Short Answer

Random motion of gas molecules means that gas particles move in all directions without following any fixed path. They travel in straight lines until they collide with another particle or with the walls of the container. After each collision, they change direction and continue moving again.

Because of this constant and unpredictable movement, gas molecules spread out quickly and fill any available space. This random motion is responsible for many gas properties, such as pressure, diffusion, and expansion.

Detailed Explanation

Random Motion of Gas Molecules

Random motion of gas molecules refers to the unpredictable and constant movement of gas particles in all possible directions. Gas molecules are never still—they are always moving. Their motion does not follow a regular or organised pattern. Instead, each molecule moves freely, travels in a straight line, collides with other molecules or container walls, changes direction, and then continues moving. This constant, irregular movement is what we call random motion.

Random motion is a very important idea in the kinetic theory of gases. It explains why gases behave differently from solids and liquids. In solids, particles vibrate in fixed positions. In liquids, particles move around but stay close. In gases, particles are far apart and move freely in random directions. This random movement gives gases unique properties like high expansion, low density, and the ability to spread quickly.

Nature of Random Motion

Gas molecules have large spaces between them because intermolecular forces are very weak. Due to this freedom, they move independently without being pulled strongly by each other. Their motion is influenced mainly by their kinetic energy, which depends on temperature. Higher temperature means faster random motion.

The movement is random because:

• molecules change direction after every collision,
• collisions happen at unpredictable times and locations,
• each molecule moves independently of others,
• motion has no fixed pattern or common direction.

Because collisions occur billions of times per second, the direction and speed of movement keep changing. This makes the motion completely irregular.

Straight-Line Motion Between Collisions

According to the kinetic theory, gas molecules travel in straight lines until they collide with something. A collision can happen with:

• another gas molecule, or
• the walls of the container.

These collisions make the molecules bounce off and change direction. After each rebound, the molecule again travels in a straight line until the next collision. This repeated pattern of straight-line motion followed by direction changes creates the random motion.

Collisions are elastic, meaning no energy is lost. Molecules keep moving continuously without slowing down unless temperature decreases.

Why Random Motion Occurs

Random motion happens because gas molecules have high kinetic energy and very little attraction between them. They are free to move anywhere within the container. Since there is no fixed path or orientation, each molecule travels independently. Their speeds and directions keep changing because of:

• thermal energy,
• collision frequency,
• uneven distribution of molecules in space.

Temperature is the main factor influencing motion. When temperature increases, molecules move faster and collide more often. When temperature decreases, their random motion slows down.

Effects of Random Motion

The random motion of gas molecules explains many important gas behaviours:

1. Gas Pressure:
   When molecules moving randomly collide with the walls of a container, they exert force. These repeated impacts create pressure.
2. Diffusion:
   Gases mix quickly because random motion spreads molecules throughout the container. This is why perfume smell spreads in a room.
3. Effusion:
   Gas molecules escape through tiny holes because of their continuous movement.
4. Expansion:
   Gases expand to fill any available space. Random motion allows molecules to spread evenly throughout the container.
5. Brownian Motion:
   Tiny particles suspended in a gas move randomly because gas molecules bombard them from all sides.

Examples in Daily Life

Many everyday experiences show random motion of gas molecules:

• The smell of incense spreads across a room.
• Air fills a balloon and spreads evenly throughout it.
• Helium gas escapes from a balloon over time.
• Smoke rises and spreads in different directions.

All these happen because gas molecules constantly move in random patterns.

Conclusion

Random motion of gas molecules means that gas particles move freely and unpredictably in all directions. They travel in straight lines between collisions and continuously change direction after colliding with other particles or container walls. This irregular movement explains important gas properties such as pressure, diffusion, expansion, and low density. Understanding random motion helps in understanding the behaviour of gases in both natural and everyday situations.