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Science 2010 Question Paper For CBSE Class X Exams

Section A

1. Write a balanced chemical equation for the reaction between sodium carbonate and hydrochloric acid indicating the physical state of the reactants and the products. (1 Marks)
2. Write the structural formula of chloromethane.(1 Marks)
3. What is the valence of silicon with atomic number 14? (1 Marks)
4. How should a ray of light be incident on a rectangular glass slab so that it comes out from the opposite side of the slab without being displaced? (1 Marks)
5. An object is kept at a distance of 4 m in front of a spherical mirror which forms its magnification? Is the mirror concave or convex?(1 Marks)
6. A girl was playing with a thin beam of light from her laser torch by directing it from different directions on a convex lens held vertically. She was surprised to see that in a particular direction the beam of light continues to move along the same direction after passing through the lens. State the reason for this observation.(1 Marks)
7. Elements magnesium and oxygen respectively belong to Group 2 and Group 16 of the Modern periodic Table. If the atomic numbers of magnesium and oxygen are 12 and 8 respectively, draw their electronic configurations and show the process of formation of their compound by transfer of electrons. (2 Marks)
8. What happens when chlorine is passed over slaked lime at 313 K? Write chemical equation of the reaction involved and state two uses of the product obtained. (2 Marks)
9. Name four gases commonly present in biogas. State two advantages of using this gas over fossil fuels. (2 Marks)
10. The electrical resistively of silver is 1.60× 10^-6Ωm. What will be the resistance of a silver wire of length 10 m and cross –sectional area 2 × 10^-6 m²? (2 Marks)
11. What is meant by spectrum of white light? How can we recombine the components of white light after a prism has separated them? (2 Marks)
12. How are the wastes produced in nuclear power plants different from those produced in a thermal power plant? What happens to the waste of a nuclear power plant? (2 Marks)
13. With the help of balanced chemical equations explain what happens when ethanol is heated with
    (i) alkaline solution of potassium permanganate,
    (ii) excess concentrated sulphuric acid at 443 K. Mention any two uses of ethanol. (3 Marks)
14. In the following table six elements A, B, C, D, E and F (here letters are not the usual symbols of the elements ) of the Modern Periodic table with atomic numbers 3 to 18 are given : (3 Marks)

(a) Which of these is (i) a noble gas, (ii) a halogen?
(b) If B combines with F, what would be the formula of the compound formed?
(c) Write the electronic configurations of C and E.

15. The image of an object placed at 60 cm in front of a lens Is obtained on a screen at a distance of 120 cm from it. Find the focal length of the lens. What would be the height of the image of the object is 5 cm high? (3 Marks)
16. How can a magnetic field be produced without using a magnet? Describe an experiment to show that a magnetic field exerts a force on a current carrying conductor. (3 Marks)
17. Derive an expression for the heat produced in a conductor of resistance R when a current I flows through it for time t. Two identical resistors of resistance R are connected in series with a battery of potential difference V for time t. The resistors are then connected in parallel with the same battery for the same time t. Compare the heat produced in the two cases. (5 Marks)
    Or
    Deduce the expression for the equivalent resistance of the parallel combination of three resistors R₁, R₂ and R₃. Consider the following electric circuit:

    

    (i) Which two resistors are connected in series?
    (ii) Which two resistors are connected in parallel?
    (iii) If every resistor of the circuit is of 2 Ω what current will flow in the circuit? (5 Marks)
18. Give reason why

    (i) Metals are good conductors, whereas non – metals are
    had conductors of electricity.
    (ii) Metals replace hydrogen from acids whereas non –metals do not .
    (iii) An iron knife dipped in a blue copper sulphate solution turns the blue solution light green.
    (iv) Sodium is kept under kerosene.
    (v) Carbon cannot reduce the oxides of sodium or aluminum. (5 Marks)

    Or
    (a) Write two differences between calcinations and roasting.
    (b) No reaction takes place when granules of a solid ‘A’ are mixed with a powder of solid ‘B’ However when the mixture is heated a reaction starts with evolution of much heat. Product ‘C’ of the reaction settles down as a liquid metal and solid product ‘D’ keeps floating over the liquid ‘C’ This reaction is sometimes used for making metal for ready use in odd places .

    (i) Based on this information make assumptions about ‘A’ and ‘B’ And corresponding dedications about ‘C’ and ‘D’ and write a balanced chemical equation for the reaction. Include in the equation the information about physical states of the reactants and reaction being exothermic.
    (ii) Name two types of chemical reactions to which this reaction Can belong. (5 Marks)

Section B

19. State the basic difference between the processes of respiration and photosynthesis.
20. Name the intermediate and the end products of glucose break down in aerobic reparation.
21. Name any two types of tropism
22. Why is variation beneficial for the species, but not necessarily ro the individual?
23. State any four personal choices you would like to make to reduce energy consumption without affecting the quality of life or work explaining how each one of them would help you to do so .
24. Describe how decomposers facilitate recycling of matter in order to maintain balance in the ecosystem. (2 Marks)
25. With the help of suitable examples explain natural selection. (3 Marks)
26. Design an experiment to demonstrate that the roots bend in the direction of water stimulus. (3 Marks)
27. Draw a neat and labeled diagram of human respiratory system. Explain in brief the role of lungs in the exchange of gases. (5 Marks)
    Or
    Draw a neat and labelled diagram of human excretory system. Describe in brief the function of kidneys, urethras, Urinary bladder and urethra. (5 Marks)