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• What defines a pure substance in chemistry?

  A single element or compound only
• What happens to pure substances at specific temperatures?

  They melt and boil at specific temperatures
• What characterizes an impure substance?

  Contains more than one type of element
• How do impure substances behave in terms of melting and boiling points?

  They melt and boil at a range of temperatures
• What is the definition of a pure substance?

  Has a definite and constant composition
• What is a mixture of oxygen and hydrogen considered?

  A mixture, not a compound
• What are formulations in chemistry?

  • Examples of mixtures
  • Contain components in specific proportions
  • Used to create useful products
• Why do scientists focus on the proportions in formulations?

  To make the most useful product
• What methods can be used to separate mixtures?

  • Filtration
  • Crystallisation
  • Simple distillation
  • Fractional distillation
• What does filtration do in separating mixtures?

  Separates insoluble solids from liquids
• What is the purpose of crystallisation in separating mixtures?

  Evaporates a solvent leaving the solute
• When is simple distillation used?

  To separate solvent from a solution
• What is required for simple distillation to work?

  Solvent must have a lower boiling point
• What does fractional distillation do?

  Separates two or more substances from a mixture
• What are key terms related to chemical analysis?

  • Chromatography
  • Formulation
  • Impure
  • Mobile phase
  • Pure
• What is chromatography used for?

  To separate substances in a mixture
• What should you practice regarding chromatography equipment?

  Describe the function of each piece
• How can you identify spots in chromatography?

  Use a colored pencil to draw lines
• What is a common method for testing gases?

  Hold a lighted splint near the gas
• What indicates the presence of hydrogen gas?

  It produces a 'pop' sound with a splint
• How can carbon dioxide be tested?

  Bubble it through limewater
• What happens to limewater when carbon dioxide is present?

  It turns cloudy
• What is the role of the mobile phase in chromatography?

  It carries the substances through the medium
• What is the stationary phase in chromatography?

  The medium that holds the substances in place