All questions
- Q.2 (B)(i) Complete the following food chain :Grass → ____ → ____ → ____ → Eagle → ____ Answer: Grass → Grasshopper → Frog → Snake → Eagle → Decomposers (bacteria and fungi) Grass is the producer; the grasshopper (primary consum... 1
- Q.2 (B)(ii) Distinguish between the following : Class Pisces and Class Reptiles Answer: Class PiscesClass Reptiles Aquatic (freshwater or marine).Mostly terrestrial; some live in water (crawling animals). Respiration by... 1
- Q.2 (B)(iii) Observe the following picture and write any two effects of this disaster :[Pictures: water gushing over an overflowing dam, and a flooded railway track with a halted local train and people walking through the water with umbrellas, i.e. a… Answer: The disaster is a flood. Two effects: transport and normal life are disrupted, and lives, property and crops are lost. Railway track... 1
- Q.2 (B)(iv) Write any four methods to reduce stress. Answer: Regular yoga, meditation and pranayama. Daily exercise or outdoor sports. Pursuing hobbies such as music, reading or gardening. Talk... 1
- Q.1 (A)(i) Alkaline earth metals have valency 2. This means that their position in the modern periodic table is in ..................... . Answer: A. Group 2 Answer: (A) Group 2 Alkaline earth metals (Be, Mg, Ca, ...) have 2 valence electrons, which they lose to show valency 2.... 1
- Q.1 (A)(ii) The reaction in which ions in the reactants are exchanged to form a precipitate is called as ........................ reaction. Answer: D. Double Displacement Answer: (D) Double Displacement In a double displacement reaction the ions of two reactants exchange places,... 1
- Q.1 (A)(iii) ......................... is used to make a solenoid type coil in an electric bulb. Answer: C. Tungsten Answer: (C) Tungsten Tungsten has a very high melting point (about 3422 °C), so its coiled filament can glow white-hot w... 1
- Q.1 (A)(iv) Light changes its direction when going from one transparent medium to another transparent medium. This process is called ......................... . Answer: D. Refraction Answer: (D) Refraction The change in the direction of light when it passes obliquely from one transparent medium to an... 1
- Q.1 (A)(v) \(\mathrm{CaO + H_2O \rightarrow Ca(OH)_2 + Heat}\) is an example of .................. reaction. Answer: A. Exothermic Answer: (A) Exothermic Heat is given out (it appears on the product side) when quicklime reacts with water, so the rea... 1
- Q.1 (B)(i) State whether true or false : A redox reaction takes place during cellular respiration. Answer: True In cellular respiration glucose is oxidised to CO₂ while oxygen is reduced to water, so oxidation and reduction take place toge... 1
- Q.1 (B)(ii) Find the odd one out : Loudspeaker, microphone, electric motor, magnet. Answer: Magnet Loudspeaker, microphone and electric motor are devices that work on the magnetic effect of electric current (electromagnetism... 1
- 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