Physics - Topic 14 - Particle Model

• What is the formula for density?

  Density = mass / volume
• What are the units of density?

  kg/m^3
• How does density depend on the spacing of atoms in matter?

  Density depends on how closely packed the atoms are in a substance.
• 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 and water).
  • Gases have much lower density due to increased spacing between particles.
• What happens to mass during a change of state?

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


  The gas produced will also weigh 20g.
• Why are changes of state considered physical changes?

  Because the material retains its original properties when reversed.
• What happens to particles when a system is heated?

  • The amount of energy the particles have increases.
  • Particles vibrate more.
  • The temperature of the system increases or the system changes state.
• What are the changes of state for solids, liquids, and gases?

  • Melting: solid to liquid
  • Freezing: liquid to solid
  • Evaporating: liquid to gas
  • Condensing: gas to liquid
  • Sublimation: solid to gas
• What is specific heat capacity?

  The energy required to raise the temperature of 1kg of a substance by 1°C.
• What is the formula for calculating energy in relation to specific heat capacity?

  E = mc∆T
• What are the units for specific heat capacity?

  Jkg⁻¹°C⁻¹
• What is specific latent heat?

  The energy to change the state of 1kg of a substance without a change in temperature.
• What is the specific latent heat of fusion?

  It is the energy required to melt or freeze a substance.
• What is the specific latent heat of vaporization?

  It is the energy required to boil or condense a substance.
• What happens to energy during melting and evaporating compared to freezing and condensing?

  • Energy is absorbed when melting and evaporating.
  • Energy is released when freezing and condensing.
• How can thermal energy loss be reduced in a system?

  • Use thermal insulators (e.g., foam).
  • Use reflective coatings to reflect IR radiation back into the system.
• What is the formula for pressure?

  Pressure = force / area
• How does pressure relate to particle collisions in a gas?

  Particles collide with a wall, changing velocity and exerting force on the wall.
• What happens to pressure when temperature increases in a gas at constant volume?

  Pressure increases as particles move faster and collide with walls more often.
• What is absolute zero in Kelvin and Celsius?

  0 Kelvin or -273°C.
• What occurs at absolute zero?

  Particles have no energy and do not vibrate at all.
• How do you convert Kelvin to Centigrade?

  T Kelvin = (T - 273) Centigrade.
• What happens to gas pressure when volume decreases?

  Pressure increases as the gas is compressed into a smaller volume.
• What is the relationship between pressure and volume for a gas at fixed mass and temperature?

  Pressure is inversely proportional to volume.
• What is the equation relating pressure and volume for a gas?

  P1V1 = P2V2
• What happens when work is done on a gas?

  Doing work on a gas increases its temperature.
• How does adding more particles to a fixed volume affect pressure?

  More particles lead to more collisions, increasing pressure.
• What happens to pressure when the volume decreases with a fixed number of particles?

  Pressure increases as particles collide with the walls more frequently.
• How does the velocity of particles change when they collide with a wall that is moving inward?

  Particles gain momentum and rebound with greater velocity.