CBSE Class 9 Science Assertion and Reason Questions: Chapter-Wise PDF Download For 2025-26 Exams

1. Assertion : A gas can easily be compressed by applying pressure. 

Reason : Since the inter-particle spaces between gases are very large, they can decrease by applying pressure. 

Answer: A

2. Assertion : Gases exert pressure on the walls of the container. 

Reason : The intermolecular force of attraction is very strong in gases. 

Answer: C

3. Assertion : It is easier to cook food at sea level as compared to higher altitudes. 

Reason : The boiling point of water increases at high altitudes. 

Answer: C

4. Assertion : When a solid melts, its temperature remains the same. 

Reason : The heat gets used up in changing the state by overcoming the forces of attraction between the particles. 

Answer: A

5. Assertion : Liquids diffuse more easily as compared to gases. 

Reason : Intermolecular forces are greater in liquids than in gases.

Answer: D

6. Assertion : The solids do not diffuse in air.
Reason : The particles are loosely packed in solids.

Answer: C

7. Assertion : The boiling point of water is 100 C.
Reason : The boiling point of water increases at higher altitudes.

Answer: C

8. Assertion : Evaporation causes cooling.

Reason : Particles of a liquid absorb energy from the surroundings to change into a vapor.

Answer: A

9. Assertion : A sponge is a solid, yet we can compress it.

Reason : The particles of a solid are tightly packed with very little space between them.

Answer: B

10. Assertion : The rate of diffusion increases with an increase in temperature.

Reason : With an increase in temperature, the kinetic energy of particles decreases.

Answer: C

1. Assertion (A): A solution of salt in water is a homogeneous mixture. 

Reason (R): The components of a homogeneous mixture are uniformly distributed throughout the mixture. 

Answer: A

2. Assertion (A): Air is a mixture. 

Reason (R): Air can be separated into its components by physical methods like fractional distillation.

Answer: A

3. Assertion (A): Milk is a colloid. 

Reason (R): Colloids are heterogeneous mixtures in which the particle size is intermediate between those in true solutions and suspensions. 

Answer: A

4. Assertion (A): When a beam of light is passed through a colloidal solution, its path becomes visible 

Reason (B): Light do not gets scattered by colloidal particles. 

Answer: C

5. Assertion : Milk is an aerosol 

Reason : Milk contains liquid as dispersed phase in liquid as dispersion medium. 

Answer: D

6. Assertion : A mixture of sugar and benzoic acid can be separated by shaking with ether.
Reason : Sugar is insoluble in water.

Answer: C

7. Assertion : Colloidal solutions are stable and the colloidal particles do not settle down.
Reason : Brownian movement counters the force of gravity acting on colloidal particles.

Answer: A

8. Assertion (A): The process of separating an insoluble solid from a liquid is known as filtration.

Reason (R): A filter paper has very small pores that allow the liquid to pass through but not the solid. 

Answer: A

9. Assertion (A): The boiling point of a solution is always lower than that of the pure solvent. Reason (R): Adding a solute to a solvent increases the vapor pressure of the solvent. 

Answer: D

10. Assertion (A): Chromatography is a technique used for separating different components of a mixture.

Reason (R): The components of the mixture are separated based on their different solubilities in a specific solvent. 

Answer: A

1. Assertion: Atomicity of ozone is three while that of oxygen is two. 

Reason: Atomicity is the number of atoms constituting a molecule. 

Answer. A

2. Assertion: For the formation of a molecule at least two atoms are needed. 

Reason: Molecules are formed by bonding between different atoms of different elements or complexes without any exception. 

Answer. B 

3. Assertion: Atom is the smallest unit of molecule

Reason: Atoms are combined with each other forming molecules. 

Answer. B

4. Assertion: Mass can neither be created nor destroyed in chemical reaction

Reason: Mass can convert its own form while chemical reaction been complete. 

Answer: C

5. Assertion: N2 and H2O are molecules. 

Reason: A molecule can have only similar kinds of atoms. 

Answer: C

6. Assertion: Molecular weight of oxygen is 16.
Reason: Atomic weight of oxygen is 16.

Answer: D

7. Assertion: Protons cannot be transferred from one atom to another.
Reason: Protons are present deep inside the atom in its nucleus.

Answer: A

8. Assertion: Water obtained from different sources like a river and a well always has the same ratio of hydrogen and oxygen by mass. 

Reason: This is an example of the Law of Definite Proportions. 

Answer: A

9. Assertion: One mole of any substance contains Avogadro's number of particles. 

Reason: The molecular mass of a substance is the mass of one mole of that substance. Answer: B

10. Assertion: An atom is electrically neutral. 

Reason: The number of protons is equal to the number of electrons. 

Answer: A

1. Assertion: Isotopes of an element have the same chemical properties.

Reason: Isotopes have the same number of protons and electrons.

Answer: A

2. Assertion: Valency of an element is determined by the number of protons in its nucleus. Reason: Valency is the combining capacity of an element, which is determined by the number of electrons in its outermost shell. 

Answer: C

3. Assertion: Electrons are located in the nucleus of an atom. 

Reason: Electrons are negatively charged particles that orbit the nucleus of an atom in specific energy levels or shells.

Answer: C

4. Assertion: Mass number of an element is always an integer. 

Reason: Mass number is the sum of the number of protons and neutrons in an atom, both of which are whole numbers. 

Answer: A

5. Assertion: The atomic number of an element can change in a chemical reaction. 

Reason: Atomic number is the number of protons in an atom, which remains

constant during a chemical reaction. 

Answers:C

6. Assertion: Isobars are identical in chemical properties.
Reason: Isobars have same atomic number.

Answers:D

7. Assertion: The size of the nucleus is very small as compared to the size of the atom.
Reason: The electrons revolve around the nucleus of the atom

Answers:B

8. Assertion: The Rutherford model of an atom failed to explain the stability of the atom.
Reason: According to Rutherford, revolving electrons would lose energy and eventually fall into the nucleus.
Answer: A

9. Assertion: Bohr’s model of the atom is considered an improvement over Rutherford’s model.
Reason: The Bohr model states that electrons occupy fixed orbits and do not radiate energy while in these orbits.
Answer: A

10. Assertion: Cations are formed when an atom loses electrons.
Reason: An atom that has lost electrons has more protons than electrons, resulting in a net positive charge.
Answer: A

1. Assertion (A): The cell membrane is selectively permeable. 

Reason (R): The cell membrane allows only certain substances to pass through it

while restricting others. 

Answer: a) Both A and R are true, and R is the correct explanation of A.

2. Assertion (A): Mitochondria are known as the powerhouses of the cell. 

Reason (R): Mitochondria are the sites of photosynthesis in plant cells. 

Answer: c) A is true, but R is false. 

3. Assertion (A): Vacuoles are storage sacs found in animal cells. 

Reason (R): Vacuoles store water, nutrients, and waste materials. 

Answer: d) A is false, but R is true.

4. Assertion (A): The cell wall is found in both plant and animal cells. 

Reason (R): The cell wall provides structural support and protection to the cell. 

Answer: d) A is false, but R is true. 

5. Assertion (A): Endoplasmic reticulum (ER) is involved in protein synthesis.

Reason (R): Rough ER is studded with ribosomes, which are the sites of protein synthesis. Answer: a) Both A and R are true, and R is the correct explanation of A.

6. Assertion : Plasma membrane is selectively permeable.
Reason : Plasma membrane allows some molecules to pass through it more easily than others.

Answer: A

7. Assertion : Leucoplasts perform photosynthesis.
Reason : Chloroplasts store fats, starch and proteins.

Answer: D

8. Assertion (A): The nucleus is called the control center of the cell.
Reason (R): The nucleus contains the cell's genetic material and controls its activities.
Answer: a) Both A and R are true, and R is the correct explanation of A.

9. Assertion (A): Osmosis is the movement of water molecules from a region of higher concentration to a region of lower concentration.
Reason (R): The movement of water molecules takes place through a selectively permeable membrane.
Answer: a) Both A and R are true, and R is the correct explanation of A.

10. Assertion (A): Lysosomes are also called suicidal bags of the cell.
Reason (R): Lysosomes contain powerful digestive enzymes to break down old and worn-out cell organelles.
Answer: a) Both A and R are true, and R is the correct explanation of A.

1. Assertion (A): Epithelial tissues are tightly packed and form a protective barrier.

Reason (R): Epithelial tissues have a high rate of cell division to replace damaged cells. 

Answer: a) Both A and R are true, and R is the correct explanation of A. 

2. Assertion (A): Connective tissues provide structural support to organs and tissues. 

Reason (R): Connective tissues are mainly composed of cells that can contract and relax. 

Answer: c) A is true, but R is false. 

3. Assertion (A): Muscular tissues are specialized for contraction and movement. 

Reason (R): Muscular tissues are composed of cells that can change shape and size. 

Answer: b) Both A and R are true, but R is not the correct explanation of A. 

4. Assertion (A): Nervous tissues are responsible for transmitting electrical

impulses. 

Reason (R): Nervous tissues are composed of cells called neurons. 

Answer: a) Both A and R are true, and R is the correct explanation of A. 

5. Assertion (A): Meristematic tissues are found in the regions of the plant that grow. 

Reason (R): Meristematic cells are specialized and have lost the ability to divide. 

Answer: (c) Assertion (A) is true but Reason (R) is false.

6. Assertion : The inner lining of intestine has tall epithelial cells.
Reason : Columnar epithelium facilitates absorption and secretion.

Answer: A

7. Assertion : Most of plant tissues are dead.
Reason : Due to sedentary existence of plants, dead cells provide mechanical strength more easily than live ones and need less maintenance.

Answer: A

8. Assertion (A): The epidermal cells of a plant root are non-specialized and do not have any specific function.
Reason (R): The root epidermal cells are a type of permanent tissue and are meant to absorb water from the soil.
Answer: d) A is false, but R is true.

9. Assertion (A): Bone is a type of dense connective tissue.
Reason (R): The matrix of bone tissue is hard and non-pliable.
Answer: a) Both A and R are true, and R is the correct explanation of A.

10. Assertion (A): The vascular tissue in plants is called complex tissue.
Reason (R): It is made of more than one type of cells, which work together as a unit.
Answer: a) Both A and R are true, and R is the correct explanation of A.

1. Assertion (A): Distance is always smaller than or equal to the displacement. 

Reason (R): Distance is the length of the actual path travelled by an object, whereas displacement is the shortest distance between the initial and final positions of an object. 

Answer: D

2. Assertion (A): An object moving in a circular path with uniform speed is accelerating. 

Reason (R): The direction of the velocity changes continuously in circular motion. 

Answer: A

3. Assertion (A): A car moving on a straight road with constant speed has zero acceleration. 

Reason (R): Acceleration is defined as the rate of change of distance. 

Answer: C

4. Assertion (A): The slope of a distance-time graph of an object in uniform motion is a straight line. 

Reason (R): In uniform motion, equal distances are covered in equal intervals of time. 

Answer: A

5. Assertion (A): For a body moving with uniform velocity, the average velocity over any time interval is equal to the instantaneous velocity at any instant. 

Reason (R): In uniform velocity, the speed and direction of motion remain constant. Answers: 

Answer: A

6. Assertion : The graph between two physical quantities P and Q is straight line, when P/Q is constant.
Reason : The straight line graph means that P is proportional to Q or P is equal to constant multiplied by Q.

Answer: A

7. Assertion : the speedometer of a car measures the instantaneous speed of the car.
Reason : Average speed is equal to the total distance covered by an object divided by the total time taken.

Answer: B

8. Assertion (A): The area under a velocity-time graph gives the displacement of the object.
Reason (R): The area under the graph is calculated by multiplying velocity by time, which gives displacement.
Answer: A

9. Assertion (A): The velocity of a freely falling object increases with time.
Reason (R): A freely falling object experiences a constant acceleration due to gravity.
Answer: A

10. Assertion (A): A body can have zero velocity but still be accelerating.
Reason (R): When a body is at the highest point of its vertical motion, its velocity is zero, but it is still under the influence of gravity.
Answer: A

1. Assertion : If the net external force on the body is zero, then its acceleration is zero. 

Reason : Acceleration does not depend on force. 

Answer: C

2. Assertion : When we sit on a chair, our body exerts a force downward and that chair needs to exert an equal force upward or the chair will collapse. 

Reason : The third law says that for every action there is an equal and opposite reaction. 

Answer: A

3. Assertion: A football has lesser inertia than a stone of the same size. 

Reason: Massive object has less inertia. 

Answer: C

4. Assertion : While walking on ice, one should take small steps to avoid slipping. 

Reason : This is because smaller steps ensure smaller friction

Answer: A

5. Assertion (A) : Newton's laws can be applied to bigger bodies 

Reason (R) : During any kind of collision the centre of mass of the system is not accelerated

Answer: B

6. Assertion : When a firefly hits a bus, each of them exerts the same force.
Reason : Firefly has more mass as compared to the windshield.

Answer: C

7. Assertion : Linear momentum is conserved in both elastic and inelastic collisions.
Reason : Total energy is conserved in all collisions.

Answer: B

8. Assertion: It is difficult to start moving a bicycle from rest, but once it is moving, it is easier to keep it in motion.
Reason: This is an example of inertia of rest and inertia of motion.
Answer: A

9. Assertion: A karate player breaks a slab of ice with a single blow.
Reason: The player applies a large force in a very short interval of time.
Answer: A

10. Assertion: Pushing a heavy car is easier if it is on a frictionless surface.
Reason: The momentum of a body is its mass multiplied by its velocity.
Answer: B

1.Assertion (A): The weight of an object on the Moon is about one-sixth of its weight on the Earth. 

Reason (R): The acceleration due to gravity on the Moon is about one-sixth of that on the Earth. 

Answer: a) Both A and R are true, and R is the correct explanation of A. 

2.Assertion (A): The gravitational force between two objects is inversely proportional to the square of the distance between them. 

Reason (R): If the distance between two objects is doubled, the gravitational force between them is halved.

Answer: c) A is true, but R is false. 

3.Assertion (A): The mass of an object is constant everywhere in the universe. 

Reason (R): The weight of an object is the gravitational force acting on it and varies with the location. 

Answer: a) Both A and R are true, and R is the correct explanation of A. 

4.Assertion (A): Gravitational force acts only between objects that are in contact with each other. 

Reason (R): Gravitational force is a long-range force that acts between any two masses regardless of the medium between them. 

Answer: d) A is false, but R is true. 

5.Assertion (A): The value of the gravitational constant (G) is the same every wherein the universe. 

Reason (R): The gravitational constant (G) determines the strength of the gravitational force between two objects with unit masses separated by a unit distance. 

Answer: a) Both A and R are true, and R is the correct explanation of A.

6. Assertion : Any two objects in the universe attract each other by a force called gravitation force.
Reason : The force of gravitation exerted by the earth is called gravity.

Answer: B

7. Assertion : Weight of a body on earth is equal to the force with which the body is attracted towards the earth.
Reason : Weight of a body is independent of the mass of the body.

Answer: C

8. Assertion (A): The value of acceleration due to gravity (g) is maximum at the surface of the Earth.
Reason (R): The value of acceleration due to gravity (g) decreases as we go above or below the surface of the Earth.
Answer: b) Both A and R are true, but R is not the correct explanation of A.

9. Assertion (A): The force of gravity on an object is always directed towards the center of the Earth.
Reason (R): The Earth attracts objects towards its center.
Answer: a) Both A and R are true, and R is the correct explanation of A.

10. Assertion (A): A freely falling object has an acceleration equal to 9.8m/s2.
Reason (R): The value of acceleration due to gravity is 9.8m/s2 on the surface of the Earth.
Answer: a) Both A and R are true, and R is the correct explanation of A.

1.Assertion: Work is done when there is a displacement is perpendicular to the direction of the force. 

Reason: If there is no displacement, work done is zero. 

Answer: D

2.Assertion: Kinetic energy of an object depends on its mass. 

Reason: Kinetic energy is directly proportional to the square of the velocity of the object. 

Answer: B

3.Assertion: Potential energy of an object decreases as it falls freely towards the ground.

Reason: The potential energy of an object depends on its mass and height above the reference level. 

Answer: A

4.Assertion: Energy can be converted from one form to another. 

Reason: According to the law of conservation of energy, total energy remains constant in any process.

Answer: A

5.Assertion: Power is the rate at which work is done or energy is transferred or transformed. 

Reason: Power is measured in joules.

Answer: C

6. Assertion : A spring has potential energy, both when it is compressed or stretched.
Reason : In compressing or stretching, work is done on the spring against the restoring force.

Answer: A

7. Assertion : When the force retards the motion of a body, the work done is negative.
Reason : Work done depends on angle between force and displacement.

Answer: B

8. Assertion: The work done by the gravitational force on a satellite revolving around the Earth in a circular orbit is zero.
Reason: The force of gravitation is perpendicular to the displacement of the satellite.
Answer: A

9. Assertion: When a person climbs up a staircase, the work done against gravity is positive.
Reason: The force of gravity acts in the downward direction, and the displacement of the person is in the upward direction.
Answer: C

10. Assertion: A ball is thrown upwards. The kinetic energy of the ball decreases as it moves up.
Reason: The kinetic energy of a body is given by the formula, KE=frac12mv2.
Answer: A

1.Assertion: Sound cannot travel in vacuum. 

Reason: Sound requires a medium for propagation. 

Answer: A, Both Assertion and Reason are correct, and the Reason is the correct explanation for the Assertion. 

2. Assertion: The speed of sound is maximum in solids and minimum in gases. 

Reason: The particles of solids are closely packed, allowing sound waves to travel faster through them.

Answer: B, Both Assertion and Reason are correct, but the Reason is not the correct explanation for the Assertion.

3. Assertion: A sound wave with a higher amplitude is perceived as louder. 

Reason: Amplitude is the measure of the energy carried by the wave. 

Answer: A, Both Assertion and Reason are correct, and the Reason is the correct explanation for the Assertion. 

4. Assertion: Ultrasonic waves are used in medical imaging. 

Reason: Ultrasonic waves have high penetrating power and can pass through tissues.

Answer: A, Both Assertion and Reason are correct, and the Reason is the correct explanation for the Assertion. 

5. Assertion: Noise pollution can lead to hearing loss. 

Reason: Prolonged exposure to loud noises can damage the eardrum and inner ear structures. 

Answer: A, Both Assertion and Reason are correct, and the Reason is the correct explanation for the Assertion.

6. Assertion : The velocity of sound increases with increase in humidity.
Reason : Velocity of sound does not depend upon the medium.

Answer: C

7. Assertion : Sound is a form of energy which produces a sensation of hearing in our ears.
Reason : When you clap, a sound is produced.

Answer: B

8. Assertion: The pitch of a sound is determined by its frequency.
Reason: The higher the frequency of a sound wave, the higher its pitch.
Answer: A

9. Assertion: The loudness of a sound is determined by its amplitude.
Reason: A larger amplitude means more energy and thus a louder sound.
Answer: A

10. Assertion: The reflection of sound is called an echo.
Reason: Sound waves bounce off a surface, and this phenomenon is called reflection.
Answer: B

1.Assertion (A): Green manure helps in improving soil fertility. 

Reason (R): Green manure plants are plough back into the soil before they mature. Answer: 

Correct Answer: A 

2.Assertion (A): Drip irrigation is an efficient method of irrigation in water-scarce areas. 

Reason (R): Drip irrigation provides water directly to the roots of plants, reducing water wastage. 

Correct Answer: A 

3.Assertion (A): Use of bio-fertilizers is beneficial for the environment. 

Reason (R): Bio-fertilizers are synthetic chemicals that enhance soil fertility. 

Correct Answer: C 

4.Assertion (A): Crossbreeding in cattle can lead to improved milk production. 

Reason (R): Crossbreeding introduces new genes that can enhance desirable traits in cattle. 

Correct Answer: A 

5.Assertion (A): Use of pesticides can have harmful effects on human health. 

Reason (R): Pesticides are designed to kill pests that affect crop production. 

Correct Answer: B

6. Assertion: Some weeds produce substances toxic for the crops.
Reason: Weeds take up nutrients and reduce the growth of crops.

Answer: B

7. Assertion: Cattle are fed with roughage and concentrates.
Reason: Roughage provides fibres while concentrates provide proteins and other nutrients.

Answer: A

8. Assertion: The use of chemical fertilizers is not considered a sustainable practice in agriculture.
Reason: Chemical fertilizers are non-biodegradable and can lead to soil and water pollution.
Answer: A

9. Assertion: Crop rotation is an effective method for pest control.
Reason: Pests and diseases are specific to a crop and their population can be controlled by growing different crops in a sequential manner.
Answer: A

10. Assertion: Poultry farming is done to raise chickens for egg production only.
Reason: Broilers are raised for meat, and layers are for egg production.
Answer: D

CBSE Class 9 Science Assertion Reason Questions | Download PDF