CBSE Set Qa1 Science Class X 1997 You Are On Answer 1 To 20 Sample Test Papers For Class 10th for students online

Science Class X
You are on answer 1 to 20

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 Name any two semiconductors which are used in the manufacture of solar cells.
Ans1. Silicon and Geruanium.

Q.2 What are "planetesimlas" ?
Ans2. 'Planetesimals' are small objects formed by the condensation of clouds of left over gases surrounding the sun.

Q.3 Name two planets found between the Sun and the Earth.
Ans3. Mercury and Venus.

Q.4 Which has a lower ignition temperature, Kerosene or LPG?
Ans4. LPG.

Q.5 An iron knife kept dipped in a blue copper sulphate turns the blue solution light green. Why?
Ans5. Iron is above copper in the activity series. Thus iron can replace copper from CuSO₄ solution. Upon dipping Fe knife in CuSO₄ solution, blue CuSO₄ gets converted into green FeSO₄ and Cu gets separated.

Q.6 Name one metal element and one non-mental element which are obtained on a large scale generally from sea water.
Ans6. Sodium (metal) and Chlorine (non-metal).

Q.7 Which two of the following compounds could belong to the same homologous series? C₂H₆O₂, C₂H₆O, C₂H₆, CH₄O
Ans7. CH₄O and C₂H₆O belong to the same (C_nH_2n+1OH) homologous series.

Q.8 Arrange the following steps in order of their sequence of occurrence in Nitrogen Cycle starting from nitrogen gas: Ammonification, Denitrification, Nitrification, Nitrogen fixation.
Ans8. N₂Nitrogen fixationAmmonificationNitrificationDenitrification
          

Q.9 Sample of blood of a person, on routine microscopic examination, revealed a high percentage of stippled Red Blood Cells. Name the pollutant responsible for this condition.
Ans9. Lead particles from automotive exhaust.

Q.10 Two lots of cooked dal are maintained at 30° and 45° C respectively. Which one of these two temperatures is likely to cause spoilage earlier?
Ans10. Sample kept at 30°C will get spoilt first because that temperature is more conducive for microbial growth.

Q.11 State two major objectives of the space research programme inour country.
Ans11. Two major objectives identified for the space research programme are:
(i) rapid development of mass communication and education especially in widely dispersed rural communities, and
(ii) timely survey and management of the country's natural resources.

Q.12 "Obtaining of energy from nuclear fusion reactions is preferable to obtaining of energy from nuclear fission reactions". Give tow reasons to justify this statement.
Ans12. Obtaining energy by nuclear fusion would be better because:
(i) the energy liberated in nuclear fusion is very high in comparision to nuclear fission.
(ii) the resulting nuclei are not radioactive and therefore do not pose environmental hazards, in contrast to the nuclear fission reactions.

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Q.13 A burner when ignited consumes 0.5 g of LPG in 55 seconds. If the calorific value of LPG is 110 KJ/g calculate the energy consumption power of the burner in kW units.
Ans13. Given,
Mass of LPG consumed = 0.5 g
Time = 55 s
Calorific Value of LPG = 110KJ/g
Therefore, Energy released = 0.5 x 110 = 55.0 kJ
                                 Energy supplied
Power of the burner
                                 Time taken
   55 kJ

   55 s
= 1 kW
Ans. The power of the burner is 1 kW

Q.14 Calculate the calorific value of wax in kJ/g units, when 10g of wax of a candle is burnt to heat 1 kg of water from 25°C to 45° C. (Specific heat of water = 4.2 J/g° C)
Ans14. Mass of water,m = 1 Kg = 1000g
Specific heat of water,C = 4.2 J/g/°C
Initial temp of water = 25°C
Final temp of water = 45°C
Rise in temp. of water, DT = 45 - 25 = 20°C

Heat supplied by wax to water,Q = mcDT
= 1000 x 4.2 x 20
= 84000J
= 84kJ
84kJ of heat is supplied by 10g of wax
                                  84kJ
Calorific value of wax
                                    10g
= 8.4kJ/g
Ans. The calorific value of wax is 8.4 kJ/g

Q.15 Although hydrogen gas has a very high calorific value still it is not used as an industrial fuel. State four reasons for this.
Ans15. Hydrogen is not used as industrial fuel because:
(i) It burns in air with explosion,
(ii) Its ignition temperature is low and is therefore highly inflammable,
(iii) Its storage and transportation is costly,
(iv) Its production is costly because it is not available free in the atmosphere.

Q.16 Given a solution of substance A, how will you test whether it is saturated or unsaturated with respect to A, at the prevailing temperature? What is observed when a hot saturated solution of a substance is allowed to cool?
Ans16. A saturated solution will not dissolve any more solute into it at the given temperature. To test whether the solution of A is saturated, we will try to dissolve some more of A in the solution. If no more A could be dissolved, the solution of A must be saturated at that temperature. A hot saturated solution when cooled becomes a 'Super-saturated Solution'.

Q.17 Draw a labelled diagram of the apparatus used for the laboratory preparation of Ethene. Write the related chemical equation.
Ans17.

                           pumice stone
Kerosene vapours Lower Hydrocarbons + H₂C=CH₂
                             red hot
for example, when hexane is subjected to cracking:


(hexane)                                      butane          ethene

Q.18 An organic compound 'X' which is sometimes used as an anti-freeze, has the molecular formula C₂H₆O 'X' on oxidation gives a compound 'Y' which gives effervescence with baking soda solution. What can 'X' and 'Y' be? Write their structural formulae.
Ans18. Since Y gives effervescence with baking soda (NaHCO₃) solution, it must be an acid. Alcohols give organic acids upon oxidation. Since the molecular formula of X is C₂H₆O, it should be ethanol (C₂H₅OH) and Y should be ethanoic acid (CH₃COOH). A mixture of alcohol and water is used as antifreeze in car radiators.


(ethanol)        (acetic acid)

Q.19 What is meant by 'Ecological Pyramids'? Draw an ecological pyramid having four trophic levels with snake as one of its components.
Ans19. An ecological pyramid is a graphical representation of energy dynamics of the food chain. These pyramids also depict trophic structure, at various levels. The base of pyramid represents producer level and with subsequent steps, shape goes on tapering indicating progressive trophic levels. The carnivores are on the top.

Q.20 How would you test for the presence of the following adulterants in the food items named? (i) Metanil yellow in gram-dal (ii) Argemone oil in an edible oil.
Ans20. (i) Metanil yellow in Dal can be tested by taking 2-3g dal shaken in a mixture of 5ml water +
2ml conc. HCl. If the colour changes to pink, metanil is present in dal.
(ii) Argemone oil in an edible oil can be tested by taking about 2ml oil in a test tube, adding 2ml conc. HNO₃ and heating it. If lower level in the test tube shows red colour, the argemone oil is present.

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