chemistry in the enviroment

• Chemical Tests for Water:

  • Anhydrous Cobalt (II) Chloride turns from blue to pink
  • Anhydrous Copper (II) Sulfate turns from white to blue
• Melting and Boiling Point Test:

  • Melting Point at 0°C and Boiling Point at 100°C
  • Distilled Water is preferred in practical chemistry over tap water due to fewer chemical impurities
• Natural Sources of Water may contain substances such as:

  • Dissolved Oxygen (important for aquatic life)
  • Metal Compounds (provide essential minerals but some are toxic)
  • Plastics (harm aquatic life)
  • Sewage (contains harmful microbes causing diseases)
  • Harmful microbes
  • Nitrates from fertilisers
  • Phosphate from fertilisers and detergents (leads to deoxygenation of water and damage to aquatic life - Eutrophication)
• Treatment of Domestic Water Supply:

  • Water pumped into screens to remove solid, insoluble impurities
  • Sedimentation process to make small clay pieces stick together and be removed
  • Filtration through sand and gravel layers to remove larger, insoluble debris
  • Carbon added to remove taste and odor
  • Chlorination process adds chlorine gas to kill bacteria, neutralized by adding sodium hydroxide
• Uses of Water:

  • Home: drinking, cooking, washing
  • Industry: water jet cutting, water blasting, car radiators, gardens, plants, solvent in refining ores, generating hydroelectricity
• Fertilisers:

  • Substances added to soil to increase crop yield
  • Contain Ammonium Salts and N.P.K (Nitrogen, Phosphorus, Potassium)
  • Functions of Elements:
  • Nitrogen: makes chlorophyll and protein, promotes healthy leaves
  • Phosphorus: promotes healthy roots
  • Potassium: promotes growth, healthy fruits, flowers
  • Reaction with alkali displaces ammonia from its compound
• Air Quality and Climate:

  • Clean air components:
  • Primary: Nitrogen (78%), Oxygen (21%)
  • Secondary: Noble gases (mainly Argon) and Carbon Dioxide (1%)
• Pollutants in Air:

  • Carbon monoxide (CO): incomplete combustion, binds with haemoglobin, constricts oxygen supply
  • Carbon Dioxide (CO2): complete combustion, increased global warming
  • Methane (CH4): decomposition, increased global warming
  • Sulfur Dioxide (SO2): combustion of fossil fuels, causes acid rain
  • Nitrogen Oxides (NO2): high temperatures reaction, causes respiratory problems, acid rain
  • Lead Compounds: combustion of leaded fuels, damages brain, nerve cells
• Greenhouse Gases Impact on Global Warming:

  • Short wavelength radiation from Sun reaches Earth
  • Thermal energy absorbed, heats oceans/lands
  • Earth radiates thermal energy
  • Greenhouse gases absorb infrared radiation, re-emit in all directions
  • Some infrared radiation comes back, reduces heat loss, leads to global warming
• To reduce climate change effects:

  • Planting trees
  • Reduction in livestock farming
  • Less use of fossil fuels
  • Increased use of hydrogen, renewable energy (wind, solar)
• To reduce acid rain effects:

  • Reduced emissions of sulfur dioxide
  • Flue-gas desulfurisation with calcium oxide
  • Use of catalytic converters in vehicles
• Photosynthesis:

  • Reaction between carbon dioxide and water to produce glucose, oxygen in the presence of chlorophyll, using light energy
  • Word Equation: Carbon Dioxide + Water → Glucose + Oxygen
  • Balanced Chemical Equation: 6CO2 + 6H2O → C6H12O6 + 6O2
• Catalytic Converters:

  • Present in car exhausts with platinum, rhodium catalysts
  • Aids redox reactions to neutralize toxic pollutants from incomplete fuel combustion
  • Reaction equations:
  • 2CO + O2 → 2CO2
  • 2NO + 2CO → N2 + 2CO2