Describe diffusion as the net movement of particles from a region of their higher concentration to a region of their lower concentration (i.e. down a concentration gradient), as a result of their random movement

Diffusion is a fundamental process in which particles move from an area of higher concentration to an area of lower concentration. This movement occurs due to the random motion of particles and is driven by the concentration gradient.

Key Concepts of Diffusion

1. Concentration Gradient:
   • A concentration gradient exists when there is a difference in the concentration of a substance between two regions. In diffusion, particles naturally move down this gradient, from areas where they are more concentrated to areas where they are less concentrated.
2. Random Movement:
   • The particles in a substance (whether they are gas, liquid, or solute in a solution) are always in constant motion due to thermal energy. This random movement leads to collisions between particles, causing them to spread out over time.
3. Net Movement:
   • While individual particles move randomly in all directions, the overall or net movement will be toward the area of lower concentration. This means that, although some particles may occasionally move back into the higher concentration area, more particles will tend to move into the lower concentration area until equilibrium is reached.

Process of Diffusion

• Initial State: Imagine a drop of dye placed in a glass of water. Initially, the dye is highly concentrated in one small area.
• Random Motion: The dye molecules begin to move randomly due to their kinetic energy. Some will collide with water molecules and disperse into areas where there are fewer dye molecules.
• Equilibrium: Over time, as more dye molecules diffuse into the less concentrated areas, the concentration gradient decreases. Eventually, the dye molecules will be evenly distributed throughout the water, achieving equilibrium where there is no net movement of dye in any direction.

Importance of Diffusion

Diffusion is crucial for many biological and chemical processes:

• Cellular Respiration: Oxygen diffuses into cells while carbon dioxide diffuses out.
• Nutrient Uptake: Nutrients from food diffuse across cell membranes into cells.
• Gas Exchange: In lungs, oxygen diffuses into blood while carbon dioxide diffuses out.