Changes of State and the Particle Model

• In solids, particles are close together with strong forces between them.
• In liquids, particles are still close together but can move past one another.
• Describe one change in the weather which would cause the puddle of water to dry up faster.

  Becomes wind
• Explain, in terms of the particles, why gases are easy to compress

  Gaps between particles so they’re easy to push particles closer
• Describe the movement of the particles of helium gas inside the balloon.

  Range of speeds in random motion
• Write down the equation which links density, mass and volume.

  density = mass / volume
• What is meant by ‘specific latent heat of vaporisation’?

  amount of energy required to change the state of a substance from liquid to gas of unit mass
• how do you work out density?


  Density (kg/m^3) = mass (kg) /volume (m^3)

  
• what can the particle model be used to explain?

  - the different states of matter

  - the differences in densities
• what is internal energy?

  internal energy is the energy stored by particles that make up a system
• what is specific latent heat?

  The amount of energy required to melt or boil 1 kg of the material.
• what is latent heat?

  The energy needed to change the state of a substance

  
• how do you work out specific latent heat?

  energy (j) = mass (kg) x specific latent heat (j/kg)

  
• how do you work out specific heat capacity?

  SHC= energy/ mass x temp change
• what can pressure cause?

  change in volume

  - the pressure of a gas causes a net outward force

  
  

  Increase in temperature

  - if you apply force, you do work. doing work on a gas increases its internal energy, which can increase its temperature
• Solid


  Particles in rows

  fixed positions

  tightly packed

  Fixed shape

  
• liquid

  Particles can flow

  Particles are all in contact

  Can take the shape of a container

  
• gas


  particles can move around randomly

  particles move quickly

  
• density =


  mass / volume
• kg/m^3


  unit of density
• We use the particle model to

  -Explain different states of matter

  -Explain differences in density
• Is there a change of mass during a change of state?

  No, mass is always conserved.