ADEPT YOURSELF
www.adeptyourself.com β’ Academic Excellence Series
CBSE CLASS IX β SCIENCE (CODE NO. 086)
SAMPLE QUESTION PAPER β SET 5 | ACADEMIC SESSION 2026β2027
General Instructions:
- The question paper comprises Five Sections: A, B, C, D and E. There are 39 questions in total.
- All questions are compulsory. However, an internal choice is provided in some questions.
- Section A consists of 20 objective type questions (Q1 to Q20) carrying 1 mark each. (Q1 to Q16 are MCQs, Q17 to Q20 are Assertion-Reasoning).
- Section B consists of 6 Very Short Answer type questions (Q21 to Q26) carrying 2 marks each.
- Section C consists of 7 Short Answer type questions (Q27 to Q33) carrying 3 marks each.
- Section D consists of 3 Long Answer type questions (Q34 to Q36) carrying 5 marks each.
- Section E consists of 3 Case-Based units of assessment (Q37 to Q39) carrying 4 marks each with sub-parts.
SECTION A β OBJECTIVE TYPE QUESTIONS (20 Marks)
Q1.
Which of the following describes the correct condition for liquefying gases into liquids?
[1]
Q2.
Two chemical substances $X$ and $Y$ combine to form a product $P$ containing both $X$ and $Y$: $X + Y \rightarrow P$. $P$ cannot be broken down into simpler substances by simple chemical reactions. $X$ and $Y$ are:
[1]
Q3.
Chromosomes are composed of which two primary biological macromolecules?
[1]
Q4.
Which of the following living plant tissues provides both mechanical support and contains chlorophyll for photosynthesis?
[1]
Q5.
A car travels from city A to city B with a uniform speed of $40\text{ km/h}$ and returns from B to A with a speed of $60\text{ km/h}$. The average speed of the car for the entire journey is:
[1]
Q6.
Which of the following represents the correct SI unit of momentum?
[1]
Q7.
An apple falls from a tree because of gravitational attraction between the earth and the apple. If $F_1$ is the magnitude of force exerted by the earth on the apple and $F_2$ is the magnitude of force exerted by the apple on the earth, then:
[1]
Q8.
What is the number of moles in $44\text{ g}$ of Carbon dioxide ($\text{CO}_2$)? [Atomic masses: $\text{C}=12\text{ u}$, $\text{O}=16\text{ u}$]
[1]
Q9.
Unripe green tomatoes turn red upon ripening due to the transformation of:
[1]
Q10.
When a body moves along a straight path with constant deceleration, its velocity-time graph is a straight line:
[1]
Q11.
Which isotope of an element is used as a fuel in nuclear reactors to produce electrical energy?
[1]
Q12.
Which of the following blood cells plays the primary role in immune defense by destroying foreign germs and bacteria?
[1]
Q13.
When the speed of a moving car is doubled, its kinetic energy:
[1]
Q14.
An acoustic ultrasound wave has a frequency of $50\text{ kHz}$. This sound is:
[1]
Q15.
Which of the following marine fishes is widely cultured under mariculture practices in India?
[1]
Q16.
What is the formula mass of Calcium Oxide ($\text{CaO}$)? [Given: $\text{Ca}=40\text{ u}$, $\text{O}=16\text{ u}$]
[1]
Q17.
Assertion (A): When common salt dissolves in water, there is no detectable increase in the volume of the solution.
Reason (R): The particles of salt get accommodated into the vacant intermolecular spaces between water molecules. [1]
(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.
Reason (R): The particles of salt get accommodated into the vacant intermolecular spaces between water molecules. [1]
(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.
Q18.
Assertion (A): Mitochondria are semiautonomous cell organelles.
Reason (R): Mitochondria possess their own DNA and ribosomes to synthesize some of their own proteins. [1]
(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.
Reason (R): Mitochondria possess their own DNA and ribosomes to synthesize some of their own proteins. [1]
(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.
Q19.
Assertion (A): When a bullet is fired from a rifle, the backward recoil velocity of the rifle is much smaller than the forward velocity of the bullet.
Reason (R): The mass of the rifle is much greater than the mass of the bullet, while their momentum changes are equal and opposite. [1]
(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.
Reason (R): The mass of the rifle is much greater than the mass of the bullet, while their momentum changes are equal and opposite. [1]
(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.
Q20.
Assertion (A): Flashes of lightning are seen before thunder is heard during a storm.
Reason (R): Light travels much faster ($3 \times 10^8\text{ m/s}$) than sound ($344\text{ m/s}$ in air). [1]
(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.
Reason (R): Light travels much faster ($3 \times 10^8\text{ m/s}$) than sound ($344\text{ m/s}$ in air). [1]
(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.
SECTION B β VERY SHORT ANSWER QUESTIONS (12 Marks)
Q21.
Convert the following Celsius temperatures to the Kelvin scale:
(a) $25^\circ\text{C}$
(b) $373^\circ\text{C}$ [2]
(a) $25^\circ\text{C}$
(b) $373^\circ\text{C}$ [2]
Q22.
Differentiate between simple permanent tissue and complex permanent tissue in plants with one example of each.
[2]
Q23.
A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of $3.0\text{ m/s}^2$ for $8.0\text{ s}$. How far does the boat travel during this time?
[2]
OR
State the universal law of gravitation. Write its mathematical formula with standard notation.
Q24.
Why does a block of plastic released under water come up to the surface of water? Explain using buoyant force.
[2]
Q25.
State two differences between manure and chemical fertilizers regarding nutrient specificity and soil structure.
[2]
Q26.
Write the chemical formulae of:
(a) Sodium sulphide
(b) Magnesium hydroxide [2]
(a) Sodium sulphide
(b) Magnesium hydroxide [2]
SECTION C β SHORT ANSWER QUESTIONS (21 Marks)
Q27.
(a) What is a colloid?
(b) State two distinguishing properties of a colloidal solution.
(c) Give an example of a colloid where the dispersed phase is a solid and the dispersion medium is a liquid. [3]
(b) State two distinguishing properties of a colloidal solution.
(c) Give an example of a colloid where the dispersed phase is a solid and the dispersion medium is a liquid. [3]
Q28.
Describe the structure and functions of the three types of epithelial tissues: (a) Squamous epithelium, (b) Cuboidal epithelium, (c) Columnar epithelium.
[3]
Q29.
A car of mass $1000\text{ kg}$ is moving at a speed of $72\text{ km/h}$. Brakes are applied to bring it to rest in $50\text{ m}$. Calculate:
(a) The initial velocity in $\text{m/s}$.
(b) The retardation produced by the brakes.
(c) The braking force acting on the car. [3]
(i) Mass on Moon?
(ii) Weight on Earth?
(iii) Weight on Moon? [Take $g_{\text{earth}} = 9.8\text{ m/s}^2$ and $g_{\text{moon}} = 1.63\text{ m/s}^2$]
(a) The initial velocity in $\text{m/s}$.
(b) The retardation produced by the brakes.
(c) The braking force acting on the car. [3]
OR
A body has a mass of $12\text{ kg}$ on Earth. What will be its:
(i) Mass on Moon?
(ii) Weight on Earth?
(iii) Weight on Moon? [Take $g_{\text{earth}} = 9.8\text{ m/s}^2$ and $g_{\text{moon}} = 1.63\text{ m/s}^2$]
Q30.
(a) Define 1 kilowatt-hour ($\text{kWh}$) of electrical energy.
(b) An electric bulb of $60\text{ W}$ is used for $6\text{ hours}$ per day. Calculate the commercial units of electrical energy consumed in one day by the bulb.
(c) What is the relationship between $\text{kWh}$ and Joules? [3]
(b) An electric bulb of $60\text{ W}$ is used for $6\text{ hours}$ per day. Calculate the commercial units of electrical energy consumed in one day by the bulb.
(c) What is the relationship between $\text{kWh}$ and Joules? [3]
Q31.
(a) State the Law of Conservation of Mass in a chemical reaction with a suitable balanced example.
(b) Calculate the formula mass of Potassium chloride ($\text{KCl}$) and Sulphuric acid ($\text{H}_2\text{SO}_4$).
[Given atomic masses: $\text{K}=39\text{ u}$, $\text{Cl}=35.5\text{ u}$, $\text{H}=1\text{ u}$, $\text{S}=32\text{ u}$, $\text{O}=16\text{ u}$] [3]
(b) Calculate the formula mass of Potassium chloride ($\text{KCl}$) and Sulphuric acid ($\text{H}_2\text{SO}_4$).
[Given atomic masses: $\text{K}=39\text{ u}$, $\text{Cl}=35.5\text{ u}$, $\text{H}=1\text{ u}$, $\text{S}=32\text{ u}$, $\text{O}=16\text{ u}$] [3]
Q32.
Differentiate between Xylem and Phloem on the basis of constituent cells, direction of transport, and physiological function.
[3]
Q33.
What is apiculture? Mention four valuable products obtained from beekeeping and name the Italian bee variety commonly reared.
[3]
SECTION D β LONG ANSWER QUESTIONS (15 Marks)
Q34.
(a) Explain the main postulates of Rutherford’s nuclear model of an atom.
(b) Why was Rutherford’s planetary model considered unstable according to electromagnetic theory?
(c) How did Neils Bohr overcome this objection in his atomic model? [5]
(b) Determine the electronic configuration and valency of:
(i) Nitrogen ($Z=7$)
(ii) Silicon ($Z=14$)
(iii) Argon ($Z=18$)
(c) Why are noble gases chemically unreactive?
(b) Why was Rutherford’s planetary model considered unstable according to electromagnetic theory?
(c) How did Neils Bohr overcome this objection in his atomic model? [5]
OR
(a) Define Valency. How is the valency of an atom related to the number of valence electrons?
(b) Determine the electronic configuration and valency of:
(i) Nitrogen ($Z=7$)
(ii) Silicon ($Z=14$)
(iii) Argon ($Z=18$)
(c) Why are noble gases chemically unreactive?
Q35.
(a) Describe the structure and functions of the Nucleus in a eukaryotic cell.
(b) Differentiate between Chromatin, Chromosomes, and Genes.
(c) What will happen if the nucleus is removed from a living eukaryotic cell? [5]
(b) State three characteristic features of cardiac muscles that distinguish them from skeletal muscles.
(c) What is the function of intercalated discs in cardiac muscle tissue?
(b) Differentiate between Chromatin, Chromosomes, and Genes.
(c) What will happen if the nucleus is removed from a living eukaryotic cell? [5]
OR
(a) Describe the structure of a Cardiac muscle fibre with the help of a neat labelled diagram.
(b) State three characteristic features of cardiac muscles that distinguish them from skeletal muscles.
(c) What is the function of intercalated discs in cardiac muscle tissue?
Q36.
(a) Prove that the sum of kinetic energy and potential energy of a freely falling body of mass $m$ remains constant at any point along its vertical trajectory of height $h$.
(b) A ball of mass $0.5\text{ kg}$ is dropped from a height of $20\text{ m}$. Calculate its:
(i) Potential energy at the initial height.
(ii) Kinetic energy just before touching the ground.
(iii) Velocity just before touching the ground. [Take $g = 10\text{ m/s}^2$] [5]
(b) What is SONAR? Explain how ultrasound echoes are used in SONAR to measure the depth of an ocean bed.
(c) A sonar device on a submarine sends out a signal and receives an echo $5\text{ s}$ later. Calculate the distance of the obstacle if the speed of sound in sea water is $1500\text{ m/s}$.
(b) A ball of mass $0.5\text{ kg}$ is dropped from a height of $20\text{ m}$. Calculate its:
(i) Potential energy at the initial height.
(ii) Kinetic energy just before touching the ground.
(iii) Velocity just before touching the ground. [Take $g = 10\text{ m/s}^2$] [5]
OR
(a) Describe the structure and working mechanism of the human ear in transmitting sound vibrations to the auditory nerve (Outer ear, Middle ear, Inner ear).
(b) What is SONAR? Explain how ultrasound echoes are used in SONAR to measure the depth of an ocean bed.
(c) A sonar device on a submarine sends out a signal and receives an echo $5\text{ s}$ later. Calculate the distance of the obstacle if the speed of sound in sea water is $1500\text{ m/s}$.
SECTION E β CASE-BASED INTEGRATED UNITS (12 Marks)
Q37. Read the following source carefully and answer the questions that follow:
[4](a) Name the separation technique described above. [1]
(b) Name two substances other than ammonium chloride that sublime upon heating. [1]
(c) Explain why ammonium chloride sublimes while sodium chloride does not. [2]
Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. When a mixture of ammonium chloride and common salt (sodium chloride) is heated in a china dish covered with an inverted funnel plugged with cotton, ammonium chloride sublimes and condenses on the cold inner walls of the funnel as a pure solid, while sodium chloride remains behind in the dish. Other substances undergoing sublimation include camphor, naphthalene, and solid carbon dioxide (dry ice).
(b) Name two substances other than ammonium chloride that sublime upon heating. [1]
(c) Explain why ammonium chloride sublimes while sodium chloride does not. [2]
OR
Explain the physical change that takes place when dry ice ($\text{solid CO}_2$) is exposed to atmospheric pressure at room temperature. [2]
Q38. Read the following source carefully and answer the questions that follow:
[4](a) State Newton’s Third Law of Motion. [1]
(b) Why do action and reaction forces never cancel each other out? [1]
(c) Explain the mechanism of rocket propulsion on the basis of Newton’s Third Law and conservation of momentum. [2]
According to Newton’s Third Law of Motion, whenever one object exerts a force on another object, the second object instantly exerts an equal and opposite force on the first object. Action and reaction forces are always equal in magnitude, opposite in direction, and act on two entirely different bodies. Therefore, they never cancel each other out. This law governs the propulsion of rockets, recoil of firearms, swimming in water, and walking on ground.
(b) Why do action and reaction forces never cancel each other out? [1]
(c) Explain the mechanism of rocket propulsion on the basis of Newton’s Third Law and conservation of momentum. [2]
OR
Explain why a person stepping out of a rowing boat onto the riverbank causes the boat to move backwards into the water. [2]
Q39. Read the following source carefully and answer the questions that follow:
[4](a) What is composite fish culture? [1]
(b) Name one surface feeder and one column feeder fish species used in composite fish culture. [1]
(c) What is the main ecological advantage of combining five or six fish species in a single pond? [2]
Composite fish culture is a highly intensive polyculture system where five or six selected fish species with different feeding habits are cultured together in a single freshwater pond. Species are chosen such that they do not compete for food. Surface feeders (Catla) feed on zooplankton; column feeders (Rohu) feed in the middle zone; bottom feeders (Mrigal and Common Carp) feed on detritus; Grass Carps consume aquatic weeds. This ensures total utilization of all ecological niches in the pond, resulting in high survival rates and commercial fish yields.
(b) Name one surface feeder and one column feeder fish species used in composite fish culture. [1]
(c) What is the main ecological advantage of combining five or six fish species in a single pond? [2]
OR
What is the major problem faced in composite fish culture regarding seed availability and how has induced breeding resolved it? [2]
CBSE CLASS IX SCIENCE (086) β SOLUTIONS & MARKING SCHEME β SET 5
SECTION A β ANSWERS
Q1. (c) Low temperature and high pressure [1]
Q2. (b) Elements [1]
Q3. (c) DNA and Proteins [1]
Q4. (c) Chlorenchyma [1]
Q5. (b) $48\text{ km/h}$ [$v_{\text{avg}} = \frac{2v_1v_2}{v_1+v_2} = \frac{2 \times 40 \times 60}{40 + 60} = \frac{4800}{100} = 48\text{ km/h}$] [1]
Q6. (b) $\text{kg}\cdot\text{m/s}$ [1]
Q7. (c) $F_1$ and $F_2$ are equal in magnitude (Newton’s Third Law / Universal Gravitation) [1]
Q8. (b) $1.0\text{ mole}$ [Molar mass of $\text{CO}_2 = 12 + 32 = 44\text{ g/mol}$; $n = \frac{44}{44} = 1.0\text{ mole}$] [1]
Q9. (b) Chloroplasts into chromoplasts [1]
Q10. (c) Sloping downwards to the right [1]
Q11. (c) Uranium-235 [1]
Q12. (b) White Blood Corpuscles (WBCs) [1]
Q13. (c) Becomes four times [$KE \propto v^2 \Rightarrow (2v)^2 = 4v^2$] [1]
Q14. (b) Inaudible to human ears because it is ultrasonic ($> 20\text{ kHz}$) [1]
Q15. (b) Pomfret and Mackerel [1]
Q16. (a) $56\text{ u}$ [Formula mass = $40 + 16 = 56\text{ u}$] [1]
Q17. (a) Both A and R are true and R is the correct explanation of A. [1]
Q18. (a) Both A and R are true and R is the correct explanation of A. [1]
Q19. (a) Both A and R are true and R is the correct explanation of A. [1]
Q20. (a) Both A and R are true and R is the correct explanation of A. [1]
SECTION B β ANSWERS
Q21.
- (a) $T(\text{K}) = 25 + 273 = \mathbf{298\text{ K}}$
- (b) $T(\text{K}) = 373 + 273 = \mathbf{646\text{ K}}$
Q22.
- Simple Permanent Tissue: Composed of only one type of cell structurally and functionally identical (e.g., Parenchyma, Collenchyma, Sclerenchyma).
- Complex Permanent Tissue: Composed of more than one type of cell working coordinates together as a single vascular conducting unit (e.g., Xylem, Phloem).
Q23.
Given: $u = 0$, $a = 3.0\text{ m/s}^2$, $t = 8.0\text{ s}$.
Distance $s = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}(3.0)(8.0)^2 = \frac{1}{2}(3)(64) = 3 \times 32 = \mathbf{96\text{ m}}$. [2]
OR
Distance $s = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}(3.0)(8.0)^2 = \frac{1}{2}(3)(64) = 3 \times 32 = \mathbf{96\text{ m}}$. [2]
OR
- Universal Law of Gravitation: Every object in the universe attracts every other object with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
- Formula: $F = G\frac{M \times m}{d^2}$, where $G = 6.673 \times 10^{-11}\text{ N}\cdot\text{m}^2/\text{kg}^2$.
Q24.
The density of plastic is less than the density of water. When submerged, the upward buoyant force exerted by displaced water is greater than the downward gravitational weight of the plastic block, pushing it upward to the surface. [2]
Q25.
- Manure: Organic natural substance, provides rich humus to soil, improves soil texture and water-holding capacity, non-nutrient specific.
- Fertilizers: Inorganic chemical salts, provide highly concentrated specific nutrients ($\text{N, P, K}$), do not add humus, and excessive use degrades soil fertility.
Q26.
- (a) Sodium sulphide: $\text{Na}^+$ and $\text{S}^{2-} \rightarrow \mathbf{\text{Na}_2\text{S}}$
- (b) Magnesium hydroxide: $\text{Mg}^{2+}$ and $\text{OH}^- \rightarrow \mathbf{\text{Mg}(\text{OH})_2}$
SECTION C β ANSWERS
Q27.
- (a) Colloid: A heterogeneous mixture in which solute particles are uniformly dispersed and have an intermediate size between $1\text{ nm}$ and $100\text{ nm}$.
- (b) Properties: (i) Particles scatter a beam of light (Tyndall effect). (ii) Particles do not settle down when left undisturbed (stable) and pass through filter paper.
- (c) Example: Sol (e.g., starch in water, milk of magnesia, paints).
Q28.
- (a) Squamous epithelium: Extremely thin, flat, and delicate cells forming a smooth lining (e.g., lining of blood vessels, lung alveoli, oesophagus); facilitates selective diffusion.
- (b) Cuboidal epithelium: Cube-like cells forming the lining of kidney tubules and salivary gland ducts; provides mechanical support and participates in secretion/absorption.
- (c) Columnar epithelium: Tall, pillar-like cells found in the lining of stomach and intestines; facilitates secretion of digestive enzymes and nutrient absorption.
Q29.
Given: $m = 1000\text{ kg}$, $u = 72\text{ km/h} = 72 \times \frac{5}{18} = 20\text{ m/s}$, $v = 0$, $s = 50\text{ m}$.
(a) Initial velocity $u = \mathbf{20\text{ m/s}}$.
(b) Using $v^2 = u^2 + 2as \Rightarrow 0 = (20)^2 + 2a(50) \Rightarrow 100a = -400 \Rightarrow a = \mathbf{-4\text{ m/s}^2}$ (Retardation = $4\text{ m/s}^2$).
(c) Braking force $F = m \times a = 1000 \times (-4) = -4000\text{ N}$. Magnitude = $\mathbf{4000\text{ N}}$. [3]
OR Given: $m = 12\text{ kg}$.
(i) Mass is constant everywhere $\Rightarrow$ Mass on Moon = $\mathbf{12\text{ kg}}$.
(ii) Weight on Earth $W_e = m \times g_e = 12 \times 9.8 = \mathbf{117.6\text{ N}}$.
(iii) Weight on Moon $W_m = m \times g_m = 12 \times 1.63 = \mathbf{19.56\text{ N}}$ (or $\frac{1}{6} \times 117.6 = 19.6\text{ N}$). [3]
(a) Initial velocity $u = \mathbf{20\text{ m/s}}$.
(b) Using $v^2 = u^2 + 2as \Rightarrow 0 = (20)^2 + 2a(50) \Rightarrow 100a = -400 \Rightarrow a = \mathbf{-4\text{ m/s}^2}$ (Retardation = $4\text{ m/s}^2$).
(c) Braking force $F = m \times a = 1000 \times (-4) = -4000\text{ N}$. Magnitude = $\mathbf{4000\text{ N}}$. [3]
OR Given: $m = 12\text{ kg}$.
(i) Mass is constant everywhere $\Rightarrow$ Mass on Moon = $\mathbf{12\text{ kg}}$.
(ii) Weight on Earth $W_e = m \times g_e = 12 \times 9.8 = \mathbf{117.6\text{ N}}$.
(iii) Weight on Moon $W_m = m \times g_m = 12 \times 1.63 = \mathbf{19.56\text{ N}}$ (or $\frac{1}{6} \times 117.6 = 19.6\text{ N}$). [3]
Q30.
- (a) **1 kilowatt-hour (kWh):** The commercial unit of electrical energy consumed by an appliance of power 1 kilowatt ($1000\text{ W}$) operated continuously for 1 hour.
- (b) Power $P = 60\text{ W} = \frac{60}{1000}\text{ kW} = 0.06\text{ kW}$, Time $t = 6\text{ h}$.
Energy consumed $E = P \times t = 0.06\text{ kW} \times 6\text{ h} = \mathbf{0.36\text{ kWh}}$ (or 0.36 units). - (c) $1\text{ kWh} = 1000\text{ W} \times 3600\text{ s} = \mathbf{3.6 \times 10^6\text{ Joules}}$.
Q31.
- (a) Law of Conservation of Mass: Mass can neither be created nor destroyed in a chemical reaction.
Example: In $\text{CaCO}_3 (100\text{ g}) \xrightarrow{\Delta} \text{CaO} (56\text{ g}) + \text{CO}_2 (44\text{ g})$, total mass of reactants ($100\text{ g}$) = total mass of products ($56 + 44 = 100\text{ g}$). - (b) (i) $\text{KCl} = 39 + 35.5 = \mathbf{74.5\text{ u}}$.
(ii) $\text{H}_2\text{SO}_4 = 2(1) + 32 + 4(16) = 2 + 32 + 64 = \mathbf{98\text{ u}}$.
Q32.
- Constituent cells: Xylem contains tracheids, vessels, xylem parenchyma, and xylem fibres (mostly dead cells); Phloem contains sieve tubes, companion cells, phloem parenchyma, and phloem fibres (mostly living cells).
- Direction of transport: Xylem transports water and minerals unidirectionally upwards from roots to leaves; Phloem translocates food bidirectionally from leaves to all plant organs.
- Energy requirement: Xylem transport operates by passive physical forces (transpiration pull); Phloem translocation requires metabolic energy (ATP).
Q33.
- Apiculture: The commercial rearing and scientific management of honeybees for the production of honey and beeswax.
- Products: Honey (nutritious food and medicine), Beeswax (used in cosmetics, polishes, candles), Royal jelly, and Bee venom.
- Italian Bee Variety: Apis mellifera.
SECTION D β ANSWERS
Q34.
OR
- (a) Rutherford’s Postulates:
1. There is a positively charged, extremely dense center in an atom called the nucleus, containing almost all the mass.
2. Electrons revolve around the nucleus in circular orbits.
3. The size of the nucleus is extremely small compared to the size of the atom. - (b) Electromagnetic Objection: An accelerating charged electron revolving in circular orbits must continuously emit radiation, lose energy, spiral inward, and collapse into the nucleus in $10^{-8}\text{ s}$, making matter unstable.
- (c) Bohr’s Resolution: Electrons revolve only in certain special non-radiating orbits called **discrete orbits** (stationary energy levels). While revolving in these discrete orbits, electrons do not radiate energy.
OR
- (a) Valency: The combining capacity of an atom of an element to attain a stable octet configuration. For elements with $1β4$ valence electrons, $\text{Valency} = \text{valence electrons}$; for $5β8$ valence electrons, $\text{Valency} = 8 – \text{valence electrons}$.
- (b) (i) Nitrogen ($Z=7$): Configuration = $2, 5 \Rightarrow \text{Valency} = 8 – 5 = \mathbf{3}$.
(ii) Silicon ($Z=14$): Configuration = $2, 8, 4 \Rightarrow \text{Valency} = \mathbf{4}$.
(iii) Argon ($Z=18$): Configuration = $2, 8, 8 \Rightarrow \text{Valency} = 8 – 8 = \mathbf{0}$. - (c) Noble gases have a completely filled outermost valence shell (duplet for $\text{He}$, octet of 8 electrons for $\text{Ne, Ar}$), giving them maximum electronic stability with zero tendency to gain, lose, or share electrons.
Q35.
OR
- (a) Nucleus Structure & Functions:
1. Enclosed by a double-layered **nuclear membrane** containing nuclear pores for macromolecular exchange.
2. Contains the **nucleolus** (site of ribosome assembly) and **chromatin** (tangled mass of DNA and histone proteins).
3. Functions: Controls all cellular metabolic activities, cellular reproduction/division, and carries hereditary genetic instructions. - (b) Chromatin vs Chromosomes vs Genes: Chromatin is the uncoiled thread-like DNA-protein complex in non-dividing cells; Chromosomes are condensed rod-shaped structures visible during cell division; Genes are functional segments of DNA carrying instructions for specific proteins.
- (c) If the nucleus is removed, metabolic coordination ceases, protein synthesis stops, and the cell ultimately dies.
OR
- (a) Cardiac Muscle Structure: Cylindrical, branched cells with a single centrally located nucleus and faint alternate cross-striations, joined end-to-end by specialized junctional cross-bridges called **intercalated discs**.
- (b) Distinction from Skeletal Muscles:
1. Involuntary in nature (not under conscious control).
2. Branched uninucleated cylindrical cells (skeletal muscles are unbranched and multinucleated).
3. Show rhythmic contraction and relaxation continuously throughout life without fatigue. - (c) Intercalated Discs: Specialized intercellular junctions that allow rapid transmission of electrical impulses from cell to cell, enabling cardiac muscle cells to contract synchronously as a single functional unit.
Q36.
OR
- (a) Proof of Conservation of Mechanical Energy:
Consider an object of mass $m$ released from height $h$.
1. At point A (height $h$, velocity $u=0$): $PE = mgh$, $KE = 0 \Rightarrow E_A = mgh + 0 = mgh$.
2. At point B (fallen distance $x$, velocity $v_1$): $v_1^2 = 0 + 2gx \Rightarrow KE = \frac{1}{2}m(2gx) = mgx$. Height $= h – x \Rightarrow PE = mg(h-x)$.
$E_B = mg(h-x) + mgx = mgh$.
3. At point C (just striking ground, height = 0, velocity $v$): $v^2 = 0 + 2gh \Rightarrow KE = \frac{1}{2}m(2gh) = mgh$, $PE = 0 \Rightarrow E_C = mgh + 0 = mgh$.
Since $E_A = E_B = E_C = mgh$, mechanical energy is conserved. - (b) Given: $m = 0.5\text{ kg}$, $h = 20\text{ m}$, $g = 10\text{ m/s}^2$.
(i) Potential energy at initial height $PE = mgh = 0.5 \times 10 \times 20 = \mathbf{100\text{ Joules}}$.
(ii) By conservation of energy, $KE_{\text{bottom}} = PE_{\text{top}} = \mathbf{100\text{ Joules}}$.
(iii) $KE = \frac{1}{2}mv^2 \Rightarrow 100 = \frac{1}{2}(0.5)v^2 \Rightarrow v^2 = \frac{200}{0.5} = 400 \Rightarrow v = \mathbf{20\text{ m/s}}$.
OR
- (a) Human Ear Mechanism:
1. Outer Ear (Pinna & Canal): Collects pressure waves and directs them to the eardrum.
2. Middle Ear (Ear ossicles: Malleus, Incus, Stapes): Amplifies pressure vibrations several-fold.
3. Inner Ear (Cochlea): Fluid-filled organ converts mechanical vibrations into electrical signals transmitted via the auditory nerve to the brain. - (b) SONAR (Sound Navigation and Ranging): Consists of a transmitter and detector installed under a ship. The transmitter emits ultrasound pulses that travel through water, strike the seabed/obstacle, and reflect back to the detector.
Formula: $2d = v \times t \Rightarrow d = \frac{v \times t}{2}$. - (c) Given: $t = 5\text{ s}$, $v = 1500\text{ m/s}$.
Distance $d = \frac{v \times t}{2} = \frac{1500 \times 5}{2} = \frac{7500}{2} = \mathbf{3750\text{ m}} = 3.75\text{ km}$.
SECTION E β ANSWERS
Q37.
- (a) Sublimation. [1]
- (b) Camphor, Naphthalene balls, Anthracene, or Solid $\text{CO}_2$ (Dry ice) (any two). [1]
- (c) Ammonium chloride has weaker intermolecular attractive forces that break easily at moderate heating temperatures, converting directly into vapor, whereas sodium chloride is an ionic compound with strong electrostatic bonds and a very high melting point ($801^\circ\text{C}$). [2]
Q38.
- (a) To every action, there is always an equal and opposite reaction. [1]
- (b) Because action and reaction forces always act on two different objects simultaneously, never on the same object. [1]
- (c) The rocket expels hot exhaust gases backward at high velocity (Action); the escaping gases exert an equal and opposite forward thrust on the rocket (Reaction), propelling it forward while conserving total momentum. [2]
Q39.
- (a) A polyculture fish farming system combining 5 or 6 different compatible fish species with non-overlapping feeding habits in a single freshwater pond. [1]
- (b) Surface feeder: Catla; Column feeder: Rohu. [1]
- (c) It avoids inter-species competition for food and space because each species occupies a distinct ecological zone (surface, middle, bottom, aquatic weeds), maximizing fish productivity per unit water area. [2]