NBSE Question Papers Science for Class 10

Class 10  Code No. 086/10/1 Series NBSE/X/2023 Roll No.  Candidates must write the Code No. on the title page of the Answer sheet. l Please check that this question paper contains 8 printed pages. l Code number given on the right hand side of the question paper should be written on the title page of the Answer sheet. l Please check that this question paper contains 42 questions. l 15 minutes time has been allotted to read this question paper. SCIENCE Time Allowed : 3 Hours Maximum Marks : 80 General Instruction: (i) Question Number 1 to 10 are Multiple Choice Questions carry 1 mark each. (ii) Question Number 11 to 20 are Assertion-Reason Type Questions carry 1 mark each. (iii) Question Number 21 to 26 are Very Short Answer Type Questions carry 1 mark each. (iv) Question Number 27 to 31 are Short Answer Type Questions-I carry 2 mark each. (v) Question Number 32 to 35 are Short Answer Type Questions-II carry 3 mark each. (vi) Question Number 36 to 39 are Long Answer Type Questions carry 5 mark each. (vii) Question Number 40 to 42 are Case Based Questions carry 4 mark each. (viii) There is no overall choice. However, internal choices have been provided. NBSE 2023 1 P.T.O.

Section A 1. What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer. 1 (a) Hydrogen gas and iron chloride are produced. (b) Chlorine gas and iron hydroxide are produced. (c) No reaction takes place. (d) Iron salt and water are produced. 2. Select from the following the statement which is true for bases. 1 (a) Bases are bitter and turn blue litmus red. (b) Bases have a pH less than 7. (c) Bases are sour and change red litmus to blue. (d) Bases turn pink when a drop of phenolphthalein is added to them. OR 50.0 mL of tap water was taken in a beaker. Hydrochloric acid was added drop by drop to water. The temperature and pH of the solution was noted. The following graph was obtained. Choose the correct statements related to this activity. 7.00 6.00 pH of Solution 5.00 4.00 3.00 2.00 1.00 0 10.0 20.0 30.0 40.0 50.0 Volume of HCl added (mL) (I) The process of dissolving an acid in water is highly endothermic. (II) The pH of the solution increases rapidly on addition of acid. (III) The pH of the solution decreases rapidly on addition of acid. (IV) The pH of tap water was around 7.0. (a) (I) and (II) (b) (I) and (III) (c) (III) and (IV) (d) (II) and (IV) 3. Which of the following are correct about ionic compounds/ 1 (I) Sharing of electrons (II) Conduct electricity in solid state (III) Soluble in water (IV) High melting point (a) (I) and (II) (b) (III) and (IV) (c) (I) and (III) (d) (II) and (IV) 4. Which of the following is not a straight chain hydrocarbon? 1 (a) H3C—CH2 —CH2 —CH2 — C|H2 (b) H3CCH2CH2CH2CH2CH3 CH3 (c) |CH3 H2C—H2C— C|H2 (d) CH3 \\ CH—CH2 —CH2 —CH3 H2 C— CH3 CH3 / 5. Which of the following statements are correct in reference to the role of A (shown in the given diagram) during a breathing cycle in human beings? 1 (I) It helps to decrease the residual volume of air in lungs. (II) It flattens as we inhale. (III) It gets raised as we inhale. (IV) It helps the chest cavity to become larger. (a) (II) and (IV) (b) (III) and (IV) (c) (I) and (II) (d) (I), (II) and (IV) OR The length of small intestine in a deer is more as compared to the length of small intestine of a tiger. The reason for this is (a) Mode of intake of food. (b) Type of food consumed. (c) Presence or absence of villi in intestines. (d) Presence or absence of digestive enzymes. NBSE 2023 2

6. The reproduction is essential for population of a species 1 (a) to decrease its number (b) to increase its number (c) for its survival (d) to become extinct 7. When two parents are crossed, the offsprings are referred to 1 (a) F1 generation (b) F2 generation (c) Either F1 or F2 (d) None of these 8. A student wants to obtain magnified image of an object AB as on a screen. Which one of the following arrangements shows the correct position of AB for him/her to be successful? 1 (a) M (b) M C A A B O B F1 O 2F1 F1 2F1 C1 N N M (d) M (c) A C A B O B O 2F1 F1 2F1 F1 C1 NN 9. If a lens can converge the sun rays at a point 20 cm. away from its optical centre, the power of this lens is 1 (a) +2D (b) –2D (c) +5D (d) –5D OR A convex mirror used for the rear view on an automobile has a focal length of 2.5 m. A car is located at a distance of 4 m from the mirror. In the above scenario the sign that should be assigned to f and u is (a) u positive, f negative (b) f positive, u negative (c) f and u are positive (d) f and u negative 10. Two conducting wires of the same material and of equal lengths and equal diameter are first connected in series and then in parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be 1 (a) 1:2 (b) 2:1 (c) 1:4 (d) 4:1 OR A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is RR′, then the ratio R/RR′ is (a) 1/25 (b) 1/5 (c) 5 (d) 25 1 Assertion-Reason Type Questions For question numbers 11 to 20 two statements are given-one labeled as 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 ahead: (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 correct explanation of the Assertion. (c) ‘A’ is true but ‘R’ is false. (d) ‘A’ is false but ‘R’ is true. 11. Assertion: The reaction, MnO2 + 4HCl → MnCl2 + 2H2O + Cl2 is an example of redox reaction. 1 Reason: In this reaction, HCl is reduced to Cl2 whereas MnO2 is oxidized to MnCl2. 1 12. Assertion: Plaster of Paris is used by doctors by setting fractured bones. Reason: When Plaster of Paris is mixed with water and applied around the fractured limbs, it sets into a hard mass. 13. Assertion: Different metals have different reactivities with water and dilute acids. 1 Reason: According to the reactivity of metals, they are positioned in the reactivity series. 14. Assertion: Carbon forms covalent compound with chlorine of formula CCl4. 1 Reason: Carbon has 4 valence electrons, valency 4, chlorine has 7 valence electrons, valency 1. OR Assertion: The element carbon forms the basic structural framework of more compounds than any other element. NBSE 2023 3 P.T.O.

Reason: The carbon-carbon bond is ionic. 15. Assertion: Pollination is different from fertilisation. 1 Reason: The process of transfer of pollens from anther to stigma is called pollination which takes place in plants. 16. Assertion: A 200 W bulb glows with more brightness than 100 W bulb. 1 Reason: 100 W bulb has more resistance than 200 W bulb. OR Assertion: When two resistances of 4W are connected in series, total resistance is 8W. Reason: When two resistances of 4W are connected in parallel total resistance is 2W. 17. Assertion: A geneticist crossed a pea plant having violet flowers with a pea plant with white flowers, he got all violet flowers in first generation. 1 Reason: White colour gene is not passed on to next generation. 1 18. Assertion: Photosynthesis is an anabolic process. Reason: The process of photosynthesis occurs in chlorophyll. 1 19. Assertion: The sky appears dark to people flying at high altitudes. Reason: The atmosphere is denser close to the earth. OR Assertion: A rainbow always appears on the same side as the sun. Reason: A rainbow is a natural spectrum which occurs after a shower. 20. Assertion: A compass needle gets defected when electric current is passed through the nearly metallic wire. Reason: The S.I unit of magnetic field strength is Oersted. 1 Section B 21. Write the chemical name and chemical formula of the salt used to remove permanent hardness of water. 1 22. The image formed by a concave mirror is observed to be real, inverted and larger than the object. Where is the object placed? 1 OR Name the part of a lens through which a ray of light passes without suffering any deviation. 23. How is the wall of small intestine adapted for performing the function of absorption of food? 1 OR Out of a goat and a tiger, which one will have a longer small intestine? Justify your answer. 24. Draw the magnetic field lines around a straight current carrying conductor. 1 25. How many male gametes are produced by pollen grains? 1 26. What is the speed of blue light travelling in vacuum? 1 27. Bile juice does not have any digestive enzyme but still plays a significant role in the process of digestion. Justify the statement. 2 OR In birds and mammals the left and right side of the heart are separated. Give reasons. 28. An object is placed at a distance of 15 cm from a concave lens of focal length 30 cm. List four characteristics (nature, position, etc.) of the image formed by the lens. 2 29. Write chemical equation for the reaction when (ii) Zinc is added to iron(ii) sulphate solution. 2 (i) Steam acts on red hot iron. OR State two reasons for the following facts: (i) Sulphur is a non-metal. (ii) Magnesium is a metal. One of the reason must be supported with a chemical equation. 30. You have three test tubes. One of them contains distilled water and the other two contains an acidic and a basic solution, respectively. If you are given only red litmus paper; how will you identify the contents of each test tube? 2 31. (i) What will be the amount of energy available to the organisms of secondary consumer trophic level of food chain, if the energy available to producer level is 10000 Joules. 2 OR (ii) Name any two items which can be easily recycled but are generally thrown in the dust-bin by us. NBSE 2023 4

32. Foetus derives its nutrition from the mother. (i) Identify the tissue used for above purpose. Explain its structure. (ii) Explain how wastes generated by developing embryo are removed. (iii) How does the birth of child take place? 3 33. (i) WShhoywatrheeiofonrimc caotmiopnooufnNdas2uOsubayltlyrahnasrfder? of electrons between the combining atoms. (ii) (iii) How is it that ionic compounds in the solid state do not conduct electricity, but they do so when in molten state? 3 OR (i) Which product is formed in the chemical reaction between a small strip of magnesium and nitric acid? (ii) What happens when a pellet of sodium is dropped in water? (iii) Identify the ‘X’ in the given reaction: P4(s) + 5O2(g) → X 34. Leaves of healthy potted plants were coated with vaseline to block the stomata. Will this plant remain healthy for long? State 3 reasons for your answer. 3 35. Give reason to justify the following: (i) The existence of decomposers is essential in a biosphere. (ii) Flow of energy in a food chain is unidirectional. 3 36. (i) What is the law of dominance of traits? Explain with an example. (ii) Why are the traits acquired during the life time of an individual not inherited? Explain. 5 37. (i) Name an instrument that measures electric current in a circuit. Define the unit of electric current. (ii) What do the following symbols mean in circuit diagram? (a) - (b) (iii) An electric circuit consisting of a 0.5 m long nichrome wire, an ammeter, a voltmeter, four cells of 1.5 V each and a plug key was set up. (a) Draw a diagram of the electric circuit to study the relation between the potential difference maintained between the points ‘X’ and ‘Y’ and the electric current flowing through XY. (b) Following graph was plotted between V and I values: Potential 1.6 Difference (V) 1.5 1.0 0.5 0 0.2 0.4 0.6 Current (I) What would be the values of V ratios when the potential difference is 0.8 V, 1.2 V and 1.6 V respectively? I What conclusion do you draw from these values? 5 38. (i) A thin converging lens forms a (a) Real magnified image. (b) Virtual magnified image of an object place in front of it. Write the positions of the object in each case. (ii) Draw a labelled ray diagram to show the image formation in each case. (iii) How will the following be affected on cutting this lens into two halves along the principal axis? (a) Focal length, (b) Intensity of image formed by half lens. 5 OR Analyse the following observation table showing variation of image distance (v) with object distance (u) in case of a convex lens and answer the questions that follow, without doing any calculations: S.No. Object distance u (cm) Image distance v (cm) 1 – 90 + 18 NBSE 2023 5 P.T.O.

2 – 60 + 20 3 – 30 + 30 4 – 20 + 60 5 – 18 + 90 6 – 10 + 100 (i) What is the focal length of the convex lens? Give reason in support of your answer. (ii) Write the serial number of that observation which is not correct. How did you arrive at this conclusion? (iii) Take an appropriate scale to draw ray diagram for the observation at S. No. 4 and find the approximate value of magnification. 39. You are given balls and stick model of six carbon atoms and fourteen hydrogen atoms and sufficient number of sticks. In how many ways one can join the models of six carbon atoms and fourteen hydrogen atoms to form 5 different molecules of C6H14. 40. Case Study-1: The following graph shows the volume of hydrogen collected in four different experiments when dil. hydrochloric acid was reacted with zinc, copper, magnesium and iron metal. 4 Volume of hydrogen Graph 1 Resistance (in W) Graph 2 Graph 3 Graph 4 0 Time (i) Name the graph that produces hydrogen gas faster. (a) Graph 1 (b) Graph 2 (c) Graph 3 (d) Graph 4 (ii) Name the metal used in experiment that gave the result for graph-4. (a) Mg (b) Zn (c) Fe (d) Cu (iii) What are the ways to speed up the slow reaction in the above experiments? OR What will happen if dil. HCl is replaced by dil. HNO3? Do you observe such graph for all these elements? 41. Case Study-2: Electrical resistivity and its inverse, electrical conductivity are fundamental properties of a material that quantifies how strongly it resists or conducts electric current. A low resistivity indicates a material that readily allows electric current to flow. Resistance is defined as the ratio of potential difference across a conductor to the current passing through it. Resistance is the property of a conductor to resist the flow of charges through it. Both resistance and resistivity describe how difficult it is to make electrical current flow through a material, but unlike resistance, resistivity is an intrinsic property. This means that all pure copper wires irrespective of their shape and size, have the same resistivity, but a long, thin copper wire has a much Cross section (in mm2) larger resistance than a thick, short copper wire. Every material has its own characteristic resistivity. For example, rubber has a far larger resistivity than copper. Resistivity of metals also varies with temperature. The resistance of almost all alloys increases with increase in temperature but the rate of change of resistance is less than that of metals. In fact, the resistance of certain alloys such as Manganin, Eureka and Constantan show practically no change in resistance to a considerable range of temperature. 4 (i) What happens to the resistivity of a wire if it is stretched? (a) It will increase (b) It will decrease (c) First increases then decreases (d) Remains the same (ii) If there are twwiorewwiriells,hWav1eamndorWe 2roefsissatmanecme?aterial and same length but have radius r and 2r respectively, then which (a) Wire W1 has more resistance as compare to W2 NBSE 2023 6

(b) Wire W2 has more resistance as compare to W1 (c) Both the wires have same resistance (d) Wire W2 has three times resistance than wire W1 (iii) Though silver is a good conductor, why it is not an ideal choice for transmission of electricity? State two reasons. OR The area of cross section of a wire becomes half when its length is stretched to double. How the resistance of the wire is affected in the new condition? 42. Case Study-3: More than a million Americans die of cardiac diseases each year. One of the major causes is high cholesterol levels in the blood. The National Cholesterol Education Program suggests that total blood cholesterol level should be:4 Blood Cholesterol Level Chart Desirable Borderline (high) High Risk Total Cholesterol < 200 200-240 > 240 Triglycerides < 150 150-500 > 500 Low Density Cholesterol < 130 130-160 >160 High Density Cholesterol > 50 50-35 < 35 Given below are blood report of two persons Total Cholesterol Triglycerides Low density cholesterol Patient A 356 180 150 Patient B 180 100 90 (i) Which of the organ can be affected in patient A? (a) Heart (b) Kidney (c) Lungs (d) Brain (ii) A person with high risk category have to be suggested a suitable diet? Which of the following are correct guidelines for the patient? (a) High sugar and starch (b) Low salt and fats (c) High proteins (d) Low sugar and proteins (iii) State some changes in lifestyle to avoid aggravation of symptoms in a patient of high blood cholestrol. OR Analyse the blood report of two persons A & B. NBSE 2023 7 P.T.O.

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