Air Around Us Class 6 MCQ with Answers

MCQs and Mock Test | NCERT - CBSE Chapter 11

Practice Air Around Us Class 6 MCQs with answers.
Learn air composition, atmosphere, oxygen, nitrogen, carbon dioxide, water vapour, and air pressure - with instant answers and performance report.

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Quick Revision: Air Around Us

  • Air is Everywhere: Air occupies space, has no colour, is transparent, and is present all around us.
  • Atmosphere: The thin layer of air surrounding Earth, extending many kilometres above the surface.
  • Composition of Air: Mixture of gases: Nitrogen (~78%), Oxygen (~21%), Carbon dioxide, water vapour, and other gases (~1%).
  • Oxygen: Supports burning and is essential for respiration. Plants produce oxygen during photosynthesis.
  • Nitrogen: Major component of air (about 78%) that does not support burning.
  • Carbon Dioxide: Small component used by plants for photosynthesis. Excess can cause suffocation.
  • Water Vapour: Present in air; condenses on cool surfaces; essential for water cycle.
  • Dust Particles: Present in air; visible in sunlight beam; can be harmful when inhaled.
  • Air in Water: Dissolved air in water provides oxygen for aquatic animals and plants.
  • Air in Soil: Spaces in soil contain air for organisms living underground and plant roots.
  • Oxygen Balance: Plants produce oxygen through photosynthesis, consuming carbon dioxide; animals consume oxygen and release carbon dioxide.
  • Uses of Air: Windmills, sailing, flying, seed dispersal, water cycle, and more.

Air Around Us Class 6 Questions and Answers (FAQ)

What is the composition of air for Class 6 Science?
Air is a mixture of gases. Its composition is: Nitrogen (~78%), Oxygen (~21%), Carbon dioxide (~0.03%), and small amounts of water vapour, argon, and other gases (about 1%). Air also contains dust particles, smoke (in polluted areas), and pollen grains. The atmosphere is the layer of air surrounding the Earth.
Why is oxygen important and how is it used in daily life?
Oxygen makes up about 21% of air and is essential for: (1) Respiration - all living organisms need oxygen to break down food and release energy, (2) Combustion - burning of fuels like wood, coal, and LPG requires oxygen, (3) Rusting of iron - oxygen reacts with iron in presence of moisture. Plants produce oxygen during photosynthesis, maintaining oxygen balance in the atmosphere.
What is the importance of water vapour and dust particles in air?
Water vapour in air is essential for the water cycle - it condenses to form clouds and returns to Earth as rain. It also affects humidity and weather. Dust particles are tiny solid particles that help in cloud formation by providing surfaces for water vapour to condense on. They also scatter sunlight, making the sky appear blue. However, excess dust can cause breathing problems and allergies.
How do plants and animals maintain the balance of oxygen and carbon dioxide in air?
Plants and animals maintain gas balance through a complementary cycle: During photosynthesis, green plants take in carbon dioxide and release oxygen. During respiration, both plants and animals take in oxygen and release carbon dioxide. Burning of fuels also consumes oxygen and releases carbon dioxide. This natural balance keeps oxygen at about 21% and carbon dioxide at about 0.03% in the atmosphere.
Why do mountaineers carry oxygen cylinders and how does air pressure change with altitude?
At high altitudes like Mount Everest, air pressure is much lower than at sea level. This means oxygen molecules are more spread out, and each breath contains fewer oxygen molecules. Since our body needs a certain amount of oxygen to function, mountaineers carry oxygen cylinders to breathe properly. Air pressure decreases as altitude increases because there is less air above pushing down.

Chapter Summary: Air Around Us

Air is a mixture of gases that surrounds the Earth, forming the atmosphere. It is transparent, colourless, and occupies space. The major components of air are nitrogen (about 78%) and oxygen (about 21%). The remaining 1% includes carbon dioxide, water vapour, and other gases, along with dust particles.

Oxygen is essential for respiration and burning. Nitrogen does not support burning. Carbon dioxide is used by plants for photosynthesis. Water vapour in air is important for the water cycle. Air also contains dust particles which can be seen in a beam of sunlight. Air is dissolved in water, providing oxygen to aquatic life. Soil also contains air in its pores, allowing organisms and plant roots to respire. Plants and animals help each other in maintaining the balance of oxygen and carbon dioxide in the atmosphere through photosynthesis and respiration.

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