Air is a vital component of our lives, and it is primarily composed of a mixture of gases. The various constituents of air include 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide, and approximately 1% water vapor. Notably, air serves crucial functions in breathing and combustion processes.Learn from School Connect Online in this chapter we will learn about Air, a cosmopolitan component of our life.
CBSE Class 6 Science Notes Chapter 15 Air Around Us
The different topics covered in CBSE Class 6 Science Chapter 15 are tabulated below:
| Section | Topic Name |
| Ex 15.1 | Is Air Present Everywhere Around Us? |
| Ex 15.2 | What Is Air Made Up Of? |
| Ex 15.3 | How Does Oxygen Become Available To Animals And Plants Living In Water And Soil? |
| Ex 15.4 | How Is The Oxygen In The Atmosphere Replaced? |
Ex : 15.1 – Is Air Present Everywhere Around Us?
Air is an invisible yet omnipresent substance that surrounds us at all times. While we may not be able to see it with our eyes, we can detect its presence through the movement of objects around us. The rustling of leaves and swaying of branches are examples of how air interacts with the environment. Additionally, we can also feel the effects of air on our skin when we feel a breeze or wind blowing.
Importance of Air
Air is essential for the survival of all living beings as it contains oxygen that our bodies need for respiration. Oxygen is required for the production of energy in our cells, which is necessary for various bodily functions.
Additionally, air is also crucial for combustion processes. Oxygen is necessary for burning, and without it, fires cannot sustain. We use air in several applications that involve burning, such as in cooking, heating, and transportation.
Moreover, life is only possible on earth because of the presence of air. The atmosphere around the earth is primarily composed of air, which provides a suitable environment for various life forms to thrive. The air protects us from harmful radiation, regulates temperature, and helps to maintain the balance of gases required for life on earth.
Ex : 15.2 – What Is Air Made Up Of?
Air is a mixture of different gases, particles, and sometimes even microorganisms. The major constituents of air are nitrogen, oxygen, and argon, but it also contains other gases such as carbon dioxide, neon, helium, and methane, among others. Additionally, air can also contain water vapor, dust, pollen, smoke, and other particles, depending on the environment.
- Air is a mixture of various gases, water vapor, and particles.
- The gases present in the air primarily include nitrogen, oxygen, and a small amount of other gases such as argon, neon, helium, and methane.
- Carbon dioxide is also present in the air, but in relatively small quantities compared to the other gases.
Water vapours
- Air can hold a certain amount of water vapor, which is the gaseous form of water.
- The amount of water vapor that air can hold depends on the temperature and pressure of the air.
- When air comes in contact with a cool surface, such as the ground or a window, it cools down, and the water vapor in the air can condense, forming droplets of liquid water. This process is what causes fog to appear.
Dust particles
- The presence of dust particles in the air can vary depending on several factors, such as the location, climate, weather, and human activities.
- In urban areas, for instance, the air may contain higher levels of dust particles due to increased human activity, construction, and vehicular emissions.
- In contrast, rural areas may have lower levels of dust particles in the air due to less human activity and cleaner environments.
Oxygen
- Oxygen is a vital component of the air we breathe, and it plays a crucial role in supporting life. It is necessary for the survival of all living beings as it is required for respiration, the process by which we convert food into energy.
- The percentage of oxygen in the air is around 20.95%, which is a relatively constant value, although it may vary slightly depending on the location and altitude. This percentage is optimal for supporting life as it provides an adequate supply of oxygen for respiration while preventing the risk of combustion.
Nitrogen
- Nitrogen is the most abundant gas in the air we breathe, making up approximately 78% of the air’s volume.
- It is an inert gas and does not support combustion or burning.
- In other words, nitrogen gas does not react with other substances and is not flammable.
Carbon dioxide
- Carbon dioxide (CO2) is a minor but important component of the air we breathe, making up around 0.03% of the air’s volume. While carbon dioxide is essential for plant growth and plays a role in regulating the earth’s climate, high levels of carbon dioxide in the air can lead to adverse health effects in humans.
- In high concentrations, carbon dioxide can cause a feeling of suffocation or shortness of breath, which can be particularly dangerous in enclosed spaces with poor ventilation.
Atmosphere
- Our earth is surrounded by a thin layer of air called the atmosphere, which extends several kilometers above the earth’s surface. As we go higher up in the atmosphere, the air becomes thinner and thinner, making it difficult to breathe and survive without special equipment.
- The atmosphere is an active and dynamic layer that interacts with the earth’s surface through various processes, such as the movement of air, cloud formation, thundering, rain, and other weather phenomena.
- Cloud formation occurs when water vapor in the air condenses into tiny water droplets or ice crystals, forming visible clouds in the sky. Thunder and lightning occur due to the build-up of electrical charges in the atmosphere, which discharge as bolts of lightning and thunderous sound waves.
- Rain is a crucial process that occurs in the atmosphere, helping to transport water from the ocean and land to the atmosphere and back again in the form of the water cycle.
Ex : 15.3 – How Does Oxygen Become Available To Animals And Plants Living In Water And Soil?
- In Plants:
Plants have tiny pores called stomata, which are typically found on the underside of leaves, although they can also occur on stems and other plant parts. Stomata are essential for plant survival because they allow for the exchange of gases, including carbon dioxide and oxygen, with the atmosphere.
During photosynthesis, plants absorb carbon dioxide from the air through their stomata and convert it into sugars and other organic compounds, releasing oxygen as a byproduct. This process is critical for maintaining the balance of oxygen and carbon dioxide in the atmosphere and supporting life on earth.
- In Animals:
All living organisms require oxygen to produce energy through respiration, and this applies to animals as well. However, different animals have evolved different respiratory organs and mechanisms to suit their specific needs and environments.
- In Aquatic Animals and Plants:
Aquatic animals like fish, crabs, and shrimp use gills to extract dissolved oxygen from water for respiration. Dolphins and whales, on the other hand, are mammals that breathe air with the help of lungs.
Aquatic plants like Hydrilla have stomata on their leaves, which allow them to absorb dissolved oxygen from the water for respiration.
- In Amphibians:
Amphibians like frogs, newts, and salamanders have a dual respiratory system, which allows them to breathe both air and water. They have lungs for breathing air and also have permeable skin that allows them to absorb oxygen directly from the water.
Crocodiles and alligators have nostrils located at the top of their snouts, which they use to breathe air while swimming through the water. They also have a unique respiratory adaptation called a “secondary palate” that allows them to breathe while holding their prey underwater.
- In Birds:
Birds have an efficient respiratory system as they need high levels of oxygen during flight. Birds have a pair of lungs with air sacs that remain open all the time so that air can easily pass through them.
- In Mammals:
Most mammals breathe with the help of lungs. They take in oxygen and give out carbon dioxide.
Ex : 15.4 – How Is The Oxygen In The Atmosphere Replaced?
- Organisms have evolved to form complex relationships with each other, where they often benefit from each other in various ways. For example, we get oxygen and food from plants, while they get carbon dioxide and other nutrients from us. This is just one example of the many intricate relationships that exist in nature.
- The exchange of gases between living organisms and their environment is essential for life to exist on earth. This exchange occurs through two important processes – respiration and photosynthesis. During respiration, organisms consume oxygen and produce carbon dioxide, while during photosynthesis, plants consume carbon dioxide and produce oxygen.
- This constant cycling of oxygen and carbon dioxide through respiration and photosynthesis helps maintain the balance of gases in the atmosphere. It also plays an important role in regulating the Earth’s climate and ensuring the survival of all living organisms.
Conclusion :
Air pollution has several causes, including the excessive burning of fuels such as wood, coal, and petroleum, the release of gases by machines and vehicles, and the emission of harmful gases by industries. These activities release pollutants such as carbon monoxide, sulfur dioxide, nitrogen oxides, and particulate matter into the air.
These pollutants can have harmful effects on human health, including respiratory problems and cardiovascular disease. Air pollution can also have adverse effects on plants and animals and contribute to climate change. It is important to take measures to reduce air pollution and protect the quality of the air we breathe.
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