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AMITY INTERNATIONAL SCHOOL, NOIDA PREBOARD EXAMINATION CLASS X (2020-21) SCIENCE Time: 3 Hour Maximum Marks: 80 General Instructions: (i) The question paper comprises four sections A, B, C and D. There are 36 questions in the question paper. All questions are compulsory. (ii) Section A - Question no. 1 to 20 - all questions and parts thereof are of one mark each. These questions contain multiple choice questions (MCQs), very short answer questions and assertion - reason type questions. Answers to these should be given in one word or one sentence. (iii) Section B - Question no. 21 to 26 are short answer type questions, carrying 2 marks each. Answers to these questions should in the range of 30 to 50 words. (iv) Section C - Question no. 27 to 33 are short answer type questions, carrying 3 marks each. Answers to these questions should in the range of 50 to 80 words. (v) Section D Question no. - 34 to 36 are long answer type questions carrying 5 marks each. Answer to these questions should be in the range of 80 to 120 words. (vi) There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions. (vii) Wherever necessary, neat and properly labeled diagrams should be drawn. SECTION A Q1. Why do we store silver chloride in dark coloured bottles? OR 3MnO2 + 4Al 1 3Mn + 2Al2O3 On the basis of the above reaction state which is more reactive, Mn or Al and why? Q2. Name the acid and base from which the following salt is obtained: calcium hydrogencarbonate 1 Q3. A molecule of carbon dioxide has: a) Only single bonds. b) Only double bonds. 1 c) Only triple bonds. d) Two double bonds and one single bond Q4. The sky appears dark instead of blue to an astronaut. State its reason. 1 Q5. Name the atmospheric phenomenon due to which the sun can be seen above the horizon about two minutes before actual sunrise. 1 Q6. Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of the magnetic field? 1 Q7. Identify the poles of the magnet in the given figure . 1 Q8. Find the amount of electric charge flowing through the circuit if an electric current of 5A is drawn by an electric appliance for 5 minute. OR A bulb is rated at 5V ,100mA. Calculate its power. 1 Q9. What is common in Cuscuta, ticks and leeches? OR Leaves of a healthy potted plant are coated with Vaseline to block the stomata. Will this plant remain healthy for long? Give reason. 1 Q10.In tobacco plant, the male gametes have twenty four chromosomes. What is the number of chromosomes in the female gamete? What is the number of chromosomes in the zygote? OR Why is variation beneficial to the species but not necessary for the individual? 1 Q11.Choose the biodegradable pollutants from the list given below: Sewage, DDT, Agricultural waste, radioactive waste OR State two problems caused by the non- biodegradable waste that we generate in our daily life. 1 Q12.What will be the percentage of blood groups in offsprings produced by the parents having following genotype? Male IA IA & Female IA IB 1 Q 13.The gene for red hair is recessive to the gene for black hair. What will be the hair colour of a person if he inherits a gene for red hair from his mother and a gene for black hair from his father? Give reason to your answer. 1 For question numbers 14, 15 and 16, two statements are given- one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below: a) Both A and R are true, and R is correct explanation of the assertion. b) Both A and R are true, but R is not the correct explanation of the assertion. c) A is true, but R is false. d) A is false, but R is true. Q14. Assertion: In the Double Displacement reaction between aqueous Potassium Iodide and aqueous Lead Nitrate, a yellow precipitate of Lead Iodide is formed. Reason: Precipitation reactions produce soluble salts 1 Q15. Assertion: In a monohybrid cross, F1 generation indicate dominant characters. Reason: Dominance occurs only in heterozygous state. 1 Q16. Assertion: Parallel rays meet at focus after refraction. Reason: Rays coming from a distant object are parallel rays. 1 OR Assertion: When a ray enters from air to water obliquely, it bends towards the normal. Reason: It is because water is optically denser than air. 1 Q. No 17 20 contain five sub-parts each. You are expected to answer any four sub- parts in these questions. Q17. Read the following and answer any four questions from 17(i) to 17 (v) 1x4 The The force that blood exerts against the wall of a vessel is called blood pressure. This pressure is much greater in arteries than in veins. The (i)The blood leaving the tissues become richer in a)Oxygen b)Water c)Haemoglobin d)carbondioxide (ii)Choose the blood vessel that carry oxygenated blood back to the heart a)Renal vein b)Pulmonary artery c)Pulmonary vein d)Vena cava (iii)Study the graph below and choose the correct option. a)A person who is standing has more diastolic pressure and less systolic pressure. b)Systolic pressure will always be higher than diastolic pressure c)Person with high blood pressure will have less systolic pressure than normal person. d)Blood pressure does not get affected by the physical activities. (iv)Blood pressure of a person is 150/90 mmHg. Choose the incorrect option. a)Suffering from hypertension b)Performing rigorous exercises c)Constriction of arteriole d)Suffering from hypotension v)Systolic pressure is higher than diastolic pressure due to a)Volume of blood in the heart is greater during systole. b)Arteries contract during systole c)Blood vessels offer resistance to flowing blood during systole. d)Blood is forced into arteries during systole Q18. Read the following and answer any four questions from 18 (i) to 18 (v) 1x4 Hydrochloric acid is produced in our stomach which helps in the digestion of food that we eat. This hydrochloric acid does no harm to the stomach as it has a special lining of a protective material. In fact, it kills the harmful bacteria that may enter the stomach along with food. However, when we take too much of some spicy food, the amount of hydrochloric acid produced increases beyond the required limit. This causes sharp pain and irritation in the stomach and is cured by taking medicines called antacids (i)The pH of the gastric juices released during digestion is: a) less than 7 b) more than 7 c) Equal to 7 d) Equal to 0 (ii) Which one of the following will turn red litmus blue? a) Vinegar b) Baking soda solution c) Lemon juice d) Hydrochloric acid (iii) An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change? a) b) c) d) Baking powder Lime Ammonium hydroxide solution Hydrochloric acid (iv) Which of the following can be used as an antacid? a) Sodium Hydroxide b) Magnesium Hydroxide c) Calcium Hydroxide d) Sodium Carbonate (v) Which of the following gives the correct increasing order of acidic strength? a) Water < Acetic acid < Hydrochloric acid b) Water < Hydrochloric acid < Acetic acid c) Acetic acid < Water < Hydrochloric acid d) Hydrochloric acid < Water < Acetic acid Q19. Read the following and answer any four questions from 19(i) to 19 (v) 1x4 We are familiar with the fact that a compass needle gets deflected when brought near a bar magnet. A compass needle is in fact, a small bar magnet. The ends of the compass needle point approximately towards north and south directions. The end pointing towards north is called north seeking or north pole. The other end that points towards south is called south seeking or south pole. Through various activities, we have observed that like poles repel, while unlike poles of magnets attract each other. The magnet exerts its influence in the region surrounding it. The region surrounding a magnet, in which the force of the magnet can be detected is called magnetic field. The lines along which the iron filings align themselves around a bar magnet represent magnetic field lines. (i) Choose the incorrect statement from the following regarding magnetic lines of force a) The direction of magnetic field at a point is taken to be the direction in which the North Pole of a magnetic compass needle points. b) Magnetic field lines are closed curves. c) If magnetic field lines are parallel and equidistant, they represent zero field strength. d) Relative strength of magnetic field is shown by the degree of closeness of the field lines. (ii) Inside the magnet, the magnetic field lines move a) from north to south b) from south the north c) away from south pole d) away from north pole (iii) Relative strength of magnetic field at a point in the space surrounding the magnet is shown by the a) length of magnet b) thickness of magnet c) degree of closeness of the field lines. d) resistance offered by the surroundings (iv) The strength of magnetic field around a current carrying conductor is a) inversely proportional to the current but directly proportional to the square of the distance from wire. b) directly proportional to the current and inversely proportional to the distance from wire. c) directly proportional to the distance and inversely proportional to the current d) directly proportional to the current but inversely proportional the square of the distance from wire. (v) A soft iron bar is inserted inside a current-carrying solenoid. The magnetic field inside the solenoid: a) Will decrease b) Will increase c) Will become zero d) Will remain the same 20. Read the following and answer any four questions from 20(i) to 20 (v) 1x4 The ability of a medium to refract light is also expressed in terms of its optical density. Optical density has a definite connotation. It is not the same as mass density. We have been using the terms rarer medium and denser medium . It actually means optically rarer medium and optically denser medium respectively. When can we say that a medium is optically denser than the other? In comparing two media, the one with the larger refractive index is optically denser medium than the other. The other medium of lower refractive index is optically rarer. The speed of light is higher in a rarer medium than a denser medium. Thus, a ray of light travelling from a rarer medium to a denser medium slows down and bends towards the normal. When it travels from a denser medium to a rarer medium, it speeds up and bends away from the normal. (i) Refractive index of glass with respect to air is 3/2. The speed of light in air is : a) 1.5 108 m/s b) 2 108 m/s c) 3 108 m/s d) 4.5 108 m/s (ii) What will be the angle of refraction for a ray of light incident normally to the surface? a) 90 b) 60 c) 30 d) 0 (iii) If refractive index of glass with respect to air is 1.5, then the refractive index of air with respect to glass will be: a) 3.00 b) 1.50 c) 0.75 d) 0.67 (iv) A student does the experiment on tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence. He can get a correct measure of the angle of incidence and the angle of emergence by following the labelling indicated in figure: a) I b) II c) III d) IV (v) The absolute refractive index of any medium is always a) 1 b) greater than 1 c) less than 1 d) zero SECTION B Q21. Label the given diagram. OR Amylase is secreted by two different glands, Name them also write the action of amylase on food. 2 Q 22. (a) Where in the human body does an ovum get fertilised ? (b) Where does a fertilised ovum develop into a baby in the human body? (c) What is the causative organism of Gonorrhoea. (d) Name one method of contraception which also protects against sexually transmitted diseases. 2 Q23. An element E exists in three allotropic forms - A, B and C. In allotrope A, the atoms of element E are joined in the shape of a football. In allotrope B, each atom of element E is bonded to three other E atoms to form a sheet like structure. In allotrope C, each atom of element E is bonded to four other E atoms to form a rigid structure. a) Identify the allotropes A, B and C. b) Name the allotrope of E which can be synthesized by subjecting pure carbon to high temperature and pressure. OR Explain the following: a) Graphite is a good conductor of electricity but diamond is not. b) Covalent compounds have low melting and boiling points? 2 Q24. Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water and a gas C is evolved. The gas C when passed through lime water, turns it milky. Identify A, B and C and name the substance formed which makes lime water turn milky. 2 Q25. The figure below shows three cylindrical copper conductors along with their cross sectional areas and lengths. Discuss in which geometrical shape the resistance will be the highest. 2 Q26. What is meant by spectrum of white light? How can we recombine the components of white light after a prism has separated them? Draw a diagram to illustrate it. 2 SECTION C Q27. (a) The sex of the children is determined by what they inherit from their father and not their mother. Justify. (b) Give an example where environmental factors like temperature determine the sex of the offspring. OR A blue colour flower plant denoted by BB is crossbred with that of white colour flower plant denoted by bb. (a) State the colour of flower you would expect in their F1 generation plants. (b) What must be the percentage of white flower plants in F2 generation if flowers of F1 plants are self-pollinated? (c) State the expected ratio of the genotypes BB and Bb in the F2 progeny. Q28. 3 Q28. a) In a food chain .comprising lion, grass and deer, which will (i) Transfer the maximum amount of energy. (ii) Receive a minimum amount of energy. b) In the following food chain, 20 J of energy was available to lion. How much would have been present in the grass? Grass Goat lion c) If a harmful chemical enters in food chain comprising snakes, peacock, mice and plants, which of these organisms is likely to have the maximum concentration of this chemical in its body? 3 Q29. Draw the diagram of sectional view of human heart and on it name and label the following parts: (a) The chamber of the heart that pumps out deoxygenated blood. (b) The blood vessel that carries away oxygenated blood from the heart. (c) The blood vessel that receives deoxygenated blood from the lower part of our body. Q30. a) Show the formation of Na2O by transfer of electrons with the help of electron dot structures. b) With the help of a balanced equation show the reaction of calcium metal with water. c) Why does calcium float on water? 3 Q31. (i) Draw the electron dot structure of ethyne and also draw its structural formula. (ii) List two characteristic features of carbon which when put together give rise to a large number of compounds. (iii) Define homologous series of carbon compounds. 3 Q32 a) Can we stir silver nitrate with a copper spoon? Why or why not? Support your answer with a reason. b) Why a brown coating is formed when an iron rod is kept dipped in copper sulphate solution for some time. What change will be observed in the colour of the solution? c)A green coating develops on the copper vessel in the rainy season. Why? 3 Q33. A spherical mirror produces an image of magnification -1 on the screen. If the object placed at a distance of 50 cm from the mirror. a) Write the type of mirror. b) Find the image distance. c) What is the focal length of the mirror? 3 3 SECTION D Q34. a) Who proposed the Modern Periodic Law? State it. b)Study the following table in which the position of six elements A, B, C, D, E and F are shown as they are in the Modern Periodic Table. Period/group 1 2 3-12 13 14 15 16 17 18 2 3 A B D E C F On the basis of the above table, answer the following questions using the letters given. (i)Name the element which forms only covalent compounds. (ii) Name the element which is a nonmetal with valency 3. (iii) Write the common name for the family to which the elements C and F belong. (iv) Give the formula of the oxide of D . What is the nature of this oxide? (v) Out of D and E, which is bigger in size and Why? OR a) Define Periodicity. b) An element X has mass number 39 and the number of neutrons is 20. Identify the group number and period of X . c) The elements 4Be, 12Mg and 20Ca each having 2 valence electrons in their valence shells are in periods 2, 3, and 4 respectively of the Modern Periodic Table. Answer the following questions associated with these elements, giving reason in each case (i)In which group should they be? (ii)Which one of these is least reactive? (iii) Which one of them has the largest atomic size? 5 Q 35. (a) Draw a diagram showing germination of pollen on stigma of a flower (b) Label pollen grain, male germ- cells, pollen tube and female germ-cell in the above diagram. (c) How is zygote formed? 5 Q36.a) Two resistors R1and R2 may form (i) a series combination or (ii) a parallel combination, and the combination may be connected to a battery of 6 volts. In which combination, will the potential difference across R1 and across R2 be the same and in which combination, will the current through R1 and through R2 be the same? b) For the circuit shown in this diagram, calculate (i) the resultant resistance. (ii) the total current. (iii) the voltage across 7 resistor. OR a)Describe an activity to demonstrate the pattern of magnetic field lines around a straight current carrying current. b) State the rule to find the direction of magnetic field associated with a current carrying conductor. c) What is the shape of a current carrying conductor whose magnetic field pattern resembles that of a bar-magnet ? 5
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