10
JKBOSE Class 10 Science Guess Paper
2026 Winter Zone • 2027 Summer Zone
Easy English • Deep Answers • Blue-Pen Notebook Style
Physics + Chemistry + Biology
Important note: This is a practice guess paper prepared from the commonly reported JKBOSE Class 10 Science 2026–27 chapter structure. It is not an official question paper and no question is guaranteed. Always match your final preparation with the latest JKBOSE notice and school instructions.
Paper Pattern & Syllabus Map
Reported theory structure: Physics, Chemistry and Biology are assessed in one Science paper. The commonly reported distribution is Physics 26 marks, Chemistry 26 marks and Biology 28 marks, with internal assessment separately. Check the official board notice for any final change.
| Section | Main Units | Reported Weight |
|---|---|---|
| Physics | Light; Human Eye; Electricity; Magnetic Effects | 26 |
| Chemistry | Reactions; Carbon; Metals; Acids, Bases & Salts | 26 |
| Biology | Life Processes; Control; Reproduction; Heredity; Environment | 28 |
Quick Roadmap
1. 50 MCQs with Answers2. 40 Very Short Answers3. 30 Short Answers4. 20 Long Answers5. Physics Derivations6. Blue-Pen Diagrams7. Final Revision Checklist
Section A — 50 MCQs with Answers
Exam tip: Read all four options first. Circle the key word in the question, then choose the most accurate option.
Q1. The SI unit of electric current is
A. Volt B. Ampere C. Ohm D. Watt
Correct answer: B — Ampere. Current is measured in ampere (A).
Q2. The mirror used as a rear-view mirror in vehicles is generally
A. Plane B. Concave C. Convex D. Cylindrical
Correct answer: C — Convex. A convex mirror gives a wider field of view.
Q3. The power of a lens is measured in
A. Metre B. Dioptre C. Newton D. Joule
Correct answer: B — Dioptre. Power is measured in dioptre (D).
Q4. The focal length of a plane mirror is
A. Zero B. One metre C. Infinite D. Negative
Correct answer: C — Infinite. A plane mirror has infinite radius and focal length.
Q5. A device used to measure current is
A. Voltmeter B. Ammeter C. Galvanometer only D. Potentiometer
Correct answer: B — Ammeter. An ammeter is connected in series.
Q6. Ohm’s law is represented by
A. V=IR B. P=VI² C. R=VI D. I=VR
Correct answer: A — V=IR. At constant temperature, V is directly proportional to I.
Q7. The resistance of a wire increases when its
A. Length decreases B. Area increases C. Length increases D. Temperature is always zero
Correct answer: C — Length increases. Resistance is directly proportional to length.
Q8. The magnetic field around a straight current-carrying conductor is
A. Circular B. Rectangular C. Absent D. Always uniform
Correct answer: A — Circular. Field lines form concentric circles.
Q9. The split ring in a DC motor is called
A. Brush B. Commutator C. Fuse D. Armature
Correct answer: B — Commutator. The commutator reverses current direction every half turn.
Q10. The sky appears blue mainly due to
A. Reflection B. Dispersion only C. Scattering D. Total internal reflection
Correct answer: C — Scattering. Shorter blue wavelengths scatter more strongly.
Q11. The image formed by a plane mirror is
A. Real and inverted B. Virtual and erect C. Real and erect D. Always enlarged
Correct answer: B — Virtual and erect. It is virtual, erect and same-sized.
Q12. The refractive index of a medium is
A. v/c B. c/v C. cv D. c+v
Correct answer: B — c/v. For a medium, n=c/v.
Q13. The chemical formula of baking soda is
A. NaCl B. Na₂CO₃ C. NaHCO₃ D. CaSO₄
Correct answer: C — NaHCO₃. Baking soda is sodium hydrogen carbonate.
Q14. A reaction in which heat is released is
A. Endothermic B. Exothermic C. Neutral only D. Photochemical only
Correct answer: B — Exothermic. Exothermic reactions release heat.
Q15. The pH of a neutral solution at room temperature is approximately
A. 0 B. 7 C. 14 D. 1
Correct answer: B — 7. Neutral water has pH about 7.
Q16. Rusting of iron requires
A. Only nitrogen B. Oxygen and moisture C. Only carbon dioxide D. Only sunlight
Correct answer: B — Oxygen and moisture. Both oxygen and water are needed.
Q17. The functional group of alcohol is
A. –COOH B. –CHO C. –OH D. –CO–
Correct answer: C — –OH. Alcohols contain the hydroxyl group.
Q18. The process of coating iron with zinc is
A. Alloying B. Galvanisation C. Distillation D. Crystallisation
Correct answer: B — Galvanisation. Zinc protects iron from corrosion.
Q19. Acids turn blue litmus
A. Blue B. Red C. Green D. Yellow
Correct answer: B — Red. Acids turn blue litmus red.
Q20. The gas released when an acid reacts with a metal carbonate is
A. O₂ B. H₂ C. CO₂ D. N₂
Correct answer: C — CO₂. Carbon dioxide is released.
Q21. The basic structural and functional unit of life is
A. Tissue B. Organ C. Cell D. Organ system
Correct answer: C — Cell. All organisms are made of cells.
Q22. Photosynthesis takes place mainly in
A. Mitochondria B. Chloroplasts C. Nucleus D. Ribosomes
Correct answer: B — Chloroplasts. Chlorophyll is present in chloroplasts.
Q23. The enzyme present in saliva is
A. Pepsin B. Trypsin C. Amylase D. Lipase only
Correct answer: C — Amylase. Salivary amylase begins starch digestion.
Q24. The functional unit of kidney is
A. Neuron B. Nephron C. Alveolus D. Villus
Correct answer: B — Nephron. A nephron filters blood and forms urine.
Q25. The hormone that controls blood sugar is
A. Insulin B. Adrenaline C. Thyroxine D. Oestrogen
Correct answer: A — Insulin. Insulin lowers blood glucose.
Q26. Reflex actions are mainly controlled by
A. Spinal cord B. Stomach C. Kidney D. Pancreas
Correct answer: A — Spinal cord. The spinal cord coordinates many reflexes.
Q27. The male reproductive part of a flower is
A. Pistil B. Stamen C. Sepal D. Petal
Correct answer: B — Stamen. Stamen consists of anther and filament.
Q28. The transfer of pollen from anther to stigma is
A. Fertilisation B. Pollination C. Germination D. Budding
Correct answer: B — Pollination. Pollination precedes fertilisation.
Q29. The genetic material in most organisms is
A. Protein B. DNA C. Starch D. Fat
Correct answer: B — DNA. DNA stores hereditary information.
Q30. A trait that appears in F1 generation in Mendel’s experiment is generally
A. Recessive B. Dominant C. Acquired D. Temporary
Correct answer: B — Dominant. The dominant trait is expressed in F1.
Q31. The ozone layer protects Earth from
A. Infrared rays B. Ultraviolet rays C. Radio waves D. Sound waves
Correct answer: B — Ultraviolet rays. Ozone absorbs much harmful UV radiation.
Q32. Organisms that make their own food are
A. Consumers B. Decomposers C. Producers D. Parasites only
Correct answer: C — Producers. Green plants are producers.
Q33. The ultimate source of energy for most ecosystems is
A. Moon B. Sun C. Soil D. Wind only
Correct answer: B — Sun. Solar energy enters food chains through producers.
Q34. A convex lens is
A. Thicker at centre B. Thinner at centre C. Flat always D. Opaque
Correct answer: A — Thicker at centre. A convex lens converges parallel rays.
Q35. The unit of electrical energy used commercially is
A. Watt B. Kilowatt-hour C. Volt D. Ampere
Correct answer: B — Kilowatt-hour. Electricity bills use kWh.
Q36. The relation for electric power is
A. P=VI B. P=V/I² C. P=R/I D. P=I/V
Correct answer: A — P=VI. Power equals potential difference multiplied by current.
Q37. The direction of magnetic field around a wire is found by
A. Left-hand rule only B. Right-hand thumb rule C. Fleming’s left rule only D. Ohm’s law
Correct answer: B — Right-hand thumb rule. Right-hand thumb rule gives field direction.
Q38. A fuse wire should have
A. Very high melting point B. Low melting point C. No resistance D. Infinite thickness
Correct answer: B — Low melting point. It melts when excessive current flows.
Q39. The process of conversion of sugar into alcohol is
A. Respiration B. Fermentation C. Transpiration D. Filtration
Correct answer: B — Fermentation. Yeast carries out fermentation.
Q40. The green pigment required for photosynthesis is
A. Haemoglobin B. Chlorophyll C. Melanin D. Keratin
Correct answer: B — Chlorophyll. Chlorophyll absorbs light energy.
Q41. The bending of light when it passes from one medium to another is
A. Reflection B. Refraction C. Diffusion D. Interference
Correct answer: B — Refraction. Refraction occurs due to change in speed.
Q42. The image in the human eye is formed on the
A. Cornea B. Retina C. Iris D. Pupil
Correct answer: B — Retina. The retina contains light-sensitive cells.
Q43. A solution with pH 2 is
A. Strongly acidic B. Neutral C. Basic D. Salt-free only
Correct answer: A — Strongly acidic. Lower pH means greater acidity.
Q44. The process of removal of wastes from body is
A. Nutrition B. Excretion C. Reproduction D. Coordination
Correct answer: B — Excretion. Excretion removes metabolic wastes.
Q45. A chromosome is made mainly of
A. DNA and proteins B. Fats only C. Starch only D. Water only
Correct answer: A — DNA and proteins. Chromosomes contain DNA associated with proteins.
Q46. The splitting of white light into colours is
A. Reflection B. Dispersion C. Conduction D. Evaporation
Correct answer: B — Dispersion. A prism can disperse white light.
Q47. A solution that resists change in pH is
A. Buffer B. Pure metal C. Distillate D. Suspension only
Correct answer: A — Buffer. A buffer resists pH change.
Q48. The energy stored in food is
A. Chemical energy B. Sound energy C. Nuclear energy only D. Magnetic energy only
Correct answer: A — Chemical energy. Food stores chemical energy.
Q49. A food chain normally begins with
A. Carnivores B. Producers C. Decomposers D. Parasites
Correct answer: B — Producers. Producers capture solar energy.
Q50. Which component of blood helps in clotting?
A. RBC B. WBC C. Platelets D. Plasma
Correct answer: C — Platelets help in blood clotting.
Section B — 40 Very Short Answer Questions
Write 2–4 clear lines. Include the unit, formula or example wherever needed.
Q1. Define electric current.2 marks
Answer: Electric current is the rate of flow of electric charge. \(I=\frac{Q}{t}\).
Q2. Write the SI unit of resistance.2 marks
Answer: The SI unit is ohm \((\Omega)\).
Q3. What is the principal focus of a concave mirror?2 marks
Answer: It is the point where rays parallel to the principal axis meet after reflection.
Q4. Define refractive index.2 marks
Answer: Refractive index is \(n=\frac{c}{v}\), where \(c\) is speed in vacuum and \(v\) is speed in the medium.
Q5. What is accommodation of the eye?2 marks
Answer: The ability of the eye lens to change its focal length to focus near and distant objects.
Q6. State one use of a convex lens.2 marks
Answer: It is used in magnifying glasses, cameras and spectacles for hypermetropia.
Q7. What is oxidation?2 marks
Answer: Oxidation may be addition of oxygen, removal of hydrogen or loss of electrons.
Q8. Define corrosion.2 marks
Answer: Corrosion is the slow damage of a metal due to reaction with substances in its environment.
Q9. What is a homologous series?2 marks
Answer: A family of organic compounds with the same functional group and successive members differing by \(–CH_2–\).
Q10. Name the acid present in vinegar.2 marks
Answer: Acetic acid (ethanoic acid).
Q11. What is pH?2 marks
Answer: pH indicates the acidic or basic nature of a solution; \(pH=-\log[H^+]\).
Q12. What is an alloy?2 marks
Answer: An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal.
Q13. Define nutrition.2 marks
Answer: Nutrition is the process of obtaining and using food for energy, growth and repair.
Q14. What is the role of bile?2 marks
Answer: Bile emulsifies fats and helps create an alkaline medium for enzyme action.
Q15. Define respiration.2 marks
Answer: Respiration is the breakdown of food to release usable energy, usually in the form of ATP.
Q16. What is a nephron?2 marks
Answer: A nephron is the structural and functional unit of the kidney.
Q17. What is a reflex action?2 marks
Answer: A quick, automatic response to a stimulus, often coordinated by the spinal cord.
Q18. Name the plant hormone responsible for phototropism.2 marks
Answer: Auxin.
Q19. Define fertilisation.2 marks
Answer: Fusion of male and female gametes to form a zygote.
Q20. What is heredity?2 marks
Answer: The transmission of traits from parents to offspring.
Q21. Define variation.2 marks
Answer: Variation means differences in traits among individuals of the same species.
Q22. What is a gene?2 marks
Answer: A gene is a segment of DNA that controls or contributes to a trait.
Q23. What is a food chain?2 marks
Answer: A sequence showing transfer of food and energy from one organism to another.
Q24. Name one decomposer.2 marks
Answer: Bacteria or fungi.
Q25. What is biomagnification?2 marks
Answer: Increase in concentration of harmful non-biodegradable chemicals at successive trophic levels.
Q26. What is ozone?2 marks
Answer: Ozone is \(O_3\), a gas that absorbs much of the Sun’s harmful ultraviolet radiation.
Q27. Define electric power.2 marks
Answer: Electric power is the rate at which electrical energy is consumed: \(P=VI\).
Q28. What is a solenoid?2 marks
Answer: A solenoid is a long coil of insulated wire that produces a magnetic field when current flows.
Q29. State Fleming’s left-hand rule.2 marks
Answer: It gives the direction of force on a current-carrying conductor in a magnetic field.
Q30. What is dispersion of light?2 marks
Answer: Dispersion is the splitting of white light into its component colours.
Q31. What is the SI unit of electric charge?
Answer: The SI unit of electric charge is coulomb (C).
Q32. What is a fuse?
Answer: A fuse is a safety device made of a low-melting-point wire that melts when excess current flows.
Q33. What is the optical centre of a lens?
Answer: It is the central point of a thin lens through which a ray passes nearly without deviation.
Q34. Define power of a lens.
Answer: Power is the reciprocal of focal length in metres: \(P=1/f\). Its unit is dioptre.
Q35. What is a displacement reaction?
Answer: A more reactive element displaces a less reactive element from its compound.
Q36. What is an indicator?
Answer: An indicator is a substance that changes colour in acidic or basic media.
Q37. Name the tissue that transports water in plants.
Answer: Xylem transports water and minerals from roots to other parts.
Q38. What is transpiration?
Answer: Transpiration is the loss of water vapour from aerial parts of a plant, mainly through stomata.
Q39. What is a hormone?
Answer: A hormone is a chemical messenger secreted by an endocrine gland and carried to target tissues.
Q40. What is sustainable development?
Answer: Development that meets present needs without reducing the ability of future generations to meet their needs.
Section C — 30 Short Answer Questions
Use headings, formulas and small diagrams. For numerical questions, write: Given → Formula → Substitution → Answer.
Q1. Explain the difference between real and virtual images.3 marks
Answer: A real image is formed by actual meeting of light rays and can be obtained on a screen. A virtual image is formed by apparent meeting of rays and cannot be obtained on a screen. A plane mirror forms a virtual, erect image.
Q2. Derive the mirror formula in its standard form.3 marks
Answer: For a spherical mirror, using the paraxial-ray approximation and similar triangles, the relation between object distance \(u\), image distance \(v\) and focal length \(f\) is \(\frac1f=\frac1v+\frac1u\). Use the Cartesian sign convention while substituting values.
Q3. Explain why a pencil appears bent in water.3 marks
Answer: Light from the submerged part travels from water to air and bends away from the normal. The eye assumes light travelled in a straight line, so the submerged part appears raised and the pencil seems bent.
Q4. State the laws of refraction.3 marks
Answer: First law: incident ray, refracted ray and normal lie in one plane. Second law: for two fixed media, \(\frac{\sin i}{\sin r}=\text{constant}=n\).
Q5. Explain myopia and its correction.3 marks
Answer: In myopia, distant objects form images before the retina. It is corrected using a concave lens, which diverges incoming rays so the eye lens forms the image on the retina.
Q6. Explain hypermetropia and its correction.3 marks
Answer: In hypermetropia, near objects appear blurred because the image tends to form behind the retina. A suitable convex lens converges rays before they enter the eye.
Q7. Describe an experiment to verify Ohm’s law.3 marks
Answer: Connect a cell, key, rheostat, resistor and ammeter in series, with a voltmeter across the resistor. Change current using the rheostat and record V and I. A straight V–I graph through the origin verifies \(V\propto I\) at constant temperature.
Q8. Explain factors affecting resistance.3 marks
Answer: For a uniform wire, \(R=\rho\frac{L}{A}\). Resistance increases with length, decreases with cross-sectional area and depends on material through resistivity. Temperature also affects resistance.
Q9. Differentiate series and parallel combinations.3 marks
Answer: In series, current is same and equivalent resistance is \(R_s=R_1+R_2+...\). In parallel, potential difference is same and \(\frac1{R_p}=\frac1{R_1}+\frac1{R_2}+...\). Parallel arrangements are used in domestic circuits.
Q10. Explain the heating effect of current.3 marks
Answer: When current flows through resistance, electrical energy changes into heat. \(H=I^2Rt\), also \(H=VIt=\frac{V^2t}{R}\). It is used in heaters, irons and fuses.
Q11. Explain the magnetic field around a straight conductor.3 marks
Answer: Current produces circular magnetic field lines around the conductor. Their direction is given by the right-hand thumb rule. Field strength increases with current and decreases with distance.
Q12. Explain the working of an electric motor.3 marks
Answer: A current-carrying coil in a magnetic field experiences force. The two sides experience opposite forces and rotate the coil. The split-ring commutator reverses current after each half turn, keeping rotation continuous.
Q13. Balance the equation and identify the reaction: Fe + H₂O → Fe₃O₄ + H₂.3 marks
Answer: Balanced equation: \(3Fe+4H_2O\rightarrow Fe_3O_4+4H_2\). It is a redox reaction; iron is oxidised and hydrogen in water is reduced.
Q14. Explain pH importance in daily life.3 marks
Answer: pH controls soil suitability, digestion and tooth decay. The stomach uses HCl for digestion; excess acid is neutralised by antacids. Tooth enamel begins to damage when mouth pH falls too low.
Q15. Explain properties of ionic compounds.3 marks
Answer: Ionic compounds are hard, have high melting points, and conduct electricity in molten or aqueous states because ions can move. They generally do not conduct in the solid state.
Q16. Explain covalent bonding in methane.3 marks
Answer: Carbon shares one electron with each of four hydrogen atoms, forming four shared pairs. Each C–H bond is covalent. Methane has a stable outer shell around carbon.
Q17. Describe human digestion briefly.3 marks
Answer: Food is chewed and mixed with saliva. In the stomach, acid and pepsin act on proteins. In the small intestine, bile emulsifies fats and pancreatic/intestinal enzymes complete digestion. Villi absorb nutrients.
Q18. Explain double circulation in humans.3 marks
Answer: The right side of the heart sends deoxygenated blood to lungs; the left side sends oxygenated blood to the body. Pulmonary and systemic circuits keep oxygenated and deoxygenated blood largely separate.
Q19. Explain nervous coordination through a reflex arc.3 marks
Answer: A receptor detects a stimulus; sensory neuron carries the impulse to the spinal cord; an interneuron connects it to a motor neuron; the effector produces a rapid response. The brain is informed afterward.
Q20. Explain asexual reproduction with examples.3 marks
Answer: Asexual reproduction involves one parent and no fusion of gametes. Binary fission occurs in Amoeba, budding in yeast and Hydra, and vegetative propagation in potato and Bryophyllum.
Q21. Explain Mendel’s monohybrid cross.3 marks
Answer: Crossing pure tall \(TT\) with pure dwarf \(tt\) gives all \(Tt\) tall plants in F1. Self-cross \(Tt\times Tt\) gives \(TT,Tt,Tt,tt\), a genotypic ratio 1:2:1 and phenotypic ratio 3:1.
Q22. Explain sex determination in humans.3 marks
Answer: Females generally have XX and males XY chromosomes. The egg always carries X, while sperm carries X or Y. X sperm produces XX offspring and Y sperm produces XY offspring; the sperm determines chromosomal sex.
Q23. Explain the 10% law of energy transfer.3 marks
Answer: Only about 10% of energy at one trophic level is transferred to the next. Much energy is used in life processes and lost as heat, so food chains usually contain few trophic levels.
Q24. Differentiate biodegradable and non-biodegradable waste.3 marks
Answer: Biodegradable waste is broken down by microorganisms, e.g. vegetable peels. Non-biodegradable waste remains for long periods, e.g. many plastics. Reduce, reuse and recycle help manage waste.
Q25. Explain why stars twinkle.3 marks
Answer: Starlight passes through moving layers of Earth’s atmosphere with changing optical densities. Repeated refraction changes the apparent position and brightness, producing twinkling.
Q26. Explain why the Sun looks reddish at sunrise and sunset.3 marks
Answer: Sunlight travels through a longer atmospheric path. Blue and violet light scatter away more, so red and orange light reach the observer more strongly.
Q27. Derive the electrical power formula.3 marks
Answer: Electrical work \(W=VQ\). Since current \(I=Q/t\), \(Q=It\). Therefore \(P=W/t=VQ/t=VI\). Using \(V=IR\), we also obtain \(P=I^2R=V^2/R\).
Q28. Explain domestic electric circuit safety.3 marks
Answer: Live, neutral and earth wires are used. A fuse/MCB interrupts excess current. Appliances are connected in parallel so each receives rated voltage. Earthing provides a low-resistance path for leakage current.
Q29. Explain why carbon forms many compounds.3 marks
Answer: Carbon is tetravalent and forms strong covalent bonds. It shows catenation, making long chains, branches and rings. It can form single, double and triple bonds with itself and other elements.
Q30. Why are domestic appliances connected in parallel?
Answer: Appliances are connected in parallel because each appliance receives the same supply voltage, can be switched independently, and failure of one appliance does not normally stop the others. The total current is divided among the branches.
Section D — 20 Long Answer Questions with Detailed Solutions
Long-answer method: Start with definition, write the principle, show the formula/steps, add a labelled diagram where useful, and finish with a conclusion.
Q1. Derive the lens formula and explain the ray diagram for a convex lens.5 marks
Answer: For a thin convex lens, let object distance be \(u\), image distance be \(v\), and focal length be \(f\). Using the ray parallel to the principal axis and the ray through the optical centre, similar triangles give the relation:
\[
\frac{1}{f}=\frac{1}{v}+\frac{1}{u}
\]
With the Cartesian sign convention, distances are substituted with their signs. Magnification is
\[
m=\frac{h_i}{h_o}=\frac{v}{u}.
\]
A convex lens can form real, inverted images when the object is beyond the focus and a virtual, erect, magnified image when the object is between the optical centre and focus.
Q2. Explain the human eye, accommodation and common defects.5 marks
Answer: The cornea and eye lens refract light. The iris controls the pupil, while the retina contains rods and cones. The optic nerve carries signals to the brain. Ciliary muscles change the curvature of the lens; this is accommodation. In myopia, a concave lens is used. In hypermetropia, a convex lens is used. Presbyopia occurs due to reduced accommodation with age and may require suitable bifocal or progressive lenses.
Q3. Derive Ohm’s law based on the V–I relationship and solve a numerical example.5 marks
Answer: At constant temperature, current through a conductor is directly proportional to potential difference:
\[
V\propto I\Rightarrow V=IR
\]
Here \(R\) is constant resistance. Example: if \(V=12\,V\) and \(R=4\,\Omega\), then
\[
I=\frac VR=\frac{12}{4}=3\,A.
\]
A graph of V against I is a straight line; its slope is resistance. Ohm’s law is not obeyed by all devices under all conditions, especially when temperature or material properties change.
Q4. Explain electric energy, power and heating effect with derivations.5 marks
Answer: Electrical work is \(W=VQ\). Since \(Q=It\), \(W=VIt\). Hence
\[
P=\frac Wt=VI.
\]
Using \(V=IR\):
\[
P=I^2R=\frac{V^2}{R}.
\]
Heat produced in time \(t\) is
\[
H=I^2Rt.
\]
These relations explain the working of heaters, toasters, electric irons and fuses. A fuse uses the heating effect to melt and break the circuit when current becomes excessive.
Q5. Describe the magnetic field of a solenoid and the working of an electric motor.5 marks
Answer: A solenoid is a coil with many turns. Its field inside is comparatively strong and nearly uniform, while outside it resembles a bar magnet. Field direction is found using the right-hand grip rule. In a motor, a current-carrying coil placed in a magnetic field experiences forces on its sides. These forces form a couple and rotate the coil. The split-ring commutator reverses current after each half rotation, maintaining torque in the same rotational direction.
Q6. Explain chemical reactions, their types and balancing with examples.5 marks
Answer: A chemical reaction forms new substances. Combination: \(CaO+H_2O\rightarrow Ca(OH)_2\). Decomposition: \(CaCO_3\rightarrow CaO+CO_2\). Displacement: \(Zn+CuSO_4\rightarrow ZnSO_4+Cu\). Double displacement: \(AgNO_3+NaCl\rightarrow AgCl+NaNO_3\). Oxidation and reduction occur together in redox reactions. Equations are balanced by making the number of atoms of every element equal on both sides.
Q7. Explain acids, bases, salts and the pH scale.5 marks
Answer: Acids produce \(H^+\) ions in water and bases produce \(OH^-\) ions or accept protons. Acids turn blue litmus red; bases turn red litmus blue. pH is given by \(pH=-\log[H^+]\). Values below 7 are acidic, 7 is neutral and above 7 is basic at room temperature. Neutralisation gives salt and water, for example \(HCl+NaOH\rightarrow NaCl+H_2O\).
Q8. Explain the versatile nature of carbon and important reactions of ethanol and ethanoic acid.5 marks
Answer: Carbon is tetravalent and shows catenation. Saturated compounds have single bonds; unsaturated compounds have double or triple bonds. Ethanol burns to produce carbon dioxide and water, and can be oxidised to ethanoic acid. Ethanoic acid reacts with sodium bicarbonate:
\[
CH_3COOH+NaHCO_3\rightarrow CH_3COONa+H_2O+CO_2.
\]
Ethanol and ethanoic acid form an ester in the presence of concentrated sulphuric acid, producing a fruity smell.
Q9. Explain extraction of metals according to their reactivity.5 marks
Answer: Highly reactive metals are obtained by electrolytic reduction of molten compounds. Moderately reactive metals are commonly obtained by roasting or calcination followed by reduction with carbon or carbon monoxide. Low-reactivity metals may occur in free state or are obtained by heating their compounds. The ore is first concentrated, then converted into oxide and reduced; refining gives pure metal. The method depends on the metal’s position in the reactivity series.
Q10. Explain nutrition in humans with a labelled flow sequence.5 marks
Answer: Food passes through mouth, oesophagus, stomach, small intestine, large intestine and anus. Saliva begins starch digestion. Stomach acid provides an acidic medium and pepsin digests proteins. Bile from liver emulsifies fats. Pancreatic enzymes digest carbohydrates, proteins and fats. Villi in the small intestine absorb digested nutrients. The large intestine absorbs water and the remaining material is removed as faeces.
Q11. Explain aerobic and anaerobic respiration and ATP formation.5 marks
Answer: Aerobic respiration uses oxygen and releases more energy:
\[
\text{Glucose}+O_2\rightarrow CO_2+H_2O+\text{energy}.
\]
It begins with glycolysis in the cytoplasm and continues in mitochondria. Anaerobic respiration occurs without oxygen; yeast produces alcohol and carbon dioxide, while muscles may form lactic acid during oxygen shortage. ATP is the usable energy currency of the cell.
Q12. Explain transportation in humans and double circulation.5 marks
Answer: The heart has four chambers. The right atrium receives deoxygenated blood and passes it to the right ventricle, which pumps it to lungs. Oxygenated blood returns to the left atrium and enters the left ventricle, which pumps it to the body. Arteries carry blood away from the heart, veins bring it back and capillaries allow exchange. Valves prevent backflow.
Q13. Explain excretion in humans and urine formation.5 marks
Answer: Each kidney contains many nephrons. Blood is filtered in the glomerulus into Bowman’s capsule. Useful substances such as glucose, ions and much water are selectively reabsorbed. Additional wastes may be secreted into the tubule. The remaining fluid becomes urine, which passes through ureters to the urinary bladder and leaves through the urethra. This process maintains water and salt balance.
Q14. Explain coordination in plants and animals.5 marks
Answer: Plants coordinate through chemical growth regulators such as auxin, gibberellin, cytokinin, abscisic acid and ethylene. Tropic movements include phototropism and geotropism. Animals use nervous and endocrine systems. Receptors detect stimuli, neurons carry impulses and glands release hormones. Reflex arcs provide quick protective responses, while the brain coordinates complex actions.
Q15. Explain reproduction in flowering plants.5 marks
Answer: The stamen produces pollen grains and the pistil contains stigma, style and ovary. Pollination transfers pollen to the stigma. A pollen tube grows toward the ovule. Male and female gametes fuse during fertilisation to form a zygote. The ovule becomes a seed and the ovary develops into a fruit. Vegetative propagation can produce genetically similar plants quickly.
Q16. Explain Mendel’s laws using a monohybrid cross.5 marks
Answer: Let tallness \(T\) be dominant over dwarfness \(t\). Pure parents \(TT\times tt\) produce F1 offspring all \(Tt\) and tall. Self-cross:
\[
Tt\times Tt\rightarrow TT,Tt,Tt,tt.
\]
Genotypic ratio is 1:2:1 and phenotypic ratio is 3 tall:1 dwarf. This demonstrates segregation of alleles during gamete formation. Dominance explains why \(Tt\) is tall, while both alleles remain present.
Q17. Explain evolution, variation and sex determination in humans.5 marks
Answer: Variation arises through mutation, recombination and environmental effects. Heritable variations can be acted upon by natural selection, producing evolutionary change over generations. Humans generally have XX females and XY males. Eggs carry X; sperm carry X or Y. XX usually develops as female and XY as male. This is chromosomal sex determination and does not justify blaming either parent for a child’s sex.
Q18. Explain ecosystems, food chains, energy flow and environmental protection.5 marks
Answer: An ecosystem contains biotic and abiotic components. Producers capture solar energy, consumers obtain energy by feeding, and decomposers recycle nutrients. Energy decreases at each trophic level; approximately 10% is transferred to the next level. Non-biodegradable pollutants may biomagnify. Protection includes reducing waste, recycling, conserving habitats, controlling emissions and using resources sustainably.
Q19. Explain ozone depletion and methods of waste management.5 marks
Answer: Ozone in the stratosphere absorbs harmful ultraviolet radiation. Certain chemicals, including older chlorofluorocarbons, release reactive chlorine that destroys ozone. Waste should be segregated at source into wet, dry and hazardous categories. Compost biodegradable waste, recycle paper/metals/glass, reduce single-use plastics and dispose of e-waste safely. The 3R principle is Reduce, Reuse and Recycle.
Q20. Explain the structure and working of the nephron with urine formation.
Answer: A nephron has a glomerulus, Bowman’s capsule, renal tubule and collecting duct. Blood enters the glomerulus under pressure and filtration takes place into Bowman’s capsule. The filtrate passes through the tubule, where useful substances such as glucose, salts and water are selectively reabsorbed. Some wastes are secreted into the tubule. The remaining fluid becomes urine and flows into the collecting duct, renal pelvis, ureter and urinary bladder. The nephron therefore removes nitrogenous wastes and helps maintain water and salt balance.
Special Physics Derivation Bank
1. Derivation of Ohm’s Law Form
At constant temperature, charge carriers move through a conductor. Experimentally, potential difference is directly proportional to current:
\[V\propto I\Rightarrow V=IR\]
Here \(R\) is the constant of proportionality called resistance. Therefore, \(R=V/I\). The V–I graph is a straight line through the origin for an ohmic conductor.
2. Derivation of Electrical Power
Electrical work done in moving charge \(Q\) through potential difference \(V\) is \(W=VQ\). Since \(I=Q/t\), we get \(Q=It\).
\[P=\frac{W}{t}=\frac{VQ}{t}=VI\]
Using \(V=IR\): \(P=I^2R\). Also, using \(I=V/R\): \(P=V^2/R\).
3. Derivation of Heating Effect
Electrical energy converted into heat is equal to electrical work:
\[H=W=VIt\]
Substitute \(V=IR\):
\[\boxed{H=I^2Rt}\]
This is Joule’s law of heating. Heat increases with the square of current, resistance and time.
4. Lens and Mirror Formula Reminder
For board numericals, use the Cartesian sign convention. The standard relation used in this level is:
\[\frac1f=\frac1v+\frac1u\]
For a lens, magnification is \(m=v/u\). For a mirror, magnification is commonly written \(m=-v/u\). Always check the sign of \(u,v,f\) before calculating.
Blue-Pen Style Diagrams for Practice
Concave Mirror: Basic Ray Idea
Draw the principal axis, pole, focus and centre of curvature. Use arrowheads to show the direction of light.
Human Eye: Simplified Labelled View
Remember: image forms on the retina; iris controls pupil size; optic nerve carries signals.
Electric Circuit for Ohm’s Law
Ammeter is connected in series. Voltmeter is connected in parallel across the resistor.
Final Revision Checklist
- Learn all SI units: ampere, volt, ohm, watt, joule and dioptre.
- Practise ray diagrams for concave mirror, convex lens and human eye defects.
- Memorise \(V=IR\), \(P=VI\), \(H=I^2Rt\), \(R=\rho L/A\), and \(n=c/v\).
- Balance at least 10 chemical equations and identify reaction types.
- Revise pH, reactivity series, carbon functional groups and corrosion.
- Practise diagrams of digestive system, respiratory system, nephron, reflex arc and flower.
- Write Mendel’s cross and learn 3:1 phenotypic and 1:2:1 genotypic ratios.
- Revise food chains, 10% law, ozone, biomagnification and waste management.
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