ADEPT YOURSELF
www.adeptyourself.com β’ Academic Excellence Series
CBSE CLASS IX β SCIENCE (CODE NO. 086)
SAMPLE QUESTION PAPER β SET 3 | 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 represents the correct order of increasing forces of attraction between their constituent particles?
[1]
Q2.
Rusting of an article made of iron is:
[1]
Q3.
Which cell organelle is involved in the formation of lysosomes and packaging of biochemical products?
[1]
Q4.
Girth of stem in plants increases due to the activity of:
[1]
Q5.
Area under a velocity-time ($v$-$t$) graph represents a physical quantity which has the SI unit of:
[1]
Q6.
A rocket or jet engine works on the fundamental principle of conservation of:
[1]
Q7.
The gravitational force between two bodies is $F$. If the mass of each body is doubled and the distance between them is halved, the new force will be:
[1]
Q8.
Which of the following molecules has atomicity equal to 4?
[1]
Q9.
A cell placed in a concentrated hypertonic sugar solution shrinks because water moves out by the process of:
[1]
Q10.
When an object undergoes uniform circular motion, its:
[1]
Q11.
Which subatomic particle was discovered by James Chadwick in 1932?
[1]
Q12.
Which animal tissue forms a shock-absorbing insulating layer below the skin and stores fats?
[1]
Q13.
When a body of mass $2\text{ kg}$ is raised to a height of $5\text{ m}$, the gravitational potential energy gained is: [Take $g = 9.8\text{ m/s}^2$]
[1]
Q14.
The sensation of sound persists in the human brain for about:
[1]
Q15.
Which of the following is a green manure crop grown and ploughed into the soil to enrich it with nitrogen and phosphorus?
[1]
Q16.
An atom of an element $X$ has 7 valence electrons. The formula of its compound with magnesium ($\text{Mg}^{2+}$) is:
[1]
Q17.
Assertion (A): Dry ice ($\text{solid CO}_2$) gets converted directly into carbon dioxide gas on decrease of pressure to 1 atmosphere without passing through the liquid state.
Reason (R): Solid carbon dioxide is stored under high pressure. [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): Solid carbon dioxide is stored under high pressure. [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 and Plastids are able to synthesize some of their own proteins.
Reason (R): Mitochondria and Plastids possess their own circular DNA and ribosomes. [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 and Plastids possess their own circular DNA and ribosomes. [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): A gun recoils backward when a bullet is fired from it.
Reason (R): The total momentum of the gun-bullet system before firing is zero, and it remains zero after firing according to the law of conservation of momentum. [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 total momentum of the gun-bullet system before firing is zero, and it remains zero after firing according to the law of conservation of momentum. [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): Sound waves travel faster on a hot summer day than on a cold winter day.
Reason (R): The velocity of sound in a gas increases with an increase in the temperature of the medium. [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 velocity of sound in a gas increases with an increase in the temperature of the medium. [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.
Why does steam produce more severe burns than boiling water at the same temperature ($100^\circ\text{C}$)?
[2]
Q22.
State two structural differences between plant cells and animal cells regarding vacuoles.
[2]
Q23.
A racing car has a uniform acceleration of $4\text{ m/s}^2$. What distance will it cover in $10\text{ s}$ after start?
[2]
OR
Why do passengers tend to fall backward when a stationary bus suddenly starts moving forward? Name the property involved.
Q24.
Why is it difficult to hold a school bag having a strap made of a thin and strong string? Explain on the basis of pressure.
[2]
Q25.
Mention two desirable agronomic characteristics for crop improvement in cereal crops and fodder crops.
[2]
Q26.
Write the chemical names and formulae of:
(a) Compound formed between Magnesium and Chlorine
(b) Compound formed between Sodium and Nitrate radical [2]
(a) Compound formed between Magnesium and Chlorine
(b) Compound formed between Sodium and Nitrate radical [2]
SECTION C β SHORT ANSWER QUESTIONS (21 Marks)
Q27.
(a) What is chromatography?
(b) State the principle on which paper chromatography works.
(c) Mention one industrial application of chromatography. [3]
(b) State the principle on which paper chromatography works.
(c) Mention one industrial application of chromatography. [3]
Q28.
Describe the location, structure, and functions of Stomata in the epidermal layer of leaves.
[3]
Q29.
A bullet of mass $20\text{ g}$ is horizontally fired with a velocity of $150\text{ m/s}$ from a pistol of mass $2\text{ kg}$. Calculate the recoil velocity of the pistol.
[3]
(a) The velocity with which it was thrown up.
(b) The maximum height it reaches. [Take $g = 9.8\text{ m/s}^2$]
OR
A ball thrown up vertically returns to the thrower after $6\text{ s}$. Find:
(a) The velocity with which it was thrown up.
(b) The maximum height it reaches. [Take $g = 9.8\text{ m/s}^2$]
Q30.
(a) State the condition under which the work done by a force is:
(i) Positive
(ii) Negative
(iii) Zero
(b) A force of $7\text{ N}$ acts on an object. The displacement is $8\text{ m}$ in the direction of the force. Calculate the work done. [3]
(i) Positive
(ii) Negative
(iii) Zero
(b) A force of $7\text{ N}$ acts on an object. The displacement is $8\text{ m}$ in the direction of the force. Calculate the work done. [3]
Q31.
(a) State Dalton’s atomic theory postulates that explain:
(i) Law of Conservation of Mass
(ii) Law of Definite Proportions
(b) Calculate the number of moles present in $52\text{ g}$ of Helium ($\text{He}$, atomic mass = $4\text{ u}$). [3]
(i) Law of Conservation of Mass
(ii) Law of Definite Proportions
(b) Calculate the number of moles present in $52\text{ g}$ of Helium ($\text{He}$, atomic mass = $4\text{ u}$). [3]
Q32.
Differentiate between bone and cartilage connective tissues on the basis of matrix composition, flexibility, and locations in the human body.
[3]
Q33.
Explain the difference between mixed cropping and crop rotation. Mention one major advantage of crop rotation.
[3]
SECTION D β LONG ANSWER QUESTIONS (15 Marks)
Q34.
(a) Describe J.J. Thomson’s model of an atom. What was its major drawback?
(b) Explain the formation of ions (cations and anions) using Sodium ($\text{Na}$, $Z=11$) and Chlorine ($\text{Cl}$, $Z=17$) as examples.
(c) An atom has mass number 35 and contains 18 neutrons. What is its atomic number, electronic configuration, and valency? [5]
(b) Define atomic mass unit ($\text{u}$).
(c) Calculate the molecular mass of:
(i) Nitric acid ($\text{HNO}_3$)
(ii) Glucose ($\text{C}_6\text{H}_{12}\text{O}_6$)
[Given atomic masses: $\text{H}=1\text{ u}$, $\text{N}=14\text{ u}$, $\text{O}=16\text{ u}$, $\text{C}=12\text{ u}$]
(b) Explain the formation of ions (cations and anions) using Sodium ($\text{Na}$, $Z=11$) and Chlorine ($\text{Cl}$, $Z=17$) as examples.
(c) An atom has mass number 35 and contains 18 neutrons. What is its atomic number, electronic configuration, and valency? [5]
OR
(a) Summarize the main features of Bohr’s atomic model.
(b) Define atomic mass unit ($\text{u}$).
(c) Calculate the molecular mass of:
(i) Nitric acid ($\text{HNO}_3$)
(ii) Glucose ($\text{C}_6\text{H}_{12}\text{O}_6$)
[Given atomic masses: $\text{H}=1\text{ u}$, $\text{N}=14\text{ u}$, $\text{O}=16\text{ u}$, $\text{C}=12\text{ u}$]
Q35.
(a) What is osmosis? How does it differ from diffusion?
(b) Explain what happens when:
(i) Dried raisins are kept in plain water for an hour.
(ii) Swollen raisins are then transferred into a concentrated salt solution.
(c) Name the semi-permeable boundary of an animal cell and describe its chemical composition. [5]
(b) How does transport of substances in Phloem differ fundamentally from transport in Xylem?
(c) What is bark of a tree? How does the cork act as a protective tissue?
(b) Explain what happens when:
(i) Dried raisins are kept in plain water for an hour.
(ii) Swollen raisins are then transferred into a concentrated salt solution.
(c) Name the semi-permeable boundary of an animal cell and describe its chemical composition. [5]
OR
(a) What are the components of Phloem tissue? State the specific function of each component.
(b) How does transport of substances in Phloem differ fundamentally from transport in Xylem?
(c) What is bark of a tree? How does the cork act as a protective tissue?
Q36.
(a) Define uniform acceleration. Draw distance-time and velocity-time graphs for an object moving with uniform positive acceleration.
(b) State the commercial unit of electrical energy and find its relation with the SI unit Joule ($1\text{ kWh} = ?\text{ J}$).
(c) A crane lifts a load of $500\text{ kg}$ vertically through a height of $20\text{ m}$ in $10\text{ s}$. Calculate the power expended by the crane. [Take $g = 10\text{ m/s}^2$] [5]
(b) Define: (i) Amplitude, (ii) Time period, (iii) Frequency, (iv) Wavelength of a sound wave.
(c) A sound wave has a frequency of $1000\text{ Hz}$ and wavelength $0.34\text{ m}$. Calculate its speed. How far will this sound travel in $2.5\text{ seconds}$?
(b) State the commercial unit of electrical energy and find its relation with the SI unit Joule ($1\text{ kWh} = ?\text{ J}$).
(c) A crane lifts a load of $500\text{ kg}$ vertically through a height of $20\text{ m}$ in $10\text{ s}$. Calculate the power expended by the crane. [Take $g = 10\text{ m/s}^2$] [5]
OR
(a) What are longitudinal and transverse waves? Give one example of each.
(b) Define: (i) Amplitude, (ii) Time period, (iii) Frequency, (iv) Wavelength of a sound wave.
(c) A sound wave has a frequency of $1000\text{ Hz}$ and wavelength $0.34\text{ m}$. Calculate its speed. How far will this sound travel in $2.5\text{ seconds}$?
SECTION E β CASE-BASED INTEGRATED UNITS (12 Marks)
Q37. Read the following source carefully and answer the questions that follow:
[4](a) Why does the temperature of a liquid remain constant during boiling even though heat is continuously supplied? [1]
(b) Define latent heat of fusion. [1]
(c) Explain why ice at $273\text{ K}$ ($0^\circ\text{C}$) is more effective in cooling a drink than water at the same temperature. [2]
The physical state of matter can be altered by heating or cooling. Latent heat is the heat energy absorbed or released by a substance during a change of state without any change in temperature. Latent heat of fusion is the amount of heat energy required to change $1\text{ kg}$ of a solid into liquid at atmospheric pressure at its melting point. Latent heat of vaporization is the heat required to change $1\text{ kg}$ of a liquid into gas at its boiling point. Because steam contains additional latent heat of vaporization, it causes more severe thermal burns than boiling water at $100^\circ\text{C}$.
(b) Define latent heat of fusion. [1]
(c) Explain why ice at $273\text{ K}$ ($0^\circ\text{C}$) is more effective in cooling a drink than water at the same temperature. [2]
OR
Explain how sweating helps to regulate and cool down human body temperature on hot days. [2]
Q38. Read the following source carefully and answer the questions that follow:
[4](a) Write the mathematical formula for the gravitational potential energy of an object of mass $m$ at height $h$. [1]
(b) A body is falling freely from a certain height. What happens to its potential energy and kinetic energy during the fall? [1]
(c) A bullet of mass $10\text{ g}$ is fired with a velocity of $400\text{ m/s}$. Calculate its kinetic energy. [2]
Work done on an object is defined as the magnitude of the force multiplied by the distance moved in the direction of the applied force ($W = F \times s$). Energy is the capacity to do work. An object in motion possesses kinetic energy, while an object elevated to a height acquires gravitational potential energy. The law of conservation of energy states that energy can neither be created nor destroyed, but only transformed from one form to another. In an ideal frictionless system, total mechanical energy ($KE + PE$) remains constant throughout the motion.
(b) A body is falling freely from a certain height. What happens to its potential energy and kinetic energy during the fall? [1]
(c) A bullet of mass $10\text{ g}$ is fired with a velocity of $400\text{ m/s}$. Calculate its kinetic energy. [2]
OR
A person holds a heavy bag of mass $25\text{ kg}$ on his head and stands stationary for $30\text{ minutes}$. Calculate the work done by the person against gravity. Justify your answer. [2]
Q39. Read the following source carefully and answer the questions that follow:
[4](a) Differentiate between broilers and layers. [1]
(b) Name one indigenous and one exotic breed of poultry commonly reared in India. [1]
(c) Mention two desirable traits for which cross-breeding is done in poultry farming. [2]
Poultry farming is undertaken to raise domestic fowl for egg production (layers) and meat production (broilers). Cross-breeding programs between Indian breeds (such as Aseel) and exotic breeds (such as Leghorn) are focused on developing new varieties with desirable traits, including tolerance to high temperatures, low maintenance requirements, and smaller body size for utilization of agricultural by-products. Broiler chickens require vitamin-rich diets (vitamins A and K) and careful housing management to prevent disease outbreaks.
(b) Name one indigenous and one exotic breed of poultry commonly reared in India. [1]
(c) Mention two desirable traits for which cross-breeding is done in poultry farming. [2]
OR
State two essential nutritional and management differences in rearing broilers compared to egg layers. [2]
CBSE CLASS IX SCIENCE (086) β SOLUTIONS & MARKING SCHEME β SET 3
SECTION A β ANSWERS
Q1. (c) Oxygen, Water, Sugar (Gas < Liquid < Solid) [1]
Q2. (b) A chemical change because new substance with different properties is formed [1]
Q3. (b) Golgi Apparatus [1]
Q4. (b) Lateral meristem (Cambium) [1]
Q5. (b) $\text{m}$ (Metre) [Area represents displacement] [1]
Q6. (c) Linear Momentum [1]
Q7. (c) $16F$ [$F’ = G\frac{(2M)(2m)}{(d/2)^2} = G\frac{4Mm}{d^2/4} = 16F$] [1]
Q8. (b) Phosphorus ($\text{P}_4$) and (d) Ammonia ($\text{NH}_3$) (Either accepted; $\text{P}_4$ is elemental tetra-atomic) [1]
Q9. (b) Exosmosis [1]
Q10. (a) Speed is constant but velocity changes continuously [1]
Q11. (c) Neutron [1]
Q12. (b) Adipose tissue [1]
Q13. (b) $98\text{ J}$ [$E_p = mgh = 2 \times 9.8 \times 5 = 98\text{ J}$] [1]
Q14. (b) $0.1\text{ s}$ ($1/10\text{ s}$) [1]
Q15. (a) Sunn hemp [1]
Q16. (c) $\text{MgX}_2$ [Valency of $\text{X} = 8 – 7 = 1$; $\text{Mg}^{2+} + \text{X}^- \rightarrow \text{MgX}_2$] [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.
Steam at $100^\circ\text{C}$ contains more heat energy than boiling water at $100^\circ\text{C}$ in the form of extra **latent heat of vaporization** ($22.6 \times 10^5\text{ J/kg}$). When steam condenses on skin, it releases this extra latent heat, causing more severe burns. [2]
Q22.
- Plant cells: Have a single, large, central permanent vacuole occupying 50β90% of cell volume, providing turgidity and rigidity.
- Animal cells: Have small, multiple, temporary vacuoles used for storage or excretion.
Q23.
Given: $u = 0$, $a = 4\text{ m/s}^2$, $t = 10\text{ s}$.
Distance $s = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}(4)(10)^2 = 2 \times 100 = \mathbf{200\text{ m}}$. [2]
OR When the bus starts suddenly, the lower part of the passenger’s body in contact with the bus moves forward with it, while the upper part tends to remain at rest due to **Inertia of Rest**, causing them to jerk backward. [2]
Distance $s = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2}(4)(10)^2 = 2 \times 100 = \mathbf{200\text{ m}}$. [2]
OR When the bus starts suddenly, the lower part of the passenger’s body in contact with the bus moves forward with it, while the upper part tends to remain at rest due to **Inertia of Rest**, causing them to jerk backward. [2]
Q24.
Pressure is inversely proportional to surface area ($P = \frac{F}{A}$). A thin strap has a very small contact surface area, which exerts large pressure on the shoulder, making it painful to carry. [2]
Q25.
- Cereal crops: Dwarfness is desired so that fewer nutrients are consumed and plants resist lodging during winds.
- Fodder crops: Tallness and profuse branching are desired to produce maximum vegetative biomass.
Q26.
- (a) Magnesium chloride: $\text{Mg}^{2+}$ and $\text{Cl}^- \rightarrow \mathbf{\text{MgCl}_2}$
- (b) Sodium nitrate: $\text{Na}^+$ and $\text{NO}_3^- \rightarrow \mathbf{\text{NaNO}_3}$
SECTION C β ANSWERS
Q27.
- (a) Chromatography: A laboratory separation technique used for the separation of solutes that dissolve in the same solvent.
- (b) Principle: Based on the differential solubilities and rates of migration of different solute components over an adsorbent medium (filter paper).
- (c) Application: Separating pigments from natural flower extracts/chlorophyll, or separating drugs from blood samples in forensic toxicology.
Q28.
- Location: Tiny microscopic pores present in the epidermis of leaves and young green stems.
- Structure: Each stoma is enclosed by two kidney-shaped (or bean-shaped) specialized **guard cells** that regulate the opening and closing of the stomatal pore.
- Functions: (i) Facilitates gaseous exchange ($\text{CO}_2$ and $\text{O}_2$) during photosynthesis and respiration. (ii) Enables transpiration (loss of water vapor), aiding temperature regulation and sap ascent.
Q29.
Given: $m_1 = 20\text{ g} = 0.02\text{ kg}$, $v_1 = 150\text{ m/s}$, $m_2 = 2\text{ kg}$, $v_2 = ?$.
By Law of Conservation of Momentum:
$\text{Total momentum after firing} = \text{Total momentum before firing}$
$m_1 v_1 + m_2 v_2 = 0 \Rightarrow (0.02 \times 150) + (2 \times v_2) = 0$
$3 + 2v_2 = 0 \Rightarrow v_2 = -\frac{3}{2} = \mathbf{-1.5\text{ m/s}}$.
(Negative sign indicates the pistol recoils backward). [3]
OR Total time $T = 6\text{ s} \Rightarrow$ Time to reach maximum height $t = \frac{6}{2} = 3\text{ s}$.
At maximum height, final velocity $v = 0$, $g = -9.8\text{ m/s}^2$.
(a) $v = u + gt \Rightarrow 0 = u – (9.8 \times 3) \Rightarrow u = \mathbf{29.4\text{ m/s}}$.
(b) Maximum height $h = ut + \frac{1}{2}gt^2 = (29.4 \times 3) – \frac{1}{2}(9.8)(3)^2 = 88.2 – 44.1 = \mathbf{44.1\text{ m}}$. [3]
By Law of Conservation of Momentum:
$\text{Total momentum after firing} = \text{Total momentum before firing}$
$m_1 v_1 + m_2 v_2 = 0 \Rightarrow (0.02 \times 150) + (2 \times v_2) = 0$
$3 + 2v_2 = 0 \Rightarrow v_2 = -\frac{3}{2} = \mathbf{-1.5\text{ m/s}}$.
(Negative sign indicates the pistol recoils backward). [3]
OR Total time $T = 6\text{ s} \Rightarrow$ Time to reach maximum height $t = \frac{6}{2} = 3\text{ s}$.
At maximum height, final velocity $v = 0$, $g = -9.8\text{ m/s}^2$.
(a) $v = u + gt \Rightarrow 0 = u – (9.8 \times 3) \Rightarrow u = \mathbf{29.4\text{ m/s}}$.
(b) Maximum height $h = ut + \frac{1}{2}gt^2 = (29.4 \times 3) – \frac{1}{2}(9.8)(3)^2 = 88.2 – 44.1 = \mathbf{44.1\text{ m}}$. [3]
Q30.
- (a) Work done $W = F s \cos\theta$:
(i) Positive: Force and displacement are in the same direction ($\theta = 0^\circ$).
(ii) Negative: Force is opposite to direction of motion ($\theta = 180^\circ$, e.g., friction).
(iii) Zero: Force is perpendicular to displacement ($\theta = 90^\circ$) or displacement is zero. - (b) Work done $W = F \times s = 7\text{ N} \times 8\text{ m} = \mathbf{56\text{ J}}$.
Q31.
- (a) (i) Law of Conservation of Mass: Atoms are indivisible particles, which can neither be created nor destroyed in a chemical reaction.
(ii) Law of Definite Proportions: The relative number and kinds of atoms are constant in a given compound. - (b) Molar mass of Helium ($\text{He}$) = $4\text{ g/mol}$.
Number of moles $n = \frac{\text{Given mass}}{\text{Molar mass}} = \frac{52\text{ g}}{4\text{ g/mol}} = \mathbf{13\text{ moles}}$.
Q32.
- Bone: Hard, rigid, non-flexible matrix composed of calcium and phosphorus compounds; supports body framework and protects internal organs (found in skeletal limbs, ribs).
- Cartilage: Solid but flexible and elastic matrix composed of proteins and sugars with widely spaced cells (chondrocytes); smoothens bone surfaces at joints (found in ear pinna, nose tip, trachea, larynx).
Q33.
- Mixed Cropping: Growing two or more crops simultaneously on the same piece of land without any fixed row pattern (e.g., Wheat + Mustard) to minimize risk of total crop failure.
- Crop Rotation: Growing different crops on a piece of land in a pre-planned succession (e.g., growing leguminous pulses after cereals).
- Advantage: Replenishes soil nitrogen naturally via Rhizobium root nodules, controls weeds/pests, and maintains long-term soil fertility.
SECTION D β ANSWERS
Q34.
OR
- (a) Thomson’s Model (Plum Pudding Model): Atom is a positively charged sphere with negatively charged electrons embedded like seeds in a watermelon.
Drawback: Failed to explain the experimental results of Rutherford’s $\alpha$-particle scattering experiment. - (b) Ion Formation:
1. $\text{Na}$ ($2,8,1$) loses 1 valence electron $\rightarrow \text{Na}^+$ cation ($2,8$, stable octet).
2. $\text{Cl}$ ($2,8,7$) gains 1 electron $\rightarrow \text{Cl}^-$ anion ($2,8,8$, stable octet). - (c) Given: Mass number $A = 35$, Neutrons $n = 18$.
Atomic number $Z = A – n = 35 – 18 = \mathbf{17}$ (Chlorine).
Electronic configuration = $\mathbf{2, 8, 7}$ (K=2, L=8, M=7).
Valency $= 8 – 7 = \mathbf{1}$.
OR
- (a) Bohr’s Model: (i) Electrons revolve only in discrete non-radiating orbits. (ii) Orbits are designated as $K, L, M, N$ shells with energy levels $n = 1, 2, 3, 4$.
- (b) Unified atomic mass unit ($\text{u}$): Equal to exactly one-twelfth ($1/12\text{th}$) of the mass of one unbonded Carbon-12 atom.
- (c) Molecular masses:
(i) $\text{HNO}_3 = 1(1) + 1(14) + 3(16) = 1 + 14 + 48 = \mathbf{63\text{ u}}$.
(ii) $\text{C}_6\text{H}_{12}\text{O}_6 = 6(12) + 12(1) + 6(16) = 72 + 12 + 96 = \mathbf{180\text{ u}}$.
Q35.
OR
- (a) Osmosis vs Diffusion: Diffusion is the random net movement of any particles (gases, liquids, solutes) from high to low concentration without a membrane; Osmosis is the specific movement of water/solvent molecules across a selectively permeable membrane from higher solvent concentration to lower solvent concentration.
- (b) (i) In plain water: Water enters raisins by endosmosis; raisins swell up.
(ii) In concentrated salt solution: Water moves out from swollen raisins by exosmosis; raisins shrink. - (c) The boundary is the **Plasma Membrane (Cell Membrane)**; chemically composed of a flexible bilayer of **lipids (phospholipids) and proteins**.
OR
- (a) Components of Phloem:
1. Sieve tubes: Tubular cells with perforated end walls; transport organic food.
2. Companion cells: Nucleated cells alongside sieve tubes; regulate food conduction.
3. Phloem parenchyma: Living cells; store food reserves and starch.
4. Phloem fibres (bast fibres): Dead sclerenchymatous fibres; provide mechanical support. - (b) Xylem conducts water and minerals unidirectionally (roots to leaves) driven by physical transpiration pull; Phloem conducts soluble food (translocation) bidirectionally (source to sink) utilizing metabolic energy (ATP).
- (c) Cork consists of dead, compactly arranged protective cells without intercellular spaces, coated with an impermeable waxy chemical called **suberin** that prevents gas/water loss and protects against mechanical injury and pathogens.
Q36.
OR
- (a) Uniform Acceleration: An object travels in a straight line and its velocity increases or decreases by equal amounts in equal intervals of time.
Graphs: $s$-$t$ graph is a parabola curving upward; $v$-$t$ graph is a straight inclined line passing through origin. - (b) Commercial unit is **kilowatt-hour (kWh)**.
$1\text{ kWh} = 1\text{ kW} \times 1\text{ h} = 1000\text{ W} \times 3600\text{ s} = 3.6 \times 10^6\text{ J} = \mathbf{3.6\times 10^6\text{ Joules}}$. - (c) Mass $m = 500\text{ kg}$, Height $h = 20\text{ m}$, Time $t = 10\text{ s}$, $g = 10\text{ m/s}^2$.
Work done $W = mgh = 500 \times 10 \times 20 = 1,00,000\text{ J}$.
Power $P = \frac{W}{t} = \frac{1,00,000}{10} = \mathbf{10,000\text{ W}} = 10\text{ kW}$.
OR
- (a) Longitudinal wave: Particles vibrate parallel to the direction of wave propagation (e.g., sound waves in air).
Transverse wave: Particles vibrate perpendicular to the direction of wave propagation (e.g., light waves, ripples on water surface). - (b) (i) Amplitude ($A$): Maximum displacement of medium particles from their mean position.
(ii) Time Period ($T$): Time taken by a particle to complete one full oscillation.
(iii) Frequency ($\nu$): Number of complete oscillations per unit time (Hz).
(iv) Wavelength ($\lambda$): Distance between two consecutive compressions or rarefactions. - (c) Given: $\nu = 1000\text{ Hz}$, $\lambda = 0.34\text{ m}$, $t = 2.5\text{ s}$.
Speed $v = \nu \times \lambda = 1000 \times 0.34 = \mathbf{340\text{ m/s}}$.
Distance $d = v \times t = 340 \times 2.5 = \mathbf{850\text{ m}}$.
SECTION E β ANSWERS
Q37.
- (a) The heat supplied during boiling is absorbed as **latent heat of vaporization** to break the intermolecular attractive forces between liquid molecules rather than increasing their average kinetic energy. [1]
- (b) The amount of heat energy required to convert $1\text{ kg}$ of a solid into liquid at atmospheric pressure at its melting point. [1]
- (c) Ice at $273\text{ K}$ absorbs extra heat energy equal to the latent heat of fusion ($3.34 \times 10^5\text{ J/kg}$) from the drink to melt into water at $0^\circ\text{C}$, cooling the drink much more effectively than water at the same temperature. [2]
Q38.
- (a) $E_p = mgh$. [1]
- (b) Its potential energy continuously decreases (as height decreases) while its kinetic energy continuously increases (as speed increases), keeping total mechanical energy constant. [1]
- (c) Mass $m = 10\text{ g} = 0.01\text{ kg}$, Velocity $v = 400\text{ m/s}$.
$E_k = \frac{1}{2}mv^2 = \frac{1}{2} \times 0.01 \times (400)^2 = 0.005 \times 160000 = \mathbf{800\text{ Joules}}$. [2]
Q39.
- (a) **Broilers** are chickens reared for meat production; **Layers** are egg-laying female chickens reared for egg production. [1]
- (b) Indigenous breed: Aseel / Kadaknath; Exotic breed: Leghorn / Rhode Island Red. [1]
- (c) (i) Increased number and quality of chicks, (ii) Dwarf broiler parent for commercial chick production / tolerance to high temperatures. [2]