topic 3

• solids have strong forces of attraction
• the particles in a solid have very little energy so only vibrate
• solids usually have the highest density
• liquids have weaker forces of attraction
• particles in a liquid have more energy
• liquids are usually less dense than solids
• gases almost have no forces of attraction
• density depends of how tightly packed the particles are
• measuring density of a solid

  1. use a balance to measure the mass
  2. for a solid shape find the volume using length x width x height
  3. for a weird shape submerge the eureka can with water - this water is displaced by the object into a measuring cylinder then that is equal to the volume of water
• measuring density of liquid

  1. measure cylinder on balance and zero the balance
  2. pour 10ml liquid into a measuring cylinder and record the liquid mass
  3. pour another 10ml into cylinder and record total volume and mass - repeat this until full
  4. for each measurement use formula to find density ( 1ml = 1cm ^3 )
  5. take average of densities
• internal energy

  1. particles in a system move or vibrate which creates energy is the kinetic energy store
  2. objects also have energy in gravitational potential store due to there position
• internal energy is if a system is the total energy in the kinetic and gravitational store
• when an object is melted or boiled the energy is used to break the intermolecular bonds instead of being used to raise the temperature
• when an objects is condensed or frozen bonds are formed which releases energy this means the internal energy decreases but the temperature doesnt until flat part on graph
• latent heat is the energy needed to change the state of a substance
• specific latent heat is the amount of energy needed to change 1kg of a substance from one state to another
• specific latent heat of solid to liquid is fusion
• specific latent heat of liquid and gas is vaporisation
• in a sealed gas container outwards gas pressure is the total force exerted by all particles in gas on a unit area of the container wall