Page 82 - Viva ICSE Science 4 : E-book

TERMS TO KNOW

1. Condensation: Changing from water vapour to liquid state as a result of cooling
2. Infl ate: Expand in size
3. Defl ate: Reduce in size
4. Odourless: Without any smell
5. Inhalation: Process of breathing in air
6. Exhalation: Process of breathing out air
7. Pollution: Presence of some harmful substances
8. Public transport: Transport which can be used by anyone after paying the fi xed charges
9. CNG: Compressed Natural Gas
10. LPG: Liquefi ed Petroleum Gas

QUICK LOOK

1. Matter exists in three diff erent states—solid, liquid and gas.
2. Particles are closely packed in solids.
3. Particles are not so closely packed in liquids. They are free to move about. Therefore liquids
fl ow easily and take the shape of the container.
4. Particles are very loosely packed in gas. Therefore, they fi ll all the available space. They do
not have a fi xed shape.
5. Air is shapeless, colourless and odourless.

6. We cannot see air. We only feel it when it moves.
7. Air is a mixture of gases (nitrogen, oxygen, carbon dioxide, argon and other gases). It also
contains germs, smoke and dust particles.
8. Properties of air
• Air occupies space • Air has weight
• Air expands on heating • Air supports burning
9. All living things need air to breathe for survival. Breathing is the process of taking in and
giving out air.
10. Act of taking air into lungs is called inhalation, while the act of giving out air is called
exhalation.
11. When any pollutant like smoke, germs, dust or harmful gases enter the air, it causes air
pollution.
12. Some natural causes of air pollution are volcanic eruption, dust storm and forest fi re. Some
causes of air pollution due to human activities are smoke from factories and vehicles,
bursting crackers and burning garbage. Bacteria and virus also cause air pollution.
13. Air pollution causes sickness like fl u, tuberculosis, asthma, headache, sneezing, coughing
and irritation of eyes.
14. Planting more trees, reducing burning of fuels, using CNG and LPG for vehicles, sensible
disposal of garbage, and good personal and housekeeping practices are some of the ways
to keep air clean.

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