Particle model of matter

• What is the formula for density?

  $\rho =$$\frac{m}{V}$
• What units is density measured in?

  Kilograms per metre cubed (kg/m³)
• What does density depend on?

  The spacing of the atoms in matter
• How do the densities of solids and liquids compare?

  Solids and liquids have similar densities
• What is the main exception to the rule that liquids have lower density than solids?

  Ice and water
• Why do gases have a lower density than solids and liquids?

  Atoms are spaced further apart in gases
• What happens to the volume and density of a gas compared to solids and liquids?

  Volume increases greatly, density decreases greatly
• What remains constant during a change of state regarding mass?

  The mass remains the same
• If 20g of liquid evaporates, how much does the gas weigh?

  20g
• Why are changes of state considered physical changes?

  Material retains original properties when reversed
• What are the changes of state between solid, liquid, and gas?

  • Melting: Solid to Liquid
  • Freezing: Liquid to Solid
  • Evaporating: Liquid to Gas
  • Condensing: Gas to Liquid
  • Sublimation: Solid to Gas
• What is internal energy?

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

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

  Energy increases, raising internal energy
• What is specific heat capacity?

  Energy required to raise 1kg by 1°C
• What is the formula for change in thermal energy?

  $\Delta E =$$m \times c \times \Delta T$
• 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 is the formula for energy during a change of state?

  $E =$$m \times L$
• When is energy absorbed or released during state changes?

  Absorbed when melting and evaporating
• What is sublimation?

  Solid goes straight to gas
• What does the temperature graph of ice illustrate?

  • A: Solid
  • B: Reaches 0°C
  • B to C: No temperature change (melting)
  • C to D: Liquid state
  • D to E: Boiling (longer process)
  • E to F: Gas heating
• What is the state of motion of gas molecules?

  Constant random motion
• How is the temperature of a gas related to its molecules?

  It relates to their average kinetic energy
• What happens to the average speed of gas molecules as temperature increases?

  The average speed increases
• What occurs when gas molecules collide with the walls of their container?

  They exert a force on the wall
• What is gas pressure defined as?

  Total force per unit area on walls
• What effect does changing the temperature of a gas at constant volume have?

  It changes the pressure exerted by the gas
• What is the name of the law that describes the relationship between temperature and pressure of a gas at constant volume?

  Pressure law