Chapter: 09. Water As A Resource
Think!
How does water get purified after boiling? Discuss.
Boiling water kills the germs (tiny harmful living organisms) present in it, making it safe for drinking. Quick Check (1) Assessment for learning
Write CS for the correct sentence/action. Write IS for the incorrect sentence/action.
Hina left the water bottle uncovered for the whole night. Early next morning, she drank water from the same bottle. Ajay blew air on a cold mirror. Water droplets formed on the mirror. He said the process is called ‘water cycle’. Garima says, “There is no need to purify water. It is always clean.” Kanika explained, “Rain or snow that falls off from heavy clouds is called precipitation.” Kunal does not like the idea of rainwater harvesting in his house. Run-Through
I. Very Short Answer Questions
A. State True or False.
Water cannot undergo any change of form. In evaporation, a liquid changes into a gas. Germs are useful living organisms. We should not have a water filter at home. B. Fill in the blanks using the given words. Waterworks Evaporation Germs Boiling Condensation
A gas can change into a liquid upon Condensation. A liquid changes into vapour upon heating in the process of Evaporation. Waterworks is a place where water is purified and made drinkable. Boiling is the easiest method to purify water. Germs are tiny, harmful living organisms that cannot be seen but can cause diseases. C. Give one/two word(s) for the following.
About 71 per cent of the Earth is made up of: A gas changes into a liquid on cooling by this process: Cholera (or Typhoid, Dysentery, Jaundice) The collection and storage of rainwater for future use: The process in which chlorine tablets are added to purify drinking water: D. Complete the concept map.
The empty oval in the leftmost branch should be filled with “Filtering” and the empty box below it would describe the process of removing dirt. Middle oval should be Boiling The empty box under “Chlorination” would describe the process of killing germs using chlorine tablets. II. Short Answer Questions
Unjumble and distinguish between the following:
a. RPCPIEINATOTI and CDEONSAOINNT Precipitation and Condensation. Precipitation is when water falls from clouds to the Earth’s surface as rain, snow, or other forms. Condensation is when water vapour (gas) in the air cools down and changes into tiny liquid water droplets, forming clouds or dew.
b. OBILING and CLOHNATIRION Boiling and Chlorination. Boiling is the process of heating water to a high temperature (like 100°C) for at least 10 minutes to kill harmful germs present in it. Chlorination is the process of adding chlorine tablets to water to purify it by killing germs, especially those causing waterborne diseases. What are impurities? List the different types of impurities. Impurities are unwanted substances that can be found in water, making it dirty or unsafe. The different types of impurities are: Insoluble impurities: These do not dissolve in water and can be seen easily (e.g., sand, mud, tiny stones, twigs). Soluble impurities: These dissolve in water and cannot be seen easily (e.g., salt, dissolved substances in soft drinks). Germs: These are very tiny and harmful living organisms that cannot be seen but can cause diseases if consumed with water. A jug of cold water was taken out from the refrigerator and kept on the table. After some time, a puddle of water could be seen around it. Why? This phenomenon is due to condensation. The cold surface of the jug causes the water vapour (gas) present in the surrounding air to cool down. As the water vapour cools, it changes back into tiny liquid water droplets, which collect on the surface of the jug and eventually form a puddle around it. The water cycle is the continuous journey that water takes as it circulates from the land to the sky, and then back to the land. This continuous circulation involves three main processes: evaporation (water turning into vapour and rising), condensation (vapour forming clouds), and precipitation (water falling back as rain or snow). III. Long Answer Questions
Draw a neat, labelled diagram of water cycle. What is rainwater harvesting? Rainwater harvesting is the collection and storage of rainwater for future use. This method aims to conserve water by gathering rain that falls on surfaces like rooftops or the ground, preventing it from running off and going to waste. The collected water can then be stored in tanks or check dams and used for various purposes, especially during periods of water scarcity or drought. How can you purify water at home? Water can be purified at home using several effective methods: Boiling: This is considered the easiest method. Water should be boiled for at least 10 minutes to kill most of the harmful germs present in it, making it safe for drinking. Filtering: Using a water filter, either a simple cloth filter or a specialized water filter, helps to remove insoluble impurities like dirt, sand, and other visible particles from the water. Chlorination: Adding chlorine tablets to the water is another way to purify it. Chlorine effectively kills various germs that can cause waterborne diseases such as jaundice and cholera. IV. Challenge
Amit left a pan full of water on the burning stove and forgot about it. When he returned to the kitchen after half an hour, he found that there was no water in the pan. He noticed that his pet cat was sitting on the shelf. Did the cat drink all the water from the pan? What do you think had happened? No, the cat did not drink all the water from the pan. What happened was that the water in the pan underwent evaporation. Since the stove was burning, the continuous heat caused the liquid water to turn into water vapour (gas), which then escaped into the air. Over half an hour, all the water evaporated. At places where there is no electricity, how do you think people cool water? At places without electricity, people often use traditional and natural methods to cool water: Earthen pots (Matkas): Water is stored in porous clay pots. The tiny pores in the clay allow a small amount of water to seep to the outer surface. This water then evaporates, taking heat away from the pot and the water inside, thus cooling it down. Wet Cloth Wrapping: Wrapping a wet cloth around a water container and placing it in a windy or shaded area can also cool the water through evaporation from the cloth’s surface. Storing in Shaded Areas or Underground: Keeping water containers in cool, shaded places or burying them partially underground helps to keep the water cool, as the ground temperature is often lower than the ambient air temperature. Why are we advised not to waste water? Discuss in class. We are advised not to waste water for several critical reasons: Limited Freshwater: Although Earth is covered mostly by water, the amount of freshwater available for human use (drinking, agriculture, industry) is very limited. Most of the Earth’s water is saltwater or trapped in glaciers and ice caps. Essential for Life: Water is fundamental for all living beings to survive. We need it for drinking, personal hygiene, growing food, and supporting ecosystems. Water Scarcity: Wasting water can lead to water scarcity, which means there isn’t enough water to meet everyone’s needs. This can cause droughts, affect crop production, and lead to conflicts over water resources. Energy and Cost: Treating, pumping, and delivering clean water requires significant energy and infrastructure, which also costs money. Wasting water means wasting these resources too. Environmental Impact: Conserving water helps maintain healthy aquatic ecosystems and reduces the strain on natural water sources, preserving biodiversity and environmental balance. V. Enrichment
C. Story Writing/Telling
Find at least six words related to water cycle and purification of water in the letter grid.
Answers to textbook exercises
