Purity of substances

• • A pure substance has fixed boiling and melting points.
  • they will melt completely at only one temperature
  • Use a thermometer to check if a substance is pure as it only boils at a fixed boiling point.
• How do impurities affect melting points?

  • Impurities lower the melting point.
  • The greater the amount of impurity the lower the melting point
  • The substance melts over a range of temperatures
• How do impurities affect boiling points?

  • impurities make the boiling point higher.
  • The greater the amount of impurity, the higher the boiling point.
  • The liquid boils over a range of temperatures.