Melting and Freezing

• Solid

  • Particles held together in a pattern
• Liquid

  • Particles move around but still held together
• Substance

  Properties are the same all the way through
• Mixture

  More than one substance
• Melting

  1. Particles gain energy

  2. Particles vibrate more

  3. Particles break out of their pattern
• Freezing

  1. Particles transfer energy to the surroundings

  2. Particles slow down

  3. Particles form a pattern and vibrate in place
• Melting point

  Temperature at which a substance changes from solid to liquid
• Each substance has its own melting point
• When the temperature of a substance is below its melting point, it is a solid
• When the temperature of a substance is above its melting point, it is a liquid or gas
• Substances

  • Helium
  • Hydrogen
  • Water
  • Ibuprofen
  • Paracetamol
  • Iron
• A pure substance has a sharp melting point
• Mixtures do not have a sharp melting point
• Cooling stearic acid

  1. Place test tube in hot water

  2. Record temperature every 10 seconds

  3. Remove from hot water and record temperature until 40°C
• Control variables

  What was kept the same to make it a fair test
• Ethanol has a melting point of -114.1°C
• At 0°C, ethanol is a liquid
• At -120°C, ethanol is a solid
• At -110°C, ethanol is a liquid
• Melting


  Change of state from solid to liquid
• As a substance melts


  Its particles vibrate faster
• As a substance melts


  Its particles start moving around
• Liquid state


  State of matter where particles move around but are still held together
• Melting point


  Temperature at which a substance melts
• A substance with a melting point of -7°C is liquid at 20°C
• A substance with a melting point of -7°C could be liquid or gas at 20°C</b>
• Melting


  1. Particles vibrate faster and move away from their places in the pattern

  2. More and more particles start moving around

  3. When all the particles are moving around, the substance has melted
• Freezing


  1. Particles start to move more slowly

  2. Particles get into a pattern and vibrate on the spot