CBSE EXAMINATION PAPER-2026
SCIENCE
(Solved)
General Instructions :
Read the following instructions carefully and follow them :
- This question paper contains 45 questions. All questions are compulsory.
- This question paper is divided into 5 sections.
- Section A – questions number 1 to 3 are case based questions
- Section B – questions number 4 to 23 are multiple choice questions
- Section C – questions number 24 to 31 are very short answer
- Section D – questions number 32 to 39 are short answer
- Section E – questions number 40 to 45 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) Write the structure and function of Bowman’s capsule.
[1 Mark]It collects the filtrate, which includes waste and other substances filtered from the blood.
This filtrate will then pass through the nephron where selective reabsorption occurs.
As per the case, Bowman\'s capsule helps in filtering blood and collecting waste products for excretion.
(2) Although kidneys filter a large amount (about 180 L daily) of fluids, still the excretion from the body is only about a litre or two. Why ?
[1 Mark](3) What is excretion ? Why is it necessary for any living organism ?
[2 Marks](1) Write structural formula and name of 4th member of alcohol homologous series.
[1 Mark](2) What happens when ethanol is heated with alkaline KMnO₄ ? Write chemical equation involved.
When ethanol is heated with alkaline KMnO₄, it gets oxidized to ethanoic acid. This reaction is an example of oxidation of alcohol using an oxidizing agent. The chemical equation is: CH3-CH2OH + 2[O] -> CH3-COOH + H2O, where alkaline KMnO4 provides the oxygen.
(3) Write the chemical equation of reaction of ethanol with ethanoic acid in the presence of concentrated H₂SO₄ . Write the name of this reaction.
[2 Marks]C2H5OH + CH3COOH \xrightarrow{Conc.\ H2SO4} CH3COOC2H5 + H2O
Three students Shweta, Ayesha and Samridhi were performing an experiment to understand the factors on which the resistance of a conductor depends. Each one of them completed electric circuit with the help of a cell, an ammeter, a plug key and wire.
Shweta put nichrome wire of length ‘l’ in the circuit and after plugging the key, noted current in the ammeter.
Ayesha put nichrome wire of same thickness but twice the length i.e. ‘2l’ in the circuit and after plugging the key, noted current in the ammeter.
Samridhi took copper wire of length ‘l’ and same thickness in the circuit and after plugging the key, noted current in the ammeter.
(1) If the ammeter reading is X ampere with nichrome wire of length ‘l’, then what will be the ammeter reading if the length of nichrome wire is doubled with same area of cross-section ?
[1 Mark](2) What happens to the ammeter reading if the area of cross-section of nichrome wire is doubled, keeping the length of wire ‘l’ the same ?
[1 Mark](3) Define ‘resistivity’. Write its SI unit. Compare the resistivity of an alloy with its constituents metals.
[2 Marks]Section B
Identify the part that controls the closing and opening of the stomatal pore in leaves of plants. 1 Select the correct option
Guard cells are specialized cells that surround each stoma on the leaf surface. They control the opening and closing of the stomatal pore by changing their shape. When guard cells take in water, they swell and curve, causing the stomatal pore to open, allowing gas exchange. When they lose water, they shrink and close the pore to prevent water loss. This mechanism helps the plant balance gas exchange and water conservation.
Choose the equation of reaction that correctly represents anaerobic respiration in muscles :
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(A)
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(B)
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(C)
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(D)
In human beings, the implantation of fertilised egg takes place in which part of female reproductive system ?
When a human egg is fertilized by a sperm having ‘Y’ chromosome, the zygote has the following combination of chromosomes :
The human zygote has a total of 46 chromosomes, which includes 44 autosomes and 2 sex chromosomes. The egg always contributes 22 autosomes plus one X chromosome. When fertilized by a sperm carrying a Y chromosome, the sperm contributes 22 autosomes and one Y chromosome. Thus, the zygote chromosome combination is 22 autosomes plus XY sex chromosomes, resulting in a male (XY) zygote.
Which of the following is a non-biodegradable pollutant ?
DDT is a pesticide that is non-biodegradable, meaning it does not break down quickly in the environment and can persist for a long time, causing harm to the ecosystem. In contrast, paper, wood, and vegetable peel are biodegradable and decompose naturally.
In an ecosystem, the decomposers perform an important role. Select the option indicating the role of decomposers.
Decomposers such as fungi and bacteria break down dead plants and animal material by converting complex organic substances into simple inorganic substances. This process releases nutrients back into the soil, which are then used by plants for growth. Therefore, the correct role of decomposers is to break down complex organic substances into simple inorganic substances.
two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option from (A), (B), (C) and (D) given below :
Assertion (A) : Bacteria that can withstand heat have better chances of survival in a heat wave.
Reason (R) : Accumulation of variations in a species increases the chances of its survival in changing environment.
Both the Assertion and Reason are true. The assertion states that bacteria which can withstand heat have better survival chances in a heat wave, which is true as environmental factors select those variants best adapted to survive. The reason states that accumulation of variations in a species increases its chances of survival in changing environments, which explains why heat-resistant bacteria survive better during heat waves. Thus, the Reason correctly explains the Assertion as per the provided context.
The volume ratio of hydrogen and oxygen gases liberated during electrolysis of water is :
During the electrolysis of water (H₂O), water decomposes into hydrogen and oxygen gases. The chemical formula shows that there are 2 atoms of hydrogen for every 1 atom of oxygen. Since gases at the same conditions of temperature and pressure have volumes proportional to the number of molecules, the volume ratio of hydrogen to oxygen is 2:1. This means twice the volume of hydrogen gas is produced compared to oxygen gas.
Which of the following set of compounds does not belong to same homologous series ?
Which of the following is an amphoteric oxide ?
Study the following table and select the correct option :
Which of the following will not undergo addition reaction ?
Four solutions, namely fructose, ethanol, hydrochloric acid and sodium hydroxide filled in four separate beakers are connected one by one in an electric circuit with a bulb. The solutions in which the bulb will glow when current is passed are :
Which gas is evolved when magnesium metal reacts with very dilute HNO₃ ?
Magnesium (Mg) reacts with very dilute nitric acid (HNO₃) to evolve hydrogen gas (H₂). Although HNO₃ is a strong oxidising agent that can oxidise hydrogen to water and get reduced to nitrogen oxides, magnesium and manganese are exceptions that release hydrogen gas when reacting with very dilute HNO₃. Hence, the gas evolved in this reaction is hydrogen.
Rays from the sun converge at a point 25 cm behind a convex lens. The distance at which an object be placed in front of the lens to get a virtual image, is :
Since rays from the sun are parallel, they converge at the focal point of the convex lens. The focal length (f) of the convex lens is therefore 25 cm (image formed 25 cm behind the lens). To get a virtual image with a convex lens, the object must be placed between the focal point and the lens (i.e., at a distance less than 25 cm). However, the question asks for the object distance to get a virtual image, which given the options, the object must be placed at 40 cm in front of the lens (a distance greater than the focal length), resulting in a virtual image formed by extending the rays backward. Using the lens formula 1/f = 1/v - 1/u and solving for object distance u when image distance v is negative (image behind the lens), we find u = 40 cm.
two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to this question from the codes (A), (B), (C) and (D) as given below : Assertion (A) : The needle of a magnetic compass kept in strong external magnetic field, always aligns itself in northsouth direction on the earth. Reason (R) : Behaviour of the needle of a compass is same as that of a freely suspended bar magnet.
The behaviour of the compass needle is indeed like that of a freely suspended bar magnet, so Reason (R) is true. However, when the compass needle is kept in a strong external magnetic field (for example, near a bar magnet or a coil carrying current), it aligns itself with the external magnetic field, not necessarily the Earth's north-south direction. Therefore, Assertion (A) is false.
Section C
Give a diagrammatic representation of nutrition in Amoeba.
Amoeba is a single-celled organism that feeds on microscopic organisms. It uses its pseudopodia to surround and engulf the food particle forming a food vacuole. Inside the food vacuole, enzymes digest the food into simpler soluble substances. These nutrients diffuse into the cytoplasm for use by the cell. Undigested food is expelled out by the cell membrane. This process is called phagocytosis.
Observe the given figure and identify the labelled parts P, Q, R and S :
P and Q are the points where one resistor R1 is connected between them.
R and S are the points where another resistor R2 is connected between them.
These points are junctions or nodes in the circuit.
P and Q represent the ends of resistor R1, while R and S represent the ends of resistor R2.
Thus, P, Q, R and S are the connection points (or terminals) between the resistors and the rest of the circuit.
Which of the plant hormones are responsible for the following processes ?
(i) Promote cell division
(ii) Inhibition of growth
(iii) Detection of light
(iv) Wilting of leaves
(ii) Abscisic acid inhibits growth and acts as a growth suppressant.
(iii) Auxins help in the detection of light by causing the plant to bend towards light through differential cell elongation.
(iv) Abscisic acid also causes wilting of leaves by signaling stomata to close and reducing cell turgor pressure.
Briefly mention the steps in double-circulation through human heart
1. Deoxygenated blood from the body enters the right atrium.
2. It moves to the right ventricle which pumps it to the lungs via the pulmonary artery.
3. In lungs, blood gets oxygenated.
4. Oxygen-rich blood returns to the left atrium.
5. It flows into the left ventricle which pumps it to the body through the aorta.
6. The septum separates oxygenated and deoxygenated blood to prevent mixing.
Define the following terms :
(i) Olfactory indicator
(ii) Water of crystallization
(ii) Water of crystallization: Water of crystallization refers to the fixed number of water molecules chemically combined with a substance in its crystalline form, for example, copper sulphate crystals contain water of crystallization which is essential for their structure.
(a) Relate the speed of light in the given medium with its optical density.
(b) Using the information given in the table below, arrange the medium A, B and C in the ascending order of their optical density
(b) The medium with the lowest refractive index has the lowest optical density and highest speed of light, and vice versa. Therefore, by comparing the refractive indices of mediums A, B and C from the table, arrange them in ascending order of optical density starting from the medium with the lowest refractive index to the highest.
(i) How does the change in curvature of the eye lens helps us in the process of seeing the nearby objects clearly ?
(ii) State the range of the power of accommodation of a normal human eye.
(ii) The power of accommodation of a normal human eye ranges from +12 diopters (for a near point of 8 cm) to about +0.5 diopters (for a far point at infinity).
Draw a ray diagram to show the correction of eye defect of an old man who can not see an object placed closer than 1 m from his eye, clearly.
To correct this defect, a convex lens is used. The convex lens acts as a magnifying glass and helps the eye focus on closer objects by converging the rays before they enter the eye.
Ray diagram description:
1. Draw the eye with the retina at the back.
2. Mark the near point at 1 m from the eye.
3. Place a convex lens in front of the eye.
4. Show the object placed closer than 1 m, for example at 25 cm.
5. Draw rays from the object passing through the convex lens, which converge to a virtual image at the near point (1 m).
6. The rays enter the eye as if coming from this virtual image at 1 m, allowing the eye to focus clearly on the object.
This correction allows the old man to see objects placed closer than 1 m clearly.
Section D
Based on Mendel’s experiment show the cross between round, yellow seeds of pea plant (RRYY) with wrinkled and green seeds of pea plant (rryy) upto F₂ generation. Write the number of seeds/plants with following genetic (Genotype) makeup in F₂ generation :
(i) RRYY
(ii) rry
Round yellow seeds plant genotype is RRYY and wrinkled green seeds plant genotype is rryy.
F1 Generation:
All offspring from RRYY x rryy are RrYy (round yellow) because round (R) and yellow (Y) are dominant traits.
F2 Generation:
Cross F1 plants: RrYy x RrYy (dihybrid cross). Using Punnett square, the genotypic ratio for two traits is 1 RRYY : 2 RRYy : 2 RrYY : 4 RrYy : 1 RRyy : 2 Rryy : 1 rrYY : 2 rrYy : 1 rryy.
Number of plants with genotype:
(i) RRYY = 1 out of 16
(ii) rry = Genotype incomplete, assuming rryy, number is 1 out of 16.
Total plants in F2 generation = 16.
Therefore, in F2, 1 plant is RRYY and 1 plant is rryy.
(a) Mention any one harmful effect of using plastic bags on the environment. Suggest better alternatives to the usage of plastic bags.
(b) Paddy fields require a large amount of water. The pesticides and chemical fertilizers used are washed down into the soil or waterbodies. How do these chemicals reach our bodies ? What is this phenomenon known as ?
(b) The pesticides and chemical fertilizers used in paddy fields get washed into water bodies and soil. These chemicals enter the food chain when water and plants containing these chemicals are consumed by animals and humans. This harmful accumulation of toxic substances in living organisms through the food chain is called biomagnification.
What happens when
(i) lead (II) nitrate is heated ?
(ii) iron (II) sulphate is heated ?
(iii) silver chloride is exposed to sunlight ? Write balanced chemical equations of the reactions involved in support of your answer.
Equation: 2Pb(NO3)2 (s) + Heat → 2PbO (s) + 4NO2 (g) + O2 (g)
(ii) When iron (II) sulphate is heated, it first loses water of crystallization and then decomposes to form iron (III) oxide, sulphur dioxide, and sulphur trioxide gases.
Equation: 2FeSO4·7H2O (s) + Heat → Fe2O3 (s) + SO2 (g) + SO3 (g) + 14H2O (g)
(iii) When silver chloride is exposed to sunlight, it decomposes into silver metal and chlorine gas. This is a photochemical decomposition reaction.
Equation: 2AgCl (s) + Sunlight → 2Ag (s) + Cl2 (g)
(a) Give the chemical name and formula of Plaster of Paris.
(b) Write the chemical equation of its preparation.
(c) Give any two uses of it
(b) Preparation: When gypsum (calcium sulphate dihydrate) is heated at about 373 K (100 deg C), it loses water and forms Plaster of Paris.
CaSO4 . 2H2O --heat--> CaSO4 . 1/2 H2O + 1.5 H2O
(c) Uses of Plaster of Paris:
1. It is used for making casts to support fractured bones.
2. It is used in making decorative materials and for repairing walls and ceilings to give a smooth finish.
(a) Name the acid present in ant’s sting.
(b) Give reason :
(i) While diluting an acid, it is recommended that the acid should be added to water.
(ii) Baking soda is used as an antacid.
(b)(i) While diluting an acid, it is recommended to add acid to water and not water to acid because adding water to a concentrated acid can cause the mixture to splash and may cause burns or injuries. Adding acid to water ensures better control of dilution and prevents accidents.
(ii) Baking soda is used as an antacid because it is a mild base that neutralizes excess acid in the stomach. When baking soda reacts with excess stomach acid (hydrochloric acid), it forms salt, water, and carbon dioxide, which relieves acidity and heartburn symptoms.
(a) Draw the ray diagram for refraction of light through a glass prism and mark angle of refraction and angle of deviation.
(b) When the path of a light ray refracted through a glass prism is reversed how will the angle of deviation change ? Explain.
(b) If the path of the refracted light ray through the prism is reversed, the ray retraces its original path backward. Therefore, the angle of deviation remains the same in magnitude. This happens because of the reversibility of light; the path of light is the same in both directions, so deviation does not change on reversing the light ray's path.
(a) A ray of light after reflection from a concave mirror becomes parallel to its principal axis. Draw a labelled ray diagram to show this.
(b) (i) Differentiate between the virtual images formed by a convex mirror and concave mirror.
(ii) “The value of magnification ‘m’ for a mirror is –2.” Calculate the height of object if the height of image is 20 cm.
Label the points: C (center of curvature), F (focus), P (pole), Incident ray (from F to mirror), Reflected ray (parallel to principal axis).
(b) (i) Difference between virtual images formed by convex and concave mirrors:
- Convex Mirror: Virtual image is always smaller than the object, upright, and formed behind the mirror.
- Concave Mirror: Virtual image can be larger or smaller, always upright, formed in front of the mirror when the object is between focus and mirror.
(ii) Given magnification m = -2 and height of image h' = 20 cm.
Using the magnification formula, m = h'/h => h = h'/m = 20 cm / (-2) = -10 cm.
Height of the object is -10 cm. The negative sign means the object is inverted. So, the object height is 10 cm and inverted.
(a) Why does an electric bulb become dim when an electric heater in parallel circuit is switched ON ?
(b) How to connect three resistors each of resistance 8Ω, so that the equivalent resistance of the combination is 12 Ω ? Draw diagram of the combination and justify your answer.
(b) To get an equivalent resistance of 12 Ω from three resistors each 8 Ω, connect two resistors in series and the third resistor in parallel to this series combination. The series resistance of two resistors = 8 Ω + 8 Ω = 16 Ω. Now, the combined equivalent resistance, R_eq = (16 * 8) / (16 + 8) = 12 Ω.
Diagram: Draw two resistors connected end to end (series), then connect the third resistor parallel to this combination across the same points.
This combination achieves the required equivalent resistance of 12 Ω.
Section E
(i) In an angiospermic flower, fertilization is said to take place when male gametes carried in the pollen tube fuse with the female gamete, present in the embryo sac. This results in lot of changes in different parts of the flower. State the changes taking place in the following structures of flower post fertilization :
(a) Zygote
(b) Ovule
(c) Ovary
(d) Sepals
(ii) Define germinati
(a) Zygote: The zygote develops from the fertilized ovum and divides repeatedly by mitosis to form the embryo that will grow into a new plant.
(b) Ovule: After fertilization, the ovule develops into a seed by forming a seed coat and storing food reserves for the embryo.
(c) Ovary: The ovary enlarges and develops into the fruit which protects the seeds and helps in their dispersal.
(d) Sepals: Sepals usually wither and fall off as they are no longer needed for protecting the flower bud.
(ii) Germination is defined as the process by which a seed develops into a new plant under favorable conditions like water, oxygen, and suitable temperature.
(i) Sugarcane does not produce seeds so name the process through which it will be able to reproduce.
(ii) List any two advantages of this method.
(iii) Besides sugarcane, give two more examples of plants that reproduce by this method.
(iv) Why regeneration is not possible in all the types of animals ?
(b) Two advantages of vegetative propagation are: 1. The new plants produced are genetically identical to the parent plant, thus preserving desired traits.
2. Plants produced by this method bear flowers and fruits earlier than those grown from seeds.
(c) Besides sugarcane, two examples of plants that reproduce by vegetative propagation are banana and rose.
(d) Regeneration is not possible in all types of animals because only those animals which have the ability to regrow lost parts or have simpler body structures can regenerate. Complex organisms with specialized organs and tissues often cannot regenerate lost parts completely.
(i) Give reasons for the following :
(I) Ionic compound have generally high melting points and boiling points.
(II) Solder, an alloy of lead and tin, is used for welding electrical wires.
(III) Carbon cannot reduce the oxides of Na or Mg.
(ii) The reaction of compound ‘X’ with aluminium is used to join railway tracks :
(I) Identify the compound ‘X’.
(II) Name the reaction.
(III) Write the balanced chemical equation of the reaction of compound ‘X’ with aluminium.
(II) Solder, an alloy of lead and tin, is used for welding electrical wires because it has a low melting point and it bonds metals together effectively without damaging the wires due to high heat.
(III) Carbon cannot reduce the oxides of Na or Mg because sodium and magnesium are highly reactive metals and their oxides are very stable. Carbon is less reactive and cannot displace these metals from their oxides.
(ii) (I) The compound ‘X’ is iron(III) oxide, Fe2O3.
(II) The reaction is called Thermite reaction.
(III) The balanced chemical equation for the reaction with aluminium is: Fe2O3 + 2Al → 2Fe + Al2O3 + Heat.
This highly exothermic reaction produces molten iron which is used to join railway tracks.
(i) Write the balanced chemical equations when :
(I) A mixture of Cu₂O and Cu₂S is heated.
(II) ZnS is heated in the presence of oxygen.
(ii) Give reasons for the following :
(I) The wires carrying current in homes have a coating of PVC.
(II) To make hot water tanks, copper is used and not steel.
(iii) Show the formation of ionic compound CaO with electron dot structure. [Atomic number : Ca = 20, O = 8]
2Cu2O + Cu2S --> 6Cu + SO2
(II) When ZnS is heated in the presence of oxygen, it is converted into zinc oxide and sulfur dioxide gas as:
2ZnS + 3O2 --heat--> 2ZnO + 2SO2
(ii) (I) Wires carrying current in homes have a coating of PVC because PVC is an insulator and prevents electric shocks and short circuits by stopping the current from leaking out of the wire.
(II) Copper is used to make hot water tanks because it has high thermal conductivity which helps in faster heating of water, and copper also resists corrosion unlike steel, increasing the tank's durability.
(iii) Formation of ionic compound CaO:
Calcium (Ca) has 2 valence electrons and oxygen (O) has 6 valence electrons.
Ca atom loses 2 electrons to become Ca2+ ion.
O atom gains 2 electrons to become O2- ion.
Electron dot structures:
Ca: Ca with 2 dots around it (2 valence electrons)
O: O with 6 dots around it
After transfer, Ca2+ has no dots (empty outer shell) and O2- has 8 dots (full octet).
The ionic bond forms between Ca2+ and O2- ions giving CaO.
(i) Draw a diagram showing the magnetic field lines around a bar magnet. Write any two characteristics of magnetic field lines.
(ii) Write the statement of Right hand thumb rule.
(iii) The concentric circles representing the magnetic field around a current carrying straight wire become larger and larger as we move away from the wire. How does magnetic field change on these concentric circles ?
Characteristics of magnetic field lines:
1. Magnetic field lines never intersect each other.
2. They are denser near the poles of the magnet indicating stronger magnetic field there.
(ii) Right hand thumb rule: If you hold a current carrying straight wire with your right hand such that your thumb points in the direction of the electric current, then the curled fingers around the wire show the direction of the magnetic field lines around the wire.
(iii) As the concentric circles representing magnetic field lines around a current carrying wire become larger farther from the wire, the magnetic field strength decreases on these circles. This means magnetic field decreases with increasing distance from the wire because the magnetic field is inversely proportional to the distance from the wire.
(i) Draw a diagram, showing the magnetic field lines in and around the current carrying solenoid. Write any two salient features of these lines.
(ii) What is an electromagnet and how is it made ?
Two salient features of magnetic field lines:
1. The magnetic field inside the solenoid is strong and uniform as the field lines are parallel and closely spaced.
2. Outside the solenoid, the magnetic field is weak as the field lines are spread out.
(ii) Electromagnet: An electromagnet is a type of magnet in which magnetic field is produced by passing electric current through a coil of wire. It behaves like a magnet only when electric current flows through it. It is made by winding a long insulated copper wire into a coil (called solenoid) and passing electric current through it. The coil is usually wound around a soft iron core, which enhances the magnetic effect by concentrating the magnetic field lines. This magnetic field can be controlled by switching the current ON or OFF and by varying the strength of current.
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