potable water

• What is potable water?

  Water that is safe to drink
• How can we obtain potable water?

  By treating fresh water or desalinating seawater
• What does pure water contain in chemistry?

  Only $H_2O$ molecules
• Why is potable water not considered pure in chemistry?

  It often contains other dissolved substances
• What are the three criteria for water to be considered potable?

  Low dissolved substances, pH 6.5-8.5, no microorganisms
• What is the acceptable pH range for potable water?

  Between 6.5 and 8.5
• What types of microorganisms should be absent in potable water?

  Bacteria and fungi
• What influences the source of potable water in different regions?

  Geographical location and climate
• What is fresh water?

  Water with low dissolved substances
• How does the UK obtain its fresh water?

  Through rainfall that collects as surface or groundwater
• What are surface water sources?

  Lakes, rivers, and reservoirs
• What are groundwater sources?

  Water found under the ground in aquifers
• What is a benefit of using surface water?

  It is easy to access and replenished by rain
• What is a drawback of surface water?

  It can dry up in hot weather
• What is the first step in treating fresh water?

  Filtering through a wire mesh
• What is the second step in treating fresh water?

  Passing it through sand and gravel
• What is the final step in treating fresh water?

  Sterilizing to kill harmful microbes
• What are the three methods to sterilize water?

  Chlorine gas, ozone, or ultraviolet light
• What is desalination?

  Extracting potable water from seawater
• What are the two techniques used for desalination?

  Distillation and reverse osmosis
• What is the process of distillation in desalination?

  Boiling salty water and condensing vapor
• How does reverse osmosis work?

  Water passes through a membrane, separating ions
• What is the outcome of both desalination techniques?

  Pure distilled water
• What are the steps involved in treating fresh water to make it potable?

  1. Filter through a wire mesh
  2. Pass through sand and gravel
  3. Sterilize to kill harmful microbes
• What are the advantages and disadvantages of desalination techniques?

  Advantages:

  • Provides a limitless supply of water
  • Useful in arid regions with little rainfall

  
  

  Disadvantages:

  • Requires a lot of energy
  • Expensive to produce large quantities
• test to confirm that distilled water is pure

  test - determine the boiling point

  result - pure water boils at 100c

  OR

  test - determine the freezing point

  result - pure water freezes at 0c
• test to identify gas used to sterilise water

  test - damp litmus paper

  result - litmus paper bleached
• why does potable water contain dissolved solids after filtered

  dissolved solid pass through the filter paper as the dissolved solid particles are really small