Purity

• What does the term 'pure' mean in everyday life?

  'Clean' or 'natural'
• How is the term 'pure' defined in chemistry?

  A substance is pure if it's completely made up of a single element or compound
• What distinguishes a pure substance from a mixture?

  A pure substance contains only one element or compound, while a mixture contains multiple compounds or elements
• What is an example of a chemically impure substance mentioned in the text?

  Fresh air
• What are alloys classified as in terms of mixtures?

  Alloys are a type of mixture called a formulation
• What are formulations and their characteristics?

  • Useful mixtures with a precise purpose
  • Made by following a 'formula'
  • Each component is present in a measured quantity
  • Contributes to the formulation's properties
• What is the specific melting point of pure ice?

  0 °C
• What is the specific boiling point of pure water?

  100 °C
• How can you test the purity of a substance using its melting or boiling point?

  By comparing the actual melting or boiling point to the expected value
• What happens to the melting point of an impure substance?

  The melting point will be too low
• What is an example of an impure substance's melting point?

  If ice melts at -2 °C, it likely has an impurity
• What is the boiling point of seawater and why is it considered impure?

  About 100.6 °C due to the presence of salt and other impurities
• How can you identify a mixture when heating it?

  Different components will melt or boil at different temperatures
• If Adil tests a compound with a melting point of 55 °C and finds it melts at a lower temperature, what does this indicate?

  It indicates that the sample contains impurities
• What should Adil expect if his sample is impure?

  The sample melts at a temperature below 55 °C
• What is the significance of the melting point in determining purity?

  The melting point helps to identify if a substance is pure or impure based on its expected value