diffusivity
Quick Summary
Diffusivity, also known as the diffusion coefficient, is a measure of how quickly a substance spreads out due to random molecular motion. It quantifies the rate at which matter flows from an area of high concentration to an area of low concentration.12
This process is fundamental to many natural phenomena. For instance, the spread of a scent through a room or the transfer of heat in fluids are examples of diffusion. The rate of diffusion is directly proportional to the concentration gradient, meaning the steeper the difference in concentration, the faster the substance will spread.1
Diffusivity values vary significantly depending on the state of matter. They are extremely small in solids, much smaller in liquids, and largest in gases. This is because molecules have greater freedom to move and spread in gases compared to liquids or solids.3
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