CBSE EXAMINATION PAPER-2026
SCIENCE
(Solved)
General Instructions :
Read the following instructions carefully and follow them :
- This question paper contains 44 questions. All questions are compulsory.
- This question paper is divided into 5 sections.
- Section A – questions number 1 to 2 are case based questions
- Section B – questions number 3 to 22 are multiple choice questions
- Section C – questions number 23 to 30 are very short answer
- Section D – questions number 31 to 38 are short answer
- Section E – questions number 39 to 44 are long answer
- There is no overall choice given in the question paper. However, an internal choice has been provided in few questions.
- Use of calculator is NOT allowed.
Section A
(1) Why is hydrotropism essential for plants ?
[1 Mark](2) What role does auxin play in the growth of plants ?
[1 Mark](3) Differentiate between movement shown by the sensitive plant and tropic movement by plants (Two points).
[1 Mark](4) How does movement of roots differ from that of shoots in response to gravity and light ?
[1 Mark]
(1) What kind of image of a star is seen by the observer in the eye-piece ?
[1 Mark](2) What kind of mirror is used in this reflecting telescope ?
[1 Mark](3) Explain with the reason, what kind of optical device (type of lens or mirror) is used at the eye-piece.
[2 Marks]Section B
Observe the given figure and select the statement that correctly states how these fungi obtain nutrition.
Fungi like bread moulds obtain nutrition by producing enzymes that break down the nutrients in the bread outside their body. They then absorb the digested nutrients, which is a mode of nutrition called saprotrophic nutrition. This method involves breaking down dead or decaying matter externally and then absorbing the simpler nutrients.
If the part ‘P’ of the flower is removed, which of the following processes will not take place ?
The part 'P' in the flower is likely the ovary, which after fertilization grows to form the fruit. If the ovary is removed, fruit formation will not take place. However, pollens are formed in the stamens and seeds develop from ovules inside the ovary. Flower formation is independent of part 'P'. Hence, removing 'P' stops the formation of fruit.
Given below are some of the statements regarding our environment :
(i) Change in our life-styles have resulted in greater amounts of waste material generation.
(ii) Changes in attitude have resulted in use of more disposable things.
(iii) Changes in packaging has resulted in much of our waste becoming non-biodegradable.
(iv) Organic farming
Which amongst these is not leading to any damage of environment ?
Statements (i), (ii), and (iii) describe activities that lead to environmental damage by increasing waste generation, usage of disposables, and producing non-biodegradable waste respectively. However, (iv) Organic farming is an environmentally friendly practice that promotes soil health and reduces pollution, thus it does not lead to environmental damage.
Identify the traits that cannot be transmitted from parents to the offsprings : (i) Swimming technique (ii) Blood group (iii) Eye colour (iv) Dancing skills
Traits like blood group and eye colour are inherited from parents because they are controlled by genes and transmitted through heredity. However, skills such as swimming technique and dancing are acquired traits, learned through practice and environment, and cannot be genetically inherited from parents to offspring.
Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds were crossed with each other which produced F₁ progeny that have only round yellow (RrYy) seeds. When F₁ plants are self-pollinated, the F₂ progeny will have which new combination of characters, as compared to the parents : (i) Round, yellow (ii) Round, green (iii) Wrinkled, yellow (iv) Wrinkled, green Correct options are :
The parents are RRyy (round, green) and rrYY (wrinkled, yellow). The F1 progeny are all RrYy, showing round and yellow seeds. When F1 plants (RrYy) are self-pollinated, the F2 generation will have combinations of traits due to independent assortment. The parental combinations are (round, green) and (wrinkled, yellow). New combinations appearing in F2 are (round, green) and (wrinkled, green), which are (ii) Round, green and (iv) Wrinkled, green respectively.
In human beings the oxygen rich blood is pumped out to the body by :
The oxygen-rich blood from the lungs enters the left atrium and then flows into the left ventricle. When the muscular left ventricle contracts, it pumps the oxygen-rich blood out to the rest of the body. This is clearly stated in the context as: 'When the muscular left ventricle contracts in its turn, the blood is pumped out to the body.' Hence, the correct answer is contraction of left ventricle.
Two statements : Assertion (A) and Reason(R). Answer these questions selecting the appropriate option from (A), (B), (C) and (D) given below :
Assertion (A) : Variations are not often seen in off-springs produced by asexual reproduction.
Reason (R) : DNA molecule generated by replication is not similar to the original DNA.
The assertion that variations are not often seen in offspring produced by asexual reproduction is true because asexual reproduction generally produces genetically identical offspring. The reason given is false because DNA generated by replication is similar to the original DNA, although small errors can occur occasionally. These minor errors cause variation, but DNA replication is mostly accurate, so the reason does not correctly explain the assertion.
Two statements : Assertion (A) and Reason (R). Answer these questions selecting the appropriate option from (A), (B), (C) and (D) given below :
Assertion (A) : Highest percentage of pesticides is found in tertiary consumers in a food chain.
Reason (R) : Chemicals / pesticides get accumulated progressively at each trophic level.
The highest percentage of pesticides is indeed found in tertiary consumers because pesticides and other harmful chemicals accumulate progressively at each trophic level in a process called biological magnification. Since these chemicals are not degradable, they increase in concentration as they move from producers to primary consumers to secondary and then to tertiary consumers. Therefore, both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).
The volume ratio of hydrogen and oxygen gases liberated during electrolysis of water is
During the electrolysis of water, water (H2O) splits into hydrogen and oxygen gases. Since water has 2 hydrogen atoms for every 1 oxygen atom, the volume of hydrogen gas produced is twice the volume of oxygen gas. Hence, the volume ratio of hydrogen to oxygen gases liberated is 2:1.
An aqueous solution turns red litmus blue. Excess addition of which of the following solution would reverse the change ?
If an aqueous solution turns red litmus blue, it indicates the solution is basic (alkaline). Adding an acid such as hydrochloric acid (HCl) would neutralize the base and make the solution acidic or neutral, causing the red litmus paper to revert from blue back to red. Hence, hydrochloric acid will reverse the change caused by the basic solution.
Which one of the following metals does not react with cold water ?
Magnesium does not react with cold water but reacts with hot water to form magnesium hydroxide and hydrogen gas. Sodium and potassium react violently with cold water, while calcium reacts with cold water less violently but still reacts. Thus, Magnesium is the correct answer as it does not react with cold water.
Alloys are homogeneous mixture of metal with a metal or non-metal. Which among the following alloys contain non-metal as one of its constituents ?
The vision defect which arises due to gradual weakening of the ciliary muscles and diminishing flexibility of eye lens is :
Presbyopia is the vision defect that occurs because of the gradual weakening of the ciliary muscles and the diminishing flexibility of the eye lens, making it difficult to see nearby objects clearly. This is different from myopia and hypermetropia, which are refractive defects related to the shape of the eyeball or the curvature of the lens, not the weakening of muscles or lens flexibility.
Two statements are given – one labelled as Assertion (A) and other labelled as Reason (R). Select the correct answer to this question from the codes (A), (B), (C) & (D) as given below :
Assertion (A) : With the help of compass, magnetic field lines can be traced outside the bar magnet. Reason (R) : The north pole of a compass needle always points towards the south pole of the magnet when brought close to it.
Assertion (A) is true because a compass needle aligns itself along the magnetic field lines and can therefore be used to trace magnetic field lines outside a bar magnet. Reason (R) is also true since the north pole of the compass needle is attracted to the south pole of the magnet. However, Reason (R) does not correctly explain the Assertion because the compass aligns along magnetic field lines regardless of which pole it points to; the ability to trace field lines depends on the needle’s alignment, not just the direction it points. Hence, both statements are true but Reason (R) is not the correct explanation of Assertion (A).
C₆H₁₂O₆(aq) + 6O₂(g) → 6CO₂(g) + 6H₂O₍ₗ₎ . The above reaction is an example of -
The given reaction represents respiration where glucose reacts with oxygen to produce carbon dioxide, water, and releases energy. Since heat and energy are released in this reaction, it is an example of an exothermic reaction. This is supported by the context where it mentions that a large amount of heat is evolved during these types of reactions.
Section C
“Transpiration in plants is a necessary evil.” Comment on the statement giving two reasons.
1. It helps in the upward movement of water and minerals from roots to leaves, which is vital for photosynthesis and growth.
2. It helps in cooling the plant by evaporation and maintains the temperature of the plant.
Thus, transpiration is necessary despite causing water loss.
Explain why food chains generally consist of three or four steps.
Varun is diabetic. His latest ultrasound reports showed a blockage in his pancreatic duct. How will this affect the dual functioning of the pancreas ?
Thus, the blockage reduces enzyme secretion affecting digestion and may worsen insulin production affecting blood sugar control.
Sunil unconsciously touched the hot iron rod and immediately withdrew his hand. Which type of action is involved ? Also define this action. Draw a flow chart to show the path followed for this action.
(b) Reflex action is an automatic, rapid, and involuntary response to a stimulus that does not involve the brain for processing but is controlled by the spinal cord.
(c) Flow chart showing the path for reflex action:
Stimulus (touching hot iron) → Receptors in skin detect heat → Sensory neuron carries impulse to spinal cord → Relay neuron in spinal cord processes impulse → Motor neuron carries impulse to muscles → Effector (muscles in hand) contracts → Response: hand is withdrawn immediately.
(a) A compound ‘A’ is used in soda-lime fire-extinguisher and decomposes on heating to form compound ‘B’. Compound ‘B’ is used for removing permanent hardness of water. Identify ‘A’ and ‘B’.
(b) Write chemical formula of Plaster of Paris. At what temperature gypsum is heated to obtain Plaster of Paris ?
(b) The chemical formula of Plaster of Paris is CaSO4 · 1/2 H2O (calcium sulphate hemihydrate). Gypsum (CaSO4 · 2H2O) is heated at around 373 K (100 deg C) to obtain Plaster of Paris.
A fuse in electric circuit is rated 4 A. Can it be used with an electric heater of rating 2 kW, 200 V ? Explain your answer.
How is an electromagnet made ? Write any two ways by which the strength of electromagnet can be increased.
(b) Two ways to increase the strength of an electromagnet are:
1. Increase the number of turns in the coil of wire.
2. Increase the current passing through the wire coil.
(a) Define volt, the unit of potential difference.
(b) Calculate the work done required to move an electron between two points A and B located at a potential difference of 100 V in an electric field.
(b) Given, potential difference V = 100 V, charge of electron q = 1.6 * 10-19 C
Work done (W) = V * q = 100 * 1.6 * 10-19 = 1.6 * 10-17 joules
Therefore, the work done to move the electron between points A and B is 1.6 * 10-17 joules.
Section D
Give reasons for the following :
(a) Adrenal gland is known as the stress gland of the body.
(b) Prenatal sex determination is banned in India.
(c) Vegetative propagation is advantageous in some plants.
(b) Prenatal sex determination is banned in India to prevent female foeticide and maintain gender equality, as misuse of this technology leads to selective abortion of female fetuses.
(c) Vegetative propagation is advantageous in some plants because it allows rapid reproduction, produces offspring identical to the parent plant, and helps plants survive in unfavorable conditions without the need for seeds.
Study the given table and answer the following questions :
(a) Depict the information given in the table in the form of a cross.
(b) Deduce the F2 phenotypic ratio/F2 ratio showing external look as well as genotypic /genetic makeup, ratio.
P Generation: TT (tall) × tt (short)
F1 Generation: All plants are Tt (tall) as T is dominant.
F1 Cross: Tt × Tt
Punnett Square for F2:
| | T | t |
| T | TT | Tt |
| t | Tt | tt |
(b) From the Punnett square, the genotypes of F2 are:
- TT (homozygous dominant): 1
- Tt (heterozygous): 2
- tt (homozygous recessive): 1
Phenotypic ratio (tall : short) = 3 : 1 (as both TT and Tt are tall, tt is short)
Genotypic ratio (TT : Tt : tt) = 1 : 2 : 1
Account for the following :
(a) White silver chloride turns grey when exposed to sunlight.
(b) Lead (II) nitrate on heating releases brown fumes.
(c) Bags of oil and fat containing food items are flushed with nitrogen gas.
(b) When lead (II) nitrate is heated, it decomposes to form lead oxide, nitrogen dioxide, and oxygen. Nitrogen dioxide is a brown gas, so brown fumes are released. The reaction is 2Pb(NO3)2 heat 2PbO + 4NO2 + O2.
(c) Bags of oil and fat containing food items are flushed with nitrogen gas to prevent spoilage. Nitrogen is an inert gas and does not react with the contents, stopping oxidation and bacterial growth that require oxygen to survive, thus increasing the shelf life of food.
(i) Which method will be used to convert each of them to their respective metal oxides ?
(a) Carbonate ore (b) Sulphide ore
(ii) Write a chemical reaction to illustrate the use of aluminium for joining cracked railway tracks.
(iii) During extraction of metals, electrolytic refining is used to obtain pure metals. Which material will be used as anode and cathode for the refining of copper metal by this process ?
(ii) Aluminium is used to join cracked railway tracks by the thermit reaction. The chemical reaction is:
Fe2O3(s) + 2Al(s) → 2Fe(l) + Al2O3(s) + Heat
This reaction produces molten iron which joins the cracks.
(iii) In electrolytic refining of copper metal, the impure copper is used as the anode and a thin sheet of pure copper is used as the cathode. The electrolyte is copper sulfate solution. During the process, pure copper is deposited at the cathode and impurities collect at the anode or fall as anode mud.
(i) Write all the reactions involved in the extraction of Zn from ZnS.
(ii) Hydrogen gas is not evolved when most of the metals react with nitric acid. Give reason.
Step 1: Concentration of ore
ZnS ore is concentrated by froth flotation process to remove impurities.
Step 2: Roasting
The concentrated ZnS is heated in excess air to convert it into zinc oxide and sulfur dioxide:
2ZnS + 3O2 → 2ZnO + 2SO2
Step 3: Reduction
Zinc oxide is reduced by carbon (coke) at high temperature to obtain zinc metal:
ZnO + C → Zn + CO
(ii) Hydrogen gas is not evolved when most metals react with nitric acid because nitric acid is a strong oxidising agent. Instead of producing hydrogen gas, nitric acid gets reduced to nitrogen oxides like NO, NO2, or N2O, depending on the concentration of nitric acid and the metal. So, the reaction involves oxidation of metal and reduction of nitric acid, and hydrogen gas is not released.
(a) Observe the given ray diagram and compare :
(i) the speed of light in medium A and the speed of light in medium B.
(ii) the optical densities of medium B and medium C.
(b) Draw a ray diagram for refraction where the optical density of medium ‘A’ becomes equal to the optical density of medium ‘C’ and optical density of medium ‘B’ is greater than the optical density of medium ‘A’ and medium ‘C’.
(ii) Optical density depends on how much light slows down in a medium. The medium where light travels slower is optically denser. Since light is slower in medium B compared to medium C (assuming from the ray diagram), medium B is optically denser than medium C.
(b) To draw the ray diagram as per the given condition: Optical density of medium A is equal to that of medium C, so light rays will pass from A to C without bending (no refraction). Optical density of medium B is greater than both, so at the boundary of A and B, and B and C, the light will bend towards the normal when entering B and bend away from the normal when leaving B to enter C. The ray will remain undeviated between A and C. Draw the incident ray entering from medium A to B bending towards normal, then bending away from normal when entering medium C from B, and straight line path from A to C where optical densities are equal.
Explain the phenomenon of rainbow formation in the sky. Draw the labelled ray diagram in support of your explanation.
A rainbow is formed when sunlight passes through water droplets present in the atmosphere after rain. The water droplets act like tiny prisms causing dispersion of white sunlight into its seven colours - red, orange, yellow, green, blue, indigo, and violet.
Explanation:
1. When sunlight enters a water droplet, it bends or refracts because light travels slower in water than in air.
2. Inside the droplet, light reflects off the inner surface of the droplet.
3. The light then refracts again as it comes out of the droplet back into air, bending at different angles for different colours because of dispersion.
4. Due to this dispersion and refraction, the white light splits into different colours.
5. Many such droplets together form a circular arc of colours called a rainbow, which is always seen opposite the Sun.
Ray Diagram:
The ray diagram shows sunlight entering a spherical water droplet, refracting at the surface, reflecting internally at the back of the droplet, and refracting again while exiting. The emerging rays display a spectrum of colours forming the rainbow.
Thus, the combined effect of refraction, reflection, and dispersion of sunlight in water droplets causes the formation of a rainbow in the sky.
On the basis of the given circuit arrangement, answer the following questions :
(a) What happens to the rod AB when the key K is closed and why ?
(b) Name and state the rule that determines this behaviour of the rod AB in the above situation.
(b) The rule that determines the direction of this force is Fleming's Left Hand Rule. It states that if the thumb, forefinger, and middle finger of the left hand are stretched such that the forefinger points in the direction of the magnetic field, the middle finger in the direction of the current, then the thumb will point in the direction of the force or motion on the conductor.
Section E
(a) Draw a labelled diagram showing open and closed stomatal pore.
(b) List the main events that occur during the process of photosynthesis.
(c) Write a balanced chemical equation showing photo-synthesis in plants.
Diagram: (Labelled to show guard cells, stomatal pore open and stomatal pore closed.)
(b) Main events during photosynthesis are:
1. Absorption of sunlight by chlorophyll in leaves.
2. Conversion of light energy into chemical energy.
3. Splitting of water molecules into hydrogen and oxygen.
4. Release of oxygen into the atmosphere.
5. Fixation of carbon dioxide from air to form glucose.
(c) The balanced chemical equation for photosynthesis is:
6CO2 + 6H2O + light energy --> C6H12O6 + 6O2.
(a) Draw a well-labelled diagram of nephron and label atleast 4 of its parts.
(b) Write the role of capillary cluster inside Bowman’s capsule.
(c) What is meant by selective reabsorption ?
1. Bowman's capsule: It is a cup-shaped structure that surrounds the glomerulus.
2. Glomerulus: A cluster of tiny blood capillaries inside Bowman's capsule where blood filtration occurs.
3. Proximal convoluted tubule: The first part of the tubular system where selective reabsorption begins.
4. Loop of Henle: A long loop that helps concentrate urine.
5. Distal convoluted tubule: Further adjusts the filtrate composition.
(b) The role of the capillary cluster (glomerulus) inside Bowman's capsule is to filter blood. The blood pressure forces water and small molecules like glucose, salts, and urea out of the blood into Bowman's capsule, forming the filtrate. Larger components like proteins and blood cells remain in the blood.
(c) Selective reabsorption is the process by which useful substances such as glucose, certain salts, and a large amount of water are reabsorbed from the filtrate in the tubules of the nephron back into the blood. This process ensures that only waste products are excreted while valuable substances are retained by the body.
(i) Carbon cannot form C⁴⁺ cation and C⁴⁻ anion. Explain.
(ii) Define homologous series of carbon compounds. Why are the melting and boiling points of C₄H₁₀ higher than C₃H₈ or C₂H₆ ?
(iii) What happens when ethanol is heated with acidified potassium dichromate ?
(ii) A homologous series is a group of carbon compounds having the same functional group but differing by a CH2 unit in successive members. Members of a homologous series show similar chemical properties and gradual change in physical properties.
The melting and boiling points of C4H10 (butane) are higher than C3H8 (propane) and C2H6 (ethane) because as the number of carbon atoms increases, the molecular size and mass increase leading to stronger van der Waals forces between molecules. Stronger forces require more energy to break, thus higher melting and boiling points.
(iii) When ethanol is heated with acidified potassium dichromate, it is oxidized to produce ethanoic acid. The colour of potassium dichromate changes from orange to green due to reduction of dichromate ions. This reaction is an example of oxidation of a primary alcohol to a carboxylic acid.
(i) How would you name the following :
II. CH₃ – C ≡ CH
(ii) When ethanol reacts with ethanoic acid in the presence of conc. H₂SO₄, a substance with sweet smell is produced. Answer the following :
I. State the class of compounds to which the sweet smelling compounds belong.
II. Write the chemical equation for the reaction.
(iii) Why soaps do not produce foam with hard water ?
(b) (i) The sweet smelling compound formed when ethanol reacts with ethanoic acid in presence of concentrated H2SO4 is an Ester. Esters are known for their pleasant and sweet smell.
(ii) The chemical equation for the reaction is:
CH3CH2OH + CH3COOH --(conc. H2SO4)--> CH3COOCH2CH3 + H2O
This is an esterification reaction where ethanol and ethanoic acid produce ethyl ethanoate (an ester) and water.
(c) Soaps do not produce foam with hard water because hard water contains calcium and magnesium salts. These salts react with soap to form an insoluble substance called scum which does not foam. Thus, soap loses its ability to lather in hard water.
(i) The given electric circuit is a part of an electrical device. Use the information given in the electric circuit diagram to calculate :
(I) Potential difference across the ends of resistor R₂ .
(II) Value of resistor R₂ .
(III) Value of resistor R₁ .
(ii) Write the factors on which resistance of a conductor depends and derive the formula for resistance of a given conductor.
(II) To find the value of resistor R₂, if the potential difference V across it and the current I through it are known, use the formula R = V / I.
(III) Similarly, to find the value of resistor R₁, use the voltage across R₁ and the current through it with the formula R = V / I.
(ii) Factors on which resistance of a conductor depends are:
1. Length of the conductor (L): Resistance is directly proportional to the length of the conductor. Greater the length, greater the resistance.
2. Cross-sectional area (A): Resistance is inversely proportional to the area of cross-section. Larger the area, smaller the resistance.
3. Material of the conductor: Different materials have different resistivities affecting the resistance.
4. Temperature: Resistance changes with change in temperature.
Derivation of formula for resistance:
Resistance R is directly proportional to length L and inversely proportional to area A, hence R ∝ L / A.
Introducing resistivity constant (ρ) dependent on material and temperature, R = ρ * (L / A).
This formula shows resistance depends on physical dimensions and material properties of the conductor.
(i) How much electric current will an electric iron draw from 220 V source if the resistance of its heating element when hot, is 55Ω ? Calculate the power consumed by the electric iron when it is operated at 220 V.
(ii) In a house, 3 bulbs of 100 watt each, are lit for 5 hours daily and an electric heater of 1.0 kW is used for half an hour daily. Calculate the total energy consumed in a month of 30 days and its cost at the rate of Rs 3.60 per kWh.
(iii) With reason explain, why are alloys commonly used to make elements of electrical heating devices.
Using Ohm's law, Current I = V / R = 220 / 55 = 4 A.
Power consumed, P = V * I = 220 * 4 = 880 W.
(ii) Power of each bulb = 100 W, Number of bulbs = 3, Daily usage = 5 hours.
Total energy consumed by bulbs daily = 3 * 100 * 5 = 1500 Wh = 1.5 kWh.
Electric heater power = 1.0 kW, used for 0.5 hours daily.
Energy consumed by heater daily = 1.0 * 0.5 = 0.5 kWh.
Total energy consumed daily = 1.5 + 0.5 = 2.0 kWh.
Energy consumed in 30 days = 2.0 * 30 = 60 kWh.
Cost of energy = 60 * 3.60 = ` 216.
(iii) Alloys are used as heating elements because they have high resistivity and high melting points. This means they can generate a lot of heat without melting and do not oxidize easily at high temperatures, making them durable and efficient for heating devices.
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