Science and Technology

Class X 2009

Note: All questions are compulsory

Each question carries marks mentioned against them.

Time 2.30 Hours                                                                                                                              Max Marks 60

Section A

Q 1 Write the relation between 1 watt, 1 volt and 1 ampere?                                                 1

Ans 1 Watt = 1 Volt X 1 Amphere

Q2 In the electrolytic refining of an impure metal which substance is used to make the anode?                                                                                                                                                                 1

Ans Copper

Q 3 What type of mirror is used to obtain a real image?                                                               1

Ans Concave mirror.

Q4 Write down chemical formula of Baking power and Baking soda?                     1

Ans Baking power =NaHCO3 + NaAl(SO4)2 + CaHPO3 + C6H10O5 and Baking soda = NaHCo3

Q5 Write down chemical name and formula of bleaching power. What are the raw materials used for its manufacturing by Hasen clever plant process?                     2

Ans Calcium oxychloride and CaOCl2  and raw materials are Ca(OH)2 and Cl2.

Q6 If you connect three resistors having valves 2 ohm 3 ohm and 5 ohm in parallel then the value of total resistance be less than 2 ohm or greater than 5 ohm or lie between 2 ohm and 5 ohm explain?                                                                                                          2

Ans. Total resistance will be less than 2ohm, which is because the sum of the reciprocals of the separate resistances is equal to the reciprocal of equivalent resistor.

Q 7 What do you mean by power of lens? What will be power of a concave lens of focal length 2 m?                                                                                                                                                                 2

Ans. The reciprocal of focal value of lense is known as the power of the lens and power of a concave lens of focal length 2 m will be +2.

Q 8 What is a fuse? How does it function?                                                                                                          2

Ans. Fuse is a piece of wire made of a bismuth alloy and offers a great deal of resistance to electric current and melts at a fairly low temperature. The main function of it is that when we overload the circuit the heat on the conductor melts the fuse and our household appliances saved from burning.

Q 9 How can you distinguish between plan, convex and concave mirrors by merely looking at the image formed in each case?                                                                                           3

Ans

 Mirror Plane mirror Convax mirror Concave mirror Image Type Virtual, reverse and same size Virtual and small size Real and enlarge size

Q 10 An object 5 cm high placed 20 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed to obtain a sharp image? Also state type of image formed?                                                                              3

Ans. Formula : 1/f=1/u+1/v  So distance from mirror to image is here v so screen should be place at 60 cm from the mirror to get sharp image and image formed will be real, enlarged and inverted.

Q11 Distinguish between polar and equatorial orbits of artificial satellites which of the above two orbits is suitable for a: (i) geostationary satellite (ii) Satellite used for weather forecasting?                                                                                                                                            3

Ans. The plane of the orbit may take in both poles as well as the center of the earth in which case the orbit is said to be polar. If the plane of the orbit lies along the equator the orbit is said to be equatorial. (i) For geostationary satellite equatorial orbit is suitable.(ii) geostationary satellite used for weather forcasting.

Q 12 Draw a flow diagram illustrating the principle used in the manufacturing of ammonia by Heber’s process?                                                                                                                         3

Ans. In 1909 Fritz Haber established the conditions under which nitrogen, N2 (g), and hydrogen, H2(g), would combine using medium temperature (~500oC)

very high pressure (~250 atmospheres, ~351kPa) a catalyst (a porous iron catalyst prepared by reducing magnetite, Fe3O4).This process produces an ammonia, NH3(g), yield of approximately 10-20%.

The reaction between nitrogen gas and hydrogen gas to produce ammonia gas is exothermic, releasing 92.4kJ/mol of energy at 298K (25oC).

 N2(g)nitrogen + 3H2(g)hydrogen heat, pressure, catalyst 2NH3(g)ammonia + 92.4 kJ mol-1

Q 13 A person is unable to see the object beyond 2 m clearly. Name the defect of vision he is suffering from? List cause due to which this defect may arise? Also state correction of this defect using appropriate lens?                                                                                                 3

Ans. Person is suffering from Myopia. It is because the focus formed is before retina. The defect can be corrected if person uses concave lense.

Q 14Name the process involved in the liberation of energy in (i) Sun and (ii) Nuclear reactor. Mention any two differences between two processes?                                                             3

Ans (i) Fusion and (ii) Fission

Differences between two are as follows:

 Fission Fusion It is splitting of a large nucleus to from two or more smaller nuclei. If two lighter nuclei are combine together to form a single nucleus the process is called fusion. Example; Nutron+Uranium235 ->Barium 141+Kripton92+3Nutrons+Energy 4 Hydrogen -> 4Helium+2 Positrons+Energy

Q15 (a) what is 24 carat gold? How will you convert it into 18 carat gold?

(b) Name an alloy of: (i) Aluminum used in construction of aircrafts. (ii) Lead used in joining metals for electrical works and (iii) Copper used in household vessels.                                                                                                                                                                5

Ans. (a)A carat as applied to gold alloys means a proportion by weight of one part in twenty-four so 24 carat gold is 100 percent pure gold. If gold proportion is reduced to 75 percent and 16 percent silver and 9 percent copper in alloys in gold than the gold will be 18 carat.

(b) (i) Duralium alloy constituents Aluminium, copper and traces of manganese and magnesium. (ii) Solder alloy constituents Lead and Tin (iii) Brass alloy constituents Copper, Zinc.

(i) Metals which can be cut with knife at room temperature.

(ii) The most ductile metal.

(iii) Metal having maximum resistance in the conduction of electricity.

(iv) Name two metals that are used to wrap materials.

5

Ans (i) The alkali metals are as lithium, sodium, potassium, rubidium, cesium, and francium are soft metals and can be cut with knife at room temperature.

(ii) Gold.

(iii)Lead metal have maximum resistance in conducting electricity.

(iv) Aluminium and Tin

Section B

Q 17 Name the enzyme present in human saliva?                                                            1

Ans Salivary amylase.

Q 18 Why blood looks red?                                                                                                                    1

Ans Presence of haemoglobin in blood.

Q 19 Name two purine nitrogenous base in DNA?                                                            1

Ans adenine (A) and guanine (G)

Q 20 Draw a labeled diagramme of a neuron?                                                                          2

Ans. A typical neuron is pictured below.

Q 21 Write full forms of IUCD and HIV?                                                                                        2

Ans Intrauterine Contraceptive Devices (IUCDs) and Human

Immunodeficiency Virus (HIV)

Q 22 (i) who isolated DNA for the first time from pus cell?

(ii) Why DNA called a polynucleotide?                                                                          2

Ans (i) Friedrich Miescher isolates DNA for the first time in1869

(ii) DNA is composed of nucleotides strung together to make a long chain so called a polynucleotide

Q 23 Define transpiration? How does transpiration help in upward movement of water from roots to leaves?                                                                                                      3

Ans. Transpiration is the loss of water from a plant in the form of water vapor. Water is absorbed by roots from the soil and transported as a liquid to the leaves via xylem. In the leaves, small pores allow water to escape as a vapor and CO2 to enter the leaf for photosynthesis. Thus a transpirational pull created in the leaves goes from leaf to stem and from stem to roots and due to this pull water continuously move upward from roots to the leaves of the plants.

Q 24 Explain the followings: (i) Acid rain (ii) Ozone depletion (iii) Global warming 3

Ans. (i) Acid rain is rain, snow or fog that is polluted by acid in the atmosphere and damages the environment.

(ii) Ozone is present in the stratosphere. The suns rays are absorbed by the ozone in the stratosphere and thus do not reach the Earth. The ozone layer protects the Earth from the ultraviolet rays sent down by the sun.  If the ozone layer is depleted by human action, by excessive release of CFCs, chlorofluorocarbons the effects on the planet could be catastrophic.

(iii) Global warming is the increase in the average temperature of the Earth’s near-surface air and oceans in recent decades and its projected continuation.The global average air temperature near the Earth’s surface rising continuously which is due to increase in emission of greenhouse gas causing greenhouse effect.

Q 25 With the help of labeled diagramme describe double fertilization in plants?   5

Ans Fertilization in Plants : In plants, pollination is followed by fertilization. Once the pollen grains are deposited on the stigma, they form tubes called pollen tubes. One pollen tube grows through the style and reaches the ovary where ovules are located. The pollen tube normally enters the ovule through a small opening called micropyle . Inside the ovule, the pollen tube releases two male gametes into the embryo sac. The embryo sac of the ovule contains the egg. One male gamete fuses with the egg. This fusion of male and female gamete is called syngamy and its product is the zygote. The other male gamete fuses with the two polar nuclei and this process is called triple fusion,where three nuclei are involved in the fusion process, one male gamete and two polar nuclei. Thus, inside each embryosac, two fusions, syngamy and triple fusion, take place. This mechanism of two fusions occurring in an embryo sac is called double-fertilisation. After fertilisation, ovary develops into the fruit, ovules develop into the seeds.