Diffusion and Escape velocity

Diffusion

The spreading of certain type of molecules throughout space occupied by another type of molecules is termed as diffusion.

Example - When a substance with a scent is kept inside a room, diffusion takes place until the scent is distributed uniformly throughout the room.

The rate of diffusion decreases in the order gas, liquid, solid.

Escape velocity

The minimum velocity at which any object should be projected from the surface of the earth to enter into space completely escaping from the gravitational attraction of the Earth, is called its escape velocity. When the mean velocity of a gas molecule exceeds its escape velocity, it leaves the atmosphere of the Earth.

The mean velocity of light gases such as hydrogen (H₂) and Helium (He) exceeds the escape velocity of the Earth and as a result they have left the atmosphere of the Earth.

Ve - Escape velocity

G - Universal Gravitational constant

M - Mass of the planet/object

r - Radius of the planet/object