Science and Technology: Model Question Sets and Predicted Questions

Group A. 1. newton (N). 2. nucleus. 3. rat. 4. False — most plastics are non-biodegradable. 5. oxygen. 6. RAM. 7. 9.8 m/s² (often taken as 10 m/s²). 8. 16. 9. mantle. 10. ammeter.

Group B. 11. Mass is matter in kilograms, constant everywhere; weight is the earth's pull in newtons, varying with g. 12. A muscle cell uses much more energy, and the energy is released in the mitochondria, so it needs more of them. 13. a = F/m = 24/8 = 3 m/s². 14. An element has one kind of atom and cannot be split chemically; a compound has two or more elements chemically combined in a fixed ratio, with new properties. 15. The circuit already contains free electrons throughout the wire; when the switch closes, all of them begin to drift almost at once, so the filament heats immediately. 16. Lahare banmara (Mikania) and water hyacinth (jalkumbhi); they smother native plants and reduce the food available to wild animals. 17. Lifting and sorting scrap iron with a crane; electric bells, relays, loudspeakers and motors. 18. 72\times\frac{1000}{3600} = 20 m/s. 19. Its gravity is too weak (about one-sixth of the earth's) to hold gas molecules, so they escape into space. 20. Earth the metal body of appliances and use the correct fuse; never touch a switch with wet hands, and switch off at the main before repairing anything.

Group C. 21. Any four of: cell wall — gives shape and protection; cell membrane — controls what enters and leaves; nucleus — controls activity and carries hereditary material; chloroplast — carries out photosynthesis; vacuole — stores water and keeps the cell turgid; mitochondrion — releases energy. Diagram must show the wall outside the membrane and a single large vacuole. 22. Respiration is the oxidation of food in cells to release energy. Aerobic: needs oxygen, releases much energy, products carbon dioxide and water. Anaerobic: no oxygen, releases little energy, products ethanol and carbon dioxide in yeast or lactic acid in muscle. 23. Bulbs = 0.2 kW × 6 h = 1.2 kWh; heater = 1.5 kW × 1 h = 1.5 kWh; daily = 2.7 units; monthly = 81 units; bill = 81\times11 = Rs 891. 24. Causes: habitat destruction by clearing forest and settlement; poaching and illegal trade; pollution of rivers and soil; invasive species; unplanned infrastructure and climate change. Measures (any two, explained): protected areas with community management and anti-poaching patrols; community forestry and plantation of native species; awareness and alternative livelihoods such as homestay tourism. 25. First law — a body keeps its state unless a net force acts: a passenger lurches forward when a bus brakes. Second law — F = ma: the same push gives a lighter trolley more acceleration. Third law — action and reaction are equal and opposite: a boat moves backward as the swimmer pushes off it.

Group A. 1. methane. 2. R. H. Whittaker. 3. ohm (Ω). 4. stomata. 5. False — weight is measured in newtons. 6. Jupiter. 7. the arithmetic and logic unit. 8. 7. 9. sublimation. 10. white blood cells.

Group B. 11. In series there is one path, the current is the same everywhere and resistances add; in parallel there are several paths, the voltage is the same across each and the total resistance is less than the smallest. 12. It creates the transpiration pull that draws water and dissolved minerals from the root to the leaf, and it cools the leaf by evaporation. 13. \frac{240}{80} = 3 g/cm³. 14. Conduction needs a material medium and passes heat from particle to particle without the particles moving away, and is fastest in metals; radiation needs no medium at all and travels as waves, as sunlight does through space. 15. Its layers slide over one another easily, so it leaves a mark on paper and feels slippery; conduction does not prevent that use. 16. Dry or salt the food, or make it into pickle; keep it covered in a cool, airy place, boil milk, and store grain in airtight containers. 17. V = IR = 0.5\times12 = 6 V. 18. A tall tree is the highest point nearby, so the lightning stroke is likely to pass through it and through anyone standing under it; open low ground or a building is safer. 19. A star makes its own light and heat by nuclear reactions and twinkles; a planet does not make light, shines by reflecting it and does not twinkle. 20. It uses dung and kitchen waste and leaves a good slurry manure; it saves firewood and the time spent collecting it, and it gives a smokeless flame, so there is less indoor air pollution and less eye and lung disease.

Group C. 21. Photosynthesis is the process in which a green plant makes glucose from carbon dioxide and water using light energy trapped by chlorophyll. Equation: carbon dioxide + water → glucose + oxygen (in sunlight, with chlorophyll). Conditions: sunlight and chlorophyll. Factors: light intensity and carbon dioxide concentration (also temperature and water supply). 22. (i) Painting or oiling — keeps air and moisture off the surface. (ii) Galvanising — the zinc layer corrodes in place of the iron and protects it even if scratched. (iii) Alloying as stainless steel — chromium forms a tight oxide film that does not flake. (iv) Electroplating with tin or chromium — gives a non-reacting coat, as in food cans; keeping the metal dry and well ventilated also helps. 23. An atom has a central nucleus containing protons (positive) and neutrons (neutral), with electrons (negative) revolving round it in shells; the atom is neutral because protons and electrons are equal in number, and almost all the mass is in the nucleus. For atomic number 20 and mass number 40: protons 20, electrons 20, neutrons 40-20 = 20. 24. Nepal lies where the Indian plate pushes under the Eurasian plate, so strain builds along the fault and is released as earthquakes; weak masonry and unplanned building make the damage worse. School precautions: hold regular drop-cover-hold drills and keep exits and corridors clear; fix cupboards, shelves and water tanks to the wall; keep a first-aid kit, torch and whistle and an open assembly ground identified; and have the building assessed and retrofitted. 25. An ecosystem is a unit in which living beings interact with one another and with their non-living surroundings. Biotic components: producers (green plants), consumers (herbivores, carnivores, omnivores) and decomposers (bacteria, fungi). Abiotic components: sunlight, air, water, soil, temperature. In the chain grass → goat → human, the grass traps sunlight; the goat gets energy by eating grass; the human by eating the goat's products. Energy flows one way and about 90 % is lost as heat at each step, so the number of links is small and the producers must always outweigh the consumers.

Group A. 1. the unit, i.e. the kilowatt-hour (kWh). 2. Fungi. 3. liver. 4. False. 5. F = ma. 6. fuse (or circuit breaker). 7. Mercury. 8. three — kilogram, metre, second. 9. elastic potential energy. 10. the cell wall.

Group B. 11. A hypothesis is a testable guess not yet confirmed; a theory is an explanation already supported by a large body of evidence. 12. Its length and the folds with villi give a very large surface, so digested food is absorbed quickly and completely. 13. W = mg = 60\times1.6 = 96 N. 14. Metals are lustrous, malleable, ductile and good conductors; non-metals are mostly dull, brittle in the solid state and poor conductors (graphite excepted). 15. Nichrome has high resistivity, so it gets very hot for the current passed, and it does not oxidise quickly at red heat; copper has low resistance and would oxidise and melt its joints. 16. Online classes and recorded lessons reach where teachers are few; e-library material, dictionaries and examination resources become available, and results, notices and teacher training can be delivered online. 17. Only about 10 % of the energy passes from one level to the next, the rest being lost mainly as heat; so after three or four steps very little remains, which also limits the number of top carnivores. 18. The earth is much larger than the moon, so its shadow is wide and the moon takes a long time to cross it; the moon's shadow on the earth is small and sweeps past quickly. 19. In a physical change no new substance forms and the change is usually reversible (ice melting); in a chemical change a new substance with new properties forms and the change is usually not reversible (iron rusting). 20. Less transpiration and infiltration, so springs dry up and the water table falls; and rain runs off bare slopes at once, causing floods below and landslides on the slope.

Group C. 21. Classification is the arrangement of living beings into groups on the basis of similarities and differences. Monera — prokaryotic, unicellular, no true nucleus; bacteria. Protista — unicellular eukaryotes, mostly aquatic; Amoeba. Fungi — eukaryotic, cell wall of chitin, saprophytic or parasitic; mushroom. Plantae — multicellular, cellulose cell wall, autotrophic; fern. Animalia — multicellular, no cell wall, heterotrophic, mostly able to move; frog. 22. Speed is distance per unit time, a scalar; velocity is displacement per unit time, a vector; acceleration is the rate of change of velocity. a = \frac{30-0}{60} = 0.5 m/s². Distance = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}\times0.5\times60^2 = 900 m. 23. (i) Filtration — insoluble solid from liquid, sand from water. (ii) Evaporation — dissolved solid from solution, salt from sea water. (iii) Magnetic separation — magnetic from non-magnetic, iron filings from sawdust. (iv) Sublimation — a subliming solid from a non-subliming one, camphor from sand; (distillation separates liquids of different boiling points, and a separating funnel separates immiscible liquids such as kerosene and water). 24. Renewable sources are those replaced by nature as fast as they are used. Hydropower — large potential, about 42,000 MW feasible, but needs heavy capital and most plants are run-of-river, so output falls in the dry season. Solar — abundant sunshine and good for scattered hill settlements, but gives no power at night and needs costly batteries. Biogas — turns dung and waste into clean fuel and manure, but needs enough cattle and warm temperatures, so it works poorly in cold high hills. 25. The earth has three main layers: the crust, a thin rocky shell; the mantle, hot semi-solid rock whose slow movement drives the plates; and the core, mainly iron and nickel, with a liquid outer and a solid inner part. Rotation, once in about 24 hours about its tilted axis, gives day and night, the apparent daily motion of the sun and stars, and the deflection of winds. Revolution, once in about 365¼ days, together with the 23.5° tilt, gives the seasons, the changing length of day and night, and the leap year every fourth year.