CBSE Class 9 Science — 80 Marks Question Paper (Set 1) with Answers
Are you a Class 9 CBSE student preparing for your mid-term Science examination? At Dhingra Classes, we understand that the new NCERT Science textbook and the updated CBSE exam pattern can feel overwhelming. That’s why we’ve created this 80 Marks Question Paper with Answers covering five crucial chapters: The Fundamental Unit of Life, Tissue, Is Matter Around Us Pure, Structure of Atom, and Motion and How Forces Affect Motion.
This paper follows the latest CBSE Class 9 exam pattern, including competency-based questions, assertion-reason questions, and case-based questions.
Q9.Assertion (A): The plasma membrane is called a selectively permeable membrane. Reason (R): It allows only certain substances to enter and exit the cell.
(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.
Answer: (a) Both A and R are true, and R is the correct explanation of A.
Short Answer Questions (2 × 3 = 6 Marks)
Q10. Why are lysosomes known as the “suicide bags” of the cell? (3 marks)
Answer: Lysosomes contain powerful digestive enzymes capable of breaking down all organic material. If the cell gets damaged or its metabolism is disturbed, lysosomes may burst, and the enzymes digest their own cell. Hence, they are called suicide bags.
Q11. Differentiate between Meristematic and Permanent tissues. (3 marks)
Answer:
Meristematic Tissue
Permanent Tissue
Consists of actively dividing cells
Cells have lost the ability to divide
Cells are small, thin-walled, and lack vacuoles
Cells are differentiated and specialized for specific functions
Found at growing tips of roots and shoots
Found throughout the plant body
Case Study Questions (2 × 4 = 8 Marks)
Q12.Read the passage and answer the questions below:
A student observes a plant cell under a microscope. She notices a rigid outer covering outside the plasma membrane. Inside the cell, she sees a large central vacuole and green structures called chloroplasts.
(a) Name the rigid outer covering observed by the student. (1 mark)
Answer:Cell wall
(b) What is the main function of this structure? (1 mark)
Answer: The cell wall provides structural strength, protection against mechanical injury, and allows the plant cell to withstand osmotic pressure without bursting.
(c) Name the green structures observed in the cell. (1 mark)
Answer:Chloroplasts
(d) Why are these green structures absent in animal cells? (1 mark)
Answer: Chloroplasts are absent in animal cells because animals cannot perform photosynthesis. They obtain food by consuming other organisms.
Q13.Read the passage and answer the questions below:
A student examines three types of muscle tissues under a microscope. She observes that one type is striated and voluntary, another is striated but involuntary, and the third is non-striated and involuntary.
(a) Identify the striated and voluntary muscle tissue. (1 mark)
Answer:Skeletal muscles (or striated muscles)
(b) Name the striated but involuntary muscle tissue. (1 mark)
Answer:Cardiac muscles
(c) Which muscle tissue is non-striated and involuntary? (1 mark)
Answer:Smooth muscles
(d) Where is cardiac muscle found in the human body? (1 mark)
Answer: Cardiac muscle is found in the heart and helps in pumping blood throughout the body.
Long Answer Question (1 × 5 = 5 Marks)
Q14. Explain the structure and function of the nucleus in a cell. (5 marks)
Answer:
Structure:
The nucleus is a double-layered structure called the nuclear membrane.
It contains chromosomes (DNA and protein) which carry hereditary information.
The nucleus contains a dense structure called the nucleolus.
Functions:
Acts as the control center of the cell, regulating metabolism and protein synthesis.
Stores genetic material (DNA) that carries hereditary information from one generation to the next.
Coordinates cell activities such as growth and cell division.
🧪 SECTION B: CHEMISTRY (25 Marks)
Multiple Choice Questions (7 × 1 = 7 Marks)
Q15. Which of the following is a homogeneous mixture?
(a) Oil and water (b) Air (c) Sand and iron filings (d) Soil
Answer: (b) Air
Q16. The scattering of light by colloidal particles is known as the __________ effect.
(a) Brownian (b) Tyndall (c) Raman (d) Newton
Answer: (b) Tyndall
Q17. Which method is best to separate camphor from a mixture of salt and camphor?
Q18. Which subatomic particle was discovered by J. Chadwick?
(a) Proton (b) Electron (c) Neutron (d) Nucleus
Answer: (c) Neutron
Q19. What is the maximum number of electrons in the K-shell?
(a) 2 (b) 8 (c) 18 (d) 32
Answer: (a) 2
Q20. The atomic number of an element is equal to the number of:
(a) Neutrons (b) Protons (c) Nucleons (d) Electrons and neutrons
Answer: (b) Protons
Q21. Which of the following is a compound?
(a) Air (b) Brass (c) Water (d) Soil
Answer: (c) Water
Assertion-Reason Question (1 × 1 = 1 Mark)
Q22.Assertion (A): A solution is a homogeneous mixture. Reason (R): The particles in a solution are uniformly distributed and cannot be seen by the naked eye.
(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.
Answer: (a) Both A and R are true, and R is the correct explanation of A.
Very Short Answer Question (1 × 2 = 2 Marks)
Q23. Differentiate between atomic number and mass number. (2 marks)
Answer:
Atomic number (Z): Number of protons in the nucleus of an atom.
Mass number (A): Sum of the number of protons and neutrons in the nucleus.
Short Answer Questions (2 × 3 = 6 Marks)
Q24. What is a colloid? Give one example. (3 marks)
Answer: A colloid is a heterogeneous mixture where the particle size is between that of a solution and a suspension, and the particles do not settle out on standing. The particles in a colloid are small enough to remain dispersed and can scatter light. Example: Milk (fat globules dispersed in water).
Q25. Explain Rutherford’s alpha-particle scattering experiment and its conclusions. (3 marks)
Answer:
Experiment: Rutherford fired fast-moving alpha particles at a thin gold foil.
Observations:
Most alpha particles passed through the foil without deflection.
The atom has a small, dense, positively charged nucleus at the center.
Electrons revolve around the nucleus.
Case Study Question (1 × 4 = 4 Marks)
Q26.Read the passage and answer the questions below:
A solution is prepared by dissolving 20 g of common salt in 80 g of water at room temperature. The student stirs the mixture until all the salt dissolves.
(a) What is the mass percentage of the solute in this solution? (2 marks)
Answer: Mass percentage = (Mass of solute / Mass of solution) × 100 = (20 / (20 + 80)) × 100 = (20 / 100) × 100 = 20%
(b) Is this solution saturated or unsaturated? Justify your answer. (2 marks)
Answer: The solution is likely unsaturated because all the salt dissolved completely. A saturated solution would have undissolved solute remaining at the bottom.
Long Answer Question (1 × 5 = 5 Marks)
Q27. Describe Bohr’s model of the atom with its postulates. (5 marks)
Answer:
Bohr’s Model:
Postulates:
Electrons revolve around the nucleus in fixed energy orbits or shells.
Electrons revolve in fixed orbits without radiating energy.
Each orbit has a fixed amount of energy.
Energy is absorbed or emitted when an electron moves from one orbit to another.
Distribution of Electrons:
K-shell: Maximum 2 electrons
L-shell: Maximum 8 electrons
M-shell: Maximum 18 electrons
⚡ SECTION C: PHYSICS (27 Marks)
Multiple Choice Questions (2 × 1 = 2 Marks)
Q28. A body is said to be in uniform motion when it:
(a) Changes direction continuously (b) Covers equal distances in equal intervals of time (c) Covers unequal distances in equal intervals of time (d) Remains at rest
Answer: (b) Covers equal distances in equal intervals of time
Q29. Which of the following is a contact force?
(a) Gravitational force (b) Magnetic force (c) Frictional force (d) Electrostatic force
Answer: (c) Frictional force
Assertion-Reason Question (1 × 1 = 1 Mark)
Q30.Assertion (A): An object at rest tends to remain at rest unless acted upon by an external force. Reason (R): This is known as the law of inertia.
(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.
Answer: (a) Both A and R are true, and R is the correct explanation of A.
Very Short Answer Questions (3 × 2 = 6 Marks)
Q31. Differentiate between distance and displacement. (2 marks)
Answer:
Distance
Displacement
Total length of the actual path covered
Shortest straight-line distance between initial and final positions
Scalar quantity (magnitude only)
Vector quantity (magnitude and direction)
Always positive
Can be positive, negative, or zero
Q32. Define momentum. Write its SI unit. (2 marks)
Answer:Momentum is the product of an object’s mass and velocity. It measures how much motion an object has.
Formula: p = mv
SI Unit:kg m/s (kilogram metre per second)
Q33. What is force? Write its SI unit. (2 marks)
Answer:Force is a push or pull that changes or tends to change the state of rest or uniform motion, direction of motion, or shape and size of a body. Force has both magnitude and direction, so it is a vector quantity.
SI Unit:Newton (N)
Short Answer Questions (3 × 3 = 9 Marks)
Q34. State Newton’s First Law of Motion. Give one example. (3 marks)
Answer:Newton’s First Law: An object stays at rest or continues in uniform motion in a straight line unless acted upon by an external unbalanced force.
Example: When a bus stops abruptly, passengers tend to fall forward because their bodies tend to remain in motion.
Q35. State Newton’s Second Law of Motion. Derive the equation F = ma. (3 marks)
Answer:
Newton’s Second Law: The rate of change of momentum of an object is directly proportional to the applied force and takes place in the direction of the force.
Q36. Explain Newton’s Third Law of Motion with an example. (3 marks)
Answer:Newton’s Third Law: For every action, there is an equal and opposite reaction. Action and reaction forces act on two different bodies simultaneously.
Example: When a rocket expels hot gases downward (action), the gases push the rocket upward (reaction) with equal force. This enables the rocket to lift off.
Case Study Question (1 × 4 = 4 Marks)
Q37.Read the passage and answer the questions below:
A car of mass 1500 kg is moving with a velocity of 20 m/s. The driver applies brakes and the car comes to rest in 5 seconds.
(a) Calculate the initial momentum of the car. (1 mark)
Answer: Initial momentum = m × u = 1500 × 20 = 30,000 kg m/s
(b) Calculate the final momentum of the car. (1 mark)
Answer: Final momentum = m × v = 1500 × 0 = 0 kg m/s
(c) Calculate the change in momentum. (1 mark)
Answer: Change in momentum = Final − Initial = 0 − 30,000 = −30,000 kg m/s
(d) Calculate the force applied by the brakes. (1 mark)
Answer: Force = Change in momentum / Time = −30,000 / 5 = −6,000 N
The negative sign indicates that the force is applied opposite to the direction of motion.
Long Answer Question (1 × 5 = 5 Marks)
Q38. State Newton’s Second Law of Motion. Derive the equation F = ma and explain conservation of momentum with an example. (5 marks)
Answer:
Newton’s Second Law: The rate of change of momentum of an object is directly proportional to the applied force and takes place in the direction of the force.
Derivation of F = ma:
Initial momentum: p₁ = mu
Final momentum: p₂ = mv
Change in momentum: Δp = m(v − u)
Rate of change of momentum = m(v − u) / t = ma
Therefore, F = ma
Conservation of Momentum: The total momentum of a system remains constant if no external unbalanced force acts on it.
Example: When a bullet is fired from a gun, the gun recoils backward. The momentum of the bullet (forward) equals the momentum of the gun (backward) in magnitude. Total momentum before firing (zero) equals total momentum after firing (zero).
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