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CBSE Pre Board Class 10 2021 : Science (Matushri Kashiben Vrajlal Valia International Vidyalaya (MKVV), Borivli, Mumbai)

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MKVV INTERNATIONAL VIDYALAYA PRELIMINARY EXAMINATION- (2020-21) CLASS - X SCIENCE MARKS-80 TIME 3HRS INSTRUCTIONS The question paper has four sections A, B, C, and D. There are 36 questions in the question paper. All are compulsory. Section-A Question no 1 -20 are of objective type ,very short answer and assertion-reason type questions. Section -B Question no 21 -26 are short answer type of 2 marks each. Section -C Question no 27 -33 are short answer type of 3 marks each. Section - D Question no 34 -36 are long answer type of 5 marks each Wherever necessary, neat and properly labelled diagrams should be drawn SECTION -A (16+16 marks) 1. During electrolysis of water, why is the volume of gas collected over one electrode is double than the gas collected over the other electrode? (1) 2. a) Which is stronger, acid with pH= 5 or acid with pH= 2? a) How does the pH change when a solution of base is diluted? (1) 3. Choose the amphoteric oxide among the following. Na O, ZnO, Al O . CO , H O (1) 4. A non-metal X exists in two different forms Y and Z. Y is the hardest known natural substance whereas Z is a good conductor of electricity. Identify Y and Z. (1) 5. Write the molecular formula of benzene and draw its structure (OR) Write the molecular formula of cyclohexane and draw its structure. (1) 6. Which metal among, sodium, calcium, aluminium and copper (a) produces fire on water? (b) does not react even with steam? (1) 7. What is the refractive index of glass with respect to water? (1) 8 8 (speed of light in water = 2.25 10 m/s, speed of light in glass = 2 10 m/s) (OR) A beam of light passes from air into a medium M. If the angle of incidence is 45 and the angle of refraction is 30 ,calculate the refractive index of medium M.(sin 45 = 1/ 2 , sin 30 = ) 8. Which of the following combinations have the same equivalent resistance between X and Y? (1) 9. How is magnification related to object distance and image distance in spherical mirrors? When will be the magnification positive? (1) 10. Why do aquatic animals breathe faster than the terrestrial animals? (1) 11. What is the role of cartilaginous rings in trachea? (1) (OR) The lung alveoli are covered with blood capillaries. Why? 12. What is the result of excessive exposure of humans to UV rays? (OR) What does an ecosystem include? (1) 13. How does nutrition in fungus differ from that in tapeworm? (1) For question numbers 14,15 and 16, two statements are given one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (a), (b), (c) and (d) as given below: (a) (b) (c) (d) Both A and R are true, and R is the correct explanation of A Both A and R are true, and R is the not the correct explanation of A A is true, but R is false. A is false, but R is true. 14. A- Convex mirror is used by dentist to examine tooth. R- Convex mirror always form a diminished erect image. (1) 15. A - Carbon has the unique ability to form bonds with other atoms of carbon giving rise to larger molecules. R - The carbon-carbon bond is very weak and hence it combines with other atoms (1) 16. A- Food chain is responsible for the entry of harmful chemicals in our bodies.(1) R- The length and complexity of food chain varies greatly. (0R) A-Some substances in nature are biodegradable, while some are non- biodegradable R-The bacteria acting on substances breakdown only the substances made from natural materials. 17. Read the following passage and answer the any four questions from a to e (4) The force that blood exerts against the wall of blood vessel is called blood pressure. This pressure is much greater in arteries than veins. The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The normal systolic pressure is 120 mm of Hg and diastolic pressure is 80 mm of Hg. blood pressure is measured with an instrument called sphygnomanometer. High blood pressure is also called hypertension and is caused by constrictions of arteriole, which result in increased resistance to blood flow,it can lead to the rupture of an artery and internal bleeding. a. Which part of the heart receives oxygen rich blood? i) Left atrium. ii) Left ventricle. iii) right atrium. iv) right ventricle b. List some lifestyle factors that lead to hypertension. c. Which blood vessel brings oxygenated blood to the human heart? i. Pulmonary artery iii. Renal artery. ii. Pulmonary vein iv. Renal vein d. A circulatory fluid in human body other than blood is i. Plasma iii. Lymph. ii. Mucus iv. Enzyme e. From the data given below, state which age group and what percent of people (male and female) are. (i) least (ii) most suffered by hypertension 18. Consider the following diagram in which L is the lens, AB is the object and A B is the image. Answer any 4 from the questions a to e based on the given diagram (4) lb a. Write the type of lens used in the above diagram. b. What is the nature and position of the image formed? c. If the position of the object is shifted 5cm away from the lens, what will be the new position of the image? d. Name the term used to express the degree of convergence or divergence of light rays by a lens. e. Define principal focus of the lens L. 19.In 1827,a German physicist Georg Simon Ohm found out the relationship between the current flowing through a conductor and the potential difference across its terminals. This relationship is stated in the form of ohm s law. This relationship can be explained by using a graph.The V-I graph given below shows two straight lines A and B for a conductor at two different temperatures T1 and T2. (4) a. b. c. d. State ohm s law. What conclusion can be obtained from the above graph? How will you obtain the resistance of a conductor from a V-I graph? Which of the lines (A or B) has higher value of resistance?Why? 20. Study the following graph and answer the questions from (i) to (iv) The graph below shows the rate of reaction of three different metals X,Y and Z with dilute sulphuric acid. (4) Assume that the three metals are Al, Mg and Fe. i. Which metal represents Z? (Or) Which metal represents Y? ii. Which metal will produce more volume of hydrogen gas? iii. What will happen if dilute nitric acid is used instead of dilute sulphuric acid? a. Al, Mg and Fe do not react b. Al and Fe will react and produce hydrogen c. Mg and Al will react and produce hydrogen d. None of the above iv. From the graph,the decreasing order of reactivity is given as (a) X>Y>Z. (b) Y>Z>X. (c) Z>Y>X. (d) Z>X>Y SECTION B (12 marks) 21. A wire of uniform thickness with a resistance of 30 is cut into three equal pieces and they are joined in parallel. Find the equivalent r sistance of parallel combination. (2) (OR) Two lamps, one rated 60W at 220V and the other 40W at 220V,are connected in parallel to the power supply at 220V a. Draw a circuit diagram to show the connections. b. Calculate the total energy consumed by the two lamps together when they are operated for 2 hours. 22. a. State right hand thumb rule. (2) b. The armature coil of a dc motor is rotating in clockwise direction. How can the direction of rotation of the coil be reversed? 23. The metal salt A is blue in colour, when salt A is heated strongly over a (2) burner, then a substance B present in it is eliminated and a white powder C is left behind. (a) Identify A,B and C (b) Give an example of a salt which also shows the above property. (OR) 15 ml of water and 10 ml of sulphuric acid are to be mixed in a beaker. (a) State the method that should be followed with reason. (b) What is this process called? 24.Consider the chemical equations given below and answer the questions : (i) CuO + H Cu + H O (ii) ZnO + C Zn + CO (2) (a) Name the substance that is oxidised and reduced respectively in each case (b) Identify the reducing agent in each case 25. Describe the type of reproduction followed by the following organisms a. Hydra b. Rhizopus. (2) 26. What are the methods used by plants to get rid of excretory products? (2) (OR) What is the function of digestive enzymes? Give two examples of digestive enzymes. SECTION C (21 marks) 27. Three ammeters A, B and C are connected in a circuit as shown in figure. The ammeter B reads 1A. (3) Calculate a. Readings of ammeters A and C b. The total resistance of the combination. 28. Draw the pattern of magnetic field lines through and around a current carrying circular loop of wire. How would the strength of magnetic field around the circular loop affected? (3) a. if the distance from the loop is increased. b. strength of the current through the loop is doubled. (OR) a. What are magnetic field lines? b. Justify the following statements i)Two magnetic field lines never intersect each other. ii)Magnetic field lines are closed curves. 29. A) Write the essential condition for the following reaction to take place. (3) 2 AgBr 2 Ag + Br Write an application of this reaction. B) When a solution of potassium iodide is added to a solution of lead nitrate in a test tube, a reaction takes place. i) What type of reaction is this ? ii) Write the balanced chemical equation to represent the above reaction. 30. A White powder is added while baking breads and cakes to make them soft and fluffy. Name the main ingredients of the powder. Explain the role of each ingredient present. Write the chemical reaction taking place when the powder is heated during baking . (3) 31.a) What do the progeny of a tall plant with round seeds and a short plant with wrinkled seeds look like? Why? b)What happens when the F1 progeny obtained above are used to produce F2 progeny by self pollination? (3) (OR) A blue colour flower plant denoted by BB is cross breed with that of white colour flower plant denoted by bb. i) State the colour of flower you would expect in their F1 generation plants. ii) what must be the percentage of white flower plants in F2 generation plants if F1 plants are self pollinated. iii)State the expected ratio of the genotypes BB and Bb in the F2 progeny. 32.Your mother always tell that fruit juices are very healthy for everyone. (3) One day she read in the newspaper that some brands of fruit juices, available in the market have been found to contain certain level of pesticides in them. She got worried as pesticides are injurious to our health. a) Explain to your mother what are pesticides and how fruit juices get contaminated with pesticides? b) It is said that harmful pesticides enter in our body as well as in the body of other organisms, they get accumulated and beyond a limit it can cause harm and damage to our organs Name the phenomena and write about it. 33. Describe the structure and functions of nephron. (3) SECTION- D (15 marks) 34.An object of height 4 cm is placed at a distance of 30 cm from the optical centre of a convex lens of focal length 20 cm. Find the position, nature and the size of the image formed. Also find the ratio of size of the image to the size of the object. Draw a ray diagram to show the image formation. (5) 35.A) Write the formula and name of first two members of homologous series whose functional group is. (5) B) State the valency of each carbon atom in (i) an alkane and (ii) an alkyne. C) Draw the electron dot structure for (a) CO (b) NH (OR) a) Write the molecular formula of the following compounds and draw their electron dot structure. i)Ethane ii) Ethene iii) Ethylene b) Write the number of covalent bonds in butane. ,36. A. Draw a diagram of human female reproductive system and label the parts: (5) i) ii) iii) that produces eggs where fusion of egg and sperm takes place. where zygote is implanted. B. What happens to human egg when it is fertilized or it is not fertilized.

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