4:Diffusion Definition and Mechanisms

Diffusion Definition and Mechanisms

• Diffusion is the random movement of a substance from a high concentration area to a low concentration area. This movement is down the concentration gradient.
• Diffusion is a passive process; no energy is required.
• Diffusion is driven by the random motion of particles.
• Molecules in liquids and gases are constantly moving and colliding with each other, which leads to their spreading out.
• Diffusion in solids does not occur.

Factors Affecting Diffusion Rate

• Decreasing the diffusion rate: Increasing the distance, decreasing temperature, and reducing the concentration gradient.
• Increasing the diffusion rate: Increasing temperature, increasing air flow, increasing the concentration difference or decreasing the distance travelled.

Diffusion and Equilibrium

• Diffusion continues until equilibrium is reached. Equilibrium is when the concentration of the substance is uniform throughout the space.
• Even at equilibrium, particles still move randomly. Individual particles move, but the net movement stops because there's no longer a concentration gradient.

Diffusion and States of Matter

• Diffusion occurs in liquids and gases, but not in solids. The molecules in liquids and gases move constantly which enables them to spread from high to low concentration regions.

Perfume Diffusion Example

• Several factors can increase the rate at which perfume spreads:
  • Warmer temperatures: Particles move faster.
  • Air movement (e.g., fans, open windows): Carries the scent particles.
  • Spraying with more force: Initial dispersal is increased.
  • Less crowded air (e.g., higher altitudes): Fewer particles to collide with.

Diagram of Diffusion (Conceptual)

• (No diagram can be created here, but imagine a diagram showing a container with a high concentration of particles on one side and a low concentration on the other. Arrows would start thick on the high concentration side, then thin out, as the particles diffuse across going towards the low concentration)

Diffusion Equilibrium

• At equilibrium, molecules are evenly distributed, but particles still move randomly.
• The net movement of particles stops at equilibrium.

This quiz covers the fundamental concepts of diffusion, including its definition, mechanisms, and the factors that affect its rate. Understand how diffusion leads to equilibrium and the conditions that can influence this process. Test your knowledge on this essential physical phenomenon.