ADEPT YOURSELF
www.adeptyourself.com β’ Academic Excellence Series
CBSE CLASS IX β SCIENCE (CODE NO. 086)
SAMPLE QUESTION PAPER β SET 1 | 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 substances undergoes sublimation upon heating?
[1]
Q2.
Tincture of iodine, a well-known antiseptic solution, is prepared by dissolving:
[1]
Q3.
Which organelle is known as the “suicide bag” of a cell due to the presence of powerful hydrolytic digestive enzymes?
[1]
Q4.
Flexibility in plants that allows easy bending of tendrils and stems without breaking is due to which tissue?
[1]
Q5.
A body thrown vertically upwards reaches a maximum height $h$. The ratio of its distance travelled to the magnitude of displacement upon returning to the ground is:
[1]
Q6.
Inertia of an object tends to cause the object to:
[1]
Q7.
The value of universal gravitational constant $G$ was determined experimentally by:
[1]
Q8.
Which of the following elements has a polyatomic molecular structure composed of 8 atoms?
[1]
Q9.
The cell wall of plant cells is mainly composed of:
[1]
Q10.
The numerical ratio of displacement to distance for a moving object is always:
[1]
Q11.
Which of the following pairs represents isobars?
[1]
Q12.
Smooth muscle fibres present in the iris of the eye, alimentary canal, and blood vessels are:
[1]
Q13.
When a body falls freely towards the earth under gravity, its total mechanical energy:
[1]
Q14.
Ultrasound equipment used in medical imaging works at sound frequencies:
[1]
Q15.
Which of the following is an indigenous breed of poultry bird in India?
[1]
Q16.
What is the formula mass of Sodium Carbonate ($\text{Na}_2\text{CO}_3$)? [Given atomic masses: $\text{Na}=23\text{ u}$, $\text{C}=12\text{ u}$, $\text{O}=16\text{ u}$]
[1]
Q17.
Assertion (A): When ice melts at $0^\circ\text{C}$, the temperature remains constant until all the ice has converted to water.
Reason (R): Heat supplied is absorbed as latent heat of fusion to overcome forces of attraction between particles. [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): Heat supplied is absorbed as latent heat of fusion to overcome forces of attraction between particles. [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): Lysosomes are capable of destroying foreign materials entering the cell.
Reason (R): Lysosomes contain powerful hydrolytic digestive enzymes made by the Rough Endoplasmic Reticulum (RER). [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): Lysosomes contain powerful hydrolytic digestive enzymes made by the Rough Endoplasmic Reticulum (RER). [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): If the net external force acting on a moving body is zero, the momentum of the body remains conserved.
Reason (R): According to Newton’s Second Law of Motion, force is directly proportional to the rate of change 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): According to Newton’s Second Law of Motion, force is directly proportional to the rate of change 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 travels faster in iron steel than in air.
Reason (R): The speed of sound depends on the density and elasticity of the medium through which it propagates. [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 speed of sound depends on the density and elasticity of the medium through which it propagates. [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.
Give two reasons why water at room temperature is a liquid, whereas an iron almirah is a solid.
[2]
Q22.
Differentiate between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER) based on structure and function.
[2]
Q23.
A train starting from rest attains a velocity of $72\text{ km/h}$ in $5\text{ minutes}$. Assuming uniform acceleration, calculate:
(a) The acceleration of the train.
(b) The distance travelled by the train during this time interval. [2]
(a) The acceleration of the train.
(b) The distance travelled by the train during this time interval. [2]
OR
State Newton’s Third Law of Motion. Identify the action and reaction forces when a swimmer swims in water.
Q24.
State Archimedes’ Principle. Mention one practical application based on this principle.
[2]
Q25.
What is inter-cropping? Mention one benefit of inter-cropping over monoculture farming.
[2]
Q26.
Write the chemical formulae of:
(a) Aluminium oxide
(b) Calcium carbonate [2]
(a) Aluminium oxide
(b) Calcium carbonate [2]
SECTION C β SHORT ANSWER QUESTIONS (21 Marks)
Q27.
(a) Define Tyndall effect.
(b) Why does a true solution (e.g., copper sulphate in water) not show Tyndall effect, whereas a colloidal solution (e.g., milk in water) does? [3]
(b) Why does a true solution (e.g., copper sulphate in water) not show Tyndall effect, whereas a colloidal solution (e.g., milk in water) does? [3]
Q28.
Describe the structure of a neuron (nerve cell) with the help of a neat labelled diagram or description of its main parts. Mention its primary function.
[3]
Q29.
An object of mass $5\text{ kg}$ is moving with a uniform velocity of $10\text{ m/s}$. It is brought to rest in $2\text{ seconds}$ by applying a constant retarding force.
(a) Calculate the initial momentum of the object.
(b) Calculate the magnitude of the retarding force applied.
(c) What is the change in momentum? [3]
(a) Calculate the initial momentum of the object.
(b) Calculate the magnitude of the retarding force applied.
(c) What is the change in momentum? [3]
OR
A stone is released from the top of a tower of height $19.6\text{ m}$. Calculate its final velocity just before touching the ground. [Take $g = 9.8\text{ m/s}^2$]
Q30.
(a) Define kinetic energy of a body. Derive the mathematical expression $E_k = \frac{1}{2}mv^2$ for a body of mass $m$ moving with velocity $v$.
(b) A car of mass $1000\text{ kg}$ moving at $20\text{ m/s}$ is accelerated to $30\text{ m/s}$. Calculate the work done on the car. [3]
(b) A car of mass $1000\text{ kg}$ moving at $20\text{ m/s}$ is accelerated to $30\text{ m/s}$. Calculate the work done on the car. [3]
Q31.
(a) What are isotopes? Explain with two examples of isotopes of carbon.
(b) State two industrial or medical applications of radioactive isotopes. [3]
(b) State two industrial or medical applications of radioactive isotopes. [3]
Q32.
Differentiate between parenchyma, collenchyma, and sclerenchyma tissues on the basis of cell wall composition, intercellular spaces, and functional role.
[3]
Q33.
What are the three main cropping seasons in India? Name two major crops grown in each season.
[3]
SECTION D β LONG ANSWER QUESTIONS (15 Marks)
Q34.
(a) Describe Rutherford’s $\alpha$-particle scattering experiment.
(b) List the three major observations and the corresponding conclusions drawn from this experiment regarding the structure of an atom.
(c) State one major limitation of Rutherford’s nuclear model of the atom. [5]
(b) Draw the electron distribution diagram for:
(i) Sodium ($\text{Na}$, atomic number = 11)
(ii) Chlorine ($\text{Cl}$, atomic number = 17)
(c) Define valency. Determine the valency of Magnesium (atomic number = 12).
(b) List the three major observations and the corresponding conclusions drawn from this experiment regarding the structure of an atom.
(c) State one major limitation of Rutherford’s nuclear model of the atom. [5]
OR
(a) State the postulates of Bohr’s model of an atom.
(b) Draw the electron distribution diagram for:
(i) Sodium ($\text{Na}$, atomic number = 11)
(ii) Chlorine ($\text{Cl}$, atomic number = 17)
(c) Define valency. Determine the valency of Magnesium (atomic number = 12).
Q35.
(a) Differentiate between a prokaryotic cell and a eukaryotic cell on any three structural bases.
(b) What happens when a plant cell is placed in:
(i) A hypotonic solution?
(ii) A hypertonic solution?
(c) Explain the phenomenon of plasmolysis with an example. [5]
(b) List the four constituent elements of Xylem and explain the specific function of each.
(c) Why are xylem and phloem called conducting or vascular tissues?
(b) What happens when a plant cell is placed in:
(i) A hypotonic solution?
(ii) A hypertonic solution?
(c) Explain the phenomenon of plasmolysis with an example. [5]
OR
(a) What are complex permanent tissues? Name the two types of complex permanent tissues found in vascular plants.
(b) List the four constituent elements of Xylem and explain the specific function of each.
(c) Why are xylem and phloem called conducting or vascular tissues?
Q36.
(a) State the Law of Conservation of Energy.
(b) Prove mathematically that the total mechanical energy of a freely falling body of mass $m$ remains conserved at all points of its journey from a height $h$.
(c) An electric heater of $1500\text{ W}$ is used for $10\text{ hours}$ daily. Calculate the electrical energy consumed in commercial units (kWh) in a month of 30 days. [5]
(b) A ship sends out ultrasound that returns from the seabed and is detected after $3.42\text{ s}$. If the speed of ultrasound through sea water is $1531\text{ m/s}$, calculate the depth of the sea.
(c) Explain how the human ear converts sound vibrations into electrical signals (brief working of outer, middle, and inner ear).
(b) Prove mathematically that the total mechanical energy of a freely falling body of mass $m$ remains conserved at all points of its journey from a height $h$.
(c) An electric heater of $1500\text{ W}$ is used for $10\text{ hours}$ daily. Calculate the electrical energy consumed in commercial units (kWh) in a month of 30 days. [5]
OR
(a) What is an echo? State two essential conditions required for a distinct echo to be heard by the human ear in air.
(b) A ship sends out ultrasound that returns from the seabed and is detected after $3.42\text{ s}$. If the speed of ultrasound through sea water is $1531\text{ m/s}$, calculate the depth of the sea.
(c) Explain how the human ear converts sound vibrations into electrical signals (brief working of outer, middle, and inner ear).
SECTION E β CASE-BASED INTEGRATED UNITS (12 Marks)
Q37. Read the following source carefully and answer the questions that follow:
[4](a) Define evaporation. How does it differ fundamentally from boiling? [1]
(b) Why do we wear cotton clothes during hot summer days? [1]
(c) State any two factors that increase the rate of evaporation of a liquid and explain how each factor influences the rate. [2]
Matter around us exists in three physical states: solid, liquid, and gas. The physical state of matter can be changed by altering temperature or pressure. When a solid is heated, its particles gain kinetic energy and vibrate more vigorously. At the melting point, the particles break free from their fixed positions and turn into liquid. Evaporation is a surface phenomenon where liquid particles at any temperature below the boiling point gain sufficient energy to escape into vapor. Evaporation causes cooling because the particles absorb latent heat from the surroundings.
(b) Why do we wear cotton clothes during hot summer days? [1]
(c) State any two factors that increase the rate of evaporation of a liquid and explain how each factor influences the rate. [2]
OR
Explain why water droplets appear on the outer surface of a glass tumbler containing ice-cold water. [2]
Q38. Read the following source carefully and answer the questions that follow:
[4](a) Write the mathematical formula for Universal Law of Gravitation between two objects of masses $M$ and $m$ separated by distance $d$. [1]
(b) Why is the value of acceleration due to gravity ($g$) greater at the poles than at the equator? [1]
(c) An object has a mass of $60\text{ kg}$ on the earth.
(i) What will be its mass on the surface of the moon?
(ii) What will be its weight on the moon? [Take $g_{\text{earth}} = 10\text{ m/s}^2$ and $g_{\text{moon}} = \frac{1}{6}g_{\text{earth}}$] [2]
According to Newton’s Universal Law of Gravitation, every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. The force of gravity due to the earth gives an acceleration to all falling objects, known as acceleration due to gravity ($g$). The value of $g$ on the earth’s surface is approximately $9.8\text{ m/s}^2$. Since the radius of the earth is greater at the equator than at the poles, the value of $g$ is greater at the poles than at the equator. Mass remains constant everywhere, while weight varies with $g$.
(b) Why is the value of acceleration due to gravity ($g$) greater at the poles than at the equator? [1]
(c) An object has a mass of $60\text{ kg}$ on the earth.
(i) What will be its mass on the surface of the moon?
(ii) What will be its weight on the moon? [Take $g_{\text{earth}} = 10\text{ m/s}^2$ and $g_{\text{moon}} = \frac{1}{6}g_{\text{earth}}$] [2]
OR
Distinguish between mass and weight on any two scientific bases. [2]
Q39. Read the following source carefully and answer the questions that follow:
[4](a) Name the two essential nutrients supplied to plants by air. [1]
(b) What are macronutrients? Name any two macronutrients supplied by soil. [1]
(c) Differentiate between manure and chemical fertilizers on any two parameters. [2]
To ensure sustainable food security for an increasing population, agricultural practices rely on crop variety improvement, crop production management, and crop protection management. Plants require 16 essential nutrients for growth. Nutrients supplied by air are carbon and oxygen; hydrogen comes from water; soil supplies the remaining 13 nutrients. Soil nutrients are classified into macronutrients (required in large quantities) and micronutrients (required in small quantities). Manure and chemical fertilizers are added to enrich soil fertility and improve crop productivity.
(b) What are macronutrients? Name any two macronutrients supplied by soil. [1]
(c) Differentiate between manure and chemical fertilizers on any two parameters. [2]
OR
What is biological pest control? Mention one advantage of using biological methods over chemical pesticides. [2]
CBSE CLASS IX SCIENCE (086) β SOLUTIONS & MARKING SCHEME β SET 1
SECTION A β ANSWERS
Q1. (b) Ammonium chloride [1]
Q2. (b) Iodine in alcohol [1]
Q3. (c) Lysosome [1]
Q4. (a) Collenchyma [1]
Q5. (c) $2h : 0$ (Displacement is zero) [1]
Q6. (c) Resist any change in its state of motion [1]
Q7. (b) Henry Cavendish [1]
Q8. (b) Sulphur ($\text{S}_8$) [1]
Q9. (b) Cellulose [1]
Q10. (d) Equal to or less than 1 [1]
Q11. (b) $^{40}_{18}\text{Ar}$ and $^{40}_{20}\text{Ca}$ (Same mass number 40, different atomic numbers) [1]
Q12. (b) Spindle-shaped, unbranched, and involuntary [1]
Q13. (c) Remains constant [1]
Q14. (c) Above 20,000 Hz (20 kHz) [1]
Q15. (b) Aseel [1]
Q16. (a) $106\text{ u}$ [Formula mass = $2 \times 23 + 12 + 3 \times 16 = 46 + 12 + 48 = 106\text{ u}$] [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.
- Water at room temperature is a liquid: Its intermolecular forces of attraction are intermediate, allowing molecules to flow, having a fixed volume but no fixed shape.
- An iron almirah is a solid: It has extremely strong intermolecular forces and rigid particles packed tightly, having a fixed shape, fixed volume, and negligible compressibility.
Q22.
- RER: Has ribosomes attached to its outer surface; synthesizes and packages proteins.
- SER: Lacks ribosomes; synthesizes lipid/fat molecules and helps in detoxifying poisons and drugs in liver cells.
Q23.
Given: $u = 0$, $v = 72\text{ km/h} = 72 \times \frac{5}{18} = 20\text{ m/s}$, $t = 5\text{ min} = 300\text{ s}$.
(a) Acceleration $a = \frac{v – u}{t} = \frac{20 – 0}{300} = \frac{20}{300} = \frac{1}{15}\text{ m/s}^2 \approx 0.067\text{ m/s}^2$.
(b) Distance $s = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2} \times \frac{1}{15} \times (300)^2 = \frac{1}{30} \times 90000 = 3000\text{ m} = 3\text{ km}$. [2]
OR
(a) Acceleration $a = \frac{v – u}{t} = \frac{20 – 0}{300} = \frac{20}{300} = \frac{1}{15}\text{ m/s}^2 \approx 0.067\text{ m/s}^2$.
(b) Distance $s = ut + \frac{1}{2}at^2 = 0 + \frac{1}{2} \times \frac{1}{15} \times (300)^2 = \frac{1}{30} \times 90000 = 3000\text{ m} = 3\text{ km}$. [2]
OR
- Newton’s Third Law: To every action, there is always an equal and opposite reaction.
- Swimmer: Action = Swimmer pushes water backwards with hands and feet; Reaction = Water pushes the swimmer forward with equal force.
Q24.
- Archimedes’ Principle: When a body is immersed fully or partially in a fluid, it experiences an upward buoyant force equal to the weight of the fluid displaced by it.
- Application: Designing ships and submarines / Lactometers used to determine milk purity / Hydrometers used for determining liquid densities.
Q25.
- Inter-cropping: Growing two or more crops simultaneously on the same field in a definite row pattern (e.g., Soyabean + Maize).
- Benefit: Ensures maximum utilization of nutrients, prevents pests and diseases from spreading to all plants of one crop, and offers greater income stability.
Q26.
- (a) Aluminium oxide: $\text{Al}^{3+}$ and $\text{O}^{2-} \rightarrow \mathbf{\text{Al}_2\text{O}_3}$
- (b) Calcium carbonate: $\text{Ca}^{2+}$ and $\text{CO}_3^{2-} \rightarrow \mathbf{\text{CaCO}_3}$
SECTION C β ANSWERS
Q27.
- (a) Tyndall effect: The phenomenon of scattering of a beam of light by colloidal particles, making the path of light visible.
- (b) In a true solution, solute particle size is extremely small ($< 1\text{ nm}$), which cannot scatter light rays. In a colloidal solution, particle size ($1\text{ to }100\text{ nm}$) is large enough to scatter incident light rays and make its path luminous.
Q28.
- Structure of a Neuron: Consists of a central cell body (Cyton) containing a nucleus and cytoplasm, branched short projections called Dendrites, a single long conducting fibre called the Axon, and terminal nerve endings.
- Function: Transmits electrical impulses and nerve signals rapidly throughout the body in response to stimuli.
Q29.
Given: $m = 5\text{ kg}$, $u = 10\text{ m/s}$, $v = 0$, $t = 2\text{ s}$.
(a) Initial momentum $p_1 = m \times u = 5 \times 10 = \mathbf{50\text{ kg}\cdot\text{m/s}}$.
(b) Acceleration $a = \frac{v – u}{t} = \frac{0 – 10}{2} = -5\text{ m/s}^2$. Force $F = m \times a = 5 \times (-5) = -25\text{ N}$. Magnitude of retarding force = $\mathbf{25\text{ N}}$.
(c) Change in momentum $\Delta p = p_2 – p_1 = 0 – 50 = \mathbf{-50\text{ kg}\cdot\text{m/s}}$. [3]
OR Given: $u = 0$, $s = 19.6\text{ m}$, $g = 9.8\text{ m/s}^2$.
Using third equation of motion: $v^2 = u^2 + 2gs \Rightarrow v^2 = 0 + 2 \times 9.8 \times 19.6 = (19.6)^2$.
Final velocity $v = \sqrt{(19.6)^2} = \mathbf{19.6\text{ m/s}}$. [3]
(a) Initial momentum $p_1 = m \times u = 5 \times 10 = \mathbf{50\text{ kg}\cdot\text{m/s}}$.
(b) Acceleration $a = \frac{v – u}{t} = \frac{0 – 10}{2} = -5\text{ m/s}^2$. Force $F = m \times a = 5 \times (-5) = -25\text{ N}$. Magnitude of retarding force = $\mathbf{25\text{ N}}$.
(c) Change in momentum $\Delta p = p_2 – p_1 = 0 – 50 = \mathbf{-50\text{ kg}\cdot\text{m/s}}$. [3]
OR Given: $u = 0$, $s = 19.6\text{ m}$, $g = 9.8\text{ m/s}^2$.
Using third equation of motion: $v^2 = u^2 + 2gs \Rightarrow v^2 = 0 + 2 \times 9.8 \times 19.6 = (19.6)^2$.
Final velocity $v = \sqrt{(19.6)^2} = \mathbf{19.6\text{ m/s}}$. [3]
Q30.
- (a) Kinetic Energy: The energy possessed by an object due to its motion.
Derivation: Work done $W = F \times s$. Since $F = ma$ and $v^2 – u^2 = 2as \Rightarrow s = \frac{v^2 – u^2}{2a}$.
For a body starting from rest ($u=0$), $W = ma \times \left(\frac{v^2}{2a}\right) = \frac{1}{2}mv^2$. Hence, $E_k = \frac{1}{2}mv^2$. - (b) Work done = Change in kinetic energy $\Delta E_k = \frac{1}{2}m(v^2 – u^2) = \frac{1}{2} \times 1000 \times (30^2 – 20^2) = 500 \times (900 – 400) = 500 \times 500 = \mathbf{2,50,000\text{ J}} = 250\text{ kJ}$.
Q31.
- (a) Isotopes: Atoms of the same element having the same atomic number but different mass numbers.
Examples: Carbon-12 ($^{12}_{6}\text{C}$) and Carbon-14 ($^{14}_{6}\text{C}$). - (b) Applications:
1. An isotope of Cobalt ($^{60}\text{Co}$) is used in the treatment of cancer.
2. An isotope of Uranium ($^{235}\text{U}$) is used as a fuel in nuclear reactors.
Q32.
- Parenchyma: Thin primary cell walls made of cellulose; large intercellular spaces; functions in storage, photosynthesis (chlorenchyma), and buoyancy (aerenchyma).
- Collenchyma: Cell walls irregularly thickened at corners with pectin; very little intercellular space; provides mechanical flexibility and tensile elasticity.
- Sclerenchyma: Thick, rigid secondary cell walls heavily thickened with lignin; no intercellular spaces (dead cells); provides rigidity, structural strength, and protection.
Q33.
- Kharif Season (JuneβOctober): Sown with the onset of monsoon (e.g., Paddy/Rice, Maize, Soyabean, Cotton).
- Rabi Season (NovemberβApril): Sown in winter and harvested in spring (e.g., Wheat, Gram, Mustard, Peas).
- Zaid Season (MarchβJune): Short summer cropping season between rabi and kharif (e.g., Watermelon, Cucumber, Muskmelon, Fodder crops).
SECTION D β ANSWERS
Q34.
OR
- (a) Rutherford bombarded a thin gold foil (1000 atoms thick) with high-energy positively charged $\alpha$-particles ($^4_2\text{He}^{2+}$).
- (b) Observations & Conclusions:
1. Observation: Most $\alpha$-particles passed straight through the foil. $\rightarrow$ Conclusion: Most space inside an atom is empty.
2. Observation: Few particles were deflected by small and large angles. $\rightarrow$ Conclusion: Positive charge occupies very small volume.
3. Observation: 1 in 12,000 particles rebounded back ($180^\circ$). $\rightarrow$ Conclusion: Entire positive charge and mass are concentrated in a dense central core called the nucleus. - (c) Limitation: According to classical physics, an accelerating charged electron moving in a circular orbit must radiate energy continuously, lose speed, spiral inwards, and collapse into the nucleus, making atoms unstable (which contradicts atomic stability).
OR
- (a) Bohr’s Postulates:
1. Electrons revolve only in certain special non-radiating orbits called discrete orbits or energy levels ($K, L, M, N$ or $n=1,2,3,4$).
2. While revolving in discrete orbits, electrons do not radiate energy. - (b) Electron Configurations:
(i) Sodium ($\text{Na}=11$): Electronic configuration = $2, 8, 1$ (K=2, L=8, M=1).
(ii) Chlorine ($\text{Cl}=17$): Electronic configuration = $2, 8, 7$ (K=2, L=8, M=7). - (c) Valency: The combining capacity of an atom of an element to achieve a stable octet.
Magnesium ($\text{Mg}=12$): Configuration = $2, 8, 2$. It loses 2 valence electrons; hence, Valency = 2.
Q35.
OR
- (a) Prokaryotic vs Eukaryotic:
1. Size is generally small ($1β10\ \mu\text{m}$) in prokaryotes; larger ($5β100\ \mu\text{m}$) in eukaryotes.
2. Nuclear region is poorly defined (nucleoid, lacking membrane) in prokaryotes; well-defined with nuclear membrane in eukaryotes.
3. Membrane-bound organelles (mitochondria, plastids, Golgi) are absent in prokaryotes; present in eukaryotes. - (b) (i) In Hypotonic solution: Water enters the cell by endosmosis; the cell swells up and becomes turgid.
(ii) In Hypertonic solution: Water leaves the cell by exosmosis; the cell shrinks. - (c) Plasmolysis: When a living plant cell loses water through exosmosis in a hypertonic solution, the cell contents shrink away from the cell wall (e.g., Rheo leaf peel mounted in strong salt/sugar solution).
OR
- (a) Complex permanent tissues are made of more than one type of cell that work together as a unit. Two types: Xylem and Phloem.
- (b) Elements of Xylem:
1. Tracheids: Elongated dead tubular cells with tapering ends; conduct water and minerals vertically.
2. Vessels: Long continuous cylindrical tubes with perforated end walls; primary water conducting channels.
3. Xylem Parenchyma: Living cells; store food and assist in sideways/lateral conduction of water.
4. Xylem Sclerenchyma (Fibres): Dead lignified fibres; provide mechanical support to the plant. - (c) They are called conducting/vascular tissues because they form continuous pipeline systems for transporting water, mineral nutrients (xylem), and soluble organic food products (phloem) throughout the plant body.
Q36.
OR
- (a) Law of Conservation of Energy: Energy can neither be created nor destroyed; it can only be transformed from one form to another, and the total energy of an isolated system remains constant.
- (b) Mathematical Proof: Consider a body of mass $m$ at height $h$.
1. At point A (height $h$, velocity $u=0$): $PE = mgh$, $KE = 0 \Rightarrow TE_A = mgh$.
2. At point B (fallen distance $x$, velocity $v_1$): $v_1^2 = 0 + 2gx \Rightarrow KE = \frac{1}{2}m(2gx) = mgx$. Height $= (h-x) \Rightarrow PE = mg(h-x)$.
$TE_B = mg(h-x) + mgx = mgh$.
3. At point C (just touching ground, height = 0, velocity $v$): $v^2 = 2gh \Rightarrow KE = \frac{1}{2}m(2gh) = mgh$, $PE = 0 \Rightarrow TE_C = mgh$.
Since $TE_A = TE_B = TE_C = mgh$, total mechanical energy is conserved. - (c) Power $P = 1500\text{ W} = 1.5\text{ kW}$. Time per day $t = 10\text{ h}$.
Daily energy $= 1.5 \times 10 = 15\text{ kWh}$.
Monthly energy (30 days) $= 15 \times 30 = \mathbf{450\text{ kWh}}$ (or 450 units).
OR
- (a) Echo: The repetition of original sound caused by reflection of sound waves from an obstacle.
Conditions: Minimum time gap between original and reflected sound must be $0.1\text{ s}$; minimum obstacle distance must be $d = \frac{v \times t}{2} = \frac{344 \times 0.1}{2} = 17.2\text{ m}$. - (b) Given: Total time $t = 3.42\text{ s}$, Speed $v = 1531\text{ m/s}$.
Distance $2d = v \times t \Rightarrow d = \frac{1531 \times 3.42}{2} = 1531 \times 1.71 = \mathbf{2618.01\text{ m}} \approx 2.62\text{ km}$. - (c) Human Ear Working:
1. Outer Ear (Pinna & Canal): Collects sound waves and directs them to the eardrum (tympanic membrane).
2. Middle Ear (Malleus, Incus, Stapes): Amplifies vibrations several times.
3. Inner Ear (Cochlea): Converts amplified pressure vibrations into electrical signals, which auditory nerves carry to the brain.
SECTION E β ANSWERS
Q37.
- (a) Evaporation: Transition of liquid into vapor occurring at any temperature below its boiling point. Boiling is a bulk phenomenon at a specific fixed temperature, whereas evaporation is a surface phenomenon occurring at all temperatures. [1]
- (b) Cotton is a good absorber of water; it absorbs sweat, exposing it to the atmosphere, which evaporates by taking latent heat from our body, causing a cooling sensation. [1]
- (c) Factors:
1. Surface area: Increase in surface area exposes more liquid molecules to air, increasing the evaporation rate.
2. Temperature / Wind speed: Higher temperature gives molecules greater kinetic energy to escape; higher wind speed carries away water vapor particles quickly. [2]
Q38.
- (a) $F = G \frac{M \times m}{d^2}$, where $G$ is universal gravitational constant. [1]
- (b) The Earth is flattened at poles and bulged at equator ($R_{\text{equator}} > R_{\text{pole}}$). Since $g = \frac{GM}{R^2}$, $g$ is inversely proportional to $R^2$; hence $g_{\text{pole}} > g_{\text{equator}}$. [1]
- (c) (i) Mass is an intrinsic property and remains constant everywhere $\Rightarrow$ Mass on moon = $\mathbf{60\text{ kg}}$.
(ii) Weight on moon $W_m = m \times g_{\text{moon}} = 60 \times \left(\frac{10}{6}\right) = \mathbf{100\text{ N}}$. [2]
Q39.
- (a) Carbon and Oxygen. [1]
- (b) Macronutrients are essential plant nutrients required in large quantities. Examples: Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulphur (any two). [1]
- (c)
1. Origin: Manure is a natural organic substance obtained by decomposition of animal excreta and plant waste; chemical fertilizers are commercially manufactured inorganic salts.
2. Soil Structure: Manure adds extensive organic humus and improves water retention; excessive fertilizer use can degrade soil fertility and destroy microorganisms. [2]