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Board Paper of Class 10 2019 Science Delhi(Set 2) - 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 1
    Name and define the SI unit of current. VIEW SOLUTION

  • Question 2
    Write the name of the main constituent of Biogas. Also, state its percentage. VIEW SOLUTION

  • Question 3
    Write the name, symbol and electronic configuration of an element X whose atomic number is 11.
    Can the following groups of elements be classified as Dobereiner's triad:
    (a) Na, Si, Cl      (b) Be, Mg, Ca
    Atomic mass of Be−9, Na−23, Mg−24, Si−28, Cl−35, Ca−40.
    Justify your answer in each case. VIEW SOLUTION

  • Question 4
    How is O2 and CO2 transported in human beings? VIEW SOLUTION

  • Question 5
    Write the structure of eye lens and state the role of ciliary muscles in the human eye. VIEW SOLUTION

  • Question 6
    Identify the acid and base which form sodium hydrogen carbonate. Write chemical equation in support of your answer. State whether this compound is acidic, basic or neutral. Also write its pH value. VIEW SOLUTION

  • Question 7
    Based on the group valency of elements write the molecular formula of the following compounds giving justification for each:
    (i) Oxide of first group elements.
    (ii) Halide of the elements of group thirteen, and
    (iii) Compound formed when an element, A of group 2 combines with an element, B of group seventeen. VIEW SOLUTION

  • Question 8
    2 g of silver chloride is taken in a china dish and the china dish is placed in sunlight for sometime. What will be your observation in this case? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction.
    Identify the type of reactions taking place in each of the following cases and write the balanced chemical equation for the reactions.
    (a) Zinc reacts with silver nitrate to produce zinc nitrate and silver.

    (b) Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead iodide.

  • Question 9
    Define the term transpiration. Design an experiment to demonstrate this process. VIEW SOLUTION

  • Question 10
    What is feedback mechanism of hormonic regulation. Take the example of insulin to explain this phenomenon. VIEW SOLUTION

  • Question 11
    What are plant hormones? Name the plant hormones responsible for the following:
    (i) Growth of stem
    (ii) Promotion of cell division
    (iii) Inhibition of growth
    (iv) Elongation of cells VIEW SOLUTION

  • Question 12
    Name the plant Mendel used for his experiment. What type of progeny was obtained by Mendel in F1 and F2 generations when he crossed the tall and short plants? Write the ratio he obtained in F2 generation plants.


    List two differences between acquired traits and inherited traits by giving an example of each. VIEW SOLUTION

  • Question 13
    Why should there be equitable distribution of resources? List three forces that would be working against an equitable distribution of our resources. VIEW SOLUTION

  • Question 14

    How can we help in reducing the problem of waste disposal? Suggest any three methods.


    Define an ecosystem. Draw a block diagram to show the flow of energy in an ecosystem.


  • Question 15
    What is a rainbow? Draw a labelled diagram to show the formation of a rainbow. VIEW SOLUTION

  • Question 16
    Write the chemical formula and name of the compound which is the active ingredient of all alcoholic drinks. List its two uses. Write chemical equation and name of the product formed when this compound reacts with−
    (i) Sodium metal
    (ii) hot concentrated sulphuric acid
    What is methane? Draw its electron dot structure. Name the type of bonds formed in this compound. Why are such compounds:
    (i) poor conductors of electricity? and
    (ii) have low melting and boiling points? What happens when this compound burns in oxygen? VIEW SOLUTION

  • Question 17
    (a) Write chemical equations for the following reactions:
          (i) Calcium metal reacts with water.
          (ii) Cinnabar is heated in the presence of air.
          (iii) Manganese dioxide is heated with aluminium powder.

    (b) What are alloys? List two properties of alloys.

  • Question 18
    An object is placed at a distance of 30 cm from a concave lens of focal length 30 cm.
    (i) Use lens formula to determine the distance of the image from the lens.
    (ii) List four characteristics of the image (nature, position, size, erect/inverted) in this case.
    (iii) Draw a labelled diagram to justify your answer of part (ii) VIEW SOLUTION

  • Question 19
    (a) With the help of a suitable circuit diagram prove that the reciprocal of the equivalent resistance of a group of resistances joined in parallel is equal to the sum of the reciprocals of the individual resistances.

    (b) In an electric circuit, two resistors of 12 Ω each are joined in parallel to a 6 V battery. Find the current drawn from the battery.


    An electric lamp of resistance 20 Ω and a conductor of resistance 4 Ω are connected to a 6 V battery as shown in the circuit. Calculate:

    (a) the total resistance of the circuit,

    (b) the current through the circuit,

    (c) the potential difference across the (i) electric lamp and (ii) conductor, and

    (d) power of the lamp. VIEW SOLUTION

  • Question 20
    What is a solenoid? Draw the pattern of magnetic field lines of (i) a current carrying solenoid and (ii) a bar magnet. List two distinguishing features between the two fields. VIEW SOLUTION

  • Question 21
    Define pollination. Explain the different types of pollination. List two agents of pollination? How does suitable pollination lead to fertilization?
    (a) Identify the given diagram. Name the parts 1 to 5.

    (b) What is contraception? List three advantages of adopting contraceptive measures. VIEW SOLUTION

  • Question 22
    In the experimental set up to show that "CO2 is given out during respiration", name the substance taken in the small test tube kept in the conical flask. State its function and the consequence of its use. VIEW SOLUTION

  • Question 23
    A student is observing the temporary mount of a leaf peel under a microscope. Draw labelled diagram of the structure of stomata as seen under the microscope
    Draw a labelled diagram in proper sequence to show budding in hydra.

  • Question 24
    List four precautions which a student should observe while determining the focal length of a given convex lens by obtaining image of a distant object on a screen. VIEW SOLUTION

  • Question 25
    While studying the dependence of potential difference (V) across a resistor on the current (I) passing through it, in order to determine the resistance of the resistor, a student took 5 readings for different values of current and plotted a graph between V and I. He got a straight line graph passing through the origin. What does the straight line signify? Write the method of determining the resistance of the resister using this graph.


    What would you suggest to a student if while performing an experiment he finds that the pointer/needle of the ammeter and voltmeter do not coincide with the zero marks on the scales when the circuit is open? No extra ammeter/voltmeter is available in the laboratory. VIEW SOLUTION

  • Question 26
    In three test tubes A, B, and C, three different liquids namely, distilled water, underground water and distilled water in which a pinch of calcium sulphate is dissolved, respectively are taken. Equal amount of soap solution is added to each test tube and the contents are shaken. In which test tube will the length of the foam (lather) be longest? Justify your answer. VIEW SOLUTION

  • Question 27
    Blue litmus solution is added to two test tubes A and B containing dilute HCl and NaOH solution respectively. In which test tube a colour change will be observed? State the colour change and give its reason.


    What is observed when 2 mL of dilute hydrochloric acid is added to 1 g of sodium carbonate taken in a clean and dry test tube? Write chemical equation for the reaction involved. VIEW SOLUTION
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