Diffusion

• Particles (molecules and ions) in a liquid and a gas move continuously. Because of this movement, particles will spread themselves evenly throughout a liquid or a gas.
• The process by which molecules diffuse from an area where they are concentrated to an area where they are less concentrated is called diffusion.
• When there is a concentration gradient, more particles will be moving down the gradient than up it
• It is important to remember that the particles:

  • will move in both directions, but there will be a net movement from high to low concentration
  • will 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.

  In a leaf:

  
• In the lungs:

  
• Diffusion in liver cells