diffusion

• States where molecules are able to diffuse

  • Solid (e.g. ice)
  • Liquid (e.g. water)
  • Gas (e.g. steam)
• Molecules in liquids and gases are constantly moving and bumping into each other, which means they tend to spread out
• Diffusion


  When molecules travel from an area of high concentration to an area of low concentration
• Example of diffusion


  • Scent from a hamburger - particles go from an area of high concentration to an area of low concentration
• Diffusion process


  1. Particles are separate when first put together

  2. They slowly start to mix due to their random motion

  3. The particles are now nearly fully diffuse

  4. The particles are fully diffuse, they will keep on moving
• Factors that speed up diffusion

  • Concentration gradient - the bigger the difference in concentration, the faster the rate
  • Distance - particles will diffuse quicker if they don't have far to travel
  • Temperature - the hotter the temperature, the faster the particles will diffuse, as they have more kinetic energy
• Biological diffusion


  Dissolved substances have to pass through the partially permeable cell membrane to get into or out of a cell
• Diffusion is one of the processes that allows this to happen
• Diffusion in humans


  • Cells use diffusion to swap the oxygen they need for the carbon dioxide they no longer want
  • Oxygen diffuses in, waste CO2 goes out
  • Alveoli in lungs and villi in the intestines
• In breathing you exchange carbon dioxide (CO2) and oxygen (O2) between alveoli in the lungs and the blood, this is an example of diffusion
• Photosynthesis and diffusion


  1. Carbon dioxide diffuses in through the stomata

  2. Oxygen and water diffuse out of the stomata
• The equation for photosynthesis is: carbon dioxide + water → oxygen + glucose