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# Effect of temperature and molecular mass on the rate of diffusion

The rate of diffusion is affected by molecular mass and temperature.

These two factors affect the kinetic energy of a particle (the energy a particle possesses when it moves).

The rate of diffusion of a substance is inversely proportional to its molecular mass at constant temperature. This means that the rate of diffusion increases as the molecular mass decreases.

Chlorine gas $(\text{71 g/mol})$ diffuses more slowly than hydrogen gas $(\text{2 g/mol})$ when both molecules have the same kinetic energy.

The rate of diffusion of a substance is directly proportional to the temperature. This means that the rate of diffusion increases as the temperature increases.

This is because the molecules of a substance at a higher temperature have greater kinetic energy (and higher velocity). They therefore diffuse at a greater rate.

Instant coffee diffuses more quickly in hot water than in cold water.