Bromine gas diffusion. Bromine vapour (orange) filling the lower of two gas jar before the seal between them is removed to demonstrate gas diffusion. Because gas molecules can move independently of each other and do so randomly, a gas spreads out from its source in a process called diffusion. The diffusion rate depends mainly on the temperature and the medium through which the diffusion takes place. In this case, the medium is air. The gas colour allows the diffusion to be observed. Sequence 3 of 4
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