Substances in Water from Natural Sources | Chemistry for Grade 11 (IGCSE) PDF Download

Substances in Water from Natural Sources

• Water serves various purposes in our daily lives:
  • Domestic applications encompass drinking, cooking, gardening, and overall hygiene.
  • Agricultural utilization involves providing drinking water for livestock and irrigating crops.
  • Industrial functions entail its use as a solvent, coolant, and in the production of steam for electricity generation.
• Natural water reservoirs, including lakes, rivers, and underground water sources like groundwater, are primary sources of water.
• Rock formations that hold water are termed aquifers.
• Water from these natural sources can contain a range of substances:
  • Dissolved oxygen
  • Metal compounds
  • Plastics
  • Sewage
  • Pathogenic microorganisms
  • Nitrates from fertilizers
  • Phosphates from fertilizers and detergents
• Rainfall can wash various substances into lakes, rivers, or groundwater, contributing to their presence.
• While some substances occur naturally, many result from human activities.

Beneficial & Harmful Substances in Water

• Some substances in natural water sources are either beneficial or harmful.
• Beneficial substances:
  • Dissolved oxygen: crucial for aquatic life to thrive.
  • Metal compounds: some offer essential minerals like calcium and magnesium.
• Potentially harmful substances:
  • Metal compounds: certain types like aluminium and lead are toxic.
  • Some plastics: detrimental to aquatic life by causing issues like entrapment and starvation.
  • Sewage: contains harmful microbes leading to diseases.
  • Nitrate & phosphates from fertilisers: promote excessive aquatic plant growth, resulting in water deoxygenation and harm to aquatic life (eutrophication).