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Board Paper of Class 10 2019 Science All India(Set 1) - Solutions

General Instructions:

(i) The question paper comprises five sections, A, B, C, D and E. You are to attempt all the sections.

(ii) All questions are compulsory.

(iii) Internal choice is given in sections B, C, D and E.

(iv) Question numbers 1 and 2 in Section A are one mark questions. They are to be answered in one word or in one sentence.

(v) Question numbers 3 to 5 in Section B are two-marks questions. These are to be answered in about 30 words each.

(vi) Question numbers 6 to 15 in Section C are three-marks questions. These are to be answered in about 50 words each.

(vii) Question numbers 16 to 21 in Section D are five-marks questions. These are to be answered in about 70 words each.

(viii) Question numbers 22 to 27 in Section E are based on practical skills. Each question is a two marks question. These are to be answered in brief.

  • Question 2
    Name any two nutrients that the spent slurry has in the biogas plant. VIEW SOLUTION

  • Question 3
    Draw a labelled ray diagram to show the path of the reflected ray corresponding to an incident ray of light parallel to the principal axis of a convex mirror. Mark the angle of incidence and angle of reflection on it. VIEW SOLUTION

  • Question 4
    A compass needle is placed near a current carrying straight conductor. State your observation for the following cases and give reasons for the same in each case:
    (a) Magnitude of electric current is increased.
    (b) The compass needle is displaced away from the conductor.

  • Question 5
    Out of HCl and CH3COOH, which one is a weak acid and why? Explain with the help of an example.
    "Sodium hydrogen carbonate is a basic salt." Justify this statement. How is it converted into washing soda? VIEW SOLUTION

  • Question 6
    Define genetics. Why is decrease in the number of surviving tigers cause of concern from the point of view of genetics?  Explain briefly. VIEW SOLUTION

  • Question 7
    A concave mirror has a focal length of 20 cm. At what distance from the mirror should a 4 cm tall object be placed so that it forms an image at distance of 30 cm from the mirror ? Also calculate the size of the image formed.


    A real image 2/3rd of the size of an object is formed by a convex lens when the object is at a distance of 12 cm from it. Find the focal length of the lens         VIEW SOLUTION

  • Question 8
    2 g of ferrous sulphate crystals are heated in a dry boiling tube.
    (a) List any two observations.
    (b) Name the type of chemical reaction taking place.
    (c) Write balanced chemical equation for the reaction and name the products formed.
    You might have noted that when copper powder is heated in a china dish, the reddish brown surface of copper powder becomes coated with a black substance.
    (a) Why has this black substance formed ?
    (b) What is this black substance ?
    (c) Write the chemical equation of the reaction that takes place.
    (d) How can the black coating on the surface be turned reddish brown? VIEW SOLUTION

  • Question 9
    What is a food chain? Why is the flow of energy in an ecosystem unidirectional? Explain briefly.


    (a) Why should National Parks be allowed to remain in their pristine form?

    (b) Why is reuse of materials better than recycling? VIEW SOLUTION

  • Question 10
    A white powder is added while baking cakes to make it soft and spongy. Name its main ingredients. Explain the function of each ingredient.  Write the chemical reaction taking place when the powder is heated during baking. VIEW SOLUTION

  • Question 11
    Two circular coils P and Q are kept close to each other, of which coil P carries a current. What will you observe in the galvanometer connected across the coil Q
    (a) if current in the coil P is changed?
    (b) if both the coils are moved in the same direction with the same speed?
    Give reasons to justify your answer in each case. VIEW SOLUTION

  • Question 12
    (a) Write two water conducting tissues present in plants. How does water enter continuously into the root xylem?
    (b) Explain why plants have low energy needs as compared to animals VIEW SOLUTION

  • Question 13
    Why does the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron take place but not in the reverse direction? Explain. VIEW SOLUTION

  • Question 14
    Mention the environmental consequences of the increasing demand for energy. List four steps you would suggest to reduce the consumption of energy VIEW SOLUTION

  • Question 15
    An ore on treatment with dilute hydrochloric acid produces brisk effervescence. Name the type of ore with one example. What steps will be required to obtain metal from the enriched ore ? Also write the chemical equations for the reactions involved in the process VIEW SOLUTION

  • Question 16
    (a) State the reason why carbon can neither form C4+ cations nor C4– anions, but forms covalent bonds. Also state reasons to explain why covalent compounds
    (i) are bad conductors of electricity.
    (ii) have low melting and boiling points.

    (b) Write the structural formula of benzene, C6H6.


    (a) Define the term 'isomer'.
    (b) Two compounds have same molecular formula C3H6O. Write the name of these compounds and their structural formula.
    (c) How would you bring the following conversions:
    (i) Ethanol to ethene
    (ii) Propanol to propanoic acid VIEW SOLUTION

  • Question 17

    (a) A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find the position, nature and size of the image formed.

    (b) Draw a labelled ray diagram showing object distance, image distance and focal length in the above case. VIEW SOLUTION

  • Question 18
    (a) How does metallic character of elements in Modern Periodic Table vary on moving from
     (i) left to right in a period?
    (ii) top to bottom in a group?
    Explain with the help of an example in each case.

    (b) If an element X is placed in group 14, what will be the nature of bond in its chloride? Write the chemical formula of the compound formed.

    (c) An element X has mass number = 35 and number of neutrons = 18. What is the atomic number of X? Write electronic configuration of X and determine its valency. VIEW SOLUTION

  • Question 19

    Compare the power used in 2 Ω resistor in each of the following circuits:


    A bulb is rated 40 W; 220 V. Find the current drawn by it, when it is connected to a 220 V supply. Also find its resistance. If the given bulb is replaced by a bulb of rating 25 W; 220 V, will there be any change in the value of current and resistance? Justify your answer and determine the change.


  • Question 20

    (a) Distinguish between cross-pollination and self-pollination. Mention the site and product of fertilization in a flower.

    (b) Draw labelled diagram of a pistil showing the following parts:

    Stigma, Style, Ovary, Female germ cell


    (a) Draw a diagram of human female reproductive system and label the parts:

    (i) which produce an egg.

    (ii) where fertilization takes place.

    (b) List two bacterial diseases which are transmitted sexually. 

    (c) What are contraceptive devices? Give two reasons for adopting contraceptive devices in humans.


  • Question 21
    (a) How do the following provide evidences in favour of evolution in organisms? Explain with an example for each.

    (i) Homologous organs

    (ii) Analogous organs

    (iii) Fossils

    (b) Explain two methods to determine the age of fossils. VIEW SOLUTION

  • Question 22
    What would you observe on adding zinc granules to freshly prepared ferrous sulphate solution? Give reason for your answer. VIEW SOLUTION

  • Question 23
    How is the presence of an acid tested with a strip of red litmus paper?


    A student is performing an experiment to study the properties of acetic acid. Answer the following questions:
    (i) Name the substance he must add to acetic acid to produce carbon dioxide.
    (ii) Give the relevant chemical equation for the reaction.
    (iii) How would he test CO2 gas in the laboratory? VIEW SOLUTION

  • Question 24
    A teacher gives a convex lens and a concave mirror of focal length of 20 cm each to his student and asks him to find their focal lengths by obtaining the image of a distant object. The student uses a distant tree as the object and obtains its sharp image, one by one, on a screen. The distances d1 and d2 between the lens/mirror and the screen in the two cases and the nature of their respective sharp images are likely to be
    (a) (20 cm, 40 cm) and (erect and erect)
    (b) (20 cm, 40 cm) and (inverted and inverted)
    (c) (20 cm, 20 cm) and (inverted and inverted)
    (d) (20 cm, 40 cm) and (erect and inverted)
    Give reason for your answer. VIEW SOLUTION

  • Question 25
    The rest position of the needles in a milliammeter and voltmeter, not in use, are as shown in Figure A. When a student uses these instruments in his experiment, the readings of the needles are in the positions shown in Figure B. Determine the correct values of current and voltage the student should use in his calculations.


    In the experiment to study the dependence of current (I) on the potential difference (V) across a resistor, a student obtained a graph as shown.
    (i) What does the graph depict about the dependence of current on the potential difference?
    (ii) Find the current that flows through the resistor when the potential difference across it is 2.5 V.

  • Question 26
    In the experiment "To prepare a temporary mount of a leaf peel to show stomata", glycerine and safranin are used. When and why are these two liquids used? Explain. VIEW SOLUTION

  • Question 27

    Draw labelled diagram to show the following parts in an embryo of a pea seed:

    Cotyledon, Plumule, Radical


    A student observed a permanent slide showing asexual reproduction in Hydra. Draw labelled diagram in proper sequence of the observations that must have been made by the student. Name the process of reproduction also. VIEW SOLUTION
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