Page 106 - ICSE Chemistry 6

Dust and Smoke
Thirst for Knowledge
Air around us also contains suspended dust par cles and smoke.
When something is burnt, smoke is produced. Smoke consists of Smoke from long chimneys is
a few gases and fi ne dust par cles. These are harmful for living harmful for birds that fl y high in
the sky.
organisms.
Have you observed long chimneys in factories? Through long
chimneys, the harmful smoke and other waste gases from the
factories are released high in the atmosphere away from human
beings.

Dust par cles are always present in the atmosphere. Their level
varies from me to me and place to place. Dust par cles play an
important role in the forma on of clouds. Water droplets condense
on dust par cles and when these par cles come together, they
form clouds.

When you breathe in air, the fi ne hair and mucus present inside
your nose prevent dust par cles from entering the respiratory Fig. 5.2: Traffi c policeman
wearing a mask
tract.

Have you seen traffi c policemen regula ng traffi c at the traffi c signal wearing a mask? They do so to
prevent the entry of dust par cles in the respiratory tract.

Respiratory Tract
Respiratory tract is the passage formed by the mouth, nose, throat and lungs through which air passes during
breathing.

Activity 5.6

Aim: To show that air contains dust par cles

Materials required: A torch
Procedure

• Close all the doors and windows of a room.

• Make the room dark by drawing the curtains.
• Pass a narrow beam of light through a torch into the room.
dust particles
Observa on: You will see randomly moving dust par cles in the beam of
light.

Conclusion: This shows that air contains dust par cles.

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