chapter 10

Composition of clean, dry air

• nitrogen - 78%

• oxygen - 21%

• carbon dioxide, water vapour, argon and other noble gases - 1%

Main Pollutants

• carbon monoxide

• sulfur dioxide

• oxides of nitrogen

• particulates

• methane

• carbon dioxide

Carbon Monoxide

sources : incomplete combustion of hydrocarbon fuels

effects : toxic/poisonous. it combines with haemoglobin in the blood and prevents it from carrying oxygen meaning we can die.

prevention : use catalytic converters in cars. they will turn harmful gases into safer gase

chemical reactions in catalytic converters -

2CO + 02 = 2CO2

2NO + 2CO = N2 + 2CO2

2NO = N2 + 02

Sulfur Dioxide

sources : combustion of fossil fuels containing sulfur.

effects : dissolves in rain forming acid, which causes corrosion of buildings, damage to aquatic organisms, pollutes crops and water supply, provokes respiratory bad effects.

prevention : using fuels containing low levels of sulfur, and desulfurisation (main way) we can use scrubbers in the chimneys of power stations so SO2 will pass through them before being released into the enviorment

(desulfurisation) - process of removing acid gases from the fumes of power stations.

Oxides of Nitrogen

sources : car engines, high temperature furnaces and when lightning occurs.

effects : produces photochemical smog, acid rain and respiratory diseases.

prevention : use catalytic convertors in cars. (harmful gases are turned into safer gases)

Particulates

(or soot particles, are small solid particles produced during combustion of fuels)

sources : incomplete combustion of fossil fuels containing carbon

effects : respiratory problems and cancer

prevention : using particulate traps (they remove particulates like filters from the gases).

complete combustion - produces CO2 + H2O

incomplete combustion - produces CO, H2O (sometimes C)

Greenhouse Gases - gases that absorb heat reflected from the surface of the earth, stopping it from escaping to the atmosphere. these heat-trapping gases are like a blanket wrapped around earth keeping the planet hotter than without them. this effect causes global warming.

Greenhouse Effect - the result of the greenhouse gases. its normal for thermal energy to be trapped under the earths surface because of the certain atmospheric gases.

Gases responsible for the greenhouse effect

• carbon dioxide

• methane

• water vapour

• nitrogen oxide

Carbon Dioxide

sources : complete combustion of fossil fuels containing carbon

effects : increase global warming which leads to climate change

Methane

sources : waste gases from digestive processes of animals, decompostion of vegetation, bacterial action in swamps

effects : increases global warming, which leadsto climate change

Reduction of Greenhouse gases :

• using less fossil fuels

• turning to renewable sources of energy (wind and solar)

• educate people to eat less meat

Chemical tests for water :

• cobalt chloride - blue to pink

• copper sulfate - white to blue

tests for purity of water - using melting and boiling point. (only pure water has sharp values, while water that is not pure will have a range of values)

Distilled water - water that has been heated to form vapour and then condensed to a liquid (containing very few impurities)

Water supply - rivers or underground sources / aquifer (rock that stores water)

Water treatment (main stages) - sedimentation, filtration (to remove solids) with carbon (remove chemicals), and chlorination (to kill pathogens)

chapter 11

carbons can form large different type of molecules. each carbon has 4 bonds.

Hydrocarbons - organic compounds made from hydrogen and carbon atoms only.

Homologous series - family of similar organic compounds such as alkanes, alkenes and alcohols. each of the homologous series compounds have the same general formula, the same functional group, similar chemical properties and show a gradual increase in physical properties such as melting and boiling point.

Alkanes

• saturated hydrocarbons with single bonds. general formula is CnH2n+2

Reactions of alkanes :

• combustion - alkane + oxygen = carbon dioxide + water (vapour)

• catalytic cracking - method used to break long chained alkanes into short chained alkanes and alkenes, using a catalyst (alumina / silica) and high temperature (around 500C)

Alkenes

• unsaturated hydrocarbons with double bonds. general formula CnH2n

Reactions of alkenes

• combustion - alkane + oxygen = carbon dioxide + water

• (addition) bromination - alkene + bromine = bromoalkane

• (addition) hydrogenation - alkene + hydrogen = alkane

• (addition) hydration - alkene + water = alcohol

(additions reaction - reaction that occurs between alkenes and other substances, where the double bond between the carbons can be broken and accept other elements in their structure).

Alcohols - all alcohols contain the hydroxyl (-OH) functional group which is the part of alcohol molecules that is responsible for their charactaristis reactions.

general formula - CnH2n+1OH

alcohol + oxygen = carbon dioxide + water

uses of ethanol

• solvent (used in perfumes, cosmetic products, drinks)

• fuel (for cars)

meth

eth ———— ane ———— ene ———— anol

prop

but

pent

hex

hept

oct

non

deca