Water Purity and Distillation

Key Objectives

• Describe how to analyze a sample of water for purity.
• Explain how to purify a sample of water by distillation.

Potable vs. Pure Water

• Potable Water: Safe to drink but not necessarily pure.
  • May contain dissolved solids.
  • pH may not be 7.
• Pure Water:
  • Contains no dissolved solids (e.g., salts).
  • Has a pH of 7 (neutral).

Analyzing Water Purity

1. Check pH Level:
   • Use universal indicator paper to test a small water sample.
   • Pure water will show a pH of 7 (green on the indicator).
   • If pH is not 7, the sample contains acids or alkalis, indicating impurity.
2. Test for Dissolved Solids:
   • Weigh an empty evaporating basin.
   • Fill it with the water sample and heat with a Bunsen burner until all water evaporates.
   • Cool and weigh the basin again.
   • Increased weight indicates the presence of dissolved solids, confirming impurity.
   • If weight does not change, no dissolved solids are present, suggesting purity.
   • Note: Dissolved gases are not tested in this procedure.

Water Purification by Distillation

• Equipment Setup:
  • Conical flask with water sample on a tripod and gauze.
  • Delivery tube leading to a test tube in a beaker of ice and water.
• Process:
  • Heat the water gently with a Bunsen burner to boil.
  • Water evaporates into steam (water vapor).
  • Steam travels through the delivery tube.
  • Condenses back to liquid in the cold test tube.
• Result:
  • The resulting distilled water is pure with no dissolved solids and a pH of 7.

Additional Resources

• For more questions and practice, refer to the revision workbook mentioned in the lecture.

These notes summarize the process of determining water purity and purifying water via distillation, as discussed in the lecture.