CBSE Science Examination Question Paper-2004
Section - A
1. Give an example of a reaction catalysed by an enzyme.
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2. Name the groups of compounds with the following functional groups :
(i) -COOH
(ii)- NH2
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3. Name two main combustible components of Biogas.
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4. Why are some stars red and some blue in colour ?
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5. In what situation do we use Fleming’s right-hand rule ?
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6. What change is made in the hardness of steel when :
(i) it is quenched, and
(ii) it is annealed ?
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7. What is meant by decarboxylation and esterification of acetic acid ?
Name the products obtained and the chemical equations for oxidation of ethanol to different stages.
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8. What is the technique employed to obtain information about the internal layer structure of earth Name the layers of earth other than its crust.
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9. What characteristics should be possessed by the fuel to be used in space rockets ? Give an example ot such fuels.
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10. With the help of a diagram show how the fission reaction of 235U with thermal neutrons develops into a chain reaction.
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11. What is meant by the pH of a solution ? What pH values can be expected for 1 M HCI and solutions and a solution made by mixing equal volumes of the two solutions
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12. How is vulcanised rubber obtained from natural rubber ? What structural change is involved in this process ? Give an example of synthetic rubbers. To which class of polymers does this rubber belong .
What are detergents chemically ? What is their advantage over soaps for washing clothes ? How does a soap solution wash out dirt from clothes ?
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13. State reasons for the following : .
(i) Zinc oxide is called an amphoteric oxide. (ii) Sodium metal is stored in bottles filled with kerosene oil. (iii) Eatables can be preserved in nitrogen gas.
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14. Write chemical equations for the reactions taking place when :
(i) a piece of zinc is placed in a solution of copper (II) sulphate. (ii) sulphur dioxide gas is dissolved in an excess of NaOH solution. (iii) a mixture of ammonia and oxygen gases is passed over platinum heated to about 1073 K-
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15. (a) Two conductors A and B of resistances 5 ohm and 10 ohm respectively can be arranged in Parailel and later on in series. In each arrangement the total voltage applied across it is 20 volts. I’1 wmcl1 arrangement will the voltage across A and B be the same and in which case will the current flowing through A and B be the same ?
(b) Calculate the total resistance for each arrangement.
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