Q1.
Apart from gases, have you ever observed anything else present in the air? Have you ever noticed tiny shining particles moving in a beam of sunlight entering a dark room through a small opening? What are these particles?
Answer
Those shining specks are dust particles suspended in the air — not a gas at all, and not part of what air is made of.
Why they shine: Dust particles are far too small to be noticed in ordinary light. When a narrow beam of sunlight enters a dark room, each particle scatters a little of that light towards your eye while the background stays dark — so the particles suddenly stand out. They dance about because the moving air keeps pushing them around.
Dust is not an integral part of the air; it is considered a pollutant. Its nature and number vary from time to time and from place to place — more on a dry, windy day near a road, less after rain.
Did you know? The major pollutants in air are particulate matter (dust, soot) and gases like carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide. The air quality index (AQI) is the tool used to describe the quality of air.