Category : 2nd Class
This lesson will help you to:
QUICK CONCEPT REVIEW
In the previous class, we have studied that air is necessary for our life. Air is present all around us. Air occupies space and it cannot be seen, only we can feel it. It gives shape to things. Let us study the components of air.
Do you know?
Air contains 78% nitrogen, 21% oxygen and 1% other gases which contain carbon dioxide, water vapour etc.
Air contains gases like nitrogen, oxygen carbon dioxide, dust, smoke and germs. Air contains water in the form of water vapour.
Air has many characteristics. Let us discuss this in detail:
1. Air occupies space.
2. Air has weight.
3. Air exerts pressure.
4. Air carries smell.
5. Air can produce sound.
Air is all around us but we cannot see it. Have you noticed your hair is blowing? This is because of air.
Moving air is called wind. When the wind blows gently, it is called breeze. It helps in drying clothes. When the wind blows very fast, it is called storm. A storm can damage your house.
A Storm can domage your house
We all need water. Water is required for drinking, bathing, cooking, washing etc. Plants and animals need water. But do you know, where water comes from?
We get water from rain. Rainwater is present in oceans, river, ponds, lake, ground water etc.
Water has no fixed shape. It can take the shape of vessel in which it is kept.
Real life Example:
Wind makes the wheel of wind- mill to otate which produces electricity.
FORMS OF WATER
Have you noticed when water is heated in a kettle, steam comes out of it. Steam is the water vapour. Water is found in three forms. Solid (ice), liquid (water) and gas (water vapour) the process of changing the water into water vapour is known as evaporation.
When water vapour gets cooled it becomes liquid (water). This process is called condensation.
When water is cooled, it becomes ice. This process is known as freezing.
In this cycle, water from oceans, lakes and rivers is converted into water vapour. Water vapour condenses into tiny droplets to form clouds. Clouds lose their water as rain or snow.
Water bodies (seas, oceans, rivers, lakes ponds and ground water) get contaminated when:
Has it happened with you that you were out on a sunny day and suddenly it started raining? Who caused this change in weather.
Weather of a place is influenced by the condition of air and quantity of water available in the atmosphere.
Weather is the condition of atmosphere at a particular time in terms of temperature, pressure, wind and moisture. The weather can be hot, cold, windy, dry or humid. Depending on the weather, there are 5 seasons in India.
1. SUMMER SEASON
This is a hot season. Summer stays from April to June. Heat waves are common in this season. Therefore, light and cotton clothes are the most favorable clothes in summer season.
2. RAINY SEASON (MONSOON)
Monsoon season comes after summer and it stays from July to August. This season is necessary for agriculture because plants and crops need water to grow.
Autumn comes after monsoon. In this season, trees shed their leaves. Temperature is neither too hot nor too cold..
4. WINTER SEASON
The months of November, December and January is the time of winter when the temperature is very low and the atmosphere is cold. This is the season when people wear woollen and warm clothes
5. SPRING SEASON
This is the most pleasant season of the year. Because this is the season of moderate temperature when atmosphere is neither extreme cold nor extreme hot. This season stays from February to March.
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