CHARLES D. WINTERS / SCIENCE PHOTO LIBRARY CHARLES D. WINTERS / SCIENCE PHOTO LIBRARY
Diffusion. Blue food colouring begins to diffuse in a beaker of water. Diffusion is caused by the tiny, random movements of molecules in a solution. Over a period of time these movements cause the dissolved substance to become evenly dispersed throughout the solvent. This food colouring, for instance, will eventually produce a uniform blue solution without being stirred.
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