chemical analysis

• What sound does hydrogen make when tested?

  'Squeaky pop'
• How is hydrogen tested in a laboratory?

  By using a burning splint in the gas
• What is the test for oxygen?

  Glowing splint relights in oxygen
• What happens to a glowing splint in oxygen?

  It relights when inserted into oxygen
• How is carbon dioxide tested?

  By bubbling it through limewater
• What is the result of bubbling carbon dioxide through limewater?

  It turns milky (cloudy)
• What is the test for chlorine gas?

  Using damp litmus paper
• What happens to damp litmus paper in chlorine gas?

  It bleaches and turns white
• What are the tests for the four gases: hydrogen, oxygen, carbon dioxide, and chlorine?

  • Hydrogen: Burning splint → 'squeaky pop'
  • Oxygen: Glowing splint → relights
  • Carbon Dioxide: Limewater → turns milky
  • Chlorine: Damp litmus paper → bleaches white
• What is a pure substance?

  A single element or compound
• How do pure substances behave when heated?

  They melt and boil at specific temperatures
• How can melting and boiling points be used?

  To distinguish pure substances from mixtures
• What does everyday language define a pure substance as?

  A substance that has had nothing added
• What is an example of a pure substance?


  Pure milk
• What is a formulation?

  A mixture designed as a useful product
• Why are formulations complex mixtures?

  Each chemical has a particular purpose
• How are formulations created?

  By mixing components in measured quantities
• What are some examples of formulations?

  Fuels, cleaning agents, paints, medicines
• What is chromatography used for?

  To separate mixtures and identify substances
• What are the two phases involved in chromatography?

  Stationary phase and mobile phase
• What does separation in chromatography depend on?

  The distribution of substances between phases
• How is the Rf value calculated?

  Distance moved by substance ÷ distance moved by solvent
• Why do different compounds have different Rf values?

  They behave differently in different solvents
• What happens to a pure compound in chromatography?

  It produces a single spot in all solvents
• What is paper chromatography?

  A technique separating compounds by speed in solvent
• How does solubility affect movement in paper chromatography?

  The more soluble, the further it travels up
• What does chromatography separate in colored substances?

  Different pigments
• What is a pigment?

  A solid, colored substance
• What can flame tests be used to identify?

  Metal ions
• What color flame does lithium produce?

  Crimson
• What color flame does sodium produce?

  Yellow
• What color flame does potassium produce?

  Lilac
• What color flame does calcium produce?

  Orange-Red
• What color flame does copper produce?

  Green
• What happens to flame colors in a mixture of ions?

  Some colors can be masked
• What precipitate do aluminium, calcium, and magnesium ions form with NaOH?

  White precipitate
• Which metal ion's precipitate dissolves in excess NaOH?

  Aluminium
• What color precipitate does copper(II) produce?

  Blue precipitate
• What color precipitate does iron(II) produce?

  Green precipitate
• What color precipitate does iron(III) produce?

  Brown precipitate