Science Class X 2000 (CBSE)
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General Instructions :
(i)   All questions are compulsary.
(ii) Question number 1 to 10 are very short answer question,carrying 1 mark each.They are to be answered in one or two sentences.
(iii) Question number 11 to 20 are short answer questions,each carrying 2 marks. Answer to them should not exceed 40 words each.
(iv)  Question numbers 21 to 30 are also short answer questions,each carrying 3 marks. Answer to them should not exceed 60 words each.
(v) Question numbers 31 to 33 are long answer questions,each carrying 5 marks. Answer to them should not normally exceed 100 words each.

Q 1. Mention any two harmful effects of Nuclear radiation on human body.


Q 2. Name any two constellations that are visible during winter in Northern hemisphere.


Q 3. Write an aquatic food chain.


Q 4. How does nuclear fuel of a star differ from that of a white dwarf?


Q 5. Which component of sunlight facilitates drying of wheat after harvesting?


Q 6. A man found that he suffers from repeated sneezing whenever he is exposed to dust. What could be the reason for such a reaction?


Q 7. Explain the role of roughage in our food.


Q 8. Which of the following belonging to a food chain is likely to have a maximum concentration of harmful chemicals in its body?
King fisher, Zooplankton, fish, phytoplankton.


Q 9. Write the structural formula of any one isomer of n-heptane (C₇ H₁₆).


Q 10. An astronomer claimed to have discovered a pulsar in a distant galaxy. Mention any one observation that he might have made to claim his discovery.


Q 11. Mention any four differences between an external combustion engine and a petrol engine.


Q 12. Describe the process of obtaining coke from coal. Name the gaseous by-product obtained in this process.


Q 13. How are antibiotics beneficial to us? Name any two groups of organism from which they are obtained.


Q 14. Why is conservation of wild life important? Give any two reasons in support of your answer.


Q 15. Explain the cleansing action of soaps. 


Q 16. List any four conditions that are essential for the life to originate and flourish on a planet.


Q 17. Heat produced on burning 5.0 g of a fuel raises the temperature of 1.0 Kg of water from 20°C to 60°C. If the specific heat of water be 4.2 J/g°C, calculate the calorifc value of the fuel.


Q 18. With the help of a diagram explain how the design of a box type solar cooker ensures minimum loss of heat from its inside.


Q 19. A person decides to take only milk and nothing else in his diet for a year. Which one of the essential nutrients will not be available to him? Mention any two symptoms of the deficiency of this nutrient.


Q 20. Draw a diagram to show the orbit of an artificial satellite of the earth. Mark the position of apogee and perigee on it.


Q 21. Describe sequentially the processes, that led to the formation of petroleum in nature. Name the aviation fuel used in aeroplane jet engines.


Q 22. Describe the process of generation of energy in the sun. Name the scientist who was the first to propose this explanation.


Q 23. What is transplantation? What are its two advantages? Name any two crops that are usually grown by this method.


Q 24. What is ten percent law? Explain with an example how energy flows through different trophic levels.


Q 25. With the help of a labelled diagram describe the method of preparation of methane the laboratory is this gas combustible? How can you test this property?


Q 26. The mass of a star is 10 times that of the sun. Describe last two stages in its life-cycle.


Q 27. Describe any three ways in which biotic and abiotic environment may cause variation in the size of population of deers in a forest.


Q 28. With the help of a labelled diagram describe the process of extraction of sulphur by Frasch process.


Q 29. The efficiency of a petrol engine is 30%. Calculate the power delivered by it if it burns 0.03Kg of petrol in one minute. The calorific value of petrol is 50 KJ/g.


Q 30. An element belonging to Group V of the Periodic Table is available in nature in two forms - A and B. The ignition temperature of A and B are 260°C and 30°C respectively element. Name its two forms. Name (i) the form that would react with concentrated solution of sodium hydroxide and
(ii) the one that would react with chlorine.
Write the equations for the reactions involved.


Q 31. State the factors that help to determine that wheat crop has matured for harvesting. Describe how biotic and abiotic factors may affect the quality of stored grain. Mention any two effects of each type of factors.


Q 32. What is a nuclear reactor? Explain how nuclear fission reaction is controlled in a reactor. Mention any two advantages and any two disadvantages of harnessing nuclear energy.


Q 33. State the three main steps involved in metallurgical processes. Explain the method of extraction of copper from its sulphide ore. Write the chemical reactions involved.