CHEMISTRY IGCSE SYLLABUS
What is the boiling point of oxygen?
-183
What is the boiling point of argon?
-186
What is the boiling point of nitrogen?
-196
Crystallisation
1) Heat in an evaporating dish above boiling water 2) Mix with a glass rod and dip in, once crystals from on the rod remove from heat
What are the steps of water treatment?
1) Screening for floating rubbish 2) Ozone disinfection to destroy microorganisms 3) The floculation/coagulant/precipitation part where solids settle and are removed 4) Rapid gravity sand filters where the water is filtered through anthracite coal and sand to remove small particles 5) Main ozone pumps to break down pesticides and other materials 6) Fluoridation which is added to prevent tooth decay 7) Carbon granules - passed through to absorb chemicals 8) Passes through microstrainers 9) Chloride disinfection provides protection from microorganisms 10) Corrosion control - phosphorus compound added to prevent corroding pipes and stop leaching
Chromatography
1) Use pencil for origin as it won't dissolve in solvent 2) Separate according to solubility in solvent 3) Distance moved by a particular spot is measured in relation to the movement of the solvent front: ratio of these is called the Rf value
How much more effective is methane than CO2 in causing the greenhouse effect?
20 times
What is the range in thickness of the earth's crust?
5-50km
What is the distance from the crust to the core of the earth?
6000km
How much nitrogen is there in the atmosphere?
78%
What is the main composition of air?
78% nitrogen 21% oxygen 0.04% carbon dioxide <1% hydrogen <1% methane <1% ozone
What is the first law of kinetic theory?
All matter is made up of very small particles
Chemical change
Breaking bonds between atoms that are difficult to reverse
Potentially renewable resource
Can be renewed but can become used up mainly because of overuse
What are the four greenhouse gases?
Carbon dioxide Methane Chlorofluorocarbons Nitrous oxide
What are the main pollutants?
Carbon dioxide - burning fossil fuels Methane - animals, paddy fields Nitrogen oxide - incomplete fuel combustion Volatile organic compounds - hydrocarbons Particulate matter - fuel combustion, farming Sulfur dioxide - burning coal or oil Carbon monoxide - car exhausts and incomplete burning Ozone - formed by VOC's and nitrogen oxides in sunlight
What is the solution to the production of nitrogen oxide within car exhausts?
Catalytic converters - 2 types of catalyst at work, the reduction and the oxidation catalyst
How would you separate a solid suspension from a liquid?
Centrifugation or filtration
How would you separate a solution of two or more solids in a liquid?
Chromatography
What are the tests for water?
Cobalt chloride paper goes from blue to pink or anhydrous copper sulphate crystals go from white to blue
What are examples of chemical changes?
Colour change Precipitate Energy change Effervescence
Sublimation
Compounds like ammonium chloride can be separated from mixtures because it sublimes: 1) Test tube, containing bung with tubes of cold water running through, inside boiling tube 2) Boiling tube contains mixture containing ammonium chloride 3) Boiling tube is heated and when ammonium chloride sublimes and is collected on the test tube
What are the uses for limestone?
Concrete Buildings and roads Steel (removes impurities in the furnace) Whitens paper Neutralises acid soils and lakes Making glass
Why must water be treated before it can be drunk by humans?
Contains nitrate fertilisers because of eutrophication Contains human and animal waste which is toxic Contains waste from industry
How does the fractional distillation of air work?
Cooled to -200 degrees so it becomes a liquid
What replaces the nitrogen in the soil?
Decaying organisms
What replaces nitrogen into the atmosphere?
Denitrifying bacteria in the soil
Carbon monoxide
Description - can't be seen or smelled Source - fossil fuel or incomplete combustion Effects - interacts with haemoglobin and is fatal
Methane
Description - colourless gas and explosive Source - rice paddies, animals and land fills Effects - contributes to greenhouse gas effect
Sulfur dioxide
Description - corrosive gas that smells like 'rotton egg' Source - volcanos and fuels Effects - Asthma and breathing problems
Nitrogen oxide
Description - red/brown gas Source - air contains N2 which reacts with oxygen in car exhausts Effects - forms ozone or acid rain
Ozone
Description - smog Source - secondary pollutant made by VOC's and NO's in sunlight Effects - health problems and breathing problems
Particulate matter
Description - solid that's suspended in the air Source - road dust, construction and burning fuels Effects - enters lungs to cause breathing problems
Lead
Description - toxic metal Source - leaded petrol use, power plants and pipes Effects - leads to lower IQ, kidney problems and heart problems
What is the effect of an increase in greenhouse gas emissions?
Earth can temporarily trap IR radiation more efficiently which leads to a rise in earth's temperatures to counter the change in the radiative equilibrium
How is pure hydrogen obtained?
Electrolysis of water
What is the importance of the nitrogen cycle?
Essential for plants and growth of organisms
How does carbon go from the atmosphere to the ground?
Feeding, photosynthesis, dissolves into sea, pressure, decay
What is the source and percentage of ozone for nitrous oxide?
Fertilisers use and fossil fuel combustion - 6%
What are the uses of argon?
Fill lightbulbs to stop the Tungsten filament burning away
Describe the nature of a solid?
Fixed volume High density Has a definite shape Doesn't flow
Describe the nature of a liquid?
Fixed volume Moderate density Takes the shape of its container Flows easily
What is the source and percentage of ozone for carbon dioxide?
Fossil fuel combustion and decay of biomass - 56%
How would you separate two or more liquids mixed together?
Fractional distillation
What is the third law of kinetic theory?
Freedom of movement and the arrangement of the particles is different in the three states of matter
What are the uses of pure nitrogen?
Freezing food, packed with food, oil tankers
How would hydrogen be used in a car?
Fuel cell - platinum catalyst with reaction of hydrogen in heat with oxygen producing energy: H2 + O2 ---> H2O
What are the problems of global warming?
Glaciers and icecaps melt Flooding from rise of sea levels Surface temp increase causing lack of water Severe weather and climate changes like drought and flooding Agriculture industry hit as change in climate
What is the cause of global warming?
Greenhouse gas effect from methane, CO2, CFC's and nitrous oxides
What are the disadvantages of the fractional distillation of air?
High industrial cost and complex equipment required
What are the advantages of using a hydrogen powered fuel cell in cars?
High yield of energy More efficient - 60% hydrogen reacts compared to 35% petrol No greenhouse gas emissions Non toxic Lower flammability than petrol
When do you not use crystallisation?
If the solvent is flammable
Evaporation
In a liquid some particles have enough energy to break the surface, as the temperature rises more particles have enough energy to escape and this can happen at all temperatures - also has a cooling effect
How is nitrogen oxide produced?
In car exhaust fumes the high heat, in the engine cylinders, allows nitrogen in the atmosphere to react with oxygen
Physical change
Involves moving, separating and mixing molecules but individual molecules don't change
What are the problems of land pollution?
Land wasted Habitat destroyed Produce methane through anaerobic decay Greenhouse gases emitted
What puts nitrogen into the soil as nitrates?
Lightening Fertilisers made from the Haber process Nitrifying bacteria which replaces nitrates from decaying animals Faeces of animals Nitrogen fixation of bacteria
What are the causes of land pollution?
Litter made to radioactive waste when buried or landfills
What are the uses of pure oxygen?
Making steel from cast iron
What are examples of physical changes?
Melting Boiling Condensing
What comes from the core of the earth?
Metal ores
Centrifugation
Mixture spun at high speed in a centrifuge until solid is deposited at the bottom of the tube - the liquid is then decanted off
Mixtures
More than one substance present; which may be in different physical states
What is the formula for the reaction within a car's exhaust?
N2 + 2O2 ---> 2NO2
How do plants obtain nitrogen?
Nitrate ions in the soil
What is gained from the fractional distillation of air?
Nitrogen, oxygen and argon (also CO2 beforehand)
Describe the nature of a gas?
No fixed volume Low density No definite shape Flows easily
What are the advantages of hydrogen as a fuel?
No greenhouse gas emission when burnt - only water High yield of energy Difficult to store as low density Difficult to transport as dangerous
What are the disadvantages of using fuel cells in cars?
Nonrenewable if generated with fossil fuel or nuclear energy Large fuel tank required No 'filling' stations Engine redesign needed Expensive
What is the arrangement of particles in a solid?
Particles arranged close Regular arrangement/lattice Not able to move freely but vibrate in a fixed position
What is the arrangement of particles in a gas?
Particles arranged irregularly Spread far apart Move randomly
What is the arrangement of particles in a liquid?
Particles closely packed Irregular arrangement Able to move past eachother
Compound
Pure substances made from two or more elements chemically combined together
What is the difference between pure and drinking water?
Pure water contains only H2O molecules whereas drinking water contains other compounds like fluorides
What are the effects of impurities?
Reduces sharpness of boiling or melting point Changes state over a range of temperatures
What is the source and percentage of ozone for chlorofluorocarbons?
Refrigerators and aerosols - 13%
How is carbon put back into the atmosphere?
Respiration, burning, decay, heating in industry
What is the Rf value formula?
Rf value = distance moved by a substance/distance moved by solvent front
What are the advantages of the fractional distillation of air?
Separates components which are close in boiling points, gives purer air and is a continuous process
How would you separate two immiscible liquids?
Separating funnel
How would you separate a liquid from a liquid?
Separating funnel or decantation
What are examples of renewable energy resources?
Solar energy HEP - hydroelectric power Biomass and biogas Geothermal energy Wind power Wave power Tidal barriers
Carbon dioxide
Source - burning fossil fuels, car exhausts Effects - greenhouse gas effect
Describe the nature of compounds?
Substances are chemically joined together The composition of the new substance is always the same Properties of the new compound are very different from those of the original elements in it Compound cannot be easily separated
Describe the nature of a mixture?
Substances only mixed not chemically joined Composition of the mixture can be varied Properties of the substances present remain the same Substances can be separated with physical methods
Element
Substances that cannot be chemically broken down into simpler substances - only contain one type of atom
Melting
Temperature raise means particles gain kinetic energy and vibrate strongly, so occupy more space causing the solid to expand. Eventually they have enough space to break the intermolecular forces holding the lattice together and so they MELT.
Why is a catalytic converter expensive?
The catalysts are expensive materials like platinum, rhodium and palladium
What happens at the second stage of a three way catalytic converter?
The oxidation catalyst is the 2nd stage which oxidises the carbon monoxide to carbon dioxide or oxidises the hydrocarbons to carbon dioxide and water: CxHyOz + O2 ---> CO2 + H2O or 2CO + O2 ---> CO2
What is the second law of kinetic theory?
The particles are moving all the time (the higher the temperature, the more energy for the particles, thus more movement)
What happens in the first stage of a three way catalytic converter?
The reduction catalyst reduces the nitrogen oxide emissions by displacing the oxygen: 2NO ---> N2 + O2 or 2NO2 ---> N2 + 2O2
What is fractional distillation?
The separation of a liquid into its different fractions or components based upon their boiling points and using a fractioning column
Nonrenewable resource
Those in a fixed quantity in the earth's crust which are being used faster than they are being replenished
Renewable resource
Those which are inexhaustible
What can the Rf value be used for?
To determine the purity of a substance
How would you separate a solution of a liquid and a solid?
To obtain the solid: evaporation or crystallisation To obtain the liquid: distillation
What is sublimation?
Turning directly from a gas to a solid or vice versa
How would you separate a solid from a solid?
Use a difference in property like density or size
What is the source and percentage of ozone for methane?
anaerobic decay of organic substances e.g. rice paddies and landfills - 18%
What is the limestone cycle?
calcium carbonate --> (heated strongly) --> lime --> (cooled and water added) --> slaked lime --> (water added) --> lime water
