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====AQA====
:[https://www.amazon.co.uk/gp/product/019835939X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=019835939X&linkCode=as2&tag=nrjc-21&linkId=57e96876985fc39b1a3d8a3e3dc238b6 ''Brownian motion, page 87, GCSE Physics; Third Edition, Oxford University Press, AQA '']
==Key Stage 5==
===Meaning===
[[Brownian Motion|Brownian motion]] is the random and unpredictable motion of a [[particle]] caused by collisions with [[molecule]]s of the surrounding substance.
===About Brownian Motion===
*[[Brownian Motion|Brownian motion]] demonstrates the [[Kinetic Theory|kinetic theory]] of [[matter]].
*[[Brownian Motion|Brownian motion]] is observed in [[particle]]s suspended in a [[fluid]].
*[[Brownian Motion|Brownian motion]] provided early evidence for the existence of [[atom]]s and [[molecule]]s.
*[[Brownian Motion|Brownian motion]] is described mathematically by the Einstein relation for [[diffusion]].
===Examples===
*The random movement of pollen grains in water observed under a [[microscope]].
*Used in determining [[Avogadro Constant|Avogadro's number]] by observing [[particle]] movement in a [[fluid]].