topic 3- particle model of matter

• What units are used for density?

  Kilograms per metre cubed (kg/m³)
• How does density depend on atomic spacing?

  Density depends on the spacing of atoms in matter
• How do the densities of solids, liquids, and gases compare?

  • Solids and liquids have similar densities
  • Liquids usually have lower density than solids (except ice)
  • Gases have far lower density than solids/liquids
• Why do gases have lower density than solids and liquids?

  Gases have increased atomic spacing and energy
• What happens to mass during a change of state?

  Mass is conserved during a change of state
• If 20g of liquid evaporates, how much gas is produced?

  20g of gas is produced
• What distinguishes physical changes from chemical changes?

  • Physical changes are reversible
  • Chemical changes are not reversible
  • Original properties are retained in physical changes
• What are the changes of state?

  • Melting
  • Freezing
  • Evaporating
  • Condensing
  • Sublimation
• What is internal energy?

  Energy stored by particles within a system
• What forms does internal energy take?

  Kinetic and potential energy
• What happens to internal energy when a system is heated?

  Internal energy increases
• What is specific heat capacity?


  Energy required to raise 1kg by 1°C
• What is specific latent heat?

  Energy needed to change state without temperature change
• What is the specific latent heat of fusion?


  Energy to melt or freeze a substance
• What is the specific latent heat of vaporisation?


  Energy to boil or condense a substance
• What happens to energy during melting and evaporating?

  Energy is absorbed
• What happens to energy during freezing and condensing?

  Energy is released
• What is sublimation?


  Solid goes straight to gas
• How is gas pressure related to molecular motion?

  Pressure is due to molecules colliding with walls
• How does temperature affect gas pressure?

  Higher temperature increases average kinetic energy
• What is the Pressure law?

  Changing temperature at constant volume changes pressure
• How does changing the volume of a gas affect pressure?

  • Gas can be compressed or expanded
  • Increasing volume decreases pressure (Boyle's law)
  • Fewer collisions per unit area lead to lower pressure
• What happens when work is done on a gas?

  It increases the gas's temperature
• How does adding more particles to a fixed volume affect pressure?

  Increases pressure due to more collisions
• What happens to particles in a smaller volume?

  Particles collide more frequently with walls
• How does particle velocity affect pressure?

  Greater velocity increases pressure from collisions
• What happens to temperature as particle velocity increases?

  Temperature increases as kinetic energy increases
• whats boyles law?

  pressure of a gas is inversely proportional to its volume