particle model of matter (p3)

• Density

  Depends on how closely particles are packed
• Measuring density of a regular object

  1. Measure length, width and depth of object

  2. Calculate volume by multiplying dimensions

  3. Use mass balance to determine mass

  4. Apply density equation
• Measuring density of an irregular object

  1. Measure mass of object using scales

  2. Fill Eureka can with water to the brim and place measuring cylinder under spout

  3. Submerge object into Eureka can, displaced water volume = volume of object

  4. Calculate object's density
• States of matter

  • Solids
  • Liquids
  • Gases
• Solids

  • Particles are tightly packed
  • Particles vibrate in fixed positions
  • Have a definite shape and volume
• Liquids

  • Particles are close together but not fixed
  • Can flow and take the shape of their container
  • Have a definite volume but no definite shape
• Gases

  • Particles are far apart
  • Can expand to fill their container
  • Have no definite shape or volume
• Changes of state

  1. Melting

  2. Freezing

  3. Sublimating

  4. Condensing

  5. Boiling
• Internal energy

  Total energy of particles from their movement and position
• Kinetic energy

  Energy due to the vibration and movement of particles
• Potential energy

  Energy due to the forces between particles and their position
• Heating a system

  Increases its internal energy and particle kinetic energy
• Specific latent heat

  Energy required for a substance to change its state with no change in temperature
• Specific latent heat of fusion

  Energy required to change a solid to a liquid
• Specific latent heat of vaporisation

  Energy required to change a liquid to a gas
• Particle motion in gases

  • Molecules are in constant random motion
  • Move in straight lines until they collide with container wall or other particle
  • Speed of molecules increases as temperature increases
• Adding more particles to a fixed volume

  Increases the pressure
• Compressing a gas in a fixed volume


  Increases the particle collision frequency and pressure
• molecules in a gas are in constant random motion
• molecules in a gas move in a straight lines
• how does temperature affect particles motion in gases

  -as temp increases so does speed of molecules

  -if volume is kept same and temp increases the kinetic energy will increase

  -meaning their are more particle collisions
• how does pressure affect particle motion in gases

  -pressure is a result of collisions between molecule's and container walls

  -more molecules, higher the pressure

  -particles collide more frequently and with greater force against the walls
• temp-pressure relationship

  -if we heat a gas up the molecules gain kinetic energy and move at higher speeds, leading to more frequent and forceful collisions with the container which increases the pressure

  -at constant volume an increase in temperature will lead to an increase in pressure
• pressure in gas

  -changing the volume of a gas affects the pressure a gas can be compressed or expanded by pressure changes

  -the pressure procedures a net force at right angles to the wall of th gas container

  -increasing volume, at a constant temp, can lead to a decrease in pressure
• increasing the pressure in a gas

  doing work on a gas increases the internal energy of the gas and can cause an increase in temp
• adding more particles to a fixed volume

  -compressing expanding gas i changing the volume

  -pumping more gas into the same volume means more particles are present, more collisions occur pressure increases

  -energy is transferred to particles when more gas is added to a fixed volume this heats up a gas
• a fixed number of particles in a smaller volume

  -particles collide with wall that is moving forward

  -particles gain momentum rebound velocity is greater than aproaching velocity

  -particle has greater velocity, pressure increases as particles collide with wall more frequently

  -temp increases as KE of particles increases