Answer:

hii nany hope this helps u and ur brother---

Explanation:

What is the signifincance of oxygen for us?

Answer: Oxygen is the second most plentiful gas in the air. Most of the living beings need oxygen for respiration. Thus, oxygen is important for survival of life on earth.

What is mesosphere?

Answer: It is the third layer of the atmosphere and it lies above the stratosphere. It extends upto a height of 80 km. The burning of meteorites on entering from space occurs in this layer.

Write briefly about nitrogen gas.

Answer: It is the gas that is most abundant in the air. Nitrogen is an important component of protein. Plants cannot take up gaseous nitrogen. They need help of various agents of nitrogen fixation in order to utilize nitrogen.

What is temperature?

Answer: It is the degree of hotness or coldness of the air. It changes between day and night and from season to season. Summers have a higher temperature than winters. It is measured using a thermometer.

Long Answer Type Questions:

Describe the composition of the air.

Answer: The air that we breathe is a mixture of many gases like oxygen, nitrogen, carbon dioxide, argon etc. The majority of the atmosphere is made up of nitrogen (78%) and oxygen (21%). The other gases that are present in small quantities are:

Carbon dioxide (0.03%),

Argon (0.93%)

Others ( helium, hydrogen, ozone)

Describe the layers of the atmosphere.

Answer: Our atmosphere is divided into five layers which are:

Troposphere – It is the most important layer of the atmosphere. The air we breathe exists here. Its average height is 13 km. Almost all the weather phenomena like rainfall, hailstorm etc. occur in this layer.

Stratosphere – This layer is just above the troposphere .It extends to a height of 50 km. It is almost free from clouds and associated weather phenomena that occur in the troposphere. It is most ideal for flying aeroplanes since it is free from weather phenomena. It contains a layer of ozone gas which protects us from the harmful effect of sun rays.

Mesosphere - It is the third layer of the atmosphere and it lies above the stratosphere. It extends upto a height of 80 km. The burning of meteorites on entering from space occurs in this layer.

Thermosphere – It is the fourth layer and the layer above the mesosphere. In this layer, temperature rises very rapidly with increase in height. Ionosphere is a part of this layer. It extends between 80 to 400 km. It helps in radio transmission. This layer is responsible for reflecting back of the radio waves that are transmitted from the earth.

Exosphere – It is the uppermost layer of the atmosphere. It has very thin air. Light gases like helium and hydrogen float into the space from here.

Write in detail about winds.

Answer: The movement of air from high pressure area to low pressure area is called wind. Winds can be gentle or very strong. Gentle winds blow away smoke or fine dust. An extremely strong wind is in the nature of a storm which can even uproot trees. A wind can be strong enough to make it difficult to walk against it. Broadly, winds can be divided into three types:

Permanent winds – These blow constantly throughout the year in a particular direction. For example – the trade winds, westerlies and easterlies.

Seasonal winds – These winds change their direction in different seasons. For example, monssons in India.

Local winds – These winds blow only during a particular period of the day or year in a small area. Land and sea breeze are examples of this.

Describe air pressure.

Answer: Air pressure is defined as the pressure exerted by the weight of air on the earth’s surface.

Nature of vertical air pressure - The pressure falls rapidly as we go up the layers of the atmosphere. Therefore, the pressure is the highest at sea level and decreases with altitude.

Nature of horizontal air pressure – Horizontally, the distribution of air pressure is influenced by the temperature of the air at a given place.

Where the temperature is high, the air gets heated up and rises, thus creating a low pressure area. This is associated with cloudy skies and wet weather. Where the temperature is low, the air is cold and therefore heavy. This heavy air sinks and creates a high pressure area. High pressure is associated with clear and sunny skies. The movement of air is always from areas of high pressure to areas of low pressure. Barometre is used to measure atmospheric pressure.

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