P6 Molecules and Matter

• What two quantities are needed to find the density of a solid or liquid?

  Mass and volume
• What happens to particles in a substance when its temperature increases?

  They move faster and gain kinetic energy
• Why are changes of state considered physical changes?

  No new substances are produced
• Why is mass conserved when a substance changes state?

  The number of particles does not change
• What is the internal energy of a substance?

  Total kinetic and potential energy of particles
• Why does a cooling substance's temperature graph have flat sections during state changes?

  Energy transfer changes internal energy, not temperature
• What is the energy transferred during a state change called?

  Latent heat
• What is specific latent heat?

  Energy to change 1 kg of substance without temperature change
• What is the specific latent heat of fusion?

  Energy to change 1 kg from solid to liquid
• What is the specific latent heat of vaporisation?

  Energy to change 1 kg from liquid to vapour
• What do flat sections on a temperature-time graph indicate?

  Substance is changing state, temperature constant
• What property of a gas relates to the average kinetic energy of its particles?

  Temperature
• What causes gas pressure on a surface?

  Force of gas particles hitting the surface
• Why does gas pressure increase with temperature in a sealed container?

  Particles move faster and hit surfaces harder
• Why does gas pressure increase when volume decreases?

  Distance between impacts decreases, increasing force
• What happens to gas pressure when volume increases?

  Pressure decreases due to fewer impacts
• What is the equation linking pressure and volume of a gas?

  Pressure × Volume = constant
• What happens to internal energy when a substance is heated?

  Internal energy increases
• What is the relationship between temperature and kinetic energy in gases?

  Temperature relates to average kinetic energy
• What happens to gas particles when heated?

  They gain kinetic energy and move faster
• Why does gas temperature rise when compressed quickly?

  Work done on gas increases its energy
• What is the effect of gas pressure on container walls?

  Exerts net force at right angles to walls
• What happens to gas particles in terms of arrangement and movement?

  Particles are spread out and move randomly
• What are the properties of gases?

  Low density, no fixed volume or shape
• What are the properties of liquids?

  Fixed volume, shape not fixed, can flow
• What are the properties of solids?

  High density, fixed volume and shape
• What are the key terms related to changes of state?

  • Boiling
  • Condensation
  • Conservation of mass
  • Density
  • Evaporation
  • Freezing
  • Fusion
  • Internal energy
  • Latent heat
  • Melting
  • Specific latent heat
  • Sublimation
  • Vaporisation
• What is the relationship between temperature and pressure in gases?

  • Temperature increases, pressure increases
  • Temperature decreases, pressure decreases
  • Pressure is directly proportional to temperature
• What happens to the kinetic energy of particles when temperature increases?

  • Kinetic energy increases
  • Particles move faster
  • Potential energy remains unchanged
• How does the arrangement and movement of particles differ in solids, liquids, and gases?

  • Solids: fixed arrangement, vibrate in place
  • Liquids: close contact, move around each other
  • Gases: spread out, move randomly at high speed
• What is the equation for calculating density?

  Density (kg/m³) = mass (kg) / volume (m³)
• What is the equation for calculating thermal energy for a change in state?

  Thermal energy (J) = mass (kg) × specific latent heat (J/kg)