All questions
- Q.1 (B)(iii) What is the reason for twinkling of stars ? Answer: Atmospheric refraction of starlight. Starlight passes through layers of air whose temperature and density, and so refractive index,... 1
- Q.1 (B)(iv) Match the columns :Column ‘A’Column ‘B’Simple microscope(a) used to observe minute objects(b) used to see distant objects(c) used for watch repair Answer: Simple microscope – (c) used for watch repair A simple microscope (a convex lens of short focal length) gives a magnified virtual im... 1
- Q.1 (B)(v) Name the behaviour of water between its temperature from 0ºC to 4ºC. Answer: Anomalous behaviour of water Between 0 °C and 4 °C water contracts on heating instead of expanding, so its density is maximum at 4 °... 1
- Q.2 (A)(i) Give scientific reasons : While going from left to right within a period, the size of atom decreases. Answer: Nuclear charge increases while electrons enter the same shell, so the outer electrons are pulled closer. Across a period the atomic... 1
- Q.2 (A)(ii) Give scientific reasons : For electric power transmission, copper or aluminium wire is used. Answer: Copper and aluminium have very low resistivity, so little electrical energy is lost as heat. Copper and aluminium are very good cond... 1
- Q.2 (A)(iii) Give scientific reasons : In some countries, ethanol is used as an additive to increase the efficiency of petrol. Answer: Ethanol is a clean fuel that burns completely and helps petrol burn more efficiently. Ethanol contains oxygen in its molecule, so a... 1
- Q.2 (B)(i) Name and state the principle used to measure the specific heat capacity of a substance. Answer: The principle of heat exchange. When a hot object and a cold object are kept in contact in an isolated system (no heat is lost to th... 1
- Q.2 (B)(ii) What is done to prevent rusting of iron door of your house ? Answer: The iron door is painted (or galvanised) so that air and moisture cannot reach the iron. Iron rusts when it is in contact with both... 1
- Q.2 (B)(iii) Distinguish between mass and weight. Answer: Mass is the amount of matter in a body; weight is the gravitational force with which the earth pulls it. MassWeight Amount of matter... 1
- Q.2 (B)(iv) The ‘rocket’ is a type of fire cracker used in Diwali.(a) Name the launcher.(b) Name the law on which its working is based. Answer: (a) A satellite launch vehicle (launcher) such as PSLV/GSLV works like it; (b) Newton’s third law of motion. (a) The Diwali rocket i... 1
- Q.2 (B)(v) What is meant by decomposition reaction ? Write the chemical reaction of decomposition of sugar on heating. Answer: A reaction in which one compound breaks into two or more simpler substances; mathrmC₁₂H₂₂O₁₁ xrightarrowΔ 12C + 11H₂O . In a decompo... 1
- Q.3 (i) An iron ball of mass 3 kg is released from a height of 125 m and falls freely to the ground. Assuming that the value of g is 10 m/s2, calculate :(a) Time taken by the ball to reach the ground.(b) Velocity of the ball on reaching the ground. Answer: (a) 5 s; (b) 50 m/s Free fall from rest: u = 0, s = h = 125 m, a = g = 10 m/s². (The mass does not affect free fall.) (a) s = ut + 1... 1
- Q.3 (ii) Write the name and symbol of the element from the description :(a) The most electronegative atom.(b) The atom having smallest atomic mass.(c) The noble gas with the smallest atomic radius. Answer: (a) Fluorine, F; (b) Hydrogen, H; (c) Helium, He (a) Fluorine (F) is the most electronegative element: it is small and has a strong... 1
- Q.3 (iii) (a) What happens when copper reacts with concentrated nitric acid ? What is the colour of the gas released during the reaction ?(b) Write its balanced chemical equation.(c) Write the names of reactants and products. Answer: Copper dissolves, forming copper nitrate, and reddish-brown nitrogen dioxide gas is given off. (a) Concentrated nitric acid is a str... 1
- Q.3 (v) Answer the following with respect to the ‘Formation of Rainbow’ :(a) Draw a neat diagram to show the formation of rainbow.(b) Name any two natural processes involved in formation of rainbow.(c) What does a small droplet of water act as ? Answer: (b) Dispersion and refraction (with internal reflection); (c) a small prism. (a) Diagram: draw a spherical water droplet. Sunlight (... 1
- Q.3 (vi) Name the following :(a) The two metals which can be cut with knife.(b) A sound is produced when certain metals are struck. Name this property of metals.(c) The non-metallic substance which is a good conductor of electricity. Answer: (a) Sodium and potassium; (b) Sonority; (c) Graphite (a) Sodium (Na) and potassium (K) are soft metals that can be cut with a knife.... 1
- Q.1 (A)(1) Out of the following which is a Pythagorean triplet ? Answer: B. (3, 4, 5) Answer: (B) (3, 4, 5) 3² + 4² = 9 + 16 = 25 = 5² . None of the other triplets satisfies (smaller) ² + (middle) ² = (lar... 1
- Q.1 (A)(2) ∠ACB is inscribed angle in a circle with centre O. If m∠ACB = 65º, then what is measure of its intercepted arc AXB ? Answer: D. 130º Answer: (D) 130º The measure of an inscribed angle is half the measure of its intercepted arc, so m(arc AXB) = 2 × 65º = 130... 1
- Q.1 (A)(3) Distance of point (3, 4) from the origin is .................... . Answer: C. 5 Answer: (C) 5 Distance from origin = √(x² + y²) = √(9 + 16) = √(25) = 5 . A distance can never be negative. 1
- Q.1 (A)(4) If radius of cone is 5 cm and its perpendicular height is 12 cm, then the slant height is ..................... . Answer: C. 13 cm Answer: (C) 13 cm l = √(r² + h²) = √(25 + 144) = √(169) = 13 cm. 1
- Q.1 (B)(1) In the following figure Δ ABC, B – D – C and BD = 7, BC = 20, then find \(\dfrac{A(\Delta ABD)}{A(\Delta ABC)}\).[Figure: Δ ABC with point D on side BC; segment AD drawn.] Answer: 7/20 Δ ABD and Δ ABC have the same height (the perpendicular from A to BC), so the ratio of their areas equals the ratio of their ba... 1
- Q.1 (B)(2) In the following figure ∠MNP = 90º, seg NQ ⊥ seg MP, MQ = 9, QP = 4, find NQ.[Figure: right-angled Δ MNP with the right angle at N; Q on hypotenuse MP with NQ ⊥ MP.] Answer: NQ = 6 By the theorem of geometric mean, NQ² = MQ × QP = 9 × 4 = 36 , so NQ = 6. 1
- Q.1 (B)(3) Angle made by a line with the positive direction of X-axis is 30º. Find slope of that line. Answer: Slope = 1/sqrt3 Slope m = tanθ = tan 30^° = 1/√(3) . 1
- Q.1 (B)(4) In cyclic quadrilateral ABCD m∠A = 100º, then find m∠C. Answer: m∠C = 80º Opposite angles of a cyclic quadrilateral are supplementary: m∠C = 180º – 100º = 80º. 1