Describe and explain diffusion in terms of kinetic particle theory

States of Matter – Diffusion

Objective

Describe and explain diffusion in terms of kinetic particle theory. 🌬️

What is Diffusion?

Diffusion is the spontaneous movement of particles from an area of higher concentration to an area of lower concentration until the concentration is uniform. Think of it like a drop of food colouring spreading through water – the colour spreads out until the whole glass looks the same. 🧪

Why Does Diffusion Happen?

According to kinetic particle theory, particles are always in motion. When particles are packed together (high concentration), they collide and push each other into empty spaces (low concentration). This random motion continues until the particles are evenly distributed. 🚀

Key Factors Influencing Diffusion

• Concentration gradient (larger difference → faster diffusion)
• Temperature (higher temperature → faster movement of particles)
• Particle size (smaller particles diffuse faster)
• Medium (gases diffuse faster than liquids, which diffuse faster than solids)

Diffusion in Gases vs. Liquids

In gases, particles are far apart and move quickly, so diffusion is very fast. In liquids, particles are closer together and move more slowly, so diffusion takes longer. In solids, particles are locked in place, so diffusion is almost negligible. ❄️

Mathematical View – Diffusion Coefficient

The rate of diffusion can be expressed by Fick’s first law:

\$J = -D \frac{dC}{dx}\$

where J is the flux (amount of substance per unit area per unit time), D is the diffusion coefficient, and dC/dx is the concentration gradient. The negative sign indicates movement from high to low concentration. 📐

Real‑World Example: Perfume in a Room

When you spray perfume in one corner of a classroom, the scent molecules spread out through the air until the whole room has the same faint smell. The speed of this spread depends on the temperature of the room and how strong the perfume is (concentration). 🎈

Diffusion in Biology – Oxygen Transport

In our lungs, oxygen molecules diffuse from the air (high concentration) into the blood (low concentration). This process is essential for life and demonstrates diffusion across a semi‑permeable membrane. 🌿

Summary Table – Diffusion Rates

Quick Quiz

1. What happens to the diffusion rate if the temperature is increased? ❓
2. Why does a small particle diffuse faster than a large one? ❓
3. Give an example of diffusion in a biological system. ❓

Answers: 1) It increases. 2) Because it has less mass and collides less often. 3) Oxygen moving from alveoli into blood. ??