Brain Grain · braingrain.in
Science — Practice Paper · Set 1
Class: 9Samacheer KalviMax Marks: 79
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 3 × 1 = 3
Choose the correct answer. (Answer all questions.)
1.Which one of the following is most likely not a case of uniform circular motion?[1]
2.Choose the correct one.[1]
3.Which of the following converts electrical energy into mechanical energy?[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
4.Buckminster Fullerene contains ______ carbon atoms.[1]
5.A substance that sublimes is ______.[1]
6.In Dobereiner’s triads, atomic mass of middle element is average of atomic masses of the ______.[1]
7.In petroleum refining, the method of separation used is ______.[1]
8.______ is a chemical used in finger print analysis.[1]
Part III — Short Answer Questions 18 × 2 = 36
Answer briefly. (Answer all questions.)
9.Xerophytes Have Deep Roots[2]
10.Naturally Occurring Toxic Substances[2]
11.Why Leafy Vegetables for Anaemia?[2]
12.Italian species of honey bee is[2]
13.What is Radiocarbon Dating?[2]
14.Why do properties vary across a period?[2]
15.The area under velocity-time graph represents the[2]
16.What is Skeletal Connective Tissue?[2]
17.The SI unit of electric current is kilogram.[2]
18.Polycarbonate (PC) and ABS plastics belong to resin code[2]
19.The term nucleons refers to[2]
20.Which mirror has negative focal length according to Cartesian sign convention?[2]
21.What is Nastic Movement?[2]
22.Roots are[2]
23.Physician who discovered scurvy can be cured by citrus fruits[2]
24.If revolution period of planet A is 8 times that of planet B, then distance ratio is[2]
25.Angle of deviation depends on refractive index of glass.[2]
26.Which is not present in sweat?[2]
Part IV — Long Answer Questions 7 × 5 = 35
Answer in detail. (Answer all questions.)
27.Explain a method to find the thickness of a hollow tea cup.[5]
28.Explain Principle, Construction and Working of a DC Motor[5]
29.Which Plastic Bottle Should Yugaa Buy?[5]
30.Uses of Presentation Software[5]
31.Speed of Light in Diamond[5]
32.Heat Needed to Convert Ice into Water at (20^\circ C)[5]
33.Differentiate[5]
🔑 Show Answer Key — Set 1
- 1. (a) Motion of the Earth around the Sun (b) Motion of a toy train on a circular track (c) Motion of a racing car on a circular track (d) Motion of the hour hand on a clock dial Answer: (c) Motion of a racing car on a circular track
- 2. (a) mm < cm < m < km (b) mm > cm > m > km (c) km < m < cm < mm (d) mm > m > cm > km Answer: (a) mm < cm < m < km
- 3. (a) Motor (b) Battery (c) Generator (d) Switch Answer: (a) Motor
- 4. 60
- 5. camphor or dry ice
- 6. first and third elements
- 7. fractional distillation
- 8. Ninhydrin
- 9. Xerophytes are plants that grow in dry habitats where water is scarce. These plants have evolved special adaptations to survive in arid and semi-arid environments. One of their most important adaptations is having deep roots that extend far into the soil to reach water sources that are located deep underground. These deep root systems allow xerophytes to absorb water from deeper soil layers where moisture is more readily available, even when the surface soil is completely dry. This adaptation enables xerophytes to maintain their water supply during prolonged periods of drought and extreme heat.
- 10. Prussic acid in apple seeds Marine toxins in fishes
- 11. Leafy vegetables are recommended for anaemia because they contain iron, which is an essential mineral required for the formation of haemoglobin in red blood cells. Haemoglobin is the protein that carries oxygen throughout the body, and iron is a crucial component of its structure. Anaemia occurs when there is insufficient haemoglobin or red blood cells, often due to iron deficiency. Leafy vegetables such as spinach, fenugreek, and other green vegetables are rich sources of iron and other nutrients. Dates are also excellent sources of iron and other minerals. Consuming iron-rich foods helps increase iron levels in the blood, promoting the formation of new haemoglobin and red blood cells, thereby treating and preventing iron-deficiency anaemia.
- 12. (a) *Apis mellifera* (b) *Apis dorsata* (c) *Apis florea* (d) *Apis cerana* Answer: (a) *Apis mellifera* <div
- 13. Radiocarbon dating is method used to determine age of fossils and dead organisms using radioactive isotope: $$^{14}C$$ (Carbon-14)
- 14. Across a period: atomic number increases valence electrons increase Hence chemical properties gradually change.
- 15. (a) velocity of the moving object (b) displacement covered by the moving object (c) speed of the moving object (d) acceleration of the moving object Answer: (b) displacement covered by the moving object <div
- 16. Supporting connective tissue forming endoskeleton is called skeletal connective tissue. Types: Bone Cartilage Functions Support body Protect organs Help locomotion
- 17. False. The statement is incorrect. The SI unit of electric current is ampere (A), not kilogram. Kilogram is the SI unit of mass. Electric current measures the flow of electric charge through a conductor, and it is measured in amperes using an ammeter. This is one of the seven fundamental SI units in the International System of Units.
- 18. (a) 2 (b) 5 (c) 6 (d) 7 Answer: (d) 7 Correction made: Original answer incorrectly mentioned option (a).
- 19. (a) protons and electrons (b) only neutrons (c) electrons and neutrons (d) protons and neutrons Answer: (d) protons and neutrons
- 20. According to the Cartesian sign convention, a concave mirror has a negative focal length. In this convention, distances measured in the direction opposite to the direction of incident light are taken as negative. For a concave mirror, the focal point and centre of curvature lie in front of the mirror on the same side as the incident light. Therefore, the focal length f is assigned a negative value. This is in contrast to a convex mirror, which has a positive focal length because its focal point is behind the mirror.
- 21. Nastic movement is a non-directional movement of plant parts in response to a stimulus. Unlike tropic movements, nastic movements do not depend on the direction of the stimulus. The direction of movement is determined by the structure of the plant organ itself, not by where the stimulus comes from. Examples include the opening and closing of flowers in response to light and temperature, and the rapid closing of leaves in Mimosa pudica in response to touch. These movements are growth-independent and occur due to changes in turgor pressure in specialized cells.
- 22. (i) positively phototropic but negatively geotropic (ii) positively geotropic but negatively phototropic (iii) negatively phototropic but positively hydrotropic (iv) negatively hydrotropic but positively phototropic Answer: (b) (ii) and (iii) <div
- 23. (a) James Lind (b) Louis Pasteur (c) Charles Darwin (d) Isaac Newton Answer: (a) James Lind
- 24. (a) 4 (b) 5 (c) 2 (d) 3 Answer: (a) 4 Using Kepler’s Third Law: $$T^2 \propto R^3$$ <div
- 25. True. The angle of deviation depends on the refractive index of the glass. When light passes through a prism or glass block, it bends due to refraction. The amount of bending, or deviation, is determined by Snell's law, which states that n₁ sin θ₁ = n₂ sin θ₂, where n represents the refractive index of the medium and θ represents the angle of incidence or refraction. A higher refractive index means the medium is optically denser and causes greater bending of light, resulting in a larger angle of deviation. Conversely, a lower refractive index causes less bending and a smaller angle of deviation. Therefore, different types of glass with different refractive indices will produce different angles of deviation for the same incident light.
- 26. (a) Urea (b) Protein (c) Water (d) Salt Answer: (b) Protein
- 27. Procedure: Determine the pitch and least count of the screw gauge. Place the tea cup between the studs. Rotate the ratchet until the cup is held gently. Note the pitch scale reading (PSR). Note the head scale coincidence (HSC). Calculate thickness using: $$\text{Thickness} = \text{PSR} + (\text{HSC} \times \text{LC})$$ Repeat readings at different positions and calculate the average.
- 28. Principle A current-carrying conductor placed in magnetic field experiences force. Direction is determined using Fleming’s Left Hand Rule. Construction Main parts: Armature coil Field magnet Split ring commutator Carbon brushes Battery Working Current passes through armature coil. Opposite sides of coil experience opposite forces. Coil rotates. Split ring reverses current every half rotation. Continuous rotation is produced. Thus electrical energy converts into mechanical energy.
- 29. She should buy bottle with: Resin Code 5 (Polypropylene) Reason Safer plastic Heat resistant Less toxic Why Avoid Others? Resin Code 1 Single-use plastic. Resin Code 3 PVC — highly toxic. Resin Code 7 Contains polycarbonate and BPA-related plastics.
- 30. Classroom teaching Business meetings Project presentations Seminars Training programs
- 31. Given: $$\mu = 2.41$$ Using: $$\mu = \frac{c}{v}$$ $$v = \frac{3 \times 10^8}{2.41}$$ $$v = 1.24 \times 10^8 m/s$$ Conclusion: Speed of light in diamond is much lower than in vacuum.
- 32. Given: $$m = 2kg$$ $$L = 334000J/kg$$ $$c = 4200J/kgK$$ Heat to Melt Ice $$Q_1 = mL$$ $$= 2 \times 334000$$ $$= 668000J$$ Heat to Raise Temperature $$Q_2 = mc\Delta T$$ $$= 2 \times 4200 \times 20$$ $$= 168000J$$ Total Heat $$Q = Q_1 + Q_2$$ $$= 668000 + 168000$$ $$= 836000J$$
- 33. (a) Kwashiorkor and Marasmus Kwashiorkor Marasmus Protein deficiency Deficiency of proteins, fats and carbohydrates Usually affects 1–5 years Usually affects infants below 1 year Swollen belly Severe wasting and thin body (b) Macronutrients and Micronutrients Macronutrients Micronutrients Needed in large amounts Needed in small amounts Examples: carbohydrates, proteins, fats and water Examples: vitamins and minerals such as iron, iodine, calcium and vitamin A <div
Brain Grain · braingrain.in
Science — Practice Paper · Set 2
Class: 9Samacheer KalviMax Marks: 79
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 3 × 1 = 3
Choose the correct answer. (Answer all questions.)
1.Which one of the following is most likely not a case of uniform circular motion?[1]
2.Choose the correct one.[1]
3.Which of the following converts electrical energy into mechanical energy?[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
4.Calcium and Argon are examples of a pair of ______.[1]
5.Acids present in plants and animals are organic acids, whereas acids in rocks and minerals are ______.[1]
6.Example for liquid metal is ______.[1]
7.______ is a structured delivery of information.[1]
8.______ named carbon.[1]
Part III — Short Answer Questions 18 × 2 = 36
Answer briefly. (Answer all questions.)
9.Define least count of any device.[2]
10.State Pascal’s law.[2]
11.Hermaphrodite organisms are[2]
12.Ceres is a[2]
13.Why do stars appear blue or red?[2]
14.Identify Acids A and B[2]
15.Differentiate Graphite and Diamond[2]
16.Things to Check on Jam Bottle Label[2]
17.Define Neutralization Reaction[2]
18.State Faraday’s Laws of Electromagnetic Induction[2]
19.Plants lose water when stomata are closed.[2]
20.High milk-yielding cattle breed is[2]
21.Define standard unit.[2]
22.Element that forms an anion by gaining electrons is[2]
23.Importance of Water Conservation[2]
24.Specific Gravity of Block[2]
25.Locomotion in Starfish[2]
26.Upthrust on Wooden Block[2]
Part IV — Long Answer Questions 7 × 5 = 35
Answer in detail. (Answer all questions.)
27.Sheep manure contains more nutrients than farmyard manure.[5]
28.Verify Laws of Reflection of Sound[5]
29.Racing Car Problem[5]
30.Orbital Period at 400 km Height[5]
31.Significance of Hexagonal Honeycomb Cells[5]
32.Derive the Equations of Motion by Graphical Method[5]
33.Mushroom Cultivation[5]
🔑 Show Answer Key — Set 2
- 1. (a) Motion of the Earth around the Sun (b) Motion of a toy train on a circular track (c) Motion of a racing car on a circular track (d) Motion of the hour hand on a clock dial Answer: (c) Motion of a racing car on a circular track
- 2. (a) mm < cm < m < km (b) mm > cm > m > km (c) km < m < cm < mm (d) mm > m > cm > km Answer: (a) mm < cm < m < km
- 3. (a) Motor (b) Battery (c) Generator (d) Switch Answer: (a) Motor
- 4. isobars
- 5. Inorganic acids
- 6. mercury
- 7. (a) Slide Show (b) Page (c) Word Art (d) Presentation Answer: (d) Presentation
- 8. Antoine Lavoisier
- 9. The least count of an instrument is the smallest measurement that can be measured accurately using that instrument. Formulae: For Vernier Caliper: $$\text{Least Count} = \frac{\text{Value of one main scale division}}{\text{Total number of vernier scale divisions}}$$ For Screw Gauge: $$\text{Least Count} = \frac{\text{Pitch}}{\text{Number of head scale divisions}}$$
- 10. Pascal's law states that pressure applied on an enclosed incompressible liquid is transmitted equally in all directions throughout the liquid. This means that when an external force is applied to a confined fluid, the resulting pressure increase is distributed uniformly throughout the entire volume of the fluid. The pressure acts perpendicular to the surfaces of the container at every point. This principle is the foundation for hydraulic machines such as hydraulic lifts, hydraulic presses, and hydraulic brakes, where a small force applied over a small area can produce a large force over a larger area.
- 11. (a) Hydra, Tapeworm, Earthworm, Amphioxus (b) Hydra, Tapeworm, Earthworm, Ascidian (c) Hydra, Tapeworm, Earthworm, Balanoglossus (d) Hydra, Ascaris, Earthworm Answer: (b) Hydra, Tapeworm, Earthworm, Ascidian <div
- 12. (a) meteor (b) star (c) planet (d) asteroid Answer: (d) asteroid Ceres is also classified as a dwarf planet.
- 13. Colour depends on temperature. Hot stars → blue/white Cooler stars → orange/red
- 14. Acid A Gives one hydrogen ion per molecule. Answer: $$HCl$$ (Hydrochloric acid) Acid B Gives two hydrogen ions per molecule. Answer: $$H_2SO_4$$ (Sulphuric acid) King of Chemicals $$H_2SO_4$$ Sulphuric acid
- 15. Graphite Diamond Each carbon forms 3 covalent bonds Each carbon forms 4 covalent bonds Soft and slippery Extremely hard Layered hexagonal structure Tetrahedral 3D structure Conducts electricity Poor conductor of electricity Opaque Transparent Correction made: Diamond conducts heat well though it is electrical insulator. <div
- 16. Date of manufacture Expiry date FPO certification Ingredients Net weight
- 17. Reaction between acid and base producing salt and water is called neutralization. $$HCl + NaOH \rightarrow NaCl + H_2O$$
- 18. First Law Whenever magnetic flux linked with a coil changes, an emf is induced. Second Law The induced emf is equal to the negative rate of change of magnetic flux. The negative sign shows Lenz's law: the induced emf opposes the change in flux. $$E = -\frac{d\Phi}{dt}$$
- 19. False. Correct Statement: Plants lose water mainly when stomata are open. When stomata are closed, the openings through which water vapour escapes are sealed, so water loss through transpiration is minimized. Stomata open during the day to allow gas exchange for photosynthesis, and this is when maximum water loss occurs. At night or during stress conditions, stomata close to conserve water.
- 20. (a) Holstein–Friesian (b) Dorset (c) Sahiwal (d) Red Sindhi Answer: (a) Holstein–Friesian <div
- 21. A standard unit is a fixed quantity of constant magnitude that is used as a reference to measure other quantities of the same nature. Standard units are internationally agreed upon and remain unchanged, ensuring consistency and uniformity in measurements across different regions and countries. For example, the metre is the standard unit of length, the kilogram is the standard unit of mass, and the second is the standard unit of time. These standard units form the basis of the SI system and allow scientists and people worldwide to communicate measurements accurately.
- 22. (a) potassium (b) calcium (c) fluorine (d) iron Answer: (c) fluorine <div
- 23. Water is precious natural resource Essential for all living organisms Freshwater availability is limited
- 24. Given: Weight in air = 60 N Weight in water = 40 N Loss of weight: $$60 - 40 = 20N$$ Specific gravity: $$\frac{60}{20} = 3$$
- 25. Locomotion in starfish occurs through the coordinated action of tube feet, which are small, sucker-like structures distributed across the arms and body surface. These tube feet are part of the water vascular system, a unique hydraulic system found only in echinoderms. The water vascular system contains fluid-filled canals that connect to each tube foot, allowing them to extend and contract. When the tube feet extend and attach to the substrate using their suckers, they pull the starfish forward in a slow, gliding motion. This mechanism enables starfish to move across the ocean floor and climb vertical surfaces with remarkable efficiency.
- 26. Given: Weight of block = 200 g Volume = (300 cm^3) Correct Concept: For a floating body: $$\text{Upthrust} = \text{Weight of body}$$ Therefore, $$\text{Upthrust} = 200\ \text{gwt}=1.96\ \text{N}$$ Correction made: Original solution incorrectly used volume as upthrust.
- 27. True
- 28. Procedure Take two long identical tubes. Place them near reflecting wall. Place ticking clock near one tube. Listen through second tube. Adjust tube positions for maximum sound. Observation Measured angles satisfy: $$\angle i = \angle r$$ Conclusion Laws of reflection of sound are verified. Angle of incidence = angle of reflection Incident sound, reflected sound and normal lie in same plane
- 29. Given: $$a = 4m/s^2$$ $$u = 0$$ $$t = 10s$$ Using: $$s = ut + \frac{1}{2}at^2$$ $$s = 0 + \frac{1}{2} \times 4 \times 10^2$$ $$s = 200m$$ Answer: Distance covered = (200m)
- 30. Given: $$h = 400km$$ Using orbital period relation: Answer: $$T = 92.3 \text{ minutes}$$
- 31. Honeycomb is made from wax secreted by worker bees. Importance of Hexagonal Shape Maximum storage with minimum wax Strong structure Stores honey and pollen Used for rearing larvae
- 32. First Equation of Motion From velocity-time graph: $$a = \frac{v-u}{t}$$ Rearranging, $$v = u + at$$ This is the first equation of motion . Second Equation of Motion Displacement is equal to area under velocity-time graph. $$s = ut + \frac{1}{2}at^2$$ This is the second equation of motion . Third Equation of Motion Using: $$t = \frac{v-u}{a}$$ Substituting into: $$s = \frac{1}{2}(u+v)t$$ We get: $$v^2 = u^2 + 2as$$ This is the third equation of motion . <div
- 33. Mushroom Culture Growing mushrooms using agricultural and industrial wastes. Steps in Mushroom Cultivation (i) Composting Paddy straw mixed with cow dung and fertilizers Maintained around (50^\circ C) (ii) Spawning Spawn acts as mushroom seed Fungal mycelium grown under sterile conditions (iii) Casing Thin soil layer added to maintain humidity and temperature. (iv) Pinning Small white buds develop into mushrooms. (v) Harvesting Temperature maintained between (15^\circ C) and (23^\circ C) Mushrooms harvested after about 3 weeks
Brain Grain · braingrain.in
Science — Practice Paper · Set 3
Class: 9Samacheer KalviMax Marks: 79
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 3 × 1 = 3
Choose the correct answer. (Answer all questions.)
1.Which one of the following is most likely not a case of uniform circular motion?[1]
2.Choose the correct one.[1]
3.Which of the following converts electrical energy into mechanical energy?[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
4.______, ______ and ______ are macronutrients required for plant growth.[1]
5.Fill in the Blanks __________[1]
6.______ is essential for solvent extraction method.[1]
7.Electric field lines ______ from positive charge and ______ in negative charge.[1]
8.Painkiller drugs are called ______.[1]
Part III — Short Answer Questions 18 × 2 = 36
Answer briefly. (Answer all questions.)
9.Question 2[2]
10.What is Catenation?[2]
11.Pressure at Bottom of Swimming Pool[2]
12.Light Year Problem[2]
13.Charge Flowing Through Bulb[2]
14.Tropic movement helping climbing plants find support is[2]
15.Smooth muscles occur in[2]
16.A physical balance is more sensitive than a beam balance.[2]
17.Define Taxonomy[2]
18.Why is a bird sitting on a high power line safe?[2]
19.Why Does Carbon Form Covalent Compounds?[2]
20.What is Nematocyst?[2]
21.What are electric lines of force?[2]
22.Metal carbonates and bicarbonates react with acids to liberate[2]
23.Dioxins and PVC Plastics[2]
24.Types of Fish Ponds[2]
25.Which does not contain natural dye?[2]
26.Which key is used to run a slide show?[2]
Part IV — Long Answer Questions 7 × 5 = 35
Answer in detail. (Answer all questions.)
27.Structure of Kidney and Urine Formation[5]
28.Hormones are present in glomerular filtrate.[5]
29.Show that smaller area produces greater pressure[5]
30.Why would a 60 kg person weigh 1680 kg on Sun?[5]
31.Why is Sulphuric Acid Called King of Chemicals?[5]
32.Athlete on Circular Track[5]
33.Nerve cell does not contain[5]
🔑 Show Answer Key — Set 3
- 1. (a) Motion of the Earth around the Sun (b) Motion of a toy train on a circular track (c) Motion of a racing car on a circular track (d) Motion of the hour hand on a clock dial Answer: (c) Motion of a racing car on a circular track
- 2. (a) mm < cm < m < km (b) mm > cm > m > km (c) km < m < cm < mm (d) mm > m > cm > km Answer: (a) mm < cm < m < km
- 3. (a) Motor (b) Battery (c) Generator (d) Switch Answer: (a) Motor
- 4. Nitrogen, phosphorus and potassium
- 5. Stimulus Response Light Phototropism Gravity Geotropism Water Hydrotropism Touch Thigmotropism
- 6. (a) Separating funnel (b) Filter paper (c) Centrifuge machine (d) Sieve Answer: (a) Separating funnel
- 7. (a) start; start (b) start; end (c) start; end (d) end; end Answer: (b) start; end
- 8. analgesics
- 9. Assertion (A): 0°C = 273.15 K. For convenience, it is rounded off to 273 K. Reason (R): To convert Celsius temperature into Kelvin, we add 273 to the given temperature. Answer: (b) Both A and R are true and R is the correct reason.
- 10. Catenation is property by which atoms of same element link together through covalent bonds. Carbon and Catenation Carbon atoms bond with one another repeatedly. They form: straight chains branched chains ring structures This leads to enormous number of organic compounds. Examples: Starch Cellulose Hydrocarbons
- 11. Given: $$h = 3m$$ $$\rho = 1000kg/m^3$$ $$g = 9.8m/s^2$$ Using: $$P = h\rho g$$ $$= 3 \times 1000 \times 9.8$$ $$= 29400Pa$$
- 12. Question: Inian says one light year is (9.46 \times 10^{15}) m. Ezhilan says it is (9.46 \times 10^{12}) km. Who is correct? Solution: Both are correct because: $$1 \text{ km} = 10^3 \text{ m}$$ $$9.46 \times 10^{15} \text{ m} = 9.46 \times 10^{12} \text{ km}$$
- 13. Given: $$I = 2.5A$$ $$t = 2 \text{ hours} = 7200s$$ Using: $$Q = It$$ $$Q = 2.5 \times 7200$$ $$Q = 18000C$$
- 14. (a) Phototropism (b) Geotropism (c) Thigmotropism (d) Chemotropism Answer: (c) Thigmotropism <div
- 15. (a) Uterus (b) Artery (c) Vein (d) All of the above Answer: (d) All of the above
- 16. True. A physical balance is more sensitive than a beam balance. A physical balance can detect smaller differences in mass and provides greater precision in measurements. This is because a physical balance has a more delicate construction and can measure mass to a higher degree of accuracy compared to a beam balance, which is a simpler instrument. The physical balance is therefore preferred in laboratories when precise measurements are required.
- 17. Taxonomy is the branch of biology that deals with the identification, naming, and classification of organisms. It involves the systematic arrangement of living organisms into hierarchical categories based on their structural, functional, and evolutionary characteristics. Taxonomists use various methods including morphological analysis, genetic studies, and evolutionary relationships to organize organisms into groups such as kingdom, phylum, class, order, family, genus, and species. The primary goal of taxonomy is to create a comprehensive and organized system that reflects the diversity of life and the evolutionary relationships among different organisms. <div
- 18. A bird sitting on a single electric wire is safe because it does not complete the circuit. Since the bird is in contact with only one wire, there is no potential difference across its body. Electric current flows only when there is a potential difference and a complete circuit. The bird's feet are at the same potential as the wire it is standing on, so no current flows through its body. However, if the bird simultaneously touches another wire at a different potential or touches the ground while on the wire, it would complete a circuit and current would flow through its body, potentially causing electrocution. This is why birds can safely perch on high power lines without harm.
- 19. Carbon forms covalent compounds rather than ionic compounds because of its electron configuration and the energy requirements involved in electron transfer. Carbon has four valence electrons in its outermost shell. To form ionic compounds, carbon would need to either lose all four electrons to form a C⁴⁺ ion or gain four electrons to form a C⁴⁻ ion. Both of these processes require extremely high amounts of energy because removing or adding four electrons is energetically unfavorable. Instead, carbon achieves a stable electron configuration by sharing electrons with other atoms through covalent bonding. By sharing electrons, carbon can complete its octet and achieve the stable electron configuration of neon without requiring the enormous energy needed for complete electron transfer. This is why carbon predominantly forms covalent compounds with other elements such as hydrogen, oxygen, nitrogen, and other carbon atoms, rather than forming ionic compounds.
- 20. A nematocyst is a specialized stinging capsule present within cnidocytes, which are specialized cells found in coelenterates such as hydra, jellyfish, and sea anemones. Each nematocyst contains a coiled, hollow thread that can be rapidly discharged when triggered by contact with prey or threats. The nematocyst serves two primary functions: it helps in the defense of the organism against predators and parasites, and it aids in the capture and immobilization of prey organisms. When discharged, the nematocyst injects toxins that can paralyze or kill small organisms, making it an effective hunting and defensive tool for these aquatic animals.
- 21. Electric lines of force are imaginary lines drawn in space around a charged body that represent the direction and strength of the electric field at any point. These lines originate from positive charges and terminate at negative charges. The direction of an electric line of force at any point is the same as the direction of the electric force that would act on a small positive test charge placed at that point. The density of these lines indicates the strength of the electric field in that region. Regions with closely spaced lines have a stronger electric field, while regions with widely spaced lines have a weaker field. Electric lines of force never intersect each other because at any point in space, the electric field can have only one direction.
- 22. (NO_2) (SO_2) (CO_2) Answer: $$CO_2$$
- 23. Formation of Dioxins Dioxins form during: burning plastics industrial processes waste incineration Especially when chlorine-containing materials burn. Linked Plastic PVC (Polyvinyl Chloride) Harmful Effects Cancer Hormonal imbalance Immune suppression Reproductive disorders Developmental defects
- 24. Fish ponds are classified into five main types based on their specific functions in fish farming. Breeding ponds are used for maintaining and breeding mature fishes to obtain fertilized eggs for reproduction. Hatchling ponds are designed specifically for hatching the fertilized eggs under controlled conditions. Nursery ponds are used for rearing young hatchlings, allowing them to grow into fry, which are juvenile fish. Rearing ponds are utilized to raise fry into fingerlings, which are slightly larger juvenile fish. Stocking or culture ponds are the largest ponds where fingerlings are raised to market size, the final stage before fish are harvested for sale. Each pond type maintains specific environmental conditions suited to the developmental stage of the fish being cultured.
- 25. (a) Potato (b) Beetroot (c) Carrot (d) Turmeric Answer: (a) Potato
- 26. (a) F1 (b) Tab (c) F5 (d) F2 Answer: (c) F5
- 27. Structure of Kidney Bean-shaped organs Located on either side of vertebral column Right kidney slightly lower Internal Structure Cortex Outer region Medulla Inner region Contains renal pyramids. Hilum Entry point for: blood vessels nerves ureter Steps in Urine Formation (i) Glomerular Filtration Blood filtered in glomerulus. Filtrate enters Bowman’s capsule. (ii) Tubular Reabsorption Useful substances reabsorbed: glucose amino acids water salts (iii) Tubular Secretion Waste ions secreted into tubule. Final urine formed. Path of Urine $$Kidney \rightarrow Ureter \rightarrow Urinary\ bladder \rightarrow Urethra$$
- 28. False. Correct Statement: Hormones are not normally present in significant amounts in glomerular filtrate. The glomerular filtrate contains water, salts, glucose, amino acids, and urea, which are small molecules that can pass through the filtration barrier of the glomerulus. However, hormones are typically large protein molecules or are bound to proteins in the blood, so they cannot pass through the glomerular filter and are retained in the blood. Proteins and blood cells are also absent from the normal glomerular filtrate because they are too large to be filtered. The presence of proteins or hormones in the filtrate would indicate a problem with the filtration barrier.
- 29. Explanation: Pressure is given by: $$P = \frac{F}{A}$$ Where: (P) = Pressure (F) = Force (A) = Area When the same force acts on a smaller area, pressure increases. Example: A nail has: a pointed end (small area) a flat head (large area) The pointed end easily penetrates wood because pressure is greater at smaller area.
- 30. The person’s mass remains 60 kg, but weight depends on gravity. $$W = m \times g = 60 \times 274 = 16440 \text{ N}$$ $$16440 \div 9.8 \approx 1678 \text{ kgf} \approx 1680 \text{ kgf}$$ So, the person’s weight on the Sun is about 16,440 N, equal to the weight of a 1680 kg mass on Earth. The person’s mass remains 60 kg.
- 31. Sulphuric acid is called the King of Chemicals because of its extensive and diverse applications in the chemical and industrial sectors. Sulphuric acid is widely used in the manufacture of numerous other chemicals and industrial products, making it one of the most important chemicals in the world. It is used in the production of fertilizers, particularly in the manufacture of superphosphate fertilizers. Sulphuric acid is also essential in the refining of petroleum, the production of dyes and pigments, the manufacture of explosives, and in metal processing industries. Additionally, it is used in the production of plastics, synthetic fibers, and many other organic and inorganic compounds. The sheer volume of sulphuric acid produced and consumed globally, combined with its critical role in numerous industrial processes, justifies its designation as the King of Chemicals. Without sulphuric acid, modern industrial production would be severely hampered, making it indispensable to the chemical industry.
- 32. Given: Diameter = 200 m Radius = 100 m Time for one round = 40 s Total time = 2 min 20 s = 140 s Speed $$v = \frac{2\pi r}{40}$$ $$= \frac{2 \times 3.14 \times 100}{40}$$ $$= 15.7m/s$$ Distance Covered $$\text{Distance} = vt$$ $$= 15.7 \times 140$$ $$= 2198m$$ Displacement Number of rotations: $$\frac{140}{40} = 3.5$$ After 3.5 rotations, athlete reaches opposite side of circle. Displacement = diameter = (200m)
- 33. (a) Axon (b) Nerve endings (c) Tendons (d) Dendrites Answer: (c) Tendons