air and water

• distilled water is used in practical chemistry rather than tap water because it contains fewer chemical impurities
• water from natural sources may contain substances like

  (a) dissolved oxygen (beneficial for aquatic life)

  (b) metal compounds (some provide essential minerals for life, some are toxic)

  (c) plastics (some harm aquatic life)

  (d) sewage (contains harmful microbes which cause disease)

  (e) harmful microbes

  (f) nitrates from fertilisers

  (g) phosphates from fertilisers and detergents

  (nitrates and phosphates lead to deoxygenation of the water and damage to aquatic life)
• treatment of domestic water supply:

  (a)sedimentation and filtration to remove solids

  (b) use of carbon to remove tastes and odours

  (c) chlorination to kill microbes

  (d) CaO to neutralise chlorine and make pH7
• uses of water in industry:

  1. coolant
  2. watering crops
  3. solvent
  4. hyroelectric power stations
• use of water homes

  1. washing, cooking, drinking
  2. general sanitation
• water test 1

  A) anhydrous cobalt chloride

  B) hydrated cobalt chloride

  
• water test 2

  A) hydrated copper sulfate

  B) anhydrous copper sulfate

  
• if the water is impure, the melting point will go down and the boiling point will go up
• eutrophication


  the gradual increase in the concentration of phosphorus, nitrogen, and other plant nutrients in an aging aquatic ecosystem such as a lake
• ammonium salts and nitrates are used as fertilisers
• jay jay

  A) nitrogen

  B) potassium

  C) phosphorus

  
• the composition of clean, dry air as approximately 78% nitrogen, N2 , 21% oxygen, O2 and the remainder as a mixture of noble gases and carbon dioxide, CO2
• carbon dioxide from the complete combustion of carbon-containing fuels
• carbon monoxide and particulates from the incomplete combustion of carbon-containing fuels
• methane from the decomposition of vegetation and waste gases from digestion in animals
• oxides of nitrogen from car engines
• sulfur dioxide from the combustion of fossil fuels which contain sulfur compounds
• carbon dioxide: higher levels of carbon dioxide leading to increased global warming, which leads to climate change / carbon monoxide: toxic gas
• particulates: increased risk of respiratory problems and cancer
• methane: higher levels of methane leading to increased global warming, which leads to climate change
• oxides of nitrogen: acid rain, photochemical smog and respiratory problems
• sulfur dioxide: acid rain
• the greenhouse gases carbon dioxide and methane cause global warming by the absorption, reflection and emission of thermal energy and reducing thermal energy loss to space