Science Class X 1999(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.1Name the orbit of the satellites that help in satellite communication.


Q.2 A torch cell converts one form of energy into another form. Name these two forms.


Q.3 Name the process that forms the basis of hydrogen bomb.


Q.4 How does the conductivity of a semi conductor change when certain impurities are added to it ?


Q.5 Name any two constituents of petroleum which are not used as fuel


Q.6. Why does common salt become moist in rainy season?


Q.7 Which property of diamond makes it a suitable material for high precision thermometers ?


Q.8 Name the Vitamin which gets oxidised when cut fruits are left exposed to air for a long time.


Q.9 In a food chain comprising lion, grass and dear, which will (i) transfer the maximum amount of energy (ii) receive minimum amout of energy.


Q.10 Whicc of the following is a true solution ?


Q.11 The lungs perform 2.4J of work during each exapnsion. How many times per minute do they expand if their power is 2 watts?


Q.12 Cadmium rods play an important role in a nuclear reactor. What happens (i) when they are completely inserted into nuclear fuel, and (ii) when they are slowly withdrawn from nuclear fuel.


Q.13 Mention any two differences between a planet and a star.


Q.14 A compound which is prpard from gypsum has the property of hardening when mixed with proper quantity of water. Identify the compound. Write the chemical equation of its preparation. Mention one important use of the compound.


Q.15 Which catagory of compounds is formed when one hydrogen atom of an alkane moleule is replaced by a hydroxyl group? Name the functional groups is the following compounds.


Q.16 How is the polar nature of water responsible for dissolving (i) Sodium Chloride (ii) sugar ?


Q.17 Give an example of a food chain consisting of four organisms at different trophic levels. Give the scientific term used to indicate the first and third trophic level.


Q.18 What is biological fixation? How is it different from nitrification ? Give an example of organism involved in each of these ?


Q.19 Differentiate between arithmatic progression and geometric progression in tems of food and population.


Q.20 What is immunity ? Name the diseases against which DPT vaccine acts as a preventive measure.


Q.21 A 100 watt electric bulb is lighted for 2 hours every day and five 40 watt tubes are lighted for four hours every day. Calculate (i) the energy consumed for 60 days and (ii) the cost of electricity consumed at the rate of Rs. 1.50 per kwh.


Q.22 Describe the sequence of changes that would take place if all the hydrogen present in the sun is converted to helium.


Q.23 Mass of the earth is optimum to facilitate existence of life on it. What would have happened if the earth had less mass than at present.


Q.24 List the characteristics which define the orbit of a satelite. Show their position in a diagram When is a satellite is said to be in a sun synchronous orbit?


Q.25 Name the main constituents of liquified petroleum gas. Why is this gas considered a bette domestic fuel than others ? (Give any four points) Give the calrofic value of LPG.


Q.26 Explain how the following metals are obtained from their compounds by the redcution process.

a) Metal X which is low in the reactivity series.

b) Metal Y which is in the middle of the series.

c) Metal z which is high up in the reactivity series.


Q.27 What are the thermosetting polymers ? Give two examples. Why can they be not processed again ?


Q.28 Describe with the help of a flow diagram the transfer of energy from sun to top carnivores.


Q.29 A doctor examined a child below the age of five years and fund cracks and scaly skin apart from wasting of muscles. Name the disease the child is suffering from. Mention two causes of its occurance. What diet should be given to over come this disease.


Q.30 Distinguish between bacteriocidal and bacteriostatic methods of food preservation. Give one example each of a food material preserved by these methods.


Q.31 Explain the working of a four-stroke engine using petrol as fuel. Draw a neat labelled diagram of the ignition stage.


Q.32 Name the chief impurity present in iron ore. What are the two requirements to obtain iron from its ore. Draw a labelled diagram of a blast furnace. State the main reactions that take place in the blast furnace. Write the chemical equations involved.


Q.33 Which nutrient serves as a ready source of energy in our body? Write its chemical formula. Write down the balanced equation for its complete oxidation. What test will you perform for its presence in a food sample ? Where is this nutrient stored in the body when present in excess?