When a beam of sunlight enters a room through a window, we can see tiny particles X suspended in a gas (or rather a mixture of gases) Y which are moving rapidly in a very haphazard manner.
(a) What could particles X be ?
(b) Name the gas (or mixture of gases) Y.
(c) What is the phenomenon exhibited by particles X known as ?
(d) What is causing the movement of particles X ?
(e) What conclusion does the existence of this phenomenon give us about the nature of matter ?

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Solution

(a) The particles, 'X' are dust particles.
(b) Gas 'Y' is Air.
(c) This phenomenon being exhibited by 'X' particles is called the Brownian motion.
(d) The fast moving air molecules are constantly hitting the tiny dust particles, causing them to move rapidly in a very haphazard manner.
(e) The gaseous matter ‘air’ is made up of tiny particles that are constantly moving.

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