Diffusion

 

What is diffusion?

Diffusion is the process by which particles of one substance move through the particles of another substance. Diffusion is how smells travel through the air and how strong liquids become weaker when added to water.

Diffusion happens by itself when the particles move from a place where there are many of them to a place where there are fewer of them. This is called moving from an area of high concentration to an area of low concentration.

 

 

Diffusion in gases

The easiest kind of diffusion is when different gases diffuse through each other.  As gas particles are very spread out, they can move and vibrate quickly. The gas spreads to areas of the room where its concentration is lower. This continues until the gas is evenly distributed around the entire room.

For example, it happens when a perfume smell spreads throughout the air in an enclosed area.

Diffusion is faster in gases than in liquids.

 

 

 

 

Diffusion in liquids

Diffusion is the movement of particles from where they are more crowded to where they are less crowded until they are evenly spread out. This happens because particles have energy that makes them move and hit each other randomly.

For example, when you mix two liquids, they diffuse into each other. Blackcurrant squash has a lot of particles in a small space. When you add water to the squash, the particles spread out and the squash becomes less strong.

 

 

Brownian Motion

Brownian motion refers to the random movement of particles in gases due to their collisions with other atoms or molecules.

When particles are free to move around, they can collide with other moving particles in the air. These collisions cause the particles to particles change their direction and speed at random.

 

 

What factors affect diffusion?

The rate of diffusion depends on a number of factors:

 

• State of matter – diffusion does not happen in solids and gases diffuse faster than liquids because their particles are farther apart and move quicker than liquid particles.
• Temperature - diffusion speeds up when the gas or liquid is hotter. This is because the particles have more energy and move faster at higher temperatures.
• Size of particles - the smaller the particle, the faster the rate of diffusion.

 

 

 

 

🔬 Knowledge Check: Diffusion

Test your knowledge on how particles move and mix in gases and liquids.

1. Diffusion is the movement of particles from:

• An area of low concentration to high concentration.
• An area of high concentration to low concentration.
• One solid object to another solid object.

2. In which state of matter does diffusion occur the fastest?

• Solids
• Liquids
• Gases

3. Why can diffusion NOT happen in a solid?

• The particles are too small to be seen.
• The particles are in fixed positions and cannot move past each other.
• There is no air inside a solid.

4. What provides the energy for particles to move during diffusion?

• Their own kinetic energy from random motion.
• Wind or water currents pushing them.
• Magnetic attraction between the particles.

5. When particles have spread out evenly through a space, we say they have reached:

• A concentration gradient.
• Equilibrium.
• The boiling point.

Click to Reveal Answers

1. High concentration to low concentration (Particles spread out from where there are many to where there are few).
2. Gases (Particles move fastest and have the most space to travel).
3. Particles are in fixed positions (They can only vibrate, not move around each other).
4. Kinetic energy from random motion (Particles move naturally and collide with each other).
5. Equilibrium (The state where particles are distributed evenly throughout the volume).

 

Summary:

 

• Diffusion is the movement of a substance from a place where there is a lot of it to a place where there is less of it.
• Diffusion happens in liquids and gases when their particles bump into each other randomly and spread out.