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.

The easiest kind of diffusion is when different gases diffuse through each other.  For example, it happens when a perfume smell spreads throughout the air in an enclosed area.  Likewise, diffusion of gases also take place in the leaves of plants.

 

 

How does diffusion happen?

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.

 

What factors affect diffusion?

Diffusion depends on two factors:

 

• The kind of substance - 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.

 

🔬 Knowledge Check: Diffusion

Test your understanding of how particles move and spread in different states of matter.

1. In which direction do particles move during the process of diffusion?

• From low concentration to high concentration
• From high concentration to low concentration
• In a fixed, circular pattern

2. Why is diffusion unable to occur in a solid?

• The particles are too far apart.
• The particles are in a fixed position and cannot move past each other.
• Solids do not contain particles.

3. Which of the following describes the movement of particles in a gas compared to a liquid?

• Gas particles move more slowly and are closer together.
• Gas particles are further apart and move more quickly.
• Liquid particles do not move at all.

4. When potassium manganate (VII) is added to water, what indicates that diffusion is taking place?

• The water turns into a solid.
• The purple colour slowly spreads out through the water.
• The crystal immediately disappears without changing the water's colour.

5. What happens when bromine gas is placed in a jar connected to a jar of air?

• The bromine particles stay in the bottom jar.
• The air particles push the bromine out of the jars.
• The particles mix until there is an even brown colour in both jars.

Click to Reveal Answers

1. From high concentration to low concentration (Particles naturally spread out from where there are many to where there are few).
2. Particles are in a fixed position (In solids, particles vibrate but cannot move from place to place).
3. Gas particles are further apart and move more quickly (This explains why diffusion is faster in gases).
4. The purple colour slowly spreads out (This shows the liquid particles moving and mixing).
5. The particles mix until there is an even colour (Random motion ensures the gas fills all available space evenly).

 

 

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.
• Diffusion is an important process for living things - it is how substances get in and out of cells.