Short Answer

Diffusion occurs faster in gases than in liquids because gas molecules move much more quickly and have large spaces between them. This allows them to spread out easily from an area of high concentration to an area of low concentration. In liquids, molecules are closer together and move more slowly, so diffusion takes more time.

The weaker force of attraction between gas molecules also helps them spread faster. Liquid molecules have stronger attraction, which slows their movement. Therefore, the rapid motion and large spaces in gases make diffusion faster compared to liquids.

Detailed Explanation :

Reason Diffusion Occurs Faster in Gases than in Liquids

Diffusion is the natural movement of particles from a region of high concentration to a region of low concentration. The speed of diffusion depends on how fast particles can move and how much space is available between them. Gases and liquids show different speeds of diffusion because their molecular arrangements and movements are very different.

Gases diffuse much faster than liquids because gas molecules have more freedom to move, more energy, and larger spaces compared to liquid molecules. Liquids diffuse at a slower rate because their particles are closer together and move with less speed. Understanding this difference helps explain many everyday observations, such as why perfume spreads quickly in air but ink takes longer to spread in water.

Factors Responsible for Faster Diffusion in Gases

1. Large Space Between Gas Molecules

Gas molecules are very far apart, leaving plenty of empty space between them. This large distance allows the molecules to move freely without bumping into each other too often.

Because of this:

• Gas molecules spread quickly.
• They mix easily with other gases.
• They can travel longer distances in a short time.

In liquids, molecules are much closer together, so they cannot move as freely. Their movement is slowed down because of frequent collisions.

2. High Speed of Gas Molecules

Gas molecules move very fast in all directions. They have higher kinetic energy compared to liquid molecules. This fast motion helps gases spread quickly from one place to another.

Examples:

• Perfume smell spreads quickly in a room.
• Smoke spreads rapidly in the air.

Liquid molecules move more slowly because they have less kinetic energy. This reduces the speed at which liquids can spread or mix.

3. Very Weak Intermolecular Forces in Gases

The force of attraction between gas molecules is extremely weak. This means gas molecules do not stick to each other and can move freely in any direction.

Due to weak attraction:

• Gas molecules separate easily.
• They mix without resistance.
• Diffusion becomes very fast.

Liquid molecules have stronger attractions, which slows down their movement. They slide over one another instead of flying freely like gas molecules.

4. Random and Rapid Movement

Gas molecules move randomly and rapidly. Their continuous and quick motion helps them occupy space quickly and mix with surrounding molecules.

Because of this random movement:

• Gas particles quickly reach all parts of a container.
• They spread evenly in the air.

Liquid molecules also move randomly but at a slower speed, making diffusion slower.

5. Frequent Collisions Result in Faster Mixing

Although gas molecules collide with each other often, their collisions do not stop them. Instead, they bounce off and continue moving in different directions. These collisions help distribute the molecules quickly throughout a space.

In liquids, collisions between molecules slow down the movement because the particles are closely packed.

Examples Showing Faster Diffusion in Gases

1. Perfume in a room:
   When perfume is sprayed, its smell spreads instantly because gas molecules diffuse very fast in air.
2. Burning incense (agarbatti):
   The fragrance spreads quickly throughout the room.
3. Smoke from a burning paper:
   Smoke rises and spreads rapidly because it is in gaseous form.
4. Oxygen and carbon dioxide exchange in our lungs:
   This exchange happens quickly because gases diffuse rapidly.

Comparison With Diffusion in Liquids

• In liquids, diffusion is slower.
• A drop of ink takes time to spread in a glass of water.
• Sugar dissolves slowly without stirring.

This slow diffusion happens because liquid molecules are closely packed and move more slowly than gas molecules.

Conclusion

Diffusion occurs faster in gases than in liquids because gas molecules move quickly, have large spaces between them, and experience very weak forces of attraction. Liquid molecules, on the other hand, are closer together and move more slowly. These differences in particle arrangement and movement explain why gases spread and mix faster. Understanding this helps explain many everyday observations related to the behavior of gases and liquids.