Chemistry Year 9 no.3

• What is a pure substance made up from?

  Only one type of particle and has a sharp melting and boiling point.
• What is a mixture made up of?

  2 or more different types of particle and will melt/ boil over a range of tempuratures
• A formulation is a mixture with specific amounts of different substances, designed to give specific properties
• What are emulsifiers?

  A molecule that allows two IMMISCIBLE substances to mix
• What does immiscible mean?

  2 liquids that do not mix together (the liquid forms layers instead)
• What does emulsion mean?

  Tiny droplets of one liquid suspended (dispersed) in another liquid

  
• Name the emulsifier diagram:

  A) Hydrophobic tail

  B) Hydrophilic head

  
• HydroPHOBIC tail means that it attracts oil

  HydroPHILIC head means that it attracts water
• • Hydrogen → lit splint burns with a squeaky pop
  • Oxygen → glowing splint relights
  • Carbon dioxide → turns limewater from clear to cloudy
  • Chlorine → bleaches damp blue litmus paper
  • Water → turns Blue Cobalt chloride paper pink
• What is the separation technique used to separate mixtures of soluble (usually coloured) substances?

  Chromatography
• Chromatography works because some of the substances are more soluble than others.

  More soluble substances move further up the paper.
• A chromatogram can be used to compare unknown mixtures with pure substances
• Flame colour test:

  • Lithium→ crimson red
  • Potassium→ lilac flame
  • Calcium→ Orange
  • Copper→ blue, green
  • Barium→ apple green
  • Sodium→ orange/yellow flame
• What is the difference between molecules and mixtures?

  Molecule: 2 or more atoms chemically bonded

  Mixtures: 2 or more compounds/ element together
• Carbonates:

  Lime water starting to precipitate ( turn milky)
• Some metal ions will form different coloured precipitates when mixed with sodium hydroxide
• Iron (II) = green

  Iron (III) = brown

  Copper = Blue

  Calcium = White

  Magnesium = White
• Silver ions reacts with halide ions to form insoluble precipitates
• Silver ions

  Chloride = White

  Bromide= Cream

  Iodide= Yellow
• Sulphates reacts with barium chloride to form a white precipitate