Why do heavier molecules diffuse more slowly?

Heavier molecules diffuse more slowly because they have greater mass, which reduces their speed and rate of movement.

Diffusion is the process by which particles spread out from an area of high concentration to an area of low concentration. This movement is due to the kinetic energy of the particles, which causes them to move randomly. The rate of diffusion is influenced by several factors, including the mass of the particles involved.

Heavier molecules have greater mass, which means they have more inertia and require more energy to move. This results in a slower speed and rate of movement compared to lighter molecules. In other words, the heavier the molecule, the slower it will diffuse. This is because the kinetic energy of a particle is inversely proportional to its mass. Therefore, particles with a larger mass will have less kinetic energy and will move more slowly.

This principle is demonstrated in Graham's law of diffusion, which states that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. This means that if you compare two gases, the one with the smaller molar mass will diffuse faster than the one with the larger molar mass.

For example, if you were to release a heavy gas like carbon dioxide and a light gas like helium in a room, the helium would spread out faster than the carbon dioxide. This is because the helium molecules are lighter and therefore move more quickly, while the carbon dioxide molecules are heavier and move more slowly.

In conclusion, the mass of a molecule plays a significant role in its rate of diffusion. The heavier the molecule, the slower it will diffuse due to its greater inertia and lower kinetic energy.