Air and water
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What are two chemical tests for water?
Cobalt (II) chloride: turns from blue to pink Copper (II) sulfate: turns white to blue
What are two problems associated with lack of water?
Water used to irrigate crops - Crops cannot grow → lack of food for populations reliant on crops No safe water for drinking: increased risk of disease
Describe the process of treatment of water supply (6)
• Water passed through metal screens and filtered for twigs/leaves • In settlement tank, soil particles settle at bottom • Aluminum sulfate added to make small particles in water stick together. Particles fall to bottom of tank • Passed through filter made of sand and gravel, removes any insoluble particles not removed • Chlorine added to kill bacteria • pH of water adjusted, water run off
What are the uses of water in industry and in the home?
Generate electricity Cooking, washing, cleaning
What is the composition of clean, dry air?
78% nitrogen, 21% oxygen and remainder: mixture of noble gases/carbon dioxide
Describe the separation of oxygen and nitrogen by fractional distillation (4)
• Water + carbon dioxide removed from air - Water by passing it through a drying agent - carbon dioxide by reacting it with sodium hydroxide • Air is cooled to -23 degrees celcius and compressed • Cold compressed air allowed to expand in larger space, air cools when expand until temp. drops to -200 degrees celcius - air is liquid - Argon, krypton and xenon are removed from oxygen by further distillation • When liquid air is warmed, nitrogen boils off first (lower boiling point) + condenses • Mixture fed to top column, oxygen condenses, nitrogen gas residue removed at top
What are the four common pollutants in the air?
carbon monoxide sulfur dioxide oxides of nitrogen lead compounds
What are the sources + effects of carbon monoxide?
S: incomplete combustion of carbon-containing substances E: reacts w/ haemoglobin, prevents from carrying oxygen, death
What are the sources + effects of sulfur dioxide?
S: combustion of fossil fuels which contain sulfur compounds E: irritates eyes and throat, causes respiratory problems and acid rain
What are the sources + effects of oxides of nitrogen?
S: car engines denitrification high temperature furnaces E: causes respiratory problems and acid rain
What are the sources + effects of lead compounds?
S: burning of petrol E: causes damage to brain + nerve cells in young children
Describe the process of catalytic conversion of oxides of nitrogen in car engines (5)
Exhaust gases from car engine passed through a honeycomb (surface covered with metal catalysts) in a catalytic converter Two compartments: Compartment 1: metals catalyse conversion of nitrogen oxides to nitrogen 2NO(g) → N2(g) + O2(g) 2NO2(g) → N2(g) + 2O2(g) Compartment 2: Carbon monoxide converted to carbon dioxide 2CO(g) + O2(g) → 2CO2(g) Carbon monoxide may also react directly with nitrogen oxides (nitric acid + nitrogen dioxide)
What is needed for iron to rust?
Water and Oxygen
What are the four methods of rust prevention?
Paint Plastic Coating Galvanising Sacrificial Protection
What is galvanising?
coating iron with zinc
What is sacrificial protection?
blocks of more reactive metal attached to iron surface
What are NPK fertilizers used for?
replace essential elements lost when plants are harvested
What causes the displacement of ammonia from its salts in soil?
Too much lime put in soil, displaces ammonia from ammonium salts, lost as gas
What is ammonia’s function in soil
To neutralise soil acidity
What is the Haber process?
Industrial manufacture of ammonia NH3
What is the equation for the Haber process?
N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
What are the raw materials required for the Haber process?
Nitrogen: from the air Hydrogen
What are the essential conditions required for the Haber process?
Temperature: 450°C Pressure: 200 atm Catalyst: Iron
How does methane cause global warming?
Absorb heat energy and prevent it escaping into space - global warming