Arihant Science Class 10 Term 1 Sample Paper

244 CBSE Sample Paper Science Class X (Term I) Answers 1. (c) 2. (b) 3. (c) 4. (d) 5. (d) 6. (a) 7. (c) 8. (d) 9. (c) 10. (b) 11. (d) 12. (b) 13. (a) 14. (c) 15. (a) 16. (c) 17. (b) 18. (a) 19. (c) 20. (d) 21. (b) 22. (c) 23. (c) 24. (a) 25. (b) 26. (c) 27. (b) 28. (d) 29. (a) 30. (b) 31. (a) 32. (d) 33. (a) 34. (b) 35. (d) 36. (b) 37. (a) 38. (b) 39. (c) 40. (d) 41. (c) 42. (c) 43. (a) 44. (d) 45. (a) 46. (b) 47. (a) 48. (d) 49. (a) 50. (d) 51. (c) 52. (b) 53. (b) 54. (a) 55. (d) 56. (c) 57. (b) 58. (b) 59. (a) 60. (d) EXPLANATIONS SAMPLE PAPER 10 1. When calcium oxide reacts with water, it forms oxidising agent. Hence, CaO is also an calcium hydroxide and release large amount of oxidising agent. heat which makes the solution hot. 7. The reaction between sodium and oxygen is CaO(s) + H2O(l) ¾® Ca(OH)2(aq) as follows The hissing sound was produced and solution 4Na(s) + O2(g) ¾® 2Na2O(g) becomes hot. It is a combination reaction and In this reaction, sodium and oxygen are exothermic in nature. combined to form a single product. Therefore, it is a combination reaction. 2. When dilute HCl is treated with sodium carbonate, then CO2 is released. Hence, gas A is 8. Sodium sulphate (Na2SO4) is formed by the CO2. reaction between sodium hydroxide (parent HCl + Na2CO3 ¾® NaCl + H2O + CO2 ­ base) and sulphuric acid (parent acid). The carbon dioxide produced turns the lime 2NaOH + H2SO4 ¾® Na2SO4 + 2H2O water quickly. (Parent base) (Parent acid) 3. Iron and zinc do not react either with cold or hot water. Potassium and sodium reacts 9. Zinc is more reactive than hydrogen, thus vigorously with water and form oxide and displace hydrogen from its solution to form evolve hydrogen gas. Hence, combination ZnSO4 and evolved hydrogen gas. 2 and 4 are correct. Zn + dil. H2SO4 ¾® ZnSO4 + H2 ­ The colourless and odourless gas is evovled 4. In (d) reaction, which is hydrogen and it burns with a pop Al2O3 + 6HCl ¾® 2 AlCl3 + 3H2O sound. The number of atom of all the elements are 10. As the ant sting contains formic acid and to equal in number on both sides of equation. neutralise this acid, base is rubbed like soap (sodium hydroxide) on affected area. 5. Acid and base reacts with each other to form salt and water. This process known as 11. When the left ventricle contracts, it forces neutralisation reaction. oxygenated blood into the aorta. Acid + Base ® Salt + Water The aorta carries the blood to all the body’s tissues. As we add base to an acid, the solution will become basic in nature where pH ranges above 12. X shows muscles of diaphragm and Y shows intercostal muscles. Contraction of these 7. So, D is the correct option. muscles helps in breathing. 6. CaO + 2 HCl ¾® CaCl2 + H2O 13. Gastric HCI provides an acidic medium which is essential for the action of gastric In this reaction, CaO is reduced to CaCl2 by enzymes. removal of oxygen atom. So, the substance that gets reduced in the reaction is called

CBSE Sample Paper Science Class X (Term I) 245 14. (iii) Ureter are the narrow tubes that carry 20. As the wavelength of yellow light is more than urine from the kidneys to the urinary bladder. green light. 1 (i) Renal artery – carries impure blood to Wavelength µ Deviation kidney. Þ The angle of refraction of yellow light (y) is (ii) Renal vein – carries pure blood out kidney. less than the angle of refraction of green light (g) i.e., y < g. (iv) Aorta – delivers oxygenated blood to the kidney. 21. As, speed of light µ 1 15. The hydrochloric acid creates an acidic refractive index medium which facilitates the action of the enzyme pepsin. \\ md > mk > mg Incorrect statements can be corrected as : Þ vd < vk < vg G The length of small intestine differs is various animals depending on the type of 22. The least deviated ray is of red colour and most food they eat. G The finger-like projections present in deviated ray is of violet colour of white light small intestine increases the surface area for absorption. spectrum. If we invert this prism, then the path G The end products of digestion of food are monosaccharides amino acids, fatty acids of light is shown and glycerol. Y 16. Pulmonary artery carries deoxygenated blood to the heart. White light X Pulmonary vein carries oxygenated blood from lungs to the heart. Prism Aorta carries oxygenated blood from the heart to the body parts. Vena cava dexygenated So, X corresponds to violet and Y corresponds to blood from the body parts to the heart. red. 17. In torches, search lights and head lights of 23. All colours of white light move with the same vehicles, the bulb is placed very near to the speed during propagation of light of different focus of the concave reflector so that the colours in air. reflected beam becomes a parallel beam of light through which we can see upto a longer 24. He should measure the distance between the distance. screen S and mirror i.e. MS. 18. After reflection, concave mirror converges As the image of a distant object is obtained at the parallel beam of light at its focus and the focus of concave mirror. focus of plane mirror is at infinity so, it focuses parallel beams at infinity. The image obtained at screen must be sharp and 19. The correct measurement of angle of then only focus of the mirror can be obtained incidence and angle of reflection through a glass slab is shown below, accurately. i 25. Mg + O2 ¾¾D ® MgO ¾¾® Mg(OH)2 e + H2 In this reaction, heat is required for the SSAAMMPPLLEEPPAAPPEERR110 completion of reaction. Hence, the reaction is endothermic in nature. No gas is evolved in this reaction. 26. Higher the pH value, less will be H+ ion concentration. The pH value is lowest at C, hence highest H+ ion concentration is present in C. 27. Reactivity series refers to the arrangement of metals in the descending or decreasing order of their reactivities. 28. The ionic compounds, usually soluble in water and they can conduct electricity. So, A and C have properties ionic of compound.

246 CBSE Sample Paper Science Class X (Term I) 29. Test tube A contains water which is neutral in 35. Caustic soda is sodium hydroxide (NaOH) nature. Whereas test tube B contains sodium with no water of crystallisation. hydroxide which is basic in nature. Calcium oxychloride is bleaching powder (CaOCl2) with no water of crystallisation. The litmus paper turns blue in basic medium (sodium hydroxide present in test tube B). Sodium hydrogen carbonate is baking soda Therefore, statement I is correct. (NaHCO3) with no water of crystallisation. Soda ash is washing soda (Na2CO3 ×10H2O) The litmus paper gives green colour in neutral with 10 molecules of water of crystallisation. solution (i.e. water present in test tube A). Hence, (ii) and (iv) are correct. Therefore, statement II is incorrect. 36. Stomata are responsible for gaseous exchange Phenolphthalein turns pink in basic medium in the plant. It is also responsible for removing (sodium hydroxide present in text tube B). extra water present in the plants. Therefore, statement III is correct. Phenolphthalein is colourless solution, on Therefore, if stomata get blocked, process of adding water it remains colourless and show transpiration, photosynthesis and respiration no change. will not occur. Hence, statement IV is incorrect. 37. The tongue helps us to taste the food, chew and swallow the food. It does not acid in 30. When equal volume of HCl and NaOH digestion of food. solutions of same concentration are mixed, then neutral salt and water are formed which 38. A kidney dialysis machine acts in a similar have pH = 7 and show green colour. way as a normal kidney by regulating the normal concentration of the blood. NaOH + HCl ¾® NaOH + H2O The urea and excess mineral salts in the body This is known as neutralisation reaction. diffuses from the patient’s blood across the selectively permeable walls of the tubules into 31. Both A and R are true and R is the correct the dialysis fluid. explanation of A. Mg burns in the presence of oxygen. 39. Let refractive index of 2nd media w.r.t 1, 2 Mg + O2 ¾® 2 MgO m2 This reaction is an example of oxidation m21 = m1 reaction. Mg gets oxidised into MgO therefore acts as reducing agent. Similarly, m31 = m3 m1 32. A is false, but R is true because AlCl3 is an acidic salt as it is a salt of strong acid (HCl) and \\ Refractive index of 3rd media w.r.t 2nd weak base (Al(OH)3 ). media 33. Both Assertion and Reason are true and Reason is the correct explanation of Assertion. m32 = m3 m2 The reaction in which energy is released is called as exothermic reaction. During = m31 ´ m1 = m31 respiration, some amount of energy is released, m21 ´ m1 m21 therefore, it is an exothermic reaction. SAMPLE PAPER 10 40. Given, f1 = - 50 cm, f2 = 10 cm 34. Both A and R true but R is not correct Total focal length, 1 = 1 + 1 explanation of A. The perpendicular distance f f1 f2 between the emergent ray and incident ray = 1 + 1 =2 when a light passes out of a glass slab is called -50 10 25 lateral displacement. \\ P = 1 = 2 = 0.08 D f 25 Lateral displacement is due to refraction of light. Since, focal length is positive, the lens will be In a thick glass slab, the perpendicular distance converging in nature. between emergent ray and incident ray increases, which in turn increases lateral displacement.

CBSE Sample Paper Science Class X (Term I) 247 41. Plants get rid of stored solid and liquid wastes 47. As medium 1 is optically rarer than medium by shedding of leaves, peeling of bark and 2, and the bending of light depends upon the falling of fruits. refractive index of medium. The three corresponding diagram are 42. The left ventricle has thicker wall than right representation of at different incidence ventricle because it has to pump the blood angles, refraction angle is different. And at a further around the body, and against certain incidence angle (q 2) the refracted higher pressure, compared with the right angle is 90° and this is the case of total ventricle. internal reflection. 43. For all angles of incidence on a glass prism, the 48. For making jewellery, the element should be ray bends towards the normal while malleable, ductile and lustrous. entering into the prism as refractive index is increased, and away from the normal while So, from the given table, element A is having emerging out of prism as refractive index is all these properties and can be used for decreased. making jewellery. 44. Given, v = - 30 cm, 49. The pH of substance Q is 12, i.e. highest among the other substances. It is basic in nature. hi = - 5 mm, ho = 10 mm \\ m = hi = - v Hence, can be used in antacids. Therefore I and II are correct. ho u 50. The substance S could be sodium bicarbonate Þ u = - ho ´ v having pH value around 8.5. It is used as hi baking soda and also used in fire extinguishers. It is basic in nature, therefore = -10 ´ - 30 = - 60 cm turns red litmus blue. -5 51. The pH value of P, Q and T are 6, 12 and 3 Using mirror formula, respectively. The acidic strength is inversely proportional to the pH value. 1+1= 1 uv f Lesser the value of pH, more acidic is the nature of the substance. Þ 1 + 1 =1 - 60 - 30 f pH value : T < P < Q Þ f = - 60 = - 20 cm Acidic strength : Q < P < T 3 Lesser the pH, more is the acidic strength. 45. Let u be the object distance from mirror. SSAAMMPPLLEEPPAAPPEERR110 Then, image distance is (u + 3). 52. Methyl yellow is not an indicator. As, magnification m = - v = hi 53. The part of the leaf which was originally u ho green (due to presence of chlorophyll) turns blue-black showing starch is present in this Þ - (u + 3) = -9 part. u3 54. The plant is kept in dark for three days to Þ u = 1.5 m destarch its leaves. u + 3 = 4.5 m = 450 cm 55. The boiling alcohol removes chlorophyll and turns green. 46. Length of mirror required to see full image = H 2 56. Before testing for starch, chlorophyll has to be removed from the leaf. \\ l= H 2 The presence of chlorophyll interferes with the starch test. the boiling alcohol removes Given, l = 58 cm chlorophyll. 58 cm = H Boiling in water will break the cell wall and 2 cell membrane making it more permeable to iodine solution. Þ H = 116 cm = 1.16 m

248 CBSE Sample Paper Science Class X (Term I) 57. When the source is changed to distant lamp, = -20 = 10 then the image will focussed at focus f 50 u because parallel beam is coming from distant source. Þ u = - 25 cm 58. The statements II and III are in correct they Focal length, 1 = 1 - 1 are corrected as when the screen moves, the f vu image will try to focus at f . = 1 - çèæ - 1 ø÷ö The parallel rays originating from a distant 10 25 object/source and incident on a convex lens may not be parallel to its principal = 1 + 1 =7 axis. 10 25 50 As the source changed to distant source, the Þ f = 50 cm = 7.14 cm image will become point sized. 7 59. Given, ho = 50 cm, hi = - 20 cm , v = - 10 cm 60. Convex lens can give virtual, real, diminished, As, magnification, m = hi = - v and magnified image. Image formation ho u depends on the position of object. Convex mirrors are used as rear view mirrors. SAMPLE PAPER 10