Chemistry - Properties of Materials (Year 8)

• Solution

  A mixture of a solute dissolved in a solvent
• Dissolving

  Solute particles spread out and mix with solvent particles
• Solute


  The substance that dissolves
• Solvent

  The substance that the solute dissolves into
• All solutions are transparent
• Transparent doesn't mean colourless
• Opaque


  Cannot see through
• Milk is not a solution, it is opaque
• Dissolving needs two substances, a solute and a solvent
• Examples of dissolving


  • Sugar in black tea
  • Instant coffee in hot water
  • Nail polish in nail polish remover
• Examples of melting


  • Butter in a frying pan
  • Ice cream on a warm day
  • Candle wax as the candle burns
• Concentrated solution


  Has a lot of solute particles
• Dilute solution


  Has fewer solute particles
• Soluble


  A solid that dissolves in a solvent
• Insoluble


  A solid that will not dissolve in a solvent
• Saturated solution


  No more solute will dissolve
• Some soluble substances are more soluble than others
• Sodium chloride has greater solubility than lead chloride
• To compare solubility, measure how much solute will dissolve in a known amount of solvent
• Solubility of different salts in 100g of water at 20°C

  • Sodium chloride: 36g
  • Copper sulfate: 32g
  • Calcium chloride: 74g
  • Potassium chlorate: 7g
  • Lead chloride: 1g
• As temperature increases


  Solubility of most solutes also increases
• You can dissolve more sugar in 100g of water at 80°C than at 20°C
• Solubility of different salts at a range of temperatures

  • Potassium nitrate
  • Sodium nitrate
  • Copper sulfate
• Water is not the only solvent, some substances dissolve in other solvents
• Investigating how temperature affects the amount of salt that will dissolve in water

  1. Identify variables

  2. Keep volume of water constant

  3. Change temperature

  4. Measure number of spatulas of salt that dissolve
• Independent variable


  The variable you change
• Dependent variable


  The variable you measure
• Control variables


  The variables you keep the same
• Paper chromatography


  1. Separate coloured inks in black ink

  2. Water is the solvent

  3. Different coloured inks separate due to different solubilities
• Permanent marker ink is not soluble in water, requires a different solvent like alcohol