Term 2

• Theory of diffusion


  Describes the movement of particles from an area of higher concentration to an area of lower concentration, resulting in an even distribution of the particles over time
• Example of diffusion


  • Spreading of toast burning in a room - burnt toast molecules move from the region where they are highly concentrated to the surrounding air, where the concentration is lower, until the fragrance spreads throughout the entire room
• Particles in a solid

  • Arranged in a tightly packed, orderly, and fixed structure, held together by strong intermolecular forces
• Effect of heating a solid

  Particles gain energy and begin to vibrate more vigorously, eventually overcoming the forces holding them together and transitioning to a liquid (melting) and then a gas (boiling)
• Effect of cooling a solid

  Particles lose energy and their vibrations decrease, resulting in a more rigid and orderly structure
• Particles in a gas

  • Spaced far apart and move freely and rapidly in all directions, with a highly disordered arrangement compared to solids and liquids
• Effect of heating a gas

  Particles gain kinetic energy and move even faster
• Effect of cooling a gas

  Particles lose kinetic energy and move more slowly
• Particles in a liquid

  • Closely packed, but not as tightly as in a solid
• Effect of heating a liquid

  Particles gain kinetic energy and move more rapidly
• Effect of cooling a liquid

  Particles lose kinetic energy and move more slowly
• When a solid turns into a gas (sublimation)


  Volume increases significantly as the particles gain enough energy to overcome forces and move freely, spreading out to occupy a much larger volume
• Example of sublimation


  • Dry ice (solid carbon dioxide) transitions directly from a solid to a gaseous state, with the volume of the carbon dioxide gas produced being much greater than the volume of the dry ice