particle model of matter

• what does the particle model represent

  particles that make up model are tiny balls

  3 states of matter solid, liquid, gas

  the particles in each state are the same but the arrangement, energy, forces of the particles are different
• solid

  forces: strong forces of attraction hold particles together in regular, fixed arrangement

  
  

  arrangement: particles close together in fixed, regular arrangement

  
  

  energy: not much energy as they only vibrate in fixed positions

  
  

  density: highest density as particles are closest together
• liquid

  forces: weaker forces of attraction between particles

  
  

  arrangement: particles close together but can move past eachother, irregular arrangements

  
  

  energy: liquid state particles have more energy than solid state but less than gas

  
  

  directions: move in random directions at low speeds

  
  

  density: less dense than gas as particles are close together
• gas

  forces: no forces of attraction between particles

  
  

  arrangement: free to move

  
  

  energy: most energy than liquid or solid state

  
  

  directions: travel in random directions at high speeds

  
  

  density: lowest density, particles furthest apart
• density formula

  mass/volume
• density

  measure of compactness of substance

  relates to mass of substance and how much space it takes up

  
  

  it varies between different states of matter
• what does density of object depend on


  what it is made of
• less dense material

  particles are more spread out
• dense material

  tightly packed particles
• what happens when you compress less dense material

  if you compress material, particles would move closer together, become more dense

  mass is same, volume decreases
• If a change of state happens:

  energy needed to change state is latent heat

  
  

  when change in state occurs energy supplied changes energy stores (internal energy) but not temperatures
• specific latent heat

  The amount of energy required to change the state of 1kg of a substance without a change of temperature.
• when you heat liquid, it boils (or evaporates) and becomes a


  gas
• when you heat solid

  melts into liquid
• changes of state can be cooling

  particles lose energy and form bonds
• Is a change of state a physical or chemical change?

  physical change, no new substance is produced. same substance but in a different form.
• if you reverse change of state, substance

  returns to original form with original properties if reversed
• describe how, when substances change state (melt, freeze, boil, evaporate, condense or sublimate), mass is conserved.


  The number of particles does not change

  
  

  they are just arranged differently

  
  

  total mass has not changed

  
  

  this is because mass is conserved, none is lost
• how is energy stored in a system

  Energy is stored inside a system by the particles (atoms and molecules) that make up the system. This is called internal energy
• Internal energy

  the sum of the kinetic and potential energies of all particles in the system
• Why do particles have internal energy

  Particles in a system vibrate and move around - kinetic energy

  particles have positions - potential energy
• What happens when you heat a system

  Heating a system transfers energy to particles. Particles gain energy and move faster, increasing their internal energy

  
  

  - this leads to change in temperature or change in state

  - if temperature changes the size of change depends on mass of substance, what its made of (specific heat capacity) , energy input
• What does temperature change depend on

  Its mass, specific heat capacity and energy input.
• when would change is state occur in heating

  - change in state occurs if substance is heated enough so particles have enough energy in kinetic energy stores to break bonds, holding them together
• What does increase in temperature change depend on

  the mass of the substance heated, the type of material and the energy input to the system.
• specific heat capacity

  amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.
• specific heat capacity formula


  ∆ E = m c ∆ θ

  
  

  change in thermal energy = mass × specific heat capacity × temperature change
• Units for specific heat capacity

  change in thermal energy = ∆ E = Joules = J

  
  

  mass = m = Kg

  
  

  specific heat capacity = c = J/kg °C

  
  

  temperature change = ∆θ = °C.
• what happens when you met or boil substance

  you are putting in energy therefore increasing internal energy, but energy is used for breaking bonds between substance rather than raising temperature
• flat spots on heating graph

  where energy is transferred by heating but not used to change temperature

  
  

  show energy transfer

  
• heating graph

  
• what happens when a substance is condensing or freezing

  bonds are forming between particles which release energy

  internal energy decreases but temperature doesn't decrease until the substance has turned to liquid (condensing) or solid (freezing)
• specific latent heat

  Amount of heat needed to change the state of 1 kilo of a substance WITHOUT a change in temperature.
• what is specific latent heat different for

  specific latent heat is different for different materials and changes between different states
• cooling energy


  this is released by a change in state
• cooling graph

  
• Specific latent heat of fusion

  change of state from solid to liquid (melting/freezing)
• Specific latent heat of vaporisation

  - change of state from liquid to vapour (evaporating/boiling/condensing)
• Energy for a change of state equation

  energy for a change of state = mass × specific latent heat

  
  

  E = m L

  
  

  energy, E, = joules, J

  mass, m, = kilograms, Kg

  specific latent heat, L = , in joules per kilogram, J/kg
• PARTICLE MOTION OF GAS