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SAI INTERNATIONAL SCHOOL

                                                        STD-VII
                                            SUBJECT - CHEMISTRY
                                TOPIC-MANAGEMENT OF WASTE WATER
                   SUB TOPIC-ALTERNATIVE METHOD OF SEWAGE DISPERSAL

                                              PRACTICE WORKSHEET-2






                         Q.                                       Questions              Skill  Marks
                         No.

                         1.     State true/ false                                        U      1


                                Chemical products such as medicines, machine oil,
                                grease etc. may kill water purifying
                                microorganisms.


                         2.     I am a chemical use in purifying water. Who am I?        U      1


                         3.          For Assertion& Reason question follow the          U      1
                                       following directions.
                                DIRECTION: Each of these questions contains an
                                Assertion followed by Reason. Read them carefully
                                and answer the question on the basis of following
                                options. You have to select the one that best
                                describes the two statements.

                                (a) If both Assertion and Reason are correct and
                                Reason is the correct explanation of Assertion.

                                (b) If both Assertion and Reason are correct, but
                                Reason is not the correct explanation of Assertion.

                                (c) If Assertion is correct but Reason is incorrect.
                                (d) If Assertion is incorrect but Reason is correct.

                                (e) If Assertion & Reason both are incorrect
                                Assertion- Air is blown into aeration tank.

                                Reasoning- Reasoning- Organic matter is broken
                                down as air blown speedily in aeration tank.
                         4.                                                              U      1
                                Organic matter is decomposed by ........ bacteria in
                                aeration tank.





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