Required Practical 8: Water

• What should you be able to describe by the end of the video?

  How to analyze and purify water
• What is potable water?

  Water that is safe to drink
• How does potable water differ from pure water?

  Potable water may contain dissolved solids
• What is the pH of pure water?

  7
• What indicates that a water sample is not pure?

  If the pH is not seven
• How can you check the pH of water?

  Using universal indicator paper
• What does a pH of seven indicate about the water sample?

  The water sample may still contain dissolved solids
• What is the first step in testing for dissolved solids in water?

  Weigh an empty evaporating basin
• What happens to the mass of the evaporating basin if dissolved solids are present?

  The mass will increase
• Why does the mass of the evaporating basin increase if dissolved solids are present?

  Because solids form crystals on the basin
• What might still be present in the water even if no dissolved solids are detected?

  Dissolved gases
• What is the method used to purify water by distillation?

  Heating water to create vapor
• What is the role of the delivery tube in the distillation process?

  To transport water vapor to the test tube
• What happens to water vapor when it enters the cold test tube?

  It condenses back into liquid water
• What is distilled water?

  Water that contains no dissolved solids
• What is the pH of distilled water?

  7
• What are the steps to analyze a sample of water for purity?

  1. Check the pH using universal indicator paper.
  2. Weigh an empty evaporating basin.
  3. Evaporate the water sample and weigh the basin again.
  4. Determine if the mass increased to check for dissolved solids.
• What are the steps to purify water by distillation?

  1. Place water sample in a conical flask.
  2. Heat the water gently with a Bunsen burner.
  3. Collect water vapor through a delivery tube.
  4. Condense vapor in a cold test tube.
  5. Collect distilled water, which is pure.