These essential MCQ questions are selected from the most important topics in CBSE Class 9 Science 2026 as per the latest NCERT syllabus. Sections include Matter in Our Surroundings, Atoms & Molecules, Cell — The Fundamental Unit of Life, Motion, Force & Laws of Motion, and Gravitation. For truly unlimited daily MCQ practice, visit Vooo AI Education.
⚗️ CBSE Class 9 Science
1Which of the following is a physical change?
Answer: C — Melting of ice
A physical change is reversible and does not produce a new substance. Melting of ice (H₂O solid → H₂O liquid) is a physical change — the chemical composition remains the same. Burning of wood, rusting of iron, and digestion of food are chemical changes because new substances with different properties are formed and the changes are largely irreversible.
A physical change is reversible and does not produce a new substance. Melting of ice (H₂O solid → H₂O liquid) is a physical change — the chemical composition remains the same. Burning of wood, rusting of iron, and digestion of food are chemical changes because new substances with different properties are formed and the changes are largely irreversible.
2The atomic number of an element is defined as the number of:
Answer: B — Protons in the nucleus
Atomic number (Z) = number of protons in the nucleus. In a neutral atom, the number of protons equals the number of electrons. Mass number (A) = protons + neutrons. Number of neutrons = A - Z. For example, Carbon has Z = 6 (6 protons) and A = 12 (6 protons + 6 neutrons). Isotopes have the same atomic number but different mass numbers.
Atomic number (Z) = number of protons in the nucleus. In a neutral atom, the number of protons equals the number of electrons. Mass number (A) = protons + neutrons. Number of neutrons = A - Z. For example, Carbon has Z = 6 (6 protons) and A = 12 (6 protons + 6 neutrons). Isotopes have the same atomic number but different mass numbers.
3An object travels 20 m in 4 seconds. What is its speed?
Answer: B — 5 m/s
Speed = Distance / Time = 20 m / 4 s = 5 m/s. Speed is a scalar quantity (only magnitude, no direction). Velocity is a vector quantity (magnitude + direction). Average speed = total distance / total time. If the object's direction is also specified, the 5 m/s becomes velocity. The SI unit of speed is metres per second (m/s).
Speed = Distance / Time = 20 m / 4 s = 5 m/s. Speed is a scalar quantity (only magnitude, no direction). Velocity is a vector quantity (magnitude + direction). Average speed = total distance / total time. If the object's direction is also specified, the 5 m/s becomes velocity. The SI unit of speed is metres per second (m/s).
4Newton's first law of motion is also called the law of:
Answer: A — Inertia
Newton's first law states that a body at rest stays at rest and a body in motion stays in motion with the same speed and direction unless acted upon by an external unbalanced force. This tendency is called inertia. More massive objects have greater inertia. Example: passengers jerk forward when a bus brakes suddenly — they were in motion and inertia keeps them moving forward.
Newton's first law states that a body at rest stays at rest and a body in motion stays in motion with the same speed and direction unless acted upon by an external unbalanced force. This tendency is called inertia. More massive objects have greater inertia. Example: passengers jerk forward when a bus brakes suddenly — they were in motion and inertia keeps them moving forward.
5The value of acceleration due to gravity (g) on Earth's surface is approximately:
Answer: B — 9.8 m/s²
The acceleration due to gravity on Earth's surface is g = 9.8 m/s² (often approximated as 10 m/s²). It is directed towards the centre of the Earth. Weight = mass × g. On the Moon, g = 1.63 m/s² (about 1/6th of Earth). The universal gravitational constant G = 6.67 × 10⁻¹¹ N m²/kg² is different from g. g varies slightly with altitude and latitude.
The acceleration due to gravity on Earth's surface is g = 9.8 m/s² (often approximated as 10 m/s²). It is directed towards the centre of the Earth. Weight = mass × g. On the Moon, g = 1.63 m/s² (about 1/6th of Earth). The universal gravitational constant G = 6.67 × 10⁻¹¹ N m²/kg² is different from g. g varies slightly with altitude and latitude.
6Which organelle controls all activities of the cell?
Answer: C — Nucleus
The nucleus is the control centre of the cell. It contains chromosomes made of DNA that carry genetic information and direct all cell activities including growth, metabolism, and reproduction. It is surrounded by a nuclear membrane with pores. Prokaryotic cells (like bacteria) lack a membrane-bound nucleus. The nucleolus inside the nucleus is the site of ribosome synthesis.
The nucleus is the control centre of the cell. It contains chromosomes made of DNA that carry genetic information and direct all cell activities including growth, metabolism, and reproduction. It is surrounded by a nuclear membrane with pores. Prokaryotic cells (like bacteria) lack a membrane-bound nucleus. The nucleolus inside the nucleus is the site of ribosome synthesis.
7Which of the following has the highest kinetic energy among particles?
Answer: C — Gas particles
Gas particles have the highest kinetic energy. In solids, particles vibrate about fixed positions. In liquids, particles can flow and have more energy than solids. In gases, particles move freely and randomly with maximum kinetic energy and maximum intermolecular distances. As temperature increases, kinetic energy of particles increases. At absolute zero (0 K or -273°C), particle movement theoretically stops.
Gas particles have the highest kinetic energy. In solids, particles vibrate about fixed positions. In liquids, particles can flow and have more energy than solids. In gases, particles move freely and randomly with maximum kinetic energy and maximum intermolecular distances. As temperature increases, kinetic energy of particles increases. At absolute zero (0 K or -273°C), particle movement theoretically stops.
8The momentum of an object of mass 2 kg moving at 5 m/s is:
Answer: C — 10 kg m/s
Momentum (p) = mass × velocity = 2 kg × 5 m/s = 10 kg m/s. Momentum is a vector quantity. Newton's second law: Force = rate of change of momentum = m × a. The law of conservation of momentum states that the total momentum of an isolated system remains constant. This explains why a gun recoils when fired — the bullet and gun have equal and opposite momenta.
Momentum (p) = mass × velocity = 2 kg × 5 m/s = 10 kg m/s. Momentum is a vector quantity. Newton's second law: Force = rate of change of momentum = m × a. The law of conservation of momentum states that the total momentum of an isolated system remains constant. This explains why a gun recoils when fired — the bullet and gun have equal and opposite momenta.
9Which type of tissue is responsible for movement in animals?
Answer: C — Muscular tissue
Muscular tissue contains cells (muscle fibres) that can contract and relax to produce movement. There are three types: striated/skeletal (voluntary, attached to bones), smooth/unstriated (involuntary, in internal organs), and cardiac (involuntary, in heart). Nervous tissue transmits signals. Epithelial tissue covers body surfaces. Connective tissue provides support and links organs.
Muscular tissue contains cells (muscle fibres) that can contract and relax to produce movement. There are three types: striated/skeletal (voluntary, attached to bones), smooth/unstriated (involuntary, in internal organs), and cardiac (involuntary, in heart). Nervous tissue transmits signals. Epithelial tissue covers body surfaces. Connective tissue provides support and links organs.
10By which process does a solid directly convert into gas without passing through the liquid state?
Answer: C — Sublimation
Sublimation is the process by which a solid directly converts to gas (vapour) without going through the liquid phase. Examples: dry ice (solid CO₂), camphor, iodine, and naphthalene balls. The reverse process (gas → solid directly) is called deposition or desublimation. Sublimation is used in freeze-drying food and in purifying substances. Evaporation is liquid → gas; condensation is gas → liquid.
Sublimation is the process by which a solid directly converts to gas (vapour) without going through the liquid phase. Examples: dry ice (solid CO₂), camphor, iodine, and naphthalene balls. The reverse process (gas → solid directly) is called deposition or desublimation. Sublimation is used in freeze-drying food and in purifying substances. Evaporation is liquid → gas; condensation is gas → liquid.
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