEMPERATURE: each atom will then have a higher kinetic energy, which increases the number of collisions
(as the particles are moving faster and crazier), and bigger and faster collisions
CONCENTRATION: a higher concentration means more atoms and molecules ­ which will then increase the
probability of collision, which increases the efficiency of a reaction
SURFACE AREA: the larger the surface area, the more reactions can take place on that certain substance,
which increases the efficiency of the reaction
CATALYST: lowers the ACTIVATION ENERGY allowing the substance to react at a lower temperature, which
decreases the amount of energy needed, allowing it to react faster
PRESSURE: the increase in pressure for gases is the same as increasing concentration for liquids; it means
that there are more of that certain atom, which therefore increases the likelihood of collision
C ATALYSTS
They are mainly used in industrial processes, as they manage to speed up the rate of reaction. They do this
by lowering the activation energy, which means that they can use less energy to complete the reaction. This
reduces costs, and is therefore very useful to the companies.
E NZYMES
Enzymes are complex molecules which act as a biological catalyst in leaving systems, such as humans
(amylase, protease etc.). They are very sensitive to temperature and pH.

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Catalysts Enzymes
Manganese Dioxide ­ Making O2 from hydrogen
Amylase
peroxide
Platinum, Rhodium & Palladium ­ used in car
Protease
exhaust pipes
Nickel - making margarine Lipase
ATOMIC S TRUCTURE &
C HEMICAL B ONDING
Nucleus has protons and
neutrons
Electrons found in a shell
around the nucleus
Protons
relative charge: +1
relative mass: 1
Electrons:
relative charge: -1
1
relative mass:
1836
Neutrons
relative charge: 0
relative mass: 1…read more

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P OTASSIUM ' S E LECTRONIC S TRUCTURE
2,8,8,1
K
Atoms transfer electrons in chemical bonds to try and achieve a full outer shell ­ as it is MORE STABLE.
I ONS
Ions are electrically atoms or groups of atoms.…read more

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E XAMPLES :
Na Cl
NaCl
Na Cl
Mg O
MgO
Mg O…read more

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Al F
AlF3
Al F
L ATTICE S TRUCTURE
A way of displaying regular patterns within atoms of oppositely charged ions is used a lattice structure:
+ - + - +
- + - + -
Lattice of NaCl
+ - + - +
I ONIC S UBSTANCES
THEY HAVE HIGH METING POINTS: strong electrostatic bonds between each ion (and these have to
break)
o The greater the charge on the ions ­ the higher the melting and boiling point.…read more

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F ORMATION
H H Cl Cl H Cl
O
O O C
H H H H
H
N O O O
H H
M ETALLIC B ONDING Positive metal ions
+ + +
+ +
`Sea' of negative ions
+ + +
D EFINITION
A metallic bond is a giant structure of positive (metal) ions, surrounded by a sea of delocalised (free)
electrons.…read more

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S TRUCTURE
C ARBON DIOXIDE :
C O C
·Double bonds ·Structured in a line ·It is stable (has a full outer shell)
D IAMOND
Single covalent Bonds
All bonds are strong
No weak Bonds
Tetrahedron of Carbon atoms
G RAPHITE
Hexagonal shape of c atoms
Only 3 covalent bonds
It is formed in layers
Weak bonds between layers
C C
C
C
C C…read more

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T HE S TRUCTURE D IAGRAM
Structure
Giant Silicon Simple
Carbon
Anything
Ionic Almost all
All
covalent
Metals Graphite substances
Diamond
Giant Structure Molecular Structure
Substances that are made up of a mixed number of
Substances made up of huge numbers of atoms, or
atoms shown by the molecular formula (eg. H2O or
ions
C6H12O6
Generally the atoms are joined by covalent bonds.…read more

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M ACROMOLECULE
A macromolecule is an extremely large molecule containing a very large number of atoms.…read more

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E XAMPLES
2Na+O Na2O
Mg + O MgO
2K + 2H2O H2+2KOH
Ca + 2H2O Ca(OH)2 + H2
3AgNO3 + Fe 3Ag + Fe(NO3)3
MgSO4 + Cu CuSO4 + Mg
R USTING
Fe2 + 3O2 Fe2O3
A REDOX reaction will occur and the iron will be oxidised. Rusting normally occurs in moisture-prone areas.
E XTRACTION & U SES OF M ETALS
Most metals found recently are higher up in the reactivity series.…read more

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Hafsa

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Paige


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