CBSE Class X Science Question Paper

CBSE Class X Science Question Paper

Time-2hrs MM. 70

1. Answer the following: (6)
(i) What is the focal length of a plane mirror.
(ii) Name the alloy used to make heating elements
(iii) If the length of a wire is doubled what will be its resistance.
(iv)For which mirror the value of m is always <1>

2. An object 2m from a lens, which forms an erect image one fourth the size of the object. Determine the focal length of the lens and what type of lens is this? (3)

3. The refractive index of one type of glass w.r.t air is 1.65 and that of water w.r.t. air is 1.33. Calculate the R.I.of water w.r.t. glass. (3)

4. Why sky appears blue in the after noon? (3)

5. At what distance should an object be placed in front of a concave mirror of focal length 50cm so that an image of triple of its size is obtained? (3)

6. Define the following: (i) one volt (ii) One KWH (iii) Power of a lens (iv) Myopia (v) Refractive index. (5)

7. Why heating elements are made up of alloys? Name one such alloy. (3)

8. How three resistances of three ohm each must be connected to give (i)4ohm (ii)2ohm and 9ohm. (3)

9. An electric heater which I connected to 230V supply line has two resistances coil A and coil B of 24ohm each. Calculate the current drawn when these resistances are connected in series and when connected in parallel . (3)

10. A wire of length L and resistance R is stretched such that its thickness becomes half, how will its resistance changes and what will be its new resistance and resistivity. (3)

11. What happens when(write a suitable reaction) (6)
(i) Name the compound used to make cake soft.
ii) Name the metal used to make bullet proof alloy.
iii)Name two metals which react with steam.
iv)Name a non metal which is lustrous.
v)Name the gas filled in chips packet.
vi)What is the formula of rust.

12. What do you mean by corrosion of metals? Why a greenish layer is seen on copper after a few days when it is exposed to moist air? (3)

13. (i)A salt X in distilled water gives a clear solution which turns the red litmus solution into blue. Explain this phenomenon
(ii) Explain why aq. Sol. Of ammonium chloride is acidic in nature? 4

14. (i)Metal M is found in nature as its carbonate MCO3 .It is used in the galvanization of iron articles .Identify the metal M and name its ore MCO3.How will you convert this ore into free metal? Explain with equations.
(ii) Metal M reacts with oxygen to form metal oxide MO.This oxide reacts with moisture and carbon dioxide of the atmosphere to form a basic carbonate. Metal M prevents rusting of iron. Identfy the metal M. (3)

15. Show with the help of reactions that Aluminium oxide is an amphoteric oxide. (2)

16. A neutral organic compound X of molecular formula C2H6O on oxidation with alkaline potassium permanganate gives an acidic compound Y.Compound X reacts with Y on warming in the presence of con.H2SO4 to give a sweet smelling substance Z what are compound X,Y and Z also write the reactions involved. (3)

17. What happens when: (3)
(i)dil sulphuric acid reacts with zinc granuals.
(ii)dil. Sulphuric acid reacts with aluminum powder
(iii) (iv) Magnesium reacts with very dilHNO3

18. What is meant by strong acid and weak acid give one example of each? (3)

19. What type of reaction takes place when: (4)
(i)Silver bromide is exposed to air
(ii)Lime stone is heated strongly
(iii)Electricity is passed through water
(iv) What happen when bleaching powder is kept open

20. Draw the electronic dot. Structure of the following: (also tell the nature of the compound formed) (4)
(i) sodium chloride (ii )C2H 2 (iii) Ammonia (iv) Water

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