Notes on Water for Class 6
What are the activities for which we use water?Water is the most essential liquid for life to exist on Earth. We use water in large quantities for various activities in our day to day life which include drinking, cooking food, brushing teeth, bathing, cleaning various things, washing clothes, industrial use, growing plants and crops and many more such activities.
Where do we get the water from?The water we get in our taps are supplied to us through a network of pipes from the water works department. This water is drawn from the nearby water sources like lakes, rivers, ponds, wells etc.
Nearly two thirds of Earth is covered with water which is in the form of oceans and seas. The ocean and sea water is saline in nature as large amounts of salts are dissolved in these waters. Because of this, ocean and sea waters is not fit for drinking and for other major activities.
However, oceans and seas play a major role in supplying water to us through an important process called water cycle.
Water CycleDuring daytime, various water sources on Earth continuously receive Sun's heat due to which water from these sources continuously change into vapor leaving behind the dissolved salts. During daytime, green plants lose the excess water from their body through a process called transpiration. Thus water vapor keeps continuously added to air through the process of evaporation and transpiration.
Evaporation is the process by which water changes into its gaseous state on heating.
How are clouds formed?Water vapor present in the air condenses into small droplets of water on cooling. This process is called condensation which plays an important role in bringing back water on to Earth. It gets cooler and cooler as we go high from Earth's surface. Water vapor, when moves up, get cooler and thus condenses into small droplets of water. These droplets of water float in the sky and appear as clouds. While floating, the tiny droplets of water come together and forms bigger drops of water. Some of these drops become so big that these are attracted by Earth's gravitational pull and fall on Earth as rain or at times, the water drops freeze to form ice and fall down as hail. In colder regions, during winter, the water vapor directly freezes to form flakes of ice which fall down on to Earth as snow.
Thus, water from various sources goes up into the air in the form of water vapor through the process of evaporation and transpiration in plants. These vapors form clouds through the process of condensation and comes back to Earth to fill the various water bodies. However, some part of the rain water is absorbed by the ground and seep into the soil and is available as ground or table water.
Such a circulation of water is known as water cycle which is a continuous process. Water cycle plays an important role in maintaining the supply of water on the land.
The amount of rainfall and its duration are different from place to place. In India, it rains during monsoon and farmers depend on monsoon for sowing seeds in the agricultural fields. At times, there are heavy rains which result in the increase in water levels of rivers, lakes, ponds and other such water bodies which damage crops. Heavy floods can even cause damage to domestic animals, property and even human life.
At times, where there are no rains for a continuous period of time, the soil continuously loses water through evaporation and through transpiration of plants. As the water is not being refilled, the soil gets dry and the level of water in various water bodies goes down and down. Some ponds and rivers nearly become dry without water. Even the ground water level goes too deep and it becomes scarce. Fields become dry and many plants dry up and die due to lack of water. Even few animals die due to lack of proper food and water. Such a terrible situation is called drought.
How can we conserve water?The water available for use by humans, plants and animals is very limited and it is decreasing due to the extensive usage by humans. The demand for water is ever increasing due to the overuse by the ever increasing population. This results in the shortage of water and we need to take necessary steps to conserve water.
Rainwater HarvestingOne of the best methods to increase the availability of water is collecting rain water and storing it for future use. Such a method is known as rainwater harvesting.
Rooftop rainwater harvesting: In this method, the rain water from the root tops is collected in storage tanks or a pit in the ground through pipes. The water collected through this method may contain soil and needs to be filtered. The rain water collected in the pit, seeps into the soil and refills the ground water.
Test Yourself1. Fill up the blanks:
(a) The process of changing of water into its vapor is called evaporation.
(b) The process of changing water vapor into water is called condensation.
(c) No rainfall for a year or more may lead to drought in that region.
(d) Excessive rains may cause floods.
2. State for each of the following whether it is due to evaporation or condensation.
(a) Water drops appear on the outer surface of a glass containing cold water. - Condensation.
(b) Steam rising from wet clothes while they are ironed. - Evaporation.
(c) Fog appearing on a cold winter morning. - Condensation.
(d) Blackboard dries up after wiping it. - Evaporation.
(e) Steam rising from a hot girdle when water is sprinkled on it. - Evaporation.
3. Which of the following statements are 'true'?
(a) Water vapor is present in air only during during monsoon. (False )
(b) Water evaporates into air from oceans, rivers and lakes but not from the soil. (False )
(c) The process of water changing into its vapor is called evaporation. (True)
(d) The evaporation of water takes place only in sunlight. (False )
(e) Water vapor condenses to form tiny droplets of water in the upper layers of air where it is cooler. (True)