All questions of Air Around Us. for Class 6 Exam

The Earth's atmosphere extends to a height of about 600 kilometers above the Earth's surface. This vast layer of air plays a crucial role in protecting life on Earth by absorbing harmful ultraviolet radiation from the Sun, regulating the planet's temperature, and providing the necessary gases for respiration and other vital processes. The atmosphere is divided into different layers, each with distinct characteristics and functions that contribute to the overall balance of the Earth's climate and ecosystems.

The Earth's Atmosphere: An Overview
The Earth's atmosphere is a critical component of our planet, providing essential conditions for life. Here’s a detailed explanation of why option 'C' is the correct answer.
What is the Atmosphere?
- The atmosphere is a layer of gases that surrounds the Earth.
- It is held in place by the Earth's gravity, preventing the gases from escaping into space.
Composition of the Atmosphere
- The atmosphere consists of a mixture of gases, including nitrogen (about 78%), oxygen (about 21%), and trace amounts of other gases such as carbon dioxide, argon, and water vapor.
- This diverse composition is crucial for various processes, including respiration in living organisms and the greenhouse effect that helps regulate the Earth's temperature.
Characteristics of the Atmosphere
- The atmosphere is not stationary; it is dynamic, with air currents, weather patterns, and temperature variations.
- It does not extend infinitely into space; it gradually thins out and transitions into the vacuum of space at high altitudes.
Importance of the Atmosphere
- The atmosphere protects life on Earth by filtering harmful solar radiation and maintaining a stable climate.
- It plays a vital role in the water cycle and weather systems, influencing ecosystems and human activities.
In summary, option 'C' accurately describes the Earth's atmosphere as a layer of gas surrounding the Earth, essential for supporting life and various environmental processes.

Understanding Why Air is Colorless and Odorless
Air is a mixture of gases that surrounds us, and its properties can often be misunderstood. The primary reason air is considered colorless and odorless is due to its composition, specifically the presence of nitrogen and oxygen.
Composition of Air
- Air is primarily composed of nitrogen (about 78%) and oxygen (about 21%).
- Other gases, like argon, carbon dioxide, and traces of other gases, make up the remaining 1%.
Lack of Color
- The gases in the air do not absorb visible light; hence, they do not impart any color.
- When light passes through air, it is not scattered in a way that would give air a color.
Lack of Odor
- Nitrogen and oxygen, the main components of air, are both odorless.
- The absence of significant concentrations of other gases that have strong smells contributes to the overall odorlessness of air.
Absence of Pollutants
- Clean air, without pollutants or other chemical compounds, maintains its colorless and odorless characteristics.
- Some pollutants can change the smell or appearance of air, but in its pure form, air remains neutral.
Conclusion
In summary, air's lack of color and odor is primarily due to its composition of nitrogen and oxygen. These gases do not absorb visible light or have distinct smells, allowing air to exist as a clear and scentless mixture. Understanding this helps us appreciate the essential nature of air in our environment.

Oxygen is vital for the process of respiration in all living organisms. During respiration, oxygen is used to release energy from sugars through a series of metabolic reactions. This energy is essential for various cellular processes that sustain life. The absence of oxygen can lead to a halt in respiration and ultimately affect the survival of organisms.

Nitrogen fixation is the process where specific bacteria convert nitrogen and oxygen from the air into nitrates, which are crucial for plants to synthesize proteins. This process plays a vital role in the nitrogen cycle, making atmospheric nitrogen available to plants in a form they can utilize for their growth and development.

When a lighted candle is covered with a glass tumbler, it eventually goes out because the flame consumes the available oxygen inside the tumbler. Without oxygen, the combustion process cannot continue, leading to the extinguishing of the flame. This experiment demonstrates the essential role of oxygen in supporting combustion.

Plants play a crucial role in maintaining the balance of carbon dioxide levels in the atmosphere by absorbing carbon dioxide during photosynthesis. Through this process, plants utilize carbon dioxide to produce glucose and oxygen, releasing the latter back into the air. This symbiotic relationship between plants and the atmosphere helps regulate the concentration of carbon dioxide, supporting ecosystems and life on Earth.

Air aids in the dispersal of pollen grains and seeds by carrying them through the wind. This mechanism enables plants to reproduce and spread their genetic material over varying distances, promoting biodiversity and ecosystem resilience.

Air aids in regulating temperature by spreading the sun's heat all over the Earth. This process helps maintain an equilibrium in temperature across different regions, influencing weather patterns and supporting various ecosystems.

When the wind blows, we primarily perceive the presence of air through its movement. While air itself is invisible, we can feel and observe its effects when it moves objects or causes changes in the environment. The wind is essentially the movement of air masses from areas of high pressure to areas of low pressure, creating various weather patterns and influencing local climate conditions. Sensing the wind's movement is one way we can directly experience the presence and effects of air around us.

Nitrogen is the most abundant gas in Earth's atmosphere, constituting about 78% of the air we breathe. Despite its abundance, plants and animals cannot directly utilize nitrogen. The process of nitrogen fixation by certain bacteria converts atmospheric nitrogen into forms that plants can absorb and utilize for their growth.

Wind energy is harnessed through windmills, which utilize the kinetic energy of moving air to perform various tasks, such as generating electricity, pumping water, or grinding grain. This renewable energy source has gained popularity for its sustainability and environmental benefits.

Oxygen in the atmosphere is constantly replenished due to the photosynthetic activities of plants and plant-like microorganisms. During photosynthesis, these organisms utilize carbon dioxide and water to produce oxygen as a byproduct. This crucial process helps maintain the balance of oxygen in the atmosphere, ensuring a continuous supply for living organisms to breathe.

The ozone layer plays a crucial role in absorbing harmful ultraviolet (UV) rays from the sun. This absorption protects living organisms on Earth from the damaging effects of excessive UV radiation, such as skin cancer and other health issues.

Industrial activities and transportation are significant sources of carbon dioxide emissions, leading to the accumulation of greenhouse gases in the atmosphere. The burning of fossil fuels in industries and vehicles releases carbon dioxide, contributing to the greenhouse effect and climate change. These anthropogenic activities have a substantial impact on Earth's climate system, emphasizing the need for sustainable practices to mitigate carbon emissions and reduce environmental impact.

Water vapor plays a significant role in the formation of various weather conditions. When water vapor in the air condenses, it forms clouds. Subsequently, these clouds can lead to precipitation in the form of rain or snowfall. Additionally, condensation of water vapor can result in the formation of dew and fog under specific atmospheric conditions, influencing local weather patterns.