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CBSE Pre Board Class 10 2019 : Science (St Xavier's Sr. Sec. School, Delhi) : Set 1

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Pre Board Examination 2019 Std. 10 08-01-2019 Set 1 SCIENCE Max. Marks : 80 Time : 3 hrs. General Instructions: i) The question paper comprises of five sections A, B, C, D and E. You are to attempt all the sections. ii) All questions are compulsory. iii) Internal choice is given in sections B, C, D and E. iv) Question numbers 1 and 2 in Section-A are one mark questions. They are to be answered in one word or in one sentence. v) Question numbers 3 to 5 in Section- B are two marks questions. These are to be answered in about 30 words each. vi) Question numbers 6 to 15 in Section-C are three marks questions. These are to be answered in about 50 words each. vii) Question numbers 16 to 21 in Section-D are 5 marks questions. These are to be answered in about 70 words each. viii) Question numbers 22 to 27 in Section- E are based on practical skills. Each question is a two marks question. These are to be answered in brief. SECTION A 1. Differentiate between vegetable peel and polythene bag. (Only definition) 1 2. Mention any two substances which are selectively reabsorbed as filtrate flows along the tubular part of nephron. 1 SECTION - B 3. An object 5cm high is held 25cm away from a converging lens of focal length 10 cm. a) Calculate the distance of the position of the image from the lens. b) What is the nature of image formed?i (OR) The refractive index of water with respect to vacuum is 4/3 and refractive index of vacuum with respect to glass is 2/3. If the speed of light in glass is 2x108m/s, find the speed of light in vacuum and water. 2 4. Write balanced chemical equation for the followings: a) K + H2O b) Fe2O3 + Al 2 5. Answer the following: a) Why does bread mold grow profusely on a moist slice of bread rather than on a dry slice? b) What is a clone? 2 SECTION C 6. If the image formed by a mirror for all positions of the object placed in front of it is always erect and diminished, what type of mirror is it? Draw a ray diagram to justify your answer. Where and why do we generally use this type of mirror? 3 7. a) b) What is biogas? Biogas is considered to be a boon to the farmers. Give reasons. Mention any two points that should be kept in mind while settling a wind energy farm. 3 8. a) b) Name a salt whose solution has pH more than 7. Write chemical formula and chemical name for Plaster of Paris. It should be stored in a moisture proof container, explain why? 3 a) b) Why do we store silver chloride in dark coloured bottles? A white compound on heating decomposes to give brown fumes and a yellow residue is left behind. Name the white compound and brown fumes. Write the chemical equation for the reaction. 3 9. 10. In a Guinea pig having black colour 100 offspring are produced. Out of which 75 were black and 25 were white. a) What is the possible genotype of pig? b) Which trait is dominant and which one is recessive? c) What is this cross called? What is the desired ratio of F1 generation? SCIENCE (Set 1) a) b) 11. a) b) c) Page 2 Std. 10 (OR) Draw neat and labeled diagram of Reflex arc. How are tropic movements different from nastic movements? 3 What will happen if mucus is not secreted by gastric glands? Two green plants are kept separately in oxygen free containers. On in dark and other in continuous light. Which one will live longer and why? What causes movement of food inside the alimentary canal? 3 12. When a high resistance voltmeter is connected directly across a resistor, its reading is 2V. An electric cell is sending the current of 0.4A, measured by ammeter in the electric circuit in which a rheostat is also connected to vary the current. a) Draw an equivalent labelled circuit diagram. b) Find the resistance of the resistor. c) Name and state the law applicable here. A graph is drawn between potential difference across the resistor and current flowing through it. Show the nature of graph thus obtained. 3 13. What are advantages of parallel circuit over series circuit? Consider the following circuit diagram. If R1 = R2 = R3 = R4 = R5 = 3ohm, find the equivalent resistance of the circuit. (OR) What do you understand by parallel combination? Five resistors are connected in a circuit as shown. Find the ammeter reading when the circuit is closed. 14. a) b) c) a) b) th An element X belongs to 13 group of the periodic table. Find its valency. What will be the formula of its sulphate? How many groups and periods are there in modern periodic table? Give reason to explain why atomic radius decreases across the period? (OR) What are the limitations of Mendeleev s periodic table? The position of four elements A, B, C and D in the periodic table are shown below: GROUP 16 ---D i) ii) iii) iv) 15. a) b) 3 GROUP 17 -A B C Which is the most reactive non metal? Name the family of A, B, C. What type of ion will be formed by D? Will C be larger or smaller than B? In a village of Karnataka, people started cultivating crops all around a lake. They added fertilizer in the fields to increase the yield. Soon they discovered that water body was entirely covered with green floating plants and fish started dying in large numbers. Give reasons for excessive growth of plants and death of fishes in the lake. What is sustainable development? 3 3 SECTION D 16. a) b) With the help of an activity, explain the method of inducing electric current in a coil with moving a magnet. What is a generator? On which principle is it based upon? What is the basic difference between AC and DC generator? Why is AC preferred over DC? 2+3 SCIENCE (Set 1) a) b) c) d) 17. a) b) c) Page 3 Std. 10 (OR) Draw a schematic diagram of a domestic circuit which has a provision of a main fuse, meter, one light bulb and a socket. Insulation cover of which colour is conventionally used for live wire? What is its function in an electric circuit? Explain the term short circuit of an electric circuit. Write the composition of fuse wire. How is fuse connected in an electric circuit? 5 Which part of eye controls the amount of light entering into eye? How does it work? Draw a ray diagram to show how nearsightedness can be corrected using lens of appropriate focal length. What is the cause of dispersion of white light on passing through a prism? 2+2+1 18. a) b) c) d) In the electrolytic refining of a metal M, what would you take as an Anode and a cathode? Define: i) Ore ii) Gangue How are alloys made? Write the constituents of solder alloy. State reasons for the following: i) Hydrogen gas is not evolved when a metal reacts with Nitric Acid? ii) Iron articles are galvanized. 5 19. a) b) c) d) Why does micelle formation take place when soap is added to water? What is Hydrogenation? Write its industrial application. Write the molecular and structural formula of Hexanal. Write a chemical equation to represent the following reactions: i) Dehydration of Ethanol. ii) Substitution Reaction between Methane and Chlorine in presence of sunlight. (OR) List any two reasons for Carbon forming a large number of compounds. Covalent compounds have low melting and boiling point. Why? Why are carbon and its compounds are used as fuels for most applications? An organic compound X is a liquid which often freezes during winter in cold countries, has the formula C2H4O2 on warming with Ethanol in presence of a few drops of concentrated Sulphuric Acid, a compound Y with a sweet smell is formed. i) Identify X and Y. ii) Write a chemical equation for the reaction involved. 5 b) Draw neat and labeled diagram of sectional view of heart and label the following: i) Largest artery ii) Upper chamber that receives oxygenated blood iii) Artery which carries deoxygenated blood iv) Largest vein that collects blood from lower part of body. How does blood platelets save our lives during injury? (OR) Draw neat and labelled diagram of human respiratory system and label the parts: i) That has cartilaginous rings ii) That encloses vocal cords iii) Dome shaped muscular partition that separates chest cavity from abdominal cavity iv) Main respiratory organ How are Alveoli designed to maximize the exchange of gases? 5 a) Draw neat and labeled diagram of a flower showing all the floral whorls and describe b) the function of each. In a bisexual flower in spite of young stamens being removed artificially, the flowers produces fruits. Provide a suitable explanation for the above situation. a) b) c) d) 20. a) b) a) 21. 5 SCIENCE (Set 1) Page 4 Std. 10 SECTION E 22. In an experiment to study the relation between the potential difference across a resistor and the current through it, a student recorded the following observations: Potential difference (v) Current (A) 1.0 0.1 2.2 0.2 3.0 0.6 4.0 0.4 2 6.4 0.6 On examining the above observations, the teacher asked the student to reject one set of readings as the readings were incorrect. Which one of the above sets of readings can be rejected? Calculate the mean value of resistance of the resistor based on the remaining four sets of observations. 23. 24. In an experiment with a rectangular slab, a student observed that a ray of light incident at an angle of 50 with the normal on one face of a slab. After refraction, strikes the opposite face of the slab before emerging out into air making an angle of 38 with the normal. What value would you assign to the angle of refraction and angle of emergence? Draw a well labeled diagram also. (OR) Draw a labeled diagram to show refraction through a glass prism. For an equilateral prism, if angle of incidence is 35 and angle of emergence is 65 , what would be its angle of deviation? 2 Four test tubes containing different solutions and different metals are shown below in the given figure : i) ii) In which of the test tubes there is a change of colour from light green to colourless? In which of the test tubes there is a change of colour from blue to green? Explain your answer. (OR) There are two substances A and B. A reacts with both Hydrochloric Acid and Sodium Hydroxide to liberate the same gas C. B reacts with Hydrochloric Acid to give a gas D that extinguishes burning matchstick. Identify A, B, C and D. 2 25 a) b) 26. 5ml each of acetic acid and water are mixed in a test tube. Explain whether a clear solution or a turbid solution will be obtained. Write the chemical equation between acetic acid and sodium hydroxide. 2 In the figure parts A and B are marked. Identify A and B and also write the conditions necessary for germinating seeds. OR What are cotyledons? How are number of cotyledons different in gram seed and maize (corn)? 2 27. What type of living organism is yeast? Give its commercial importance. -x-x-x-x-x-x- 2

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