New Words : 1. Weather : The condition of the wind, rain, sunshine, or temperature of a particular place at a particular time. 2. Rotation : The movement of the earth on its axis. 3. Revolution : The movement of the earth round the sun 4. Evaporation : The process of changing water into water vapour. 5. Condensation: The process of changing water vapour into water. 6. Chlorination : Adding chlorine to water. 7. Decantation : The process of pouring clear liquid without disturbing the settled insoluble substances. 8. Pollution : The process of making air, water or soil dirty
Remember These Points -
+ The condition of wind, rain, sunshine, clouds or temperature of a particular place at a particular time is called weather. + The change of weather depends on the sun, rain and wind. + The movement of the earth round the sun and its distance from the sun results in different seasons. + Humidity is the amount of water vapour present in the air. + Breeze, gale, storm, thunderstorm, etc. are all types of winds. + Water vapour (gas) changes into water (liquid) by the process of condensation. + Water can be purified by processes like boiling, decantation, filtration and chlorination. + We should conserve water. + The activities of human beings are responsible for polluting water.
Fill in the blanks:
1. While rotation of the earth causes day and night, the revolution of the earth causes seasons. 2. Warm air is lighter than cold air. 3. The process by which water vapour changes into water is called condensation. 4. Air is a mixture of different gases. 5. A strong wind is called gale. 6. Water covers nearly 70 percent of the earth's surface. 7. Filter paper does not allow impurities to pass through. 8. Cholera and Jaundice are spread through polluted water. 9. Water is boiled to kill germs.
True and False statements
1. Evenings are cooler than afternoons. [T] 2. Evaporation takes place all the time. [T] 3. The more the humidity the more pleasant is the weather. [F] 4. Wind exerts pressure. [T] 5. Clean and pure water is available everywhere. [F] 6. The heat of the sun cannot evaporate water. [F] 7. Chlorine tablets can purify water. [T] 8. Industries do not cause water pollution. [F] 9. Jaundice is spread through polluted water. [T]
Answer the following questions
1. What do you mean by weather?
The condition of wind, rain, sunshine, clouds or temperature of a particular place at a particular time is called weather.
2. How does the sun help to change weather conditions?
Our earth moves round the sun in an elliptical orbit. On its axis, the earth is tilted at an angle. While orbiting the sun, one side of the earth is close to the sun and the other side is away from the sun. The part which is closer to the sun has summer season and the part which is away from the sun has winter season. So, the sun plays a very significant role in changing the weather conditions.
3. Define rotation and revolution.
The movement of the earth on its axis is called rotation.
Our earth moves round the sun in an elliptical orbit. This movement of the earth is called revolution.
4. How does water get polluted?
Water gets polluted due to various factors. The activities of human beings are greatly responsible for polluting water.
i) People use lakes, rivers and ponds for bathing. washing clothes, bathing animals, etc. These activities greatly pollute the water bodies. ii) Sometimes industines situated on the banks of rivers allow the harmful chemicals and waste materials to flow into the nearby water body. Iii) In some towns and cities, Sewage water is disposed into the water bodies directly.
5. What is water cycle?
The cycle of evaporation. Condensation and precipitation of water goes on continuously in nature. This is called water cycle.
6. Give a brief account of the different forms of precipitation.
Dew - During nights the water vapour Condenses into tiny drops and settles on plants grass and on window panes. These drops of water are called dew. Frost - When nights become very cold, dewdrops freeze to form ice. This is called frost. Fog - Sometimes very Small drops of water gather together to form thick clouds close to the land or sea. This is called fog Hail - When the rain drops pass through very cold air in the atmosphere, they freeze to form balls of ice. These balls of ice are Called Hail. Snow - Sometimes the clouds become very Hence, water vapour condenses to form small Soft white pieces of ice in place of water. This is called snow.
7. Describe three processes used commonly for purifying water.
We Can purify water in the following ways -
a) Boiling - Boiling is a very simple way to purify water. We should boil water for at least ten minutes to kill the germs. b) Filtration - The process of separating suspended and insoluble impurities from liquid through a filter is known as filtration. In this process, water is passed through the filter paper. Filter paper does not allow impurities to pass through. Only the clean water is collected below. c) Chlorination - Chlorination is the process of adding chlorine tablets to kill the germs present in water.
8. In what ways do human beings pollute water?
Human beings pollute water in several ways:
Trash and Litter: People often throw garbage, plastic, and other waste into rivers, lakes, and oceans, making the water dirty and harming aquatic life. Chemical Discharges: Factories and households release harmful chemicals, like oil and detergents, into water bodies, poisoning the water and affecting animals and plants. Sewage and Human Waste: Improperly treated sewage and waste from toilets can end up in water, spreading diseases and contaminating drinking water sources. Industrial Runoff: Industrial activities release pollutants into water through runoff, carrying toxins from factories into waterways. Excessive Fertilizers: Agricultural runoff with excess fertilizers reaches water sources, causing harmful algae blooms and disrupting the water ecosystem.
It's important to protect water by properly disposing of waste, using fewer harmful chemicals, and treating sewage and industrial waste before it enters water bodies.
Differentiate between the followings
Fog and Dew
Sometimes very Small drops of water gather together to form thick clouds close to the land or sea. This is called fog
During nights the water vapour Condenses into tiny drops and settles on plants grass and on window panes. These drops of water are called dew.
Hail and snow
When the raindrops pass through very cold air in the atmosphere, they freeze to form balls of ice. These balls of ice are called Hail.
Sometimes the clouds become very cold. Hence, water Vapour condenses to form small soft white pieces of ice in place of water. This ice is called snow.
Condensation and Evaporation
The process of changing water vapour into water is called Condensation.
The process of changing water into water vapour is Called Evaporation.
Decantation and Filtration
The process of pouring clear liquid without disturbing the settled insoluble substances is known as Decantation.
The process of separating suspended and insoluble impurities from liquid through a filter is known as filtration.
Land breeze and Sea breeze
Wind that blows from the land to the sea during the night time is called Land breeze.
Wind that blows from the sea to the land. during the day time is called Seabreeze.