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Prepared by: learnloophq@gmail.com

Last edited 25 days ago by Learn LoopHQ.

Chapter: 06. Air And Atmosphere

⁠

Section A: Multiple Choice Questions (MCQs)

(b) It cannot be compressed easily.

(d) Oxygen

(b) Hydrated iron oxide

(b) Burning fossil fuels

Section B: Fill in the Blanks

wind

colourless

photosynthesis

humidity

respiration

Nitrogen

dry ice

ethyl mercaptan

global warming

water vapour

Section C: True/False Questions

False

True

False

True

False

True

False

Section D: Explanations of Terms

Atmosphere: A thin layer or blanket of air that surrounds the Earth, held in place by Earth’s gravity.

Humidity: The amount of water vapour present in the air.

Photosynthesis: The process by which green plants make their own food (glucose) from carbon dioxide and water using sunlight and chlorophyll, releasing oxygen.

Rusting: The process where iron objects develop a reddish-brown, flaky substance (rust) when exposed to moist air over time.

Air Pollutants: Harmful and unwanted substances that contaminate the air, causing negative effects on living and non-living things.

Section E: Short Answer Questions

Three characteristics of air are: It has mass, it occupies space, and it can be compressed easily.

Exhaled air has more carbon dioxide than inhaled air because carbon dioxide is a waste product released by the body’s cells during respiration.

Divers carry oxygen cylinders because they cannot utilize the oxygen dissolved in water for breathing, and they need a direct supply of oxygen to survive underwater.

During heavy rains, soil gets filled with water, which displaces the air trapped between soil particles. This forces organisms like earthworms to come out of the soil to breathe.

Nitrogen is a key component of proteins, which are necessary for the growth of living organisms. In industries, nitrogen is used in fertilizers to increase soil fertility.

The greenhouse effect is the process where certain gases in the atmosphere (like carbon dioxide) trap heat from the Sun, preventing it from escaping Earth. Carbon dioxide is a major contributor to this effect.

The depletion of the ozone layer is a concern because it allows more harmful ultraviolet (UV) radiation from the Sun to reach the Earth’s surface, which can lead to skin diseases and cancer in humans.

Section F: Diagram-Based Questions

a. Gas A: Carbon dioxide b. Gas B: Oxygen c. Process: Photosynthesis

a. Property: This experiment demonstrates that air occupies space. b. If the glass is slightly tilted, air bubbles would escape from the mouth of the glass, and water would then enter the glass, filling the space previously occupied by air.

Section G: Identifying and Differentiating Concepts

Respiration vs. Burning: a. Amount of Energy Released: Respiration releases a small amount of energy in the form of heat only, whereas burning releases a large amount of energy in the form of both heat and light. b. Speed of the process: Respiration is a slow process that occurs continuously, while burning is a fast process that occurs rapidly.

Air Pollutants (AP) or Essential Air Components (EAC): a. Oxygen: EAC b. Sulphur dioxide: AP c. Nitrogen: EAC d. Carbon monoxide: AP e. Water vapour: EAC

Section H: Environmental Awareness / Everyday Use

It is important to “grow more and more trees” because trees absorb carbon dioxide, a major greenhouse gas and pollutant, from the atmosphere. They also release oxygen, thus naturally cleaning and purifying the air, which helps combat air pollution.

The “Pollution Under Control (PUC)” certificate is significant because it verifies that a vehicle’s emissions are within permissible limits set by environmental regulations. This helps ensure that vehicles are not excessively contributing to air pollution, promoting cleaner air quality in cities.

Section I: Long Answers

Air is a mixture of gases with varying compositions, but approximately, it consists of about 78% Nitrogen, 21% Oxygen, 0.03% Carbon dioxide, 0.93% other gases (like noble gases), and variable amounts of water vapour and dust particles. The presence of water vapour can be demonstrated by placing ice cubes in a dry glass; tiny water droplets will form on the outer surface due to condensation of water vapour from the air. The presence of dust particles can be shown by observing a beam of sunlight entering a dark room through a small hole; tiny shining dust particles can be seen moving in a zigzag way within the beam.

The natural balance of oxygen and carbon dioxide in the atmosphere is maintained through the interconnected processes of respiration, combustion, and photosynthesis. Living organisms consume oxygen and release carbon dioxide through respiration, and the burning of fuels also uses oxygen while releasing carbon dioxide. Green plants, however, use this carbon dioxide for photosynthesis and release oxygen back into the atmosphere. Human activities like deforestation (cutting down trees) disrupt this balance by reducing the number of plants that absorb carbon dioxide. Similarly, the extensive burning of fossil fuels (coal, oil, gas) in industries and vehicles releases large amounts of additional carbon dioxide, overwhelming nature’s ability to balance it. These activities lead to an increase in atmospheric carbon dioxide, contributing to environmental concerns like global warming.

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