The Atmosphere Chapter Notes | Footprints Class 7: Book Solutions, Notes & Worksheets PDF Download

Introduction

• The atmosphere is like a protective blanket around Earth, comprising a mixture of gases that make life possible.
• Its gravitational force keeps it in place, ensuring a stable environment for life to thrive.
• Oxygen, a vital gas in the atmosphere, is essential for the survival of living beings as it is used in respiration.
• The atmosphere acts as a shield, protecting Earth from the harmful ultraviolet rays of the Sun.

Composition of the Atmosphere

• Nitrogen makes up the largest portion of the atmosphere at 78%. It is inert and does not readily react with other substances.
• Oxygen, making up 21% of the atmosphere, is essential for respiration in most living organisms.
• Argon comprises 0.93% of the atmosphere and is also chemically inert.
• Carbon dioxide, though a minor component at 0.03%, plays a crucial role in photosynthesis and the greenhouse effect.
• Other trace gases like neon, helium, krypton, xenon, hydrogen, and ozone are present in very small amounts but can have significant effects on atmospheric processes.
• Water vapor, while variable, plays a crucial role in the weather and climate systems through the processes of evaporation and condensation.

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Structure of the Atmosphere

• The atmosphere is divided into five layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
• Each layer has its unique characteristics, such as temperature trends and the presence of certain gases.
• The troposphere is where most weather phenomena occur and is also where most of the atmosphere's mass is concentrated.
• The stratosphere contains the ozone layer, which absorbs and scatters the Sun's ultraviolet radiation, protecting life on Earth.
• The mesosphere is where meteoroids burn up upon entering Earth's atmosphere, creating shooting stars.
• The thermosphere is where the auroras occur and where the International Space Station orbits.
• The exosphere gradually transitions into outer space and is where atmospheric particles escape into space.

Significance of the Atmosphere

• The atmosphere is essential for life on Earth, providing the air we breathe and the climate that sustains ecosystems.
• Oxygen supports combustion, allowing for the burning of fuels for energy.
• Nitrogen is vital for plant growth and is used in the production of various compounds.
• Carbon dioxide is absorbed by plants for photosynthesis, the process by which they produce food.
• Water vapor plays a crucial role in the water cycle, sustaining life and shaping Earth's climate.

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Weather and Climate

• Weather refers to the short-term conditions of the atmosphere, including temperature, precipitation, humidity, and wind.
• Climate, on the other hand, refers to the long-term patterns of weather in a particular area.
• Both weather and climate are influenced by factors such as temperature, pressure, humidity, and wind patterns.

Temperature

• Temperature is a measure of the average kinetic energy of molecules in a substance.
• The Sun's radiation heats the Earth, with the highest temperatures found near the Equator and lower temperatures near the poles.
• Factors such as latitude, altitude, distance from the sea, prevailing winds, ocean currents, and slope of the land all influence temperature patterns on Earth.

The Heat Zones

• The Earth is divided into three heat zones based on the amount of solar radiation received: the Torrid Zone, Temperate Zone, and Frigid Zone.
• Each zone has its unique climate and vegetation, influenced by the angle of the Sun's rays and the length of daylight.

Atmospheric Pressure

• Atmospheric pressure is the force exerted by the weight of the air above a given point on Earth's surface.
• It decreases with altitude, as there is less air above to exert pressure.
• Factors such as altitude, temperature, moisture, and the rotation of Earth all influence atmospheric pressure.

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Winds

• Winds are caused by the uneven heating of Earth's surface, which creates areas of high and low pressure.
• They move from areas of high pressure to areas of low pressure, creating the wind patterns we observe.
• Different types of winds, such as planetary, periodic, and local winds, have specific characteristics and play important roles in shaping Earth's climate and weather.

Humidity

• Humidity is the amount of water vapor present in the air.
• It varies with temperature, with warmer air holding more moisture than cooler air.
• The hydrological cycle, which includes processes like evaporation, condensation, and precipitation, regulates humidity and plays a crucial role in Earth's climate system.