Diffusion

• Particles (molecules and ions) in a liquid and a gas move continuously, this means that particles will spread themselves evenly throughout a liquid or a gas.
• Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.
• In diffusion, particles will:

  • move in both directions, but there will be a net movement from high to low concentration
  • end up evenly spread throughout the liquid or gas, but will continue to move
• Some substances move into and out of living cells by diffusion.
• Some of the substances transported in and out of cells by diffusion are oxygen and carbon dioxide in gas exchange, and of the waste product urea from cells into the blood plasma for excretion in the kidney.
• The rate of diffusion can be affected by:

  • the concentration gradient
  • temperature
  • the surface area of the cell membrane separating the different regions
• Define diffusion.

  The movement of molecules from an area of higher concentration to an area of lower concentration.