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Subject:Mathematics Science English Social Studies Hindi Physics Chemistry Biology Computer Science

Forests are not responsible for (a) providing medicinal plants. (b) maintaining the flow of water into the streams. (c) creating flood conditions. (d) absorbing rainwater and maintaining the water table

Soln: Answer is (c) creating flood conditions. Explanation: Forests dos do not create flood rather they stops the flood by percolating the rainwater.

ScienceClass 7CBSE

The branchy part of a tree above the stem is known as (a) crown (b) canopy (c) sapling (d) humus

Soln: The answer is (a) crown Explanation: Crown is the top part of the tree it consists of all the branches and leaves of the tree.

ScienceClass 7CBSE

Which of the products is not obtained from a forest? (a) Honey (b) Catechu (c) Gum (d) Ginger

Soln: Answer is (d) Ginger Explanation: Ginger is not obtained from forests it is cultivated in the farms.

ScienceClass 7CBSE

Pick the option which gives the names of a tree and an animal, respectively from the following. (a) semal, hornbill (b) sal, khair (c) chinkara, blue bull (d) neem, palash

Soln: Answer is (a) semal, hornbill Explanation: Semal is the name of tree and hornbill is the name of an animal.

ScienceClass 7CBSE

Which of the following is not the name of a tree? (a) Teak (b) Sal (c) Porcupine (d) Kachnar

Soln: The answer is (c) Porcupine Explanation: Porcupine is an animal whereas Teak, Sal and Kachnar are trees.

ScienceClass 7CBSE

Which of the following is not prepared from the wood obtained from forest? (a) Paper (b) Thermocol (c) Matchsticks (d) Plywood

Soln: The answer is (b) Thermocol Explanation: Paper, Matchsticks and plywood are prepared from the wood obtained from forest whereas thermocol is prepared from synthetic fibers.

ScienceClass 7CBSE

Which of the following has the strongest stem? (a) A tree (b) A creeper (c) A climber (d) A bush

Soln: The answer is (a) A tree

ScienceClass 7CBSE

Which among the following forest animals is the smallest? (a) Fox (b) Boar (c) Bison (d) Porcupine

Soln: The answer is (d) Porcupine

ScienceClass 7CBSE

Boojho visited a forest near his town with his classmates and his teacher. As they were entering the forest, their class teacher told them not to make noise in the forest as noise could disturb the (a) birds (b) animals (c) both birds and animals (d) plants

Soln: Answer is (c) both birds and animals

ScienceClass 7CBSE

Which of the following serve as green lungs? (a) The green pigment of the plants (b) Forests (c) Kitchen gardens (d) Greenhouse gases

Soln: Answer is (b) Forests Explanation: Plants release oxygen during photosynthesis which is used by all the organisms. Plants help to maintain the concentrations of CO2 and Oxygen. Hence they are called as green lungs.

ScienceClass 7CBSE

Describe various steps of cleaning wastewater in a wastewater treatment plant.

Soln: Treatment of wastewater involves physical, chemical, and biological processes, which remove physical, chemical and biological matter that contaminates the wastewater. Wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are removed. Water then goes to a grit and sand removal tank. The speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This is the sludge. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water. The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity. Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water.

ScienceClass 7CBSE

Fill in the blanks in the following statements using words given in the box. (air, handpumps, cholera, water, large, ground) A very _____ number of our people defecate in the open. It may cause _ pollution and soil pollution. Both the surface water and _ water get polluted. _ water is the source for wells, tubewells and _. Thus it becomes the most common route for _ borne diseases like _____, dysentery, etc.

Soln: A very large number of our people defecate in the open. It may cause water pollution and soil pollution. Both the surface water and ground water get polluted. Ground water is the source for wells, tube-wells and handpumps. Thus it becomes the most common route for water borne diseases like cholera, dysentery, etc.

ScienceClass 7CBSE

The terms sewage, sewers and sewerage are interlinked with each other. Can you explain, how?

Soln: The terms ‘sewage, ‘sewers’ and ‘sewerage are interlinked with each other because sewage is a mixture of wastewater coming out of homes and other places. Sewers are pipes which carry sewage and sewerage is a network of sewage carrying pipes.

ScienceClass 7CBSE

What are the different types of inorganic and organic impurities generally present in sewage?

Soln: (i) Inorganic impurities – nitrates, phosphates and metals. (ii) Organic impurities – fruit and vegetable wastes, oil, urea, human faeces, animal waste, pesticides and herbicides.

ScienceClass 7CBSE

A mixture (x) in water contains suspended solids, organic impurities, inorganic impurities (a), nutrients (b), disease-causing bacteria and other microbes. Give names for (x), (a) and (b)?

Soln: (x) sewage (a) nitrates, phosphates and metal (b) phosphorus and nitrogen

ScienceClass 7CBSE

Three statements are provided here which define the terms – (a) sludge (b) sewage and (c) wastewater. Pick out the correct definition for each of these terms. (a) The settled solids that are removed in wastewater treatment with a scraper. (b) Water from the kitchen used for washing dishes. (c) Wastewater released from homes, industries, hospitals and other public buildings.

Soln: Sludge Wastewater Sewage

ScienceClass 7CBSE

Given below is a jumbled sequence of the processes involved in a wastewater treatment plant. Arrange them in their correct sequence. (a) Sludge is scraped out and skimmer removes the floating grease. (b) Water is made to settle in a large tank with a slope in the middle. (c) Large objects like plastic bags are removed by passing wastewater through bar screens. (d) Sand, grit and pebbles are made to settle by decreasing the speed of incoming wastewater. (e) Wastewater enters a grit and sand removal tank.

Soln: (c) Large objects like plastic bags are removed by passing wastewater through bar screens. (e) Wastewater enters a grit and sand removal tank. (d) Sand, grit and pebbles are made to settle by decreasing the speed of incoming wastewater. (b) Water is made to settle in a large tank with a slope in the middle. (a) Sludge is scraped out and skimmer removes the floating grease.

ScienceClass 7CBSE

19. Match the items of Column I with the items of Column II with reference to sewage. Column I Column II a) Inorganic impurities i) Phosphorus and Nitrogen b) organic impurities ii) Nitrates and Phosphates c) Nutrients iii) Cholera and Typhoid d) Bacteria iv) Pesticides and Herbicides

Soln: Column I Column II a) Inorganic impurities ii) Nitrates and Phosphates b) organic impurities iv) Pesticides and Herbicides c) Nutrients i) Phosphorus and Nitrogen d) Bacteria iii) Cholera and Typhoid

ScienceClass 7CBSE

Why should we not throw (a) used tea leaves into the sink? (b) cooking oil and fats down the drain?

Soln: a) Used tea leaves may block the sink. b) Cooking oil and fats gets harden and block the sink.

ScienceClass 7CBSE

A man travelling in a train threw an empty packet of food on the platform. Do you think this is a proper waste disposal method? Elaborate.

Soln: No, what man does is not a proper disposal method. One must always put the waste in a nearby dustbin or carry it until a proper place to dispose of food packet is found.

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