Particle model/ forces and matter

• Thermal energy


  Energy stored in the movement of the particles that make up the substances in a system
• Temperature


  • A measure of the movement of the particles
  • Not the same as thermal energy
• When a solid stores more thermal energy


  The vibrations of its particles increase
• When a liquid or gas stores more energy


  The speeds of the particles increase
• A kettle full of boiling water stores more energy than a cup full of water at the same temperature
• Flowers put into liquid nitrogen (-196°C) become very brittle and shatter if dropped
• Insulation


  Materials used to reduce the transfer of thermal energy to the surroundings
• Specific heat capacity


  The amount of energy it takes to increase the temperature of 1 kilogram of a substance by 1°C
• Changes of state


  1. Solid to liquid (melting)

  2. Liquid to gas (boiling)

  3. Gas to liquid (condensing)

  4. Liquid to solid (freezing)
• Specific latent heat


  The amount of energy it takes to make 1 kg of a substance change state
• Steam causes more severe burns than boiling water due to the release of latent heat of evaporation
• Melting ice experiment


  Put ice in beaker, heat with hot water, measure temperature every minute until all ice melted
• Specific latent heat


  Energy required to change the state of 1kg of a substance without changing its temperature
• Energy = 5kg x 2257 000 J/kg
• Total energy = 11285000J
• Steam releases the latent heat of evaporation when it condenses


  This causes more hurt from a scald than the same mass of boiling water
• Properties of water in its solid (ice), liquid and gas forms
• Melting ice


  1. Put crushed ice in beaker

  2. Heat with hot water

  3. Measure temperature every minute

  4. Note when ice starts and finishes melting
• Measuring specific heat capacity

  1. Put water in polystyrene cup on balance

  2. Put thermometer in water

  3. Use immersion heater and joulemeter

  4. Record temperature change and energy used
• Temperature of a gas

  Measure of the average kinetic energy of the particles in the gas
• The Sun never shines on parts of the Moon's south pole craters, which are the coldest recorded places in the Solar System at below -240°C
• Pressure of a gas

  • Due to forces on the container walls from the moving particles hitting them
  • Increases with temperature as particles move faster
• Absolute zero is -273°C, where a gas would have zero pressure and particles not moving
• Kelvin temperature scale


  Measures temperature relative to absolute zero, with 1K = 1°C interval
• Average kinetic energy of gas particles is directly proportional to the Kelvin temperature
• Deformation


  Change in shape of an object due to forces
• Elastic materials


  • Return to original shape when forces removed
  • Inelastic materials keep new shape after forces removed
• Malleable materials


  • Metals that can be hammered into shape
• Metals can be elastic for small forces but inelastic for large forces
• Inelastic materials


  • Suggested: clay, plasticine
• Force and extension


  • Extension is change in length when forces applied
  • Linear relationship between force and extension for springs
  • Non-linear for other materials like rubber bands
• Investigating force and extension of springs

  1. Set up apparatus with spring and ruler

  2. Hang different weights and measure extension

  3. Repeat for different springs

  4. Calculate spring constant from results
• Spring constant


  Force needed to produce 1m extension
• Springs storing energy


  • Mousetrap spring twisted to store elastic potential energy