P6: Molecules and Matter

• Density

  Units: kilograms per cubic meter (kg/m³) or grams per cubic centimeter (g/cm³)
• Specific latent heat

  The amount of energy required to change the state of 1 kg of a substance without changing its temperature
• Formula for specific latent heat

  Q=mL
• Specific latent heat of fusion

  The energy required to change 1 kg of a substance from solid to liquid
• Specific latent heat of vaporization

  The energy required to change 1 kg of a substance from liquid to gas
• Changes during melting

  1. Solid turns into liquid

  2. Particles gain energy

  3. Particles vibrate more

  4. Particles overcome fixed positions
• Changes during boiling

  1. Particles gain enough energy to break free from liquid state

  2. Particles become a gas
• Specific heat capacity

  The amount of heat energy required to raise the temperature of 1 kg of a substance by 1°C
• Formula for calculating energy change using specific heat capacity

  Q=mcΔT
• Internal energy

  The total energy stored in the particles of a substance, including both kinetic and potential energy
• Particle arrangement in a solid

  • Closely packed in a fixed, orderly structure
  • Can only vibrate about their fixed positions
• Particle arrangement in a liquid

  • Close together but can move past each other
  • Allows the liquid to flow
• Particle arrangement in a gas

  • Far apart and move freely
  • Fill the container they are in
• Pressure (in the context of gases)

  The force exerted per unit area by gas particles as they collide with the walls of their container
• Boyle's Law

  The pressure of a gas is inversely proportional to its volume, provided the temperature is constant
• Formula representing Boyle's Law

  Pressure X Volume = Constant
• Absolute zero

  The lowest possible temperature where particles have minimum thermal energy, theoretically at 0 K or -273.15°C
• Kinetic theory of gases

  • Gas particles are in constant, random motion
  • Pressure exerted by a gas results from collisions of the particles with the container walls
• Increasing temperature

  • Increases the kinetic energy of gas particles
  • Leads to more frequent and forceful collisions
  • Increases the pressure
• Temperature

  Average kinetic energy of particles is directly proportional to the temperature measured in kelvin