CBSE Class 10 Science Question Paper 2024 (Set 3

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CBSE Class 10 Science Question Paper 2024 PDF (Set 3 - 31/5/3) is available for download here. CBSE conducted the Science exam on March 2, 2024, from 10:30 AM to 1:30 PM. The total marks for the theory paper are 80. The question paper contains 20% MCQ-based questions, 40% competency-based questions, and 40% short and long answer type questions. As per the students, the difficulty level of the Science exam was moderate.

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CBSE Class 10 Science Question Paper 2024 (Set 3 - 31/5/3) with Answer Key

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CBSE Science Question Paper (Set 3 – 31/5/3) 2024 Solution

Question	Answer	Detailed Solution
1. Select from the following the conditions responsible for the rapid spread of bread mould on a slice of bread: (i) Formation of large number of spores (ii) Presence of moisture and nutrients in bread (iii) Low temperature (iv) Presence of hyphae (A) (i) and (ii) (B) (ii) and (iv) (C) (ii) and (iii) (D) (iii) and (iv)	(A) (i) and (ii)	Mold requires moisture and nutrients to grow and spread rapidly. Hyphae help the mold spread across surfaces, while spores ensure reproduction under favorable conditions.
2. The incorrect statement about placenta is: (A) It is a disc embedded in the uterine wall. (B) It contains villi on the embryo’s side of the tissue. (C) It has a very small surface area for glucose and oxygen to pass from mother to the embryo. (D) The embryo gets nutrition from the mother’s blood through it.	(C) It has a very small surface area for glucose and oxygen to pass from mother to the embryo.	The placenta has a large surface area, which maximizes nutrient and gas exchange between the mother and the embryo. A small surface area would make this process inefficient.
3. An aqueous solution ‘A’ turns phenolphthalein solution pink. When another solution ‘B’ is added, the pink color disappears. Few drops of ‘A’ added to this reaction make it pink again. The changes in the nature of the solution are: (A) acidic → basic → basic (B) basic → acidic → acidic (C) acidic → basic → acidic (D) basic → acidic → basic	(D) basic → acidic → basic	Phenolphthalein is pink in basic solutions and colorless in acidic ones. The sequence indicates neutralization followed by restoration of basicity.
4. The correct sequence of events when someone’s hand touches a hot object unconsciously is: (A) Receptors in skin → Motor neuron → Relay neuron → Sensory neuron → Effector muscle in arm (B) Receptors in skin → Relay neuron → Sensory neuron → Motor neuron → Effector muscle in arm (C) Receptors in skin → Sensory neuron → Relay neuron → Motor neuron → Effector muscle in arm (D) Receptors in skin → Sensory neuron → Effector muscle in arm → Motor neuron → Relay neuron	(C) Receptors in skin → Sensory neuron → Relay neuron → Motor neuron → Effector muscle in arm	Reflex arcs bypass the brain to ensure rapid response to stimuli. This sequence follows the sensory-receptor-neuron pathway.
5. To balance the equation: xZn(NO3)2 → yZnO + zNO2 + O2, the values of x, y, and z are: (A) 4, 2, 2 (B) 4, 4, 2 (C) 2, 2, 4 (D) 2, 4, 2	(C) 2, 2, 4	The balanced equation is: 2Zn(NO3)2 → 2ZnO + 4NO2 + O2, ensuring conservation of mass.
6. Which of the following is a redox reaction but not a combination reaction? (A) C + O2 → CO2 (B) 2H2 + O2 → 2H2O (C) 2Mg + O2 → 2MgO (D) Fe2O3 + 3CO → 2Fe + 3CO2	(D) Fe2O3 + 3CO → 2Fe + 3CO2	This reaction involves oxidation of CO to CO2 and reduction of Fe2O3 to Fe, qualifying it as a redox reaction.
7. An aqueous solution of sodium chloride prepared in distilled water has a pH of: (A) 6 (B) 8 (C) 7 (D) 3	(C) 7	NaCl, being a neutral salt of a strong acid and base, produces a neutral pH of 7 in water.
8. A metal ‘X’ used in the thermite process forms an amphoteric oxide ‘Y’ when heated with oxygen. ‘X’ and ‘Y’ are: (A) Mn, MnO2 (B) Al, Al2O3 (C) Fe, Fe2O3 (D) Mg, MgO	(B) Al, Al2O3	Aluminum reacts with oxygen to form aluminum oxide (Al2O3), an amphoteric substance reacting with both acids and bases.
9. The process in which soluble products of photosynthesis are transported in plants is called: (A) Transpiration (B) Evaporation (C) Conduction (D) Translocation	(D) Translocation	Translocation refers to the transport of sugars and nutrients from leaves to other parts of the plant.
10. Sense organ in which olfactory receptors are present is: (A) Nose (B) Skin (C) Tongue (D) Inner ear	(A) Nose	Olfactory receptors, responsible for the sense of smell, are located in the nasal cavity.
11. Which one of the following is not a natural ecosystem? (A) Pond ecosystem (B) Grassland ecosystem (C) Forest ecosystem (D) Cropland ecosystem	(D) Cropland ecosystem	Croplands are artificial ecosystems as they are cultivated and managed by humans, unlike natural ecosystems.
12. A uniform magnetic field exists in the plane of paper. An electron and a positron enter as shown. The forces on them are: (A) Both pointing into the plane of the paper (B) Both pointing out of the plane of the paper (C) Electron into the plane, positron out of the plane (D) Electron out of the plane, positron into the plane	(C) Electron into the plane, positron out of the plane	Using the right-hand rule and reversing for negative charge, the electron is forced into the plane and positron out of the plane of the paper.
13. How will the image formed by a convex lens be affected, if the upper half of the lens is wrapped with black paper? (A) The size of the image will be one-half (B) Image of upper half of the object will not form (C) Brightness of the image will reduce (D) Lower half of the inverted image will not form	(C) Brightness of the image will reduce	Covering part of the lens reduces light transmission, leading to a dimmer image without altering its size or position.
14. The phenomena of light involved in the formation of a rainbow are: (A) Refraction, reflection, and dispersion (B) Refraction, dispersion, and internal reflection (C) Reflection, dispersion, and internal reflection (D) Refraction, dispersion, scattering, and total internal reflection	(B) Refraction, dispersion, and internal reflection	Light undergoes refraction, dispersion into its constituent colors, and internal reflection inside water droplets to form a rainbow.
15. The color of light for which the refractive index of glass is minimum is: (A) Red (B) Yellow (C) Green (D) Violet	(A) Red	Red light has the longest wavelength, leading to the least deviation and minimum refractive index in glass.
16. The current carrying device which produces a magnetic field similar to that of a bar magnet is: (A) A straight conductor (B) A circular loop (C) A solenoid (D) A circular coil	(C) A solenoid	A solenoid produces a magnetic field similar to that of a bar magnet with distinct north and south poles.
17. Assertion (A): Electrons move from lower to higher potential in a conductor. Reason (R): A dry cell maintains electric potential difference across a conductor. (A) Both A and R are true, and R is the correct explanation of A (B) Both A and R are true, but R is not the correct explanation of A (C) A is true, but R is false (D) A is false, but R is true	(B) Both A and R are true, but R is not the correct explanation of A	Electrons move from negative (lower potential) to positive (higher potential), while the dry cell maintains the required potential difference.
18. Assertion (A): Some vegetable oils are healthy. Reason (R): Vegetable oils generally have long unsaturated carbon chains. (A) Both A and R are true, and R is the correct explanation of A (B) Both A and R are true, but R is not the correct explanation of A (C) A is true, but R is false (D) A is false, but R is true	(A) Both A and R are true, and R is the correct explanation of A	Unsaturated fatty acids in vegetable oils reduce bad cholesterol levels, promoting heart health.
19. Assertion (A): The sex of children is determined by what they inherit from their mother. Reason (R): Women have XX sex chromosomes. (A) Both A and R are true, and R is the correct explanation of A (B) Both A and R are true, but R is not the correct explanation of A (C) A is true, but R is false (D) A is false, but R is true	(D) A is false, but R is true	Sex is determined by the father’s sperm carrying either an X or Y chromosome, not by the mother, who always provides an X chromosome.
20. Assertion (A): Green plants trap only 1% of the energy of sunlight that falls on their leaves. Reason (R): All green plants are the producers in a food chain. (A) Both A and R are true, and R is the correct explanation of A (B) Both A and R are true, but R is not the correct explanation of A (C) A is true, but R is false (D) A is false, but R is true	(B) Both A and R are true, but R is not the correct explanation of A	While plants are producers, the 1% energy trapping efficiency refers to photosynthesis, which is independent of their role in the food chain.
21. (a) Why do athletes sometimes suffer from muscle cramps during running? (b) How is this type of respiration different from aerobic respiration?	(a) Lactic acid accumulation causes cramps. (b) Anaerobic respiration produces lactic acid and less energy than aerobic respiration.	(a) During vigorous exercise, insufficient oxygen leads to anaerobic respiration in muscles, producing lactic acid that causes cramps. (b) Aerobic respiration requires oxygen and produces carbon dioxide, water, and more energy, whereas anaerobic respiration does not require oxygen and yields lactic acid and less energy.
22. Write the molecular formula and molecular mass of the third homologue of alcohols. How does the boiling point of alcohols change as you move to higher homologues?	Formula: C3H8O, Mass: 60 g/mol. Boiling point increases with molecular size.	The third homologue is propanol (C3H8O), with a molecular mass of 60 g/mol. As molecular size and mass increase in alcohols, intermolecular forces (hydrogen bonding) become stronger, leading to a higher boiling point.
23. (a) Copper powder is heated in a china dish. Name the product formed and its color. Write the chemical equation for the reaction.	(a) Product: Copper(II) oxide (black).	(a) Copper reacts with oxygen when heated to form black copper(II) oxide: 2Cu + O2 → 2CuO.
OR 23.(b) Write the chemical equation for the reaction between aqueous barium chloride and sodium sulfate. Name the precipitate and the ions present in it.	(b) Precipitate: BaSO4 (white).	(b) A double displacement reaction forms insoluble barium sulfate (BaSO4): BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq). Precipitate ions: Ba2+ and SO42-.
24. Identify the organ in the human female reproductive system where sperm encounters the egg cell. What happens if it is blocked? Name the surgical technique used to block it.	Organ: Fallopian tube. Blockage causes infertility. Surgical method: Tubectomy.	Sperm encounters the egg in the fallopian tube. If blocked, fertilization cannot occur, leading to infertility. Tubectomy is the surgical procedure used to block the fallopian tubes for contraception.
25. The linear magnification produced by a spherical mirror is +3. Answer the following: (a) What type of mirror is it? (b) Where is the object placed? (c) List two properties of the image formed (apart from magnification).	(a) Concave mirror. (b) Between pole and focus. (c) Virtual and erect.	(a) A concave mirror produces positive magnification for virtual images. (b) The object is placed between the mirror’s pole and focus. (c) The image formed is virtual, erect, and magnified.
26. The filament of an electric lamp draws a current of 0.5 A, which lights for 2 hours. Calculate the charge that flows through the circuit.	Charge (Q): 3600 C.	The relationship between charge (Q), current (I), and time (t) is given by the formula: Q = I × t t = 2 hours = 2 × 3600 = 7200 seconds. Q = 0.5 A × 7200 s = 3600 C. Final Answer: The charge that flows through the circuit is 3600 C.
27. Answer the following questions in the context of electrolysis of water: (a) Why is this reaction/process called a decomposition reaction? (b) Giving reason, state whether this reaction is exothermic or endothermic. (c) Name the gases collected at the anode and cathode. (d) What is the mass ratio of the gases collected at the anode and cathode?	(a) Decomposition reaction. (b) Endothermic reaction. (c) Anode: Oxygen (O₂), Cathode: Hydrogen (H₂). (d) Mass ratio: 1:8.	(a) The electrolysis of water is a decomposition reaction because water (H₂O) splits into hydrogen (H₂) and oxygen (O₂) gases when an electric current is passed through it. (b) This reaction is endothermic as energy in the form of electricity is required to break the bonds in water molecules. (c) At the anode, oxygen gas (O₂) is collected. At the cathode, hydrogen gas (H₂) is collected. (d) The molar masses of hydrogen and oxygen are 2 g/mol and 32 g/mol, respectively. The mass ratio of hydrogen to oxygen is therefore 1:8.
28. Differentiate between food chain and food web. In a food chain consisting of deer, grass, and tiger, if the population of deer decreases, what will happen to the population of organisms belonging to the first and third trophic levels?	Difference: Food Chain: Linear sequence. Food Web: Interconnected chains. Population Impact: Grass (1st level): Increase. Tigers (3rd level): Decrease.	Food Chain: A simple linear sequence showing energy flow from one organism to the next. Food Web: A complex network of interconnected food chains in an ecosystem. If deer population decreases: - Grass (1st trophic level): Increases due to reduced grazing. - Tigers (3rd trophic level): Decrease as their food source diminishes.
29. Name a plant growth hormone synthesized at the shoot tip. Explain its effect on the growth of a plant in response to light.	Hormone: Auxin. Effect: Phototropism – growth towards light.	Auxin is a plant hormone synthesized at the shoot tip. - Auxins promote cell elongation. - In response to light, auxins accumulate on the shaded side of the shoot, causing faster elongation of cells on that side. - This uneven growth causes the shoot to bend towards the light, a phenomenon called phototropism.
30. Name the ore of mercury and state the form in which it is found in nature. Write the chemical equations along with the condition required for the reactions involved in the extraction of mercury from its ore.	Ore: Cinnabar (HgS). Form: Mercury(II) sulfide. Reaction: 2HgS + 3O₂ → 2Hg + 2SO₂.	Mercury is extracted from its ore cinnabar (HgS), which is found as mercury(II) sulfide. - Cinnabar is roasted in the presence of oxygen to produce mercury vapor and sulfur dioxide: 2HgS + 3O₂ → 2Hg + 2SO₂ - The mercury vapor is cooled and condensed to obtain liquid mercury.
31. Mendel crossed pure tall pea plants (TT) with pure short pea plants (tt) and obtained F₁ progeny. When the plants of F₁ progeny were self-pollinated, plants of F₂ progeny were obtained. (a) What did the plants of F₁ progeny look like? Give their gene combination. (b) Why could the gene for shortness not be expressed in plants of F₁ progeny? (c) Write the ratio of the plants obtained in F₂ progeny and state the conclusion that can be drawn from this experiment.	(a) Appearance: Tall (Tt). (b) Reason: Gene for shortness is recessive. (c) Ratio: 3 Tall:1 Short. Conclusion: Dominance and segregation.	(a) The plants of F₁ progeny were tall because the tallness trait (T) is dominant over shortness (t). The gene combination was Tt (heterozygous tall). (b) The gene for shortness (t) is recessive and is masked by the dominant gene for tallness (T) in the heterozygous condition. (c) In F₂ progeny, the phenotypic ratio was 3 Tall:1 Short, while the genotypic ratio was 1 TT:2 Tt:1 tt. Conclusion: Mendel's experiment shows that traits are controlled by dominant and recessive factors that segregate during gamete formation.
32. A 2000 W heater has a resistance of about 25 Ω, whereas a 100 W bulb has a resistance of 500 Ω. When 220 V is applied on these, then which of the two: (a) Can carry large currents? (b) May be used with an electrical circuit having 1.0 A rating? (c) Will be fitted with a 15 A electric board and not with a 5 A electric board? Justify your answer in each case.	(a) 2000 W heater. (b) 100 W bulb. (c) 2000 W heater – requires a 15 A board.	(a) The 2000 W heater can carry a larger current (I = V/R = 220/25 = 8.8 A) compared to the 100 W bulb (I = 220/500 = 0.44 A). (b) The 100 W bulb, which draws only 0.44 A, can safely be used in a 1.0 A circuit. (c) The 2000 W heater, which requires 8.8 A, needs a 15 A board, while the 100 W bulb can work on a 5 A board. Justification: The current requirements must match the circuit and board ratings.
33. (a) Study the diagram given below and answer the questions that follow: (i) Name the defect of vision depicted in this diagram stating the part of the eye responsible for this condition. (ii) List two causes of this defect. (iii) Name the type of lens used to correct this defect and state its role in this case.	(i) Defect: Hypermetropia (lens or eyeball). (ii) Causes: Short eyeball, weak lens. (iii) Correction: Convex lens (focuses light on the retina).	(i) The defect is Hypermetropia (farsightedness), caused by a short eyeball or a weak lens, resulting in light focusing behind the retina. (ii) Causes: - Short eyeball: Prevents proper focusing. - Weak lens: Lacks sufficient converging power. (iii) Correction: A convex lens is used to converge the light rays, allowing them to focus on the retina for clear vision.
33(b). What is dispersion of white light? State its cause. Draw a diagram to show dispersion of a beam of white light by a glass prism.	Dispersion: Splitting of white light. Cause: Different wavelengths refract at different angles.	Dispersion is the phenomenon of splitting white light into its constituent colors (spectrum) when it passes through a prism. Cause: Different wavelengths of light bend by different amounts due to varying refractive indices of the medium. Violet light bends the most, while red light bends the least. Diagram:A prism showing the dispersion of light into seven colors (VIBGYOR). The diagram should depict the splitting of a single white ray into multiple colored rays.
34.(a). Design an experiment to demonstrate that carbon dioxide is essential for photosynthesis. Write the observation and conclusion of the experiment.	Observation: Leaf without CO₂ does not turn blue-black. Conclusion: CO₂ is essential for photosynthesis.	- Place a potted plant in the dark for 48 hours to destarch its leaves. - Cover one leaf with a conical flask containing KOH (absorbs CO₂). - Expose the plant to sunlight for a few hours. - Test both leaves for starch using iodine. Observation: The leaf exposed to air turns blue-black, while the leaf inside the flask does not. Conclusion: CO₂ is essential for photosynthesis.
34(b). (i) In the experimental setup shown, atmospheric air is passed into lime water with a syringe in diagram (I), while in diagram (II), air is exhaled into lime water. The time taken for lime water to turn milky in both test tubes is different. Give a reason. (ii) Draw the diagram of an open stomatal pore and label (i) Guard cells, and (ii) Chloroplast on it. Mention two functions performed by stomata.	(i) Reason: Exhaled air has more CO₂. (ii) Functions: Gas exchange and transpiration.	(i) Reason:- In diagram (I), atmospheric air has a lower CO₂ concentration (~0.04%), so lime water takes longer to turn milky. - In diagram (II), exhaled air contains higher CO₂ concentration (~4%), so lime water turns milky faster. (ii) Diagram:An open stomatal pore labeled with Guard Cells and Chloroplasts. Functions:- Gas exchange: Stomata facilitate the exchange of oxygen and carbon dioxide for photosynthesis and respiration. - Transpiration: Stomata allow the release of water vapor, aiding in temperature regulation and nutrient transport.
35. (a)A few crystals of ferrous sulphate were taken in a dry boiling tube and heated. Tiny water droplets were observed in the tube after some time. (i) From where did these water droplets appear? Explain. (ii) What colour change will be observed during heating? (iii) How many molecules of water are attached per molecule of FeSO₄? Write the molecular formula of crystalline forms of (I) Copper sulphate and (II) Sodium carbonate. (iv) State how is Plaster of Paris obtained from gypsum. Write two uses of Plaster of Paris.	(i) Water of crystallization. (ii) Green to white. (iii) FeSO₄·7H₂O, CuSO₄·5H₂O, Na₂CO₃·10H₂O. (iv) Heating gypsum at 373 K. Uses: Casts, decorative materials.	(i) The water droplets are from the water of crystallization in FeSO₄·7H₂O, which evaporates on heating. (ii) FeSO₄·7H₂O turns from green to white as it loses water. (iii) FeSO₄·7H₂O has 7 water molecules. Other formulas: - CuSO₄·5H₂O - Na₂CO₃·10H₂O (iv) Plaster of Paris (CaSO₄·1/2H₂O) is obtained by heating gypsum (CaSO₄·2H₂O) at 373 K. Uses: - Making casts for broken bones. - Crafting decorative materials and false ceilings.
35(b). An acid ‘X’ present in tamarind when mixed with ‘Y’ produces a mixture ‘Z’. ‘Y’ is prepared from common salt and helps in faster cooking. (i) Write the common names of ‘X’, ‘Y’, and ‘Z’, and the chemical formula of ‘Y’. (ii) How is ‘Y’ prepared and how does it help in making cakes soft and spongy? Illustrate the reaction with a suitable chemical equation. (iii) Write the name and chemical formula of a mild base other than ‘Y’ used as an antacid.	(i) X: Tartaric acid, Y: Baking soda, Z: Baking powder. Formula of Y: NaHCO₃. (ii) Preparation: Solvay process. Reaction: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. (iii) Antacid: Mg(OH)₂.	(i) Common Names and Formula: - X: Tartaric acid (found in tamarind). - Y: Baking soda, NaHCO₃. - Z: Baking powder (a mixture of tartaric acid and baking soda). (ii) Preparation of Baking Soda (Y): Baking soda is prepared using the Solvay process: NaCl + H₂O + CO₂ + NH₃ → NaHCO₃ + NH₄Cl. Role in Cakes:When heated or mixed with tartaric acid, baking soda releases CO₂, which creates bubbles in the dough, making it soft and spongy. Reaction: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. (iii) Other Mild Base: Magnesium hydroxide (Mg(OH)₂), commonly known as Milk of Magnesia, is used as an antacid.
36(a). (i) Which type of circuits—series or parallel—should be used when you have to operate different electrical gadgets in your house? List two reasons for your answer. (ii) Find the current flowing through the following electric circuit (circuit diagram provided).	(i) Parallel circuits. Reasons: 1. Independent operation of devices. 2. Consistent voltage across devices. (ii) Current: 0.5 A.	(i) Circuit Type: Parallel circuits should be used. Reasons:1. In a parallel circuit, each gadget receives the same voltage as the source, ensuring proper functioning. 2. If one gadget fails, others continue to operate independently. (ii) Current Calculation:Total resistance (R_total): - Two 6Ω resistors in parallel: 1/R = 1/6 + 1/6 = 2/6 = 1/3. Thus, R = 3Ω. - Total resistance: 3Ω + 3Ω + 3Ω = 9Ω. - Current (I) using Ohm's law: I = V/R = 4.5V / 9Ω = 0.5 A.
36(b). The values of current (I) flowing in a given resistor for the corresponding values of potential difference (V) are given: I (Amperes): 0.5, 1.0, 2.0, 3.0, 3.5 V (Volts): 1.5, 3.0, 6.2, 9.3, 10.8 (i) Plot a graph between V and I. (ii) Calculate the resistance of the resistor with the help of the graph. (iii) What does the graph represent? (iv) Why should this graph pass through the origin?	(i) Graph: Linear relationship. (ii) Resistance: ~3.13 Ω. (iii) Represents Ohm's Law. (iv) Passes through origin as V = 0 when I = 0.	(i) Graph: Plot V (y-axis) against I (x-axis). The graph is a straight line passing through the origin. (ii) Resistance: Using two points on the graph: R = ΔV / ΔI. From V₁ = 1.5V, I₁ = 0.5A, and V₂ = 6.2V, I₂ = 2.0A: R = (6.2 - 1.5) / (2.0 - 0.5) = 4.7 / 1.5 ≈ 3.13 Ω. (iii) Graph Representation: The graph represents Ohm’s Law (V ∝ I), indicating a constant resistance. (iv) Pass through Origin: The graph passes through the origin because when current (I) is 0, potential difference (V) across the resistor is also 0.
37. A highly polished surface such as a mirror reflects most of the light falling on it. In our daily life we use two types of mirrors—plane and spherical. (a) Define the principal axis of a concave mirror. (b) A ray of light is incident on a concave mirror, parallel to its principal axis. If this ray after reflection passes through the principal axis from a point at a distance of 10 cm from the pole of the mirror, find the radius of curvature of the mirror. (c)(i) An object is placed at a distance of 10 cm from the pole of a convex mirror of focal length 15 cm. Find the position of the image.	(a) Principal axis: Line through pole and center of curvature. (b) R = 20 cm. (c)(i) Position: 6 cm behind the mirror.	(a) Principal Axis: The straight line passing through the pole and the center of curvature of a concave mirror. (b) Radius of Curvature: Focal length (f) = 10 cm. Radius of curvature (R) = 2 × f = 20 cm. (c)(i) Image Position: Using mirror formula: 1/f = 1/v + 1/u Given: f = +15 cm (convex mirror), u = -10 cm. 1/v = 1/15 + 1/10 = 5/30 = 1/6 → v = +6 cm. The image is 6 cm behind the mirror.
(c)(ii) OR A mirror forms a virtual, erect, and diminished image of an object. Identify the type of this mirror. Draw a ray diagram to show the image formation in this case.	(c)(ii) Mirror: Convex mirror.	(c)(ii) Mirror Type: Convex mirror forms a virtual, erect, and diminished image. Ray Diagram: A convex mirror reflects rays such that they appear to diverge from the focus.
38. Carbon is a versatile element that forms the basis of all living organisms. A large variety of compounds is formed because of its tetravalency. (a) What are hydrocarbons? (b) List two properties by virtue of which carbon can form a large number of compounds. (c)(i) Write the formula of the functional group present in (1) aldehydes, and (2) ketones. Write the chemical equation for the reaction that occurs between ethanoic acid and ethanol in the presence of a catalyst.	(a) Hydrocarbons: Compounds of C and H. (b) Properties: Tetravalency, Catenation. (c)(i) Aldehyde: -CHO, Ketone: -C=O. Reaction: Esterification.	(a) Hydrocarbons: Organic compounds composed only of carbon and hydrogen. (b) Properties of Carbon: - Tetravalency: Carbon forms four covalent bonds. - Catenation: Ability to form long chains with other carbon atoms. (c)(i) Functional Groups: - Aldehydes: -CHO. - Ketones: -C=O. Reaction: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O (Esterification).
(c)(ii) OR What are structural isomers? Write the structures of two isomers of butane (C4H10).	(c)(ii) Isomers: n-Butane, Isobutane.	(c)(ii) Structural Isomers of Butane: - n-Butane: CH3CH2CH2CH3. - Isobutane: (CH3)3CH.
39. Pollination is an important process in sexual reproduction of plants. (a) Write the main difference between self-pollination and cross-pollination. (b) Name the part of the flower which attracts insects for pollination. What happens to this part after fertilisation? (c)(i) Define fertilisation. What is the fate of ovules and the ovary in a flower after fertilisation?	(a) Self-pollination: Same plant. Cross-pollination: Different plants. (b) Part: Petals; Fall off after fertilisation. (c)(i) Ovules → Seeds; Ovary → Fruit.	(a) Difference:- Self-pollination: Transfer of pollen within the same flower or plant. - Cross-pollination: Transfer of pollen between flowers of different plants of the same species. (b) Part: Petals attract insects. After fertilisation, petals wither and fall off. (c)(i) Fertilisation: Fusion of male and female gametes to form a zygote. - Ovules develop into seeds. - Ovary develops into fruit.
(c)(ii) OR In a germinating seed, which parts are known as future shoot and future root? Mention the function of cotyledon.	(c)(ii) Shoot: Plumule; Root: Radicle; Cotyledon: Stores food.	(c)(ii) Future Shoot: Plumule. Future Root: Radicle. Function of Cotyledon: Stores food for the developing embryo during germination.