Ch 1Exploration: Entering the World of Secondary Science
2-Mark Questions
Think of a prediction you or your family made recently (for example, the outcome of a cricket match). Was it based on evidence and reasoning, or mainly on guesswork? How can scientific thinking improve such predictions?
A prediction becomes scientific when it is based on evidence and reasoning rather than guesswork. Scientific thinking improves it by asking what evidence supports it, what assumptions are being made, and how the prediction can be tested against observation.
Describe one situation where an approximate answer is good enough, and one where you would need a very exact value.
An approximate answer is enough for estimating monthly rice needed by a family; an exact value is needed for a medicine dose, laboratory measurement, or aircraft fuel calculation where small errors matter.
Choose a real-life object (maybe a pressure cooker or a mobile phone) or a problem (maybe a traffic jam near your school). Make a sketch listing what kind of ideas from physics, chemistry, biology, earth science, or mathematics are involved. Show how at least two branches of science connect with your example.
For a pressure cooker, physics explains pressure and heat transfer, chemistry explains changes in food while cooking, biology explains killing microbes and softening tissues, and mathematics helps estimate time and fuel use. These branches connect because higher pressure changes boiling point and cooking reactions.
Ch 2Cell: The Building Block of Life
2-Mark Questions
Differentiate between the following pairs of terms based on the clues given in parentheses: (i) Cell membrane and cell wall (permeability) (ii) RER and SER (structure) (iii) Chloroplasts and chromoplasts (pigments)
Cell membrane is selectively permeable, while cell wall is freely permeable and rigid. RER has ribosomes on its surface, while SER lacks ribosomes. Chloroplasts contain chlorophyll; chromoplasts contain other coloured pigments.
Two similar animal cells are placed in two different solutions: y Cell X is placed in pure water. y Cell Y is placed in a concentrated salt solution. Cells are observed after some time. Cell X swells, and Cell Y shrinks. Which statement provides the correct explanation for the above observations? (i) Salt molecules moved into Cell Y, causing it to shrink. (ii) Water moved into Cell X and more water moved out of Cell Y than the salt solution entered in it. (iii) Water moved into Cell X and moved out of Cell Y through the cell membrane. (iv) Solute movement caused osmosis in both cells.
(iii) Water moved into Cell X and moved out of Cell Y through the cell membrane.
Look at the diagram of a cell in Fig. 2.20. Identify the parts labelled from (a) to (g) and correctly match them with their functions given below: (i) Controlling all the activities of a cell. (ii) Site of cellular respiration. (d) (iii) Storage organelle that also provides rigidity to the (a) (e) cell. (b) (iv) Separates the cell contents from surroundings. (c) (f) (v) Provides structural rigidity to the cell. (vi) Packs and stores materials received from ER. (g) (vii) Helps in manufacturing food.
Match each labelled part to its function as follows: (i) controlling all the activities of the cell — nucleus; (ii) site of cellular respiration — mitochondrion; (iii) storage organelle that also gives the cell rigidity — vacuole; (iv) separates the cell contents from the surroundings — cell membrane (plasma membrane); (v) provides structural rigidity to the cell — cell wall; (vi) packs and stores materials received from the endoplasmic reticulum — Golgi apparatus; (vii) helps in manufacturing food — chloroplast.
Ch 3Tissues in Action
2-Mark Questions
Meristematic tissues divide repeatedly. What property of their cells allows them to do this? (i) They have thick walls for protection. (ii) They contain large vacuoles that store nutrients. (iii) They have thin walls, dense cytoplasm and large prominent nucleus. (iv) They are functionally differentiated cells.
(iii) They have thin walls, dense cytoplasm and large prominent nucleus.
If a plant is unable to transport food from leaves to roots which tissue is malfunctioning? (i) Xylem (ii) Phloem (iii) Epidermis (iv) Sclerenchyma
(ii) Phloem.
Why are the epithelial tissues that line an animal’s internal organs usually only one or a few cells thick? (i) To store food efficiently. (ii) To provide maximum strength. (iii) To allow quick exchange of materials across them. (iv) To reduce friction.
(iii) To allow quick exchange of materials across them.
Ch 4Describing Motion Around Us
2-Mark Questions
My father went to a shop from home which is located at a distance of 250 m on a straight road. On reaching there, he discovered that he forgot to carry a cloth bag. He came home to take it, went to the shop again, bought provisions and came back home. How much was the total distance travelled by him? What was his displacement from home?
Total distance = 1000 m; displacement = 0 m.
A student runs from the ground floor to the fourth floor of a school building to collect a book and then comes down to their classroom on the second floor. m, find: (i) the total vertical distance travelled, and (ii) their displacement from the starting point.
(i) 18 m (ii) 6 m upward.
A girl is riding her scooter and finds that its speedometer reading is constant. Is it possible for her scooter to be accelerating and if so, how?
Yes. If speed is constant but direction changes, velocity changes, so the scooter is accelerating.
Ch 5Exploring Mixtures and their Separation
2-Mark Questions
Which of the following mixtures are correctly classified as homogeneous (Hm) and heterogeneous (Ht)? Choose the correct option. (i) Air — Hm, Milk — Ht, Sugar solution — Hm, Smoke — Hm (ii) Brass — Ht, Fog — Ht, Vinegar — Ht, Muddy water — Hm (iii) Copper sulfate solution — Hm, Salt solution — Hm, Milk — Hm, Bronze — Hm (iv) Muddy water — Ht, Milk — Ht, Blood — Ht, Brass — Hm
(iv) Muddy water — Ht, Milk — Ht, Blood — Ht, Brass — Hm.
Choose the correct options, and explain the reason for the correct and incorrect options. Which among the following mixtures show the Tyndall Effect? A mixture of: (a) air and dust particles (b) copper sulfate and water (c) starch and water (d) acetone and water (i) a and b (ii) b and d (iii) a and c (iv) c and d
(iii) a and c.
A mixture can be categorised as a solution, a suspension, or a colloid, each possessing distinct properties. Utilise the words or phrases provided in the box to fill in the .2. Words and phrases may be used more than once. Words and Phrases Large-sized particles; Particles remain evenly distributed; Small-sized particles (less than 1 nm diameter); Moderate-sized particles (1 – 1000 nm); Settles down when left undisturbed (more than 1000 nm in diameter); Does not settle down; Scatters light; Separates by filtration; Transparent; Salt solution; Milk; Sand in water; Smoke; Heterogeneous mixture; Cannot be separated by filtration; Mud; Butter; Brass. .2. .2 Solution Suspension Colloid Properties Properties Properties __________________________ __________________________ __________________________ __________________________ __________________________ __________________________ Examples Examples Examples __________________________ __________________________ __________________________ __________________________ __________________________ __________________________
Solution: homogeneous, particles less than 1 nm, transparent, do not settle, not separated by filtration; examples salt solution and brass. Suspension: heterogeneous, particles more than 1000 nm, settle on standing, separable by filtration; examples sand in water and mud. Colloid: heterogeneous, particles 1-1000 nm, scatter light, do not settle, not separated by ordinary filtration; examples milk, smoke and butter.
Ch 6How Forces Affect Motion
2-Mark Questions
Using a horizontal force F, a table is moved across the floor at a constant velocity. How much is the frictional force exerted by the floor on the table?
F, in the direction opposite to the applied force.
For a ball moving on a smooth frictionless surface, choose the appropriate option that will make the following statements physically correct. (i) If no net force is applied on the ball, the velocity of the ball will remain the same/increase/decrease. (ii) If a net force is applied on the ball in the direction of its motion, the magnitude of the velocity of the ball will remain the same/ increase/decrease. (iii) If a net force is applied on the ball in a direction opposite to the direction of its motion, the magnitude of the velocity of the ball will remain the same/increase/decrease.
(i) remain the same (ii) increase (iii) decrease.
Two blocks P and Q on a smooth horizontal surface are shown in Fig. 6.36a and Fig. 6.36b. N are acting in opposite directions on block P, while block Q is moving with a constant velocity. 5 N Q (a) (b) Fig. 6.36 Which of the following statement is correct? (i) P experiences a net force and Q does not experience a net force. (ii) P does not experience a net force and Q experiences a net force. (iii) Both P and Q experience a net force. (iv) Neither P nor Q experiences a net force.
(i) P experiences a net force and Q does not experience a net force.
Ch 7Work, Energy, and Simple Machines
2-Mark Questions
State whether True or False. (i) Work is said to be done when a force is applied, even if the object does not move. (ii) Lifting a bucket vertically upward results in positive work done on the bucket. (iii) The SI unit for both work and energy is joule (J). (iv) A motionless stretched rubber band has kinetic energy. (v) Energy can change from one form to another.
(i) False (ii) True (iii) True (iv) False (v) True.
Fill in the blanks. (i) Work done = ______ × ______ (in the direction of force). (ii) 1 joule of work is done when a force of ______ newton displaces an object by 1 metre in the direction of the force. (iii) The expression for kinetic energy of a body of mass m and velocity v is ______. (iv) The potential energy of an object of mass m at a small height h from the Earth’s surface is ______. (v) Power is defined as the ______ at which work is done.
(i) Force; displacement (ii) 1 (iii) 1/2 mv² (iv) mgh (v) rate.
When a ball thrown upwards reaches its highest point, tick which of the following statement(s) are correct? (i) The force acting on the ball is zero. (ii) The acceleration of the ball is zero. (iii) Its kinetic energy is zero. (iv) Its potential energy is maximum.
(iii) and (iv).
Ch 8Journey Inside the Atom
2-Mark Questions
Choose the correct options and explain the reason for the correct and incorrect options in the context of Ernest Rutherford’s gold foil experiment: (i) The experiment clearly showed the existence of neutrons in the nucleus. (ii) The results disproved the plum pudding model and led to the idea of a nucleus at the centre of the atom. (iii) The large deflection of a few alpha particles indicated that most of the mass of the atom and positive charge are packed into a tiny centre. (iv) The way alpha particles were deflected showed that electrons move around the nucleus.
(ii) and (iii) are correct.
Which of the following statements are correct or incorrect according to the Bohr’s atomic model? Give a reason for each statement. (i) Electrons lose energy while moving in fixed orbits and slowly fall into the nucleus. (ii) Electrons can exist anywhere around the nucleus with no fixed energy. (iii) Electrons revolve around the nucleus in orbits of fixed energy without losing energy. (iv) Electrons can be found between energy levels as they move around the nucleus.
(iii) is correct.
The composition of the nuclei of three atomic species X, Y, and Z are given as follows. X Y Z 17 17 18 20 Explain the relation between the following: (i) Y and Z (ii) Z and X
(i) Y and Z are isotopes. (ii) Z and X are isobars.
Ch 9Atomic Foundations of Matter
2-Mark Questions
A particular element (A) has one electron in its third shell. There is another element (B) with six electrons in its second shell. (i) How many electrons does A tend to give or take to become stable? (ii) What kind of ion would it form? (iii) How many electrons does B tend to give or take to become stable? (iv) What kind of ion would it form? (v) If A and B were to combine, what kind of bond would be formed? (vi) What would be the formula for the compound thus formed?
(i) A gives 1 electron. (ii) A⁺ cation. (iii) B takes 2 electrons. (iv) B²⁻ anion. (v) Ionic bond. (vi) A₂B.
An element X has six electrons in its outer shell and forms a diatomic molecule. (i) Why would that be so? (ii) What kind of bond would it form? (iii) Draw the structure of the molecule it would form. (iv) A certain other element Y has two electrons in its second shell. Draw the structure of the molecule that X would form with Y.
With six valence electrons, X needs two more electrons to complete its octet, so two X atoms share two pairs of electrons to form a covalent diatomic molecule X₂. With Y having two valence electrons, X and Y combine according to valencies; the exact drawn structure should be checked against the classroom notation expected.
You want to design a new ionic compound, where the total positive charge is 6+ and the total negative charge is 6 –. Which of the following combinations gives the correct number of ions? (i) 2 Al3+ and 3 Cl– (ii) 3 Mg2+ and 1 PO43– (iii) 2 Fe3+ and 3 O2– (iv) 3 Ca2+ and 2 SO42–
Option (iii), 2 Fe³⁺ and 3 O²⁻, gives the correct charge balance. The total positive charge = 2 × (3+) = 6+ and the total negative charge = 3 × (2−) = 6−, so they balance exactly to form the neutral compound Fe₂O₃. The other options are unbalanced: (i) 2 Al³⁺ (6+) with 3 Cl⁻ (3−), (ii) 3 Mg²⁺ (6+) with 1 PO₄³⁻ (3−), and (iv) 3 Ca²⁺ (6+) with 2 SO₄²⁻ (4−) all leave unequal positive and negative charges.
Ch 10Sound Waves: Characteristics and Applications
2-Mark Questions
Which observation best supports the idea that sound is a mechanical wave? (i) Sound shows reflection (ii) Sound needs a medium to propagate (iii) Sound has frequency (iv) Sound carries energy
(ii) Sound needs a medium to propagate.
For a sound wave propagating in a medium, increasing its frequency will increase its (i) wavelength (ii) speed (iii) number of compressions per second (iv) time period
(iii) number of compressions per second.
If 20 compressions pass a point in 4 seconds, the frequency is (i) 80 Hz (ii) 5 Hz (iii) 10 Hz (iv) 0.2 Hz
5 Hz.
Ch 11Reproduction: How Life Continues
2-Mark Questions
A flower’s anthers are removed before it matures. Later, pollen from another plant of the same species is dusted onto its stigma and seeds are produced. Which process has been ensured here? (i) Self-pollination (ii) Cross-pollination (iii) Fertilisation (iv) Tissue culture
(ii) Cross-pollination.
Arrange the following stages of sexual reproduction in plants in the correct order: (i) Pollen germination on stigma (ii) Fertilisation (iii) Pollination (iv) Formation of zygote
Correct sequence: (iii), (i), (ii), (iv).
Assertion (A): The zygote formed after fertilisation immediately attaches to the uterus wall. Reason (R): The uterus wall is always prepared to receive the zygote. (i) Both A and R are true, and R is the correct explanation of A. (ii) Both A and R are true, but R is not the correct explanation of A. (iii) A is true, but R is false. (iv) A is false, but R is true.
(iv) A is false, but R is true.
Ch 12Patterns in Life: Diversity and Classification
2-Mark Questions
Meena and Hari observed an animal in their garden. Hari called it an insect while Meena said it was an earthworm. Choose the correct option which confirms that it is an insect. (i) Bilateral symmetrical body (ii) Body with jointed legs (iii) Cylindrical body (iv) Body with little segmentation
(ii) Body with jointed legs.
Sponges represent one of the simplest animal body plans. Their bodies lack true tissues and organs. Which feature of sponge cells supports its classification under the animal kingdom? (i) Absence of mitochondria (ii) Ability to photosynthesise (iii) Presence of a cell membrane (iv) Presence of a cell wall
(iii) Presence of a cell membrane.
Observe two different animals in your immediate environment. What features help you distinguish between them? How do these features help place them into different groups?
Features such as body segmentation, number of legs, wings, backbone, body covering and movement distinguish animals. For example, an ant has jointed legs and an external skeleton, placing it among arthropods, while a lizard has a backbone and scales, placing it among vertebrates/reptiles.
Ch 13Earth as a System: Energy, Matter, and Life
2-Mark Questions
Choose the most appropriate option to describe the role of biogeochemical cycles in an ecosystem. (i) To provide food directly to all organisms. (ii) To recycle essential nutrients between biotic and abiotic components. (iii) To create new elements for use by living things. (iv) To remove pollutants and toxins from the organism.
(ii) To recycle essential nutrients between biotic and abiotic components.
Which of the following is primarily responsible for warming of the Earth? (i) Solar radiation is immediately absorbed by carbon dioxide, which then releases it as heat. (ii) The atmosphere’s tiny particles absorb incoming solar radiation, which directly heats the Earth. (iii) The Earth’s surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases. (iv) The Earth’s environment is heated only by the solar radiation reflected by the clouds.
(iii) The Earth’s surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases.
Explain how climate change affects the water cycle. Illustrate with examples.
Climate change intensifies the water cycle by increasing evaporation and changing cloud and rainfall patterns. Some regions may face heavier rain and floods, while others face drought. Melting glaciers and altered monsoon patterns also change river flow and groundwater recharge.
Frequently asked questions
- Think of a prediction you or your family made recently (for example, the outcome of a cricket match). Was it based on evidence and reasoning, or mainly on guesswork? How can scientific thinking improve such predictions?
- A prediction becomes scientific when it is based on evidence and reasoning rather than guesswork. Scientific thinking improves it by asking what evidence supports it, what assumptions are being made, and how the prediction can be tested against observation.
- Describe one situation where an approximate answer is good enough, and one where you would need a very exact value.
- An approximate answer is enough for estimating monthly rice needed by a family; an exact value is needed for a medicine dose, laboratory measurement, or aircraft fuel calculation where small errors matter.
- Choose a real-life object (maybe a pressure cooker or a mobile phone) or a problem (maybe a traffic jam near your school). Make a sketch listing what kind of ideas from physics, chemistry, biology, earth science, or mathematics are involved. Show how at least two branches of science connect with your example.
- For a pressure cooker, physics explains pressure and heat transfer, chemistry explains changes in food while cooking, biology explains killing microbes and softening tissues, and mathematics helps estimate time and fuel use. These branches connect because higher pressure changes boiling point and cooking reactions.
- Differentiate between the following pairs of terms based on the clues given in parentheses: (i) Cell membrane and cell wall (permeability) (ii) RER and SER (structure) (iii) Chloroplasts and chromoplasts (pigments)
- Cell membrane is selectively permeable, while cell wall is freely permeable and rigid. RER has ribosomes on its surface, while SER lacks ribosomes. Chloroplasts contain chlorophyll; chromoplasts contain other coloured pigments.
These important questions are selected from the NCERT Class 9 Science textbook book-back exercises to help you revise the most useful questions. Mark weightage (5/2/1) follows the usual exam pattern and may vary by exam — always check your latest syllabus and question pattern. Open each chapter for the complete set of questions and answers.