Chemistry IGCSE Comprehensive Exam
Review Latest Updated Graded A+
Acid Rain - ANSWER-Caused when water and oxygen in the atmosphere react with
sulphur dioxide to produce sulphuric acid or with various oxides of nitrogen to give nitric
acid. SO2 and NO2 come mainly from power stations and factories burning fossil fuels
or from motor vehicles. Effects: kills trees, causes life in ponds and rivers to die, affects
limestones e.g. statues. Solution: Catalytic converters in cars to convert oxides of
nitrogen into nitrogen gas but have no effect on SO2. Also, "scrubbers" in chimneys.
Acids and Alkalis - ANSWER-All acids contain H, all alkalis contain OH.
Alkanes and Alkenes - ANSWER-Alkanes: CnH2n+2
Alkenes: CnH2n
Alkenes have a carbon-carbon double bond so are unsaturated because they don't
have as many hydrogens as possible. To test for unsaturation, shake with bromine
water. If unsaturated, bromine will turn from red/brown to colourless because an
addition reaction will have taken place. The double bond will have broken and joined to
a bromine atom.
Alloys - ANSWER-An alloy is a mixture of metals, e.g. brass is a mixture of copper and
zinc. In an alloy, the different metals have slightly differently sized atoms. This breaks
up the regular arrangement and makes it more difficult for the layers to slide.
Anion - ANSWER-Negative Ion
Blast Furnace - ANSWER-Ingredients: Coke, Iron Ore (haematite), Limestone
CaCO3 --> CaO + CO2
CO2 + C --> 2CO
C + O2 --> CO2
Fe2O3 + 3CO --> 2Fe + 3CO2
CaO + SiO2 --> CaSiO3 (slag)
Slag floats on top of molten iron so can be tapped off. Used for road building.
Carbon Dioxide - ANSWER-Making: Dilute HCl and CaCO3 in form of marble chips. Or
heat a metal carbonate and it turns to carbon dioxide and metal oxide.
Test: turns lime water milky.
Uses: Fizzy drinks because it dissolves in water under pressure. Fire extinguishers
because the gas is denser than air so sinks onto the flames and prevents any more
oxygen from reaching them.
Cation - ANSWER-Positive Ion
Changes of State - ANSWER-Solid --> Liquid - Melting
Liquid --> Solid - Freezing
, Liquid --> Gas - Boiling
Gas --> Liquid - Condensing
Solid --> Gas and Gas --> Solid - Sublimation
Collecting Gases - ANSWER-Three ways: downwards delivery, upward delivery or over
water. Also, in a gas syringe if you want to measure the volume.
Remember hydrogen extinguishes a lighted splint with a "pop."
Combustion - ANSWER-Complete combustion is burning an alkane/alkene with excess
oxygen and produces carbon dioxide and water. Incomplete combustion is burning an
alkane/alkene with a limited amount of oxygen and this produces carbon monoxide
instead of carbon dioxide.
Covalent Bonding - ANSWER-Between 2 non-metals
1) insoluble in water
2) brittle solids, liquids or gases at room temperature
3) don't conduct electricity when molten
4) lower melting and boiling points - molecules are held together by weak intermolecular
forces that are easy to break
Diatomic Gases: a nitrogen molecule has a triple bond, a carbon dioxide molecule has
two double bonds, an oxygen molecule has two double bonds.
Definitions for Organic Chemistry - ANSWER-Isomer - same molecular formula but
different structural formula
Homologous Series - family of compounds with similar properties because they have
similar bonding.
Diffusion - ANSWER-The spreading out of particles in a gas or a liquid. The lighter the
particles, the faster they diffuse. This is demonstrated by the experiment with cotton
wool soaked in ammonia solution at one end of a tube and cotton wool soaked in HCl at
the other end. The white cloud of ammonium chloride forms closer to the hydrochloric
end. Also to speed up diffusion, you can stir a liquid or heat up the liquid or gas.
Flame Test - ANSWER-Red shows lithium ions
Orange shows sodium ions
Lilac shows potassium ions
Brick Red shows calcium ions
Gas - ANSWER-Particles are much further apart and there are almost no forces of
attraction between them.
Giant Covalent Structures - ANSWER-Diamond - 4 strong bonds so very high melting
and boiling points. Cannot conduct electricity because no free ions to move and carry
charge. Insoluble. Silican dioxide has similar properties to diamond.
Review Latest Updated Graded A+
Acid Rain - ANSWER-Caused when water and oxygen in the atmosphere react with
sulphur dioxide to produce sulphuric acid or with various oxides of nitrogen to give nitric
acid. SO2 and NO2 come mainly from power stations and factories burning fossil fuels
or from motor vehicles. Effects: kills trees, causes life in ponds and rivers to die, affects
limestones e.g. statues. Solution: Catalytic converters in cars to convert oxides of
nitrogen into nitrogen gas but have no effect on SO2. Also, "scrubbers" in chimneys.
Acids and Alkalis - ANSWER-All acids contain H, all alkalis contain OH.
Alkanes and Alkenes - ANSWER-Alkanes: CnH2n+2
Alkenes: CnH2n
Alkenes have a carbon-carbon double bond so are unsaturated because they don't
have as many hydrogens as possible. To test for unsaturation, shake with bromine
water. If unsaturated, bromine will turn from red/brown to colourless because an
addition reaction will have taken place. The double bond will have broken and joined to
a bromine atom.
Alloys - ANSWER-An alloy is a mixture of metals, e.g. brass is a mixture of copper and
zinc. In an alloy, the different metals have slightly differently sized atoms. This breaks
up the regular arrangement and makes it more difficult for the layers to slide.
Anion - ANSWER-Negative Ion
Blast Furnace - ANSWER-Ingredients: Coke, Iron Ore (haematite), Limestone
CaCO3 --> CaO + CO2
CO2 + C --> 2CO
C + O2 --> CO2
Fe2O3 + 3CO --> 2Fe + 3CO2
CaO + SiO2 --> CaSiO3 (slag)
Slag floats on top of molten iron so can be tapped off. Used for road building.
Carbon Dioxide - ANSWER-Making: Dilute HCl and CaCO3 in form of marble chips. Or
heat a metal carbonate and it turns to carbon dioxide and metal oxide.
Test: turns lime water milky.
Uses: Fizzy drinks because it dissolves in water under pressure. Fire extinguishers
because the gas is denser than air so sinks onto the flames and prevents any more
oxygen from reaching them.
Cation - ANSWER-Positive Ion
Changes of State - ANSWER-Solid --> Liquid - Melting
Liquid --> Solid - Freezing
, Liquid --> Gas - Boiling
Gas --> Liquid - Condensing
Solid --> Gas and Gas --> Solid - Sublimation
Collecting Gases - ANSWER-Three ways: downwards delivery, upward delivery or over
water. Also, in a gas syringe if you want to measure the volume.
Remember hydrogen extinguishes a lighted splint with a "pop."
Combustion - ANSWER-Complete combustion is burning an alkane/alkene with excess
oxygen and produces carbon dioxide and water. Incomplete combustion is burning an
alkane/alkene with a limited amount of oxygen and this produces carbon monoxide
instead of carbon dioxide.
Covalent Bonding - ANSWER-Between 2 non-metals
1) insoluble in water
2) brittle solids, liquids or gases at room temperature
3) don't conduct electricity when molten
4) lower melting and boiling points - molecules are held together by weak intermolecular
forces that are easy to break
Diatomic Gases: a nitrogen molecule has a triple bond, a carbon dioxide molecule has
two double bonds, an oxygen molecule has two double bonds.
Definitions for Organic Chemistry - ANSWER-Isomer - same molecular formula but
different structural formula
Homologous Series - family of compounds with similar properties because they have
similar bonding.
Diffusion - ANSWER-The spreading out of particles in a gas or a liquid. The lighter the
particles, the faster they diffuse. This is demonstrated by the experiment with cotton
wool soaked in ammonia solution at one end of a tube and cotton wool soaked in HCl at
the other end. The white cloud of ammonium chloride forms closer to the hydrochloric
end. Also to speed up diffusion, you can stir a liquid or heat up the liquid or gas.
Flame Test - ANSWER-Red shows lithium ions
Orange shows sodium ions
Lilac shows potassium ions
Brick Red shows calcium ions
Gas - ANSWER-Particles are much further apart and there are almost no forces of
attraction between them.
Giant Covalent Structures - ANSWER-Diamond - 4 strong bonds so very high melting
and boiling points. Cannot conduct electricity because no free ions to move and carry
charge. Insoluble. Silican dioxide has similar properties to diamond.
