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0620 IGCSE® Chemistry Ultimate Revision Notes

Ch1 States of matter
Ch2 Separating substances
Ch3 Atoms and elements
Ch4 Atoms combining
Ch5 Reacting masses, and chemical equations
Ch6 Using moles
Ch7 Redox reactions
Ch8 Electricity and chemical changes
Ch9 Energy changes, and reversible reactions
Ch10 The speed of a reaction
Ch11 Acids, bases, and salts
Ch12 The Periodic Table
Ch13 The behaviour of metals
Ch14 Making use of metals
Ch15 Air and water
Ch16 Some non-metals and their compounds
Ch17 Organic chemistry
Ch18 Polymers





























































Ch19 In the lab

Ch1 States of matter
Brownian motion
Seen as motion of bright pollen
Hit randomly by molecules
Zig-zag path
Caused by random motion of particles
Diffusion
Seen as mixing and spreading of particles, until evenly mixed
Net movement of particles from high concentration regions to low ones (down []
gradient)
Caused by random motion of particles, bouncing off in all directions
Rate of diffusion affected by mass
Lower mass particles travel faster as they bounce away further in collision
Rate of diffusion affected by temperature
Higher temperature
Higher energy
Collision with more energy
Bounce away further
Move faster
State

shape

volum Motion of arrangeme D i s t a n c e force
e
particles
nt
b e t w e e n
particles

Solid

fixed

fixed

Liquid T a k e fixed
shape of
container
Gas

Vibrate in F i x e d To u c h i n g / S t r o n g
f i x e d pattern / very close
forces
position
lattice
Move about random
and slide
past each
other

Close together W e a k e r
than in
solid

Fill the N o t Move about random
container fixed
v e r y
quickly and
collide with
each other

Far apart



































































Changing state
Melting
Get more energy
Vibrate more

Little / no

Expand
Energy used to break away from their positions
Boiling
Get more energy
Move faster
Collision rate ^, bounce away further apart
Expand
Energy used to overcome the forces between them
Evaporation
Some particles get more energy
Escape and form a gas
Mp & bp
Decided by type of bond, then strength of bond
Different amount of heat energy is needed to overcome them






































































Gas pressure
Caused by collision of particles on wall of container
When temperature ^
Collision rate ^
Force of collision ^
Pressure ^
When compressed
Smaller space
Collision rate ^

Ch2 Separating substances
Mixture
≥ 1 substance mix together
Not chemically combined
Pure substance
No other substances mix with it
Can be checked by mp & bp
Definite and sharp
If not pure: lower mp, higher bp





































Saturation
No more solute can be dissolved
At that temperature

Ch3 Atoms and elements
Atoms
Smallest particles of nature
Can’t break down further by chemical means
Elements: contain only one kind of atom of same n(p)
N(p) = atomic number
To identify an atom
N(nucleon) = n(p) + n(n) = mass number
Periodic table
Period = n(shells)
Group = n(outer shell e)
Determines chemical reactivity












































































Radioactivity
Can cause sickness
Kill cells
Mutation
Vomit
Hair falls out
Gums bleed
Can be used
To check for leaks of pipes
To monitor thickness of metal sheet / paper
To treat cancer by killing cancer cells
As medical traces
Sterilisation to kill microorganisms

Ch4 Atoms combining
Compound
Atoms of different elements in the same ratio
Bonded together, can’t be separated by physical means
Mixture
Can contain any number of different substances in any ratio
Substances not joined by chemical means
Physical methods can be used to separate substances within it
Chemical change
New chemical substances are formed
Energy change
How & why react
Group number
N(e)
Lose or gain
To get stable octet noble gas outer-shell electron arrangement
Ionic bond
ESA between oppositely charged ions --> strong
Arranged in a lattice of alternating cations and anions to minimise repulsion, ions
not free —> don’t conduct electricity
Metal atoms lose e and non-metal atoms gain them
Reason for proportion of ions: no overall charge
Brittleness: layers repel when a force is applied
Most can dissolve in water —> ions mobile (also when molten) —> conducts
electricity
Covalent bond
ESA between nuclei and shared e- pair
Non-metal atoms share eSingle bond: share one pair of e- etc
...
a
...
m
...
f
...
g
...
s
...
7Cu + 0
...
997Fe + 0
...
7Fe + 0
...
1Ni
Hard and rustproof
Used for cutlery, and equipment in chemical factories
Basic oxygen converter
Oxygen reacts with C & S forming gaseous CO2 and SO2 which go off
P turns to P2O5(s)
CaO added to react with SiO2 and P2O5 to form slag

Ch15 Air and water
Measuring percentage of O2 in air
Heat copper wire which is in a glass tube connecting to two plungers
Push air to and fro
After complete reaction, cool
Calculate percentage of volume decrease
Fractional distillation of air
Pump into a plant, filtered to remove dust, CO2, H2O
Compression and cooling
Expansion
Repeats for many cycles
Liquid air pumped into fractionating column
Uses of main air components
O2
Divers and astronauts
Oxygen pump in hospitals
Basic oxygen converter, blast furnace
Welding to react with ethyne
N2
Freezing food
Store tissue sample
Food packaging

























































































































Pollution
CO
Incomplete combustion of fossil fuels
No smell so difficult to be detected
Poisonous by binding to Hb permanently, reduce oxygen capacity
Causing oxygen starvation
SO2
Impurities in fossil fuels used in power stations
Irritates eyes and throat
Causes respiratory problems
Acid rain (pH4)
Attack buildings, statues
Lower pH in rivers and lakes, killing aquatic animals
Makes mineral ions in soil solutions less available to roots
Kills trees and insects
Acidic nitrogen oxides (NO2)
Nitrogen from air reacts with oxygen inside hot car engines, hot furnaces and
lightning
Because very high temperature gives enough energy for reaction to occur

Respiratory problems
Acid rain
Lead compounds
Combustion of petrol addition
Damages children’s brains
Damages adults’ kidneys and nervous system
Catalytic converter
Pt, Pd & Rh coated on ceramic honeycomb, or beads (to increase SA) as catalyst
2NO(g) --> N2(g) + O2(g) (reduction)
2CO(g) + O2(g) --> 2CO2(g) (oxidation)
2NO(g) + 2CO(g) --> N2(g) + 2CO2(g)
Unburnt hydrocarbon burnt to water
Products released through exhaust pipe
Rusting
4Fe(s) + 3O2(g) + 4H2O(l) --> 2Fe2O3•2H2O(s)
Prevention
Cover iron by paint, grease
Galvanising
Coat steel / iron with Zn
Using electrolysis / dipping into molten zinc
Keeps air & moisture away
If damaged, protect by sacrificial protection
Sacrificial protection
A more reactive metal is oxidised instead of iron e
...
Zn



















































































































Water
Uses
Home: drinking, cooking, washing, flushing
Farms: drink for animals, water crops
Industry: solvent, washing, cooling
Power stations: to drive turbines to generate electricity as steam
Source: aquifer rock holding groundwater
Treatment
Screening: trap big particles
Coagulation: add coagulant to stick small particles together
Flotation: to float coagulated particles and skim them off
Filtration: sand, charcoal (also remove bad tastes and smells) to remove
insoluble particles
Chlorination: to kill microorganisms
Fluoridation: add fluoride compounds to fight tooth decay

Haber process
Nitrogen from fractional distillation of air
Hydrogen from
Reaction of natural gas with steam: CH4(g) + 2H2O(g) —(catalyst)—>
CO2(g) + 4H2(g)
Cracking hydrocarbons
Electrolysis of brine
Two gases mixed and scrubbed to remove impurities
Compression
Compressed gas flows to the converter:
450˚C
Higher temperature lowers yield, increases cost
Lower temperature slows down rate of reaction
200 atm
Higher pressure increases cost, more dangerous
Lower pressure slows down rate, lowers yield
Ammonia in mixture condensed to a liquid and collected, constantly removed
also increase yield
Unreacted hydrogen and nitrogen are recycled to react again
Fertiliser
Any substance added to the soil
To make it more fertile
Animal manure is a natural one
May reduce oxygen capacity if in drinking water supply
Eutrophication
(named) fertiliser leached into, rivers / streams / lakes
producer growth / algal bloom / algae growth / plant growth
death of producers
increased decomposition / increased decomposers
increased respiration (aerobic)
decomposers use up the oxygen in the water
organisms / fish / creatures, die / suffocate / migrate, due to lack of oxygen





















































































































Sulfur
From metals ores e
...
zinc blende (ZnS), galena (PbS)
From underground sulfur beds
From petroleum
Removed to reduce pollution
E
...
H2S in natural gas: 2H2S(g) + O2(g) -->2S(s) + 2H2O(l)
Uses
Make sulfuric acid












Ch16 Some non-metals and their compounds

Vulcanising rubber to toughen it
Making chemicals e
...
drugs, pesticides, cosmetics
Add to cement to make sulfur concrete, not attacked by acid rain
Sulfur dioxide
Colourless
Has strong, choking smell
Dissolves in water to form sulfurous acid
A reducing agent, can bleach coloured compounds
Uses
Manufacture of sulfuric acid
Bleach wool, silk and wood pulp to make paper
Food preservative as it stops the growth of microorganisms
Sulfuric acid
Contact process
Combustion of S in air to form SO2
Oxidation of SO2
Mix with air: 2SO2(g) + O2(g) <—> 2SO3(g)
450˚C
Lower: rate falls, catalysts work not as good
Higher: yield falls, cost increases
2 atm
Lower: rate falls, yield falls
Higher: yield doesn’t increase very much, cost increases
Vanadium(V) oxide (V2O5) catalyst in beds
SO3 dissolved in conc
...
sulfuric acid
Uses
Fertilisers
Pigments
Plastics
Soaps




























































































































Greenhouse effect
Short λ radiation from the sun passes through the atmosphere
The ground absorbs short λ radiation and re-emits it as long λ radiation
Only some radiation escapes from the Earth
Most radiation is reflected by greenhouse gases and heats the Earth
Climate change
Flood and drought reduce agricultural yield, famine
Melting land-ice in the poles, rising sea levels
Some species can’t adapt to the new climate and die out

Limestone
From skeleton of aquatic organisms
The carbonate part was from the carbon cycle (CO2 dissolves in water forming
carbonate)
As they die, remains fall to sea floor
Limestone rock forms slowly after millions of yrs
Uses of crushed limestone
Blast furnace to extract iron from hematite
For road building
Chips for concrete
Uses of powdered limestone
To neutralise soil acidity
Flue gas desulfurisation
Heat with clay, gypsum and ground to form cement
Lime / quicklime
From thermal decomposition of limestone in a rotary kiln
Uses
Making steel from iron
To neutralise soil acidity
As a drying agent in industry
Slaked lime
From hydration of lime
Uses
Making limewater to test CO2
To neutralise soil and lake acidity
Flue gas desulfurisation






























































































Flue gas desulfurisation
To remove sulfur dioxide from waste gases at power stations
Using a runny mixture of powdered limestone or slaked lime
Ca(OH)2(s) + SO2(g) --> CaSO3(s) + H2O(l)
/ CaCO3(s) + SO2(g) --> CaSO3(s) + CO2(g)
2CaSO3(s) + O2(g) + 4H2O(l) --> 2CaSO4•2H2O(s)

Ch17 Organic chemistry
Fossil fuels
Coal
From remains of vegetation in ancient swamps
Buried under thick sediment
Converted to coal by pressure and heat over millions of yrs
Petroleum
From remains of dead organisms that fell to the ocean floor under thick
sediment
Converted to petroleum under pressure over millions of yrs
Natural gas
Bacteria decompose plant material anaerobically
High temperature and high pressure cause them to be gas































































































































Petroleum refinery
Larger the hydrocarbon molecule
Higher mp & bp
Lower volatility
Higher viscosity
Lower flammability
Refinery gas
1~4 C
Bottled gases for cooking and heating
Gasoline / petrol
5~6 C
Fuel for cars
Naphtha
6~10 C
Feedstock for chemicals and plastics
Kerosene / paraffin
10~15 C
Jet fuel, oil stoves, lamps
Diesel / gas oil
15~20 C
Fuel for diesel engines
Fuel oil
20~30 C
Fuel for power stations, ships and home heating
Lubricating fraction
30~50 C
Oil for car engines & machinery; waxes and polishes
Bitumen
>50 C
Road surfaces and roofs

Cracking
Importance
Gives smaller molecules
More reactive, so more useful
Heating to vaporise long-chain hydrocarbon
Pass over catalyst (Al2O3, SiO2, ceramic zeolite)
High temperature: 450~800˚C
High pressure: 2~70atm
Homologous series
Same general formula
Same functional groups
Similar chemical properties
Differs by CH2
Gradually changing physical properties
Isomer
Same molecular formula
Different structural formula
Branched isomers have lower mp & bp
Branches make molecules difficult to get close
Weaker attraction so less heat required to overcome
Unsaturation
Not all C-C bonds are single
Contain C=C
Addition reactions
Hydrogenation
Reagent: H2(g)
High temperature: 140˚C
High pressure: /
Catalyst: Ni
For manufacture of margarine
Hydration
Reagent: H2O(g) / steam
High temperature: 300˚C
High pressure: 60atm
Catalyst: H3PO4
for manufacture of ethanol
Halogenation
Decolourise orange bromine water
As a test for unsaturation






















































































































Ethanol

Uses
Solvent
As fuel
For alcoholic drinks
Manufacture by fermentation
Reagent: glucose
Anaerobic: absence of oxygen
pH7
35˚C
Presence of yeast
Adv
Uses renewable resources
Growing crops help to absorb CO2, carbon neutral
Dis
Land required (o
...
)
Slow
Yeast stops working at low level of ethanol
Glucose used up
Enzymes denatured by higher temperature due to the exothermic
reaction
High [ethanol] kills yeasts
Low purity: requires fractional distillation
May drive up food price, causing famine
Manufacture by hydration
Adv
Fast
Pure
Dis
Nonrenewable
High temperature required
Manufacture of ethanoic acid
Fermentation
Oxidation of ethanol by bacteria
Using oxidising agent
Acidified potassium manganate(VII)
Potassium dichromate(VI)






















































































































Esterification
Carboxylic acid + alcohol
Heat under reflux
Conc
...
g
...

Optimum temperature: 37˚C
Optimum pH: 7
...
HCl(aq)
Proteins
Boil with 6M HCl(aq) for 24 hrs

Ch19 In the lab
Preparation of gases
CO2
CaCO3(s) + 2HCl(aq) --> CaCl2(aq) + H2O(l) + CO2(g)
H2
Zn(s) + 2HCl(aq) --> ZnCl2(aq) + H2(g)
O2
2H2O2(aq) --(MnO2)--> 2H2O(l) + O2(g)
gas

test

result

NH3 Hold a damp red litmus paper in it

Turns blue

CO2 Bubble through limewater

Turns cloudy / milky

Cl2

Hold damp indicator paper in the gas, in a fume Indicator bleached
cupboard

H2

Hold a lighted splint to it

Burns with a ‘squeaky’ pop

O2

Hold a glowing splint to it

Bursts into flame / relights

SO2 Soak a filter paper in acidified KMnO4(aq), From purple to colourless
place it in gas














































Flame test
Clean a Pt wire by dipping it into conc
...
s

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