Class -10 Sub- Science (Physics and Chemistry ) Important questions for board purpose Note: Students are requested to solve these questions in separate notebook/a-4 sheets. 1. Burning of fossil fuels result in global warming.give reasons to justify this statement. 2. Explain the term blind spot with reference to eye. 3. What is scum and how is it formed? 4. An object of height 2.5 cm is placed at a distance of 15 cm from the optical centre O of a convex lens of focal length 10 cm. Draw ray diagram to find the position and size of the image formed. Mark optical centre O, principle focus F and height of the image in the diagram. 5. What is meant by galvanization? Suggest two more methods that are adopted for the same purpose. 6. Give the uses of Biogas. What are the advantages of Biogas. 7. Describe an activity to show variation of resistance with area of cross-section of a conductor. 8. (a) Give an example for a combination reaction which is exothermic. (b) Identify the oxidizing agent, the reducing agent in the following reaction : H 2 S + Cl 2 2HCl +S (c) Name the phenomenon due to which the taste and smell of oily food changes when kept for a long time in open. Suggest one method to prevent it. A reddish brown colored metal used in electrical wires when powdered and heated strongly in an open china dish, its color turns black. When hydrogen gas is passed over this black substance, it regains its original color. Based on the above information, answer the following questions: (a) Name the metal and the black colored substance. (b) Write balanced chemical equations for both the chemical reactions. 9. The position of three elements A,B and C in the periodic table are shown below: Group 16 Group 17 - - - A - - B C (a) For the circuit shown in the diagram, calculate (i) Value of current through the 30 Ω resistor. (ii) Total resistance of the circuit. (b) Give two advantages of connecting electrical devices in parallel with battery.
(a) Three 2Ω resistors, A,B and C, are connected as shown in figure. Each of them dissipates energy and can withstand a maximum power of 18W without melting. Find the Maximum current that flow through the three resistors. (b) A potential difference V is applied across a conductor of length L and diameter d. How is The resistance R of the conductor affected, when in turn (i) V is halfed (ii) L is halved and (iii) D is doubled? Justify your answer in each case. 10. (a) Explain why an aqueous solution of sodium sulphate Is neutral while an aqueous solution of sodium carbonate is basic in nature. (b) Consider the following salts : Na 2 CO 3. NaCl, NH 4 Cl, CH 3 COONa. Which of these salts will give (i) acidic solution (ii) neutral solution (iii) basic solution? 11. Consider the following salts: Na 2 CO 3. NaCL,NH 4 CI, CH 3 COONa. Which of these salts will give (1) Acidic solution (2) neutral solution (3) basic solution? 12. How can ethanol and ethanoic acid be differentiated on the basis of physical and chemical properties? 13. (a) Redraw the diagram given below. Showing the direction of light after reflection from the mirro. (b) The mirror outside the driver side of a vehicle is usually a convex mirror. Printed on such a mirror is usually the warning Objects in the mirror are closer than they appear. What is the reason for this warning? What is the advantage of using it? 15- Explain the underlying principle and working of an electric generator with a suitable well labeled diagram. What is the function of brushes?
16 How does the resistance of a wire vary with its area of cross-section? 17 Name any two nuclear fuels used for the process of nuclear fission. 18 What were the limitations of Newland's law of octaves? 19 Describe an activity to show that the colors of white light splitted by a glass prism can be recombined to get white light by another identical glass prism. Also draw a ray diagram to show the recombination of the spectrum of white light. 20 Name the acid produced in our stomach. What happens if there is an excess of acid in the stomach? How can it be cured? Name one antacid. (a) Three acidic solutions A, B and C have ph=0, 3 and 5 respectively. (i) Which solution has the highest concentration of H+ ions? (ii) Which solution has the lowest concentration of 1-1+ ions? (b) How concentrated sulphuric acid can be diluted? Describe the process. 21 An element 'X' belongs to 3rd period and group 16 of the Modern Periodic Table (a) Determine the number of valence electrons and the valency of 'X'. (b) Molecular formula of the compound when 'X' reacts with hydrogen and write its electron dot structure. (c) Name the element 'X' and state whether it is metallic or non-metallic. 22 The image of an object formed by a mirror is real, inverted and is of magnification 1. (a) If the image is at a distance of 40 cm from the mirror, where is the object placed? (b) Where would the image be if the object is moved 20 cm towards the mirror? (c) State reason and also draw the ray diagram for the new position of the object to justify your answer. 23 The atomic number of Na and Mg is 11 and 12 respectively and they belong to the same period. (a) Which one would have smaller atomic size? (b) Which one would be more electropositive? (c) To which group would each one belong? 24 Far point of a myopic person is 40 cm. What type of lens should he wear so as to see the distant objects clearly? Calculate the focal length and the power of the lens he should use. 25- With the help of a suitable example, explain how ionic compounds are formed. State any three general properties of ionic compounds. 26- (a) Explain how does a cell maintain current in a circuit.
(b) In the circuit given below the resistance of the path xty = 2 0 and that xzy = 6 Q. (i) Find the equivalent resistance between ex and y. (ii) Find the current in the main circuit. (iii) Calculate the current that flows through the path xty and xzy. 27- (a) What do you understand by exothermic and endothermic reactions? Explain with one example each. (b) Translate the following statements into balanced chemical equations: (i) Sodium metal reacts with water to give sodium hydroxide and hydrogen gas. (ii) Ammonium chloride solution is added to barium hydroxide solution to give ammonium hydroxide and barium chloride. (c) When SO2 gas is passed through saturated solution of hydrogen sulphide, the following reaction occurs: SO 2 + 2H 2 S 2H 2 0 + 2S For this reaction, name the substance oxidized, reduced, the oxidizing agent and the reducing agent. 28- (a) What is the difference between direct current and alternating current? Write one important advantage of using alternating current. (b) An air conditioner of 2kW is used in an electric circuit having a fuse of 10A rating. If the potential difference of the supply is 220 V, will the fuse be able to withstand when the air conditioner is switched on? Justify your answer. (a) Draw a schematic labeled diagram of a domestic wiring circuit which includes. (i) a main fuse (ii) a power meter (iii) one light point and (iv) a power plug (b) Why is it necessary to connect an earth wire to electric appliances having metallic covers?
29 Define the term volt. 30 The following diagram displays a chemical reaction. Observe carefully and answer the following questions. 31- The following bulbs are rated 40 W, 60 W, and 100 W. Which one will glow the brightest when connected in series to a supply of 220 V? 32 A person suffering from an eye-defect uses lenses of power 1 D. Identify the eye defect. Draw a suitable to illustrate how this type of lens corrects the defect. Give the nature of corrective lens to be used. Also, calculate the focal length of corrective lens. With the help of a labeled diagram explain why sun appears reddish at the sunrise and the sunset? 33 How did Dobereiner classify the elements? Give one example. What were the limitations of his classifications? 34 (a) What happens to the lens and ciliary muscles when you are looking at nearby objects? (b) Name the component of the light that deviates the least and the one that deviates the most while passing through the prism. (c) Name two phenomenon involved in the formation of rainbow. 35 It Give three practical applications of neutralization reaction. 36 Write chemical name and formula of the following: (a) (b) (c) Salt formed by combination of weak acid like carbonic acid and strong base like sodium hydroxide. Basic substance formed by chloro-alkali process. A substance added in cakes to make them fluffy.
37 A metal 'E' is stored under kerosene oil. When a small piece of it is left open in the air, it catches fire. When the product formed is dissolved in water it turns red litmus blue. (a) Name the metal E. (b) Write the chemical equation for the reaction when it is exposed to air and when the product is dissolved in water. (c) Explain the process by which the metal is obtained from its molten chloride. 38. An organic compound A of molecular formula C 2 H 4 on reduction gives another compound B of molecular formula C 2 H 6. B on reduction with chlorine in the presence of sunlight gives C of molecular formula C 2 H 5 C1. (a) Name the compounds A, B and C. (c) Write the chemical equation for the conversions of A to B and B to C. Also name the type of reaction. A compound B (molecular formula, C 2 H 4 0 2 ) reacts with Na- metal to form a compound C and evolves a gas which burns with pop sound. Compound B on treatment with an alcohol A in the presence of a. mineral acid forms a sweet smelling compound D (molecular formula C 3 H 6 0 2 ). On addition of NaOH to B, it also gives C and water. D on treatment with NaOH gives back C and A. 39- (a) One half of a convex lens of focal length 10 cm is covered with a black paper. Can such a lens produce an image of a complete object placed at a distance of 30 cm from the lens? Draw a ray diagram to justify your answer. 40 What is the role of the two conducting stationary brushes in a simple electric motor? 41 Name the major fuel component of biogas. How can biogas be obtained? 42 State Snell's law of refraction. 43 State what happens when zinc granules are heated with sodium hydroxide. Write balanced equation and the name of main product formed. 44 In what way household appliances should be connected and why? 45 The far point of a myopic person is 80 cm in front of the eyes. What is the nature and power of the lens required to enable him to see very distant objects distinctly? List two causes leading to myopia of the eye. 46 Observe the diagram and answer the following questions: (a) Identify the gases evolved at anode and at cathode. (b) Why the amounts of gases collected does not have the same volume? (c) Name the type of reaction.
47 How does the strength of magnetic field at the centre of a circular coil of wire depend on: (a) the radius of the coil? (b) the number of turns of wire in the coil? (c) the strength of the current flowing in the coil? Enlist three properties of magnetic lines of force. 48 Explain how the following trends vary down the group and across a period (a) Electropositive character (b) Atomic size 49- Name a metal that (a) can be cut with knife. (b) is liquid at room temperature. (c) has 3 valence electrons. 50- What are fossil fuels? List any four methods to conserve them. 51- Give reasons for the following: (a) Carbon can reduce zinc oxide to zinc but not calcium oxide to calcium. (b) Copper and aluminium wires are usually used for electricity transmission. (c) Alloys are used in electrical heating devices rather than pure metals. (d) Gold ornaments look new even after several years of use. (e) An iron grill should be painted frequently. 52- (a) Write chemical equation of reactions of ethanoic acid with: (i) sodium (ii) sodium carbonate (iii) ethanol in presence of conc. H 2 SO 4. (b) State the role of concentrated H2504 in the esterification reaction. (c) State one use of ethanoic acid. (a) Soaps cannot be used in hard water, why? (b) Give the chemical composition of detergents. (c) Give one advantage of the detergent over soaps. (d) With the help of diagram, explain the cleansing action of soap. 53- (a) Name an instrument that measures electric current in a circuit. Define the unit of electric current. (b) What do the following symbols mean in the circuit diagrams? (d) An electric circuit consisting of a 0.5 m long.nichrome wire XY, an ammeter, a voltmeter, four cells of 1.5 V each and a plug key was set up.
(i) Draw a diagram of this electric circuit to study the relation between the potential difference maintained between the points X and Y and the electric current flowing through XY. (ii) Following graph was plotted between V and I values: What would be the values of V/I ratios when the potential difference is 0.8V, 1.2V and 1.6V respectively? What conclusion do you draw from these values? 54- Write reactions involved in extraction of metals. 55- Define rancidity and give solution for it.