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

3 Types of fossil fuels - Petroleum, Coal, Natural gas

Petroleum - complex homogeneous mixture of different hydrocarbon molecules, which also contain natural gas. its a thick, sticky, black liquid found under porous rock.

method used to extract fractions from Petroleum - Fractional Distillation

• Refinery gas - heating and cooking

• Gasoline - fuel for cars

• Naphtha - producing chemicals

• Diesel - fuel for diesel engines

• Bitumen - sufracing roads (and roofs)~

each fraction has similar properties and boiling points (depending on the number of carbons in the chain)

Polymers - large macromolecules made up of many small repeating units called monomers, joined by polymerisation.

addition polumerisation - formation of polymers by addition reactions between many monomers with double bonds, where the double bond breaks and attaches the adjacent monomer. it uses high pressure, a certain temperature and a catalyst. in addition polymerisation, just the polymer is formed.

condensation polymerisation - formation of polymers by condensation reactions between 2 or more different monomers, where the functional groups of each monomer are the ones that react and form a bond. another molecule is produced which is usually water. (it is being eliminated)

chapter 12

testing for the presence of Haliades - Silver NItrate

• add acid (nitric acid) to eliminate all impurities of the solution

• add silver nitrate and observe the color

if turns WHITE - Cl

if turns CREAM - Br

if turns YELLOW - I

testing for the presence of cations - Flame test

• to clean the wire, dip it into acid and flame it

• dip the wire into the solution and then put it on the Busen Burner, and observe the color of the flame

if turns BRIGHT RED - Li

if turns YELLOW / ORANGE - Na

if turns LILAC - K

if turns ORANGE / BIRCK RED - Ca

if turns PALE GREEN - Ba

if turns BLUE / GREEN - Cu

testing for Alkenes / unsaturated hydrocarbons - using Bromine Water

• if we add an alkene, the alkene will decolorise the bromine water (turns colorless) as the double bond in the alkene breaks to react with Br

• if we add an alkane, the water will remain brown since alkanes are saturated and will not react with the Br