CBSE Class 5 Science Air Around Us Worksheet

Ln.4 AIR AROUND US

I. Fill in the blanks.

Question 1. The second biggest content of air is __________.
Answer: Oxygen
In simple words: Nitrogen is the main gas in air (78%), and oxygen is the second largest part (21%).

Exam Tip: Remember the major composition percentages: Nitrogen is about 78% and Oxygen is about 21%.

Question 2. As we go up to higher altitudes __________ becomes thinner.
Answer: Air
In simple words: Air pressure and the amount of oxygen decrease as you climb higher mountains.

Exam Tip: This is why mountaineers carry oxygen cylinders when climbing very high peaks like Mount Everest.

Question 3. All weather changes takes place in __________ layer of atmosphere.
Answer: Troposphere
In simple words: Rain, clouds, wind, and snow happen in the lowest layer of the atmosphere.

Exam Tip: Associate the Troposphere directly with weather phenomena.

Question 4. The air we breathe in is called __________ air.
Answer: Inhaled
In simple words: Inhaled means the air we take into our lungs.

Exam Tip: Do not confuse inhaled (taken in) with exhaled (given out).

Question 5. Clouds are rare in __________ layer of atmosphere.
Answer: Stratosphere
In simple words: The stratosphere is mostly calm and free of weather disturbances, which is why commercial planes fly there.

Question 6. __________ is a mixture of gases.
Answer: Air
In simple words: Air is not a single substance; it is a blend of nitrogen, oxygen, argon, carbon dioxide, and other gases.

Exam Tip: Air is classified as a mixture because its components retain their individual properties.

Question 7. The air we breathe out is called __________ air.
Answer: Exhaled
In simple words: Exhaled air is pushed out of our lungs after the body uses some of the oxygen.

Exam Tip: Exhaled air contains more carbon dioxide and water vapor than inhaled air.

Question 8. Exhaled air has a higher percentage of __________ than the inhaled air.
Answer: Carbon dioxide
In simple words: Our body produces carbon dioxide as waste during respiration, which we breathe out.

Exam Tip: Inhaled air has very little carbon dioxide (about 0.04%), while exhaled air has about 4%.l

Question 9. Plants carry out a process called __________ in addition to respiration.
Answer: Photosynthesis
In simple words: Plants make their own food using sunlight, water, and carbon dioxide, releasing oxygen.

Exam Tip: Photosynthesis is unique to green plants and helps maintain oxygen levels in the atmosphere.

II. Name the following.

Question 1. An envelope of air around the earth.
Answer: Atmosphere
In simple words: The blanket of gases surrounding our planet is called the atmosphere.

Exam Tip: Gravity holds the atmosphere close to the Earth.

Question 2. The layer of atmosphere above Troposphere.
Answer: Stratosphere
In simple words: The stratosphere sits right above the troposphere and contains the ozone layer.

Exam Tip: Memorize the order of atmospheric layers starting from the Earth's surface.

Question 3. The lowest layer of atmosphere.
Answer: Troposphere
In simple words: It is the layer closest to the ground where we live and breathe.

Exam Tip: Troposphere is the densest layer containing most of the atmosphere's mass.

Question 4. The layer that reflects radio waves back to the earth.
Answer: Ionosphere (or Thermosphere)
In simple words: Radio communication is possible because this layer bounces radio signals back down to Earth.

Exam Tip: Mentioning Thermosphere or Ionosphere is acceptable at this grade level.

Question 5. The layer which is a part of Stratosphere.
Answer: Ozone layer
In simple words: The ozone layer protects living beings by absorbing harmful ultraviolet rays from the sun.

Exam Tip: Ozone layer depletion is a major environmental concern.

III. Choose the correct answer.

Question 1. As we go to higher altitudes air becomes [more/less]
(a) more
(b) less
Answer: (b) less
Air density decreases at higher altitudes.
In simple words: Higher up in the mountains, air is thinner and less dense.

Exam Tip: Atmospheric pressure and density decrease with altitude.

Question 2. The percentage of oxygen gas in air is [78%/21%].
(a) 78%
(b) 21%
Answer: (b) 21%
Oxygen constitutes approximately 21% of the atmosphere.
In simple words: Out of 100 parts of air, 21 parts are oxygen.

Exam Tip: Do not confuse 78% (Nitrogen) with 21% (Oxygen).

Question 3. Inspired air is rich in [oxygen/nitrogen].
(a) oxygen
(b) nitrogen
Answer: (a) oxygen
Inspired (inhaled) air contains high levels of oxygen required for respiration.
In simple words: We breathe in air to absorb oxygen into our blood.

Exam Tip: Inspired air has about 21% oxygen.

Question 4. Blood in the [lungs/heart] take oxygen from the air we breathe in.
(a) lungs
(b) heart
Answer: (a) lungs
Gaseous exchange takes place in the alveoli of the lungs.
In simple words: Lungs transfer oxygen from inhaled air directly into the bloodstream.

Exam Tip: The heart pumps the blood, but the lungs oxygenate it.

Question 5. All living things take in [oxygen/carbon dioxide] during respiration.
(a) oxygen
(b) carbon dioxide
Answer: (a) oxygen
Respiration in living organisms requires oxygen to break down food and release energy.
In simple words: Oxygen is essential for living creatures to survive and produce energy.