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CBSE Class 9th Science Solved Practice Paper SA–II: Set–V

Dec 7, 2015 17:00 IST

    Find CBSE Class 9 Science Solved Practice Paper for the Sumamtive Assessment – II. These questions will not only help the students to prepare for exams in a better manner, but will also help them in understanding the depth with which a topic should be studied.

    Few sample questions from the Question Paper are given below:

    Q. Name the viral disease which is about to be completely eradicated from the world. Mention its preventive measures?

    Ans. Poliomyelitis or Polio is the viral disease which is about to be completely eradicated from the world. It can be prevented by immunization with oral polio vaccine.

    Q. What are the main features of Rutherford`s nuclear model of an atom?

    Ans.  Rutherford`s nuclear model of an atom had the following features:

    (i) An atom has a positively charged centre called the nucleus. Almost all the mass of an atom resides in the nucleus.

    (ii) The electrons follow a circular path while revolving around the nucleus.

    (iii) The size of the nucleus is much smaller than the size of the atom.   

    Q. (a) What are fungi? Why are they called as saprophytes?

        (b) What is the function of cnidoblasts cells in Hydra?

    Ans. (a) Fungi are heterotrophic eukaryotic organisms. They are called as saprophytes since they use decaying organic material as their food.

            (b) Cnidoblasts cells are the specific stinging cells found on the tentacles of Hydra whose function is to capture its prey.

    Q. What do you understand by Ozone layer depletion?

    Ans. Ozone layer protects us from the various harmful radiations coming from the Sun. It has been recently found that it is getting depleted due to its reaction with various man-made

    compounds like CFCs (carbon compounds) having both fluorine and chlorine. This resulted in a reduction of the ozone layer. A hole has been recently discovered in the ozone layer above the Antartica. The consequences for life on Earth due to its further reduction are difficult to imagine. However, efforts are being made to stop any further damage to the ozone layer.

    Q. An element “X” has 15 protons, 15 electrons and 16 neutrons.

    Answer the following questions:

    a) What is its atomic number of “X”?

    b)  Identify the element.

    c)  What is its valency? What is the number of valence electrons in “X”?

    d)  What is the type of ion formed by “X”? Why?

    e) Name the scientists who discovered electrons and protons.

    Ans.

    (a) Given, number of Protons in “X”= 15.

    We know that, Atomic Number = Number of Protons         

    Therefore, its atomic number is 15.

    (b) It`s an element with atomic number 15. Element with atomic number 15 is Phosphorus (P).

    (c) Valency of Phosphorus:

    Given, Number of Electrons = 15

    Therefore, it`s Electronic Configuration is 2,8,5.

    Hence, it has a Valency of 3 since it has 5 valence electrons and it requires 3 more to complete its octet.

    (d) Ion formed by “X”

    Here, X is Phosphorus. It forms an Anion by gaining 3 electrons (P3-) to complete its octet.

    (e) The scientist who discovered electrons is JJ Thomson. The scientist who discovered protons is E Goldstein. Later Rutherford presented a much better idea of protons.

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