3-Particle model of matter

• particle theory

  • each particle is a small, solid, inelastic sphere
  • solids- strong forces of attraction(bonds), vibrate in a fixed position, have definite shape and volume
  • liquids- weak forces of attraction, free to move around, fairly compact, don't have definite shape but have definite volume
  • gases- very weak forces of attraction, free to move around by themselves, don't have definite shape or volume
• changes of state

  • from solid to liquid - melting - particles gain more energy and start to vibrate more which weakens forces of attraction/ bonds between them. At the melting point they will have enough energy to break free of their bonds and melt into a liquid
  • from liquid to gas - boiling - particles move around faster . Gas particles may expand or increase pressure in a container
  • from gas to liquid - condensing
  • from liquid to solid - freezing
• density

  • density = mass divided by volume
  • Density (kg/m cubed) is a measure of how much mass (kg) a substance has per unit of its volume (m cubed)
• To convert g/cm3 to kg/m3 you have to:

  multiply the g/cm3 value by 1000
• required practical - finding the density of a regular object

  1. measure the mass of the solid on the mass balance
  2. measure the length, width, height using a ruler
  3. calculate the volume of the block
  4. calculate density = mass / volume
• required practical - finding the density of an irregular object

  1. measure the mass of the object using a mass balance
  2. fill the eureka can with water up till it's at level with the spout
  3. carefully lower the object into the can
  4. check the volume of water that came out of the eureka can into the measuring cylinder
  5. calculate density = mass / volume
• required practical - finding the density of a liquid

  1. record the mass of an empty measuring cylinder
  2. measure the mass of 100cm3 of water in a measuring cylinder
  3. subtract the mass of the cylinder from the mass of cylinder and water
  4. calculate density = mass / volume
  5. repeat the experiment a few times to find a mean
• specific latent heat is the energy required to change the state of 1kg of a particular substance without a change in temperature
• specific latent heat of cooling is the energy released to change the state of 1kg of a particular substance without a change in temperature
• • The specific latent heat of fusion refers to when a substance changes from a solid to a liquid (or vice versa).
  • The specific latent heat of vaporisation refers to when a substance changes from a liquid to a gas (or vice versa).
• specific latent heat equation

  • energy (J) = mass (kg) x specific latent heat (J/kg)
• • pressure is continuous force exerted by particles on or against an object by colliding against it
  • pressure = force / area
  • pressure depends on how many collisions there are, how much energy each collision involves
• how temperature affects pressure

  • heat transfers energy to the particle's kinetic energy stores
  • faster movement of particles causing more collisions
  • each collision will involve more force
• how temperature affects pressure

  • increase the number of particles and keeping the volume of the container the same
  • this will ensure there are more particles to collide with the walls and therefore more collisions
• how volume affects pressure

  • a smaller container with the same volume of particles which means less travel is needed
  • less travel means more collisions
• pressure in flexible containers

  • temperature and concentration will change the volume rather than the pressure as it will expand