air and water

Question 1

chemical tests for water

Answer 1

• turns white anhydrous copper (II) suphate blue

- turns blue cobalt chloride paper pink

Question 2

treatment of water steps

Answer 2

1. water pumped in, screen traps big unwanted particles
2. coagulant added - chemical to make small suspended particles stick together (e.g. of coagulant - iron (III) sulphate
3. air blown through floatation tanks to make coagulated particles float and r skimmed off
4. water passed through bed of fine sand for filtration
5. further filters (e.g. charcoal) to remove bad taste/smell
6. chlorine added to kill bacteria
7. sometimes fluoride added to fight tooth decay
8. water pumped to shortage reservoir for storage

Question 3

use of water industry

Answer 3

• haber process
• contact process
• solvent/producing chemicals
• producing steam for turbines

Question 4

implications of an inadequate supply of water

Answer 4

• food shortages and famine due to a lack of crops which cannot grow without a clean water supply
• poor sanitation leads to spread of bacteria and disease as drinking water becomes infected

Question 5

percentage composition of air

Answer 5

• 78% nitrogen
• 21% oxygen
• remainder is mix of noble gases and carbon dioxide

Question 6

how is oxygen and nitrogen seperated from air

Answer 6

step1 - liquefaction of air
step2 - fractional distillation of air
nitrogen has a lower boiling point and thus gets collected first. Dust is filtered out from the air first

Question 7

common pollutants in air

Answer 7

• carbon monoxide
• sulphur dioxide
• oxides of nitrogen
• lead compounds

Question 8

carbon monoxide pollutant properties

Answer 8

• from the incomplete combustion of carbon-containing substances
• these gases enter our respiratory system and bind with haemoglobin in the blood to form carboxyhemoglobin. This reduces the oxygen-carrying capacity of the blood which can lead to fatigue and death

Question 9

sulphur dioxide pollutant properties

Answer 9

• from the combustion of fossil fuels which contain sulfur compounds
• dissolves in rain to form acid rain
• Acid rain can: enter rivers and increase acidity which will harm aquatic life, corrode metalwork and buildings, contaminate water which can harm humans, causes respiratory problems

Question 10

oxides of nitrogen pollutant properties

Answer 10

• in car engines when oxygen and nitrogen from the air react at high temperatures
• can also occur naturally during lightning
• similar effects to sulphur dioxide
• in car engines catalytic converters convert oxides of nitrogen into nitrogen and oxygen which are harmless

Question 11

what are catalytic converters

Answer 11

convert oxides of nitrogen into nitrogen and oxygen which are harmless

Question 12

lead compounds pollutant properties

Answer 12

• from leaded petrol and some industries which use leaded compounds
• harm nervous system in humans
• causes brain damage in humans

Question 13

rusting of iron

Answer 13

• requires air and water

- occurs when iron gets oxidised and is a redox reaction

Question 14

iron rusting prevention

Answer 14

• coating with paint and oil to exclude oxygen
• galvanising: coating steel with zinc, this is because zinc is more reactive than iron so it reacts with oxygen and water and corrodes instead of the iron.. This will prevent iron from rusting
• sacrificial protection: if the coating is damaged or scratched, the iron is still protected from rusting by the sacrificial method (magnesium can also be used)