topic p3- particle model of matter

• molecules

  a cluster of non-metal atoms that are chemically bonded together
• 3 types of molecules

  • molecule of an atom
  • molecule of an element
  • molecule of a compound
• the density of an object depends on what it's made up of and how the particles are arranged
• density (kg/m^3)=

  mass (kg)/ volume (m^3)
• solid

  • strong forces of attraction
  • close together
  • vibrate
  • fixed shape and volume
  • high density
• liquid

  • weaker forces of attraction
  • irregular arrangements
  • move in random directions at low speed
  • less dense than solids
• gas

  • no forces of attraction
  • free to move in random directions or high speeds
  • less dense than liquids
• the higher the temperature of a gas,

  the higher the average energy in the kinetic energy stores of the gas particles
• gas pressure is caused by gas particles colliding with a surface and exerting a net force on it
• a gas at constant volume

  • temperature increases
  • particles get faster and collide with the container more often
  • pressure increases
• a gas at constant temperature

  • volume increases
  • particles spread out and collide with the container less often
  • pressure decreases
• to find the density of a solid object

  1. use a balance to measure its mass
  2. if its a regular solid, measure the length, width and height using a ruler; then work out the volume by multiplying them together
  3. for an irregular solid, you can find its volume by submerging it in a eureka can filled with water; the water displaced by the object will be transferred to the measuring cylinder
  4. record the volume of water in the measuring cylinder; this is the volume of the object
  5. use the mass and volume to work out the object's density
• internal energy

  the total energy stored by the particles that make up a system
• internal energy of a system

  total amount of energy in kinetic and potential energy stores of all it's particles
• changes of state

  
• the specific latent heat of a substance is the amount of energy needed to change 1kg of it from one state to another without changing its temperature
• energy=

  mass x specific latent heat