CBSE EXAMINATION PAPER-2025

A person while climbing up a rocky hill comes into a panic state and fear. His body starts reacting in a ‘flight-or-flight’ condition to adjust to the dangerous and stressful situation.

Based on the above facts, answer the questions that follow.

The most common method of extraction of metals from their oxide ores is :

Choose the incorrect statement about the common reaction used in hydrogenation of vegetable oils.

Match Column-I with Column-II and select the correct option from the choices provided.

The part of the brain which maintains the posture and balance of the body is :

The plant hormone present in greater concentration in the areas of rapidly dividing cells is :

Select a pair of bisexual flowers from the following :

The gastric glands present in the wall of the stomach release :

Absolute refractive index of water and glass is ⁴⁄₃ and ³⁄₂ respectively. If the speed of light in glass is 2 × 10⁸ m/s, the speed of light in water is:

When a beam of white light passes through a region of very fine dust particles, the colour of light that scatters the most in that region is :

A wire of length ‘l’ is gradually stretched so that its length increases to 3l. If its original resistance is R, then its new resistance will be :

Which one of the following statements is not true about a bar magnet ?

Other than the abiotic components, which of the given biotic components are not required to make an aquarium with small herbivorous fishes a self-sustaining system ?

(i) Aquatic plants and aquatic animals

(ii) Terrestrial plants and terrestrial animals

(iii) Decomposers as bacteria and fungi

(iv) Consumers as clown fishes and sea urchins

Assertion (A) : Hydrogen gas is not evolved when a metal reacts with nitric acid.

Reason (R) : Nitric acid is a strong reducing agent and reduces the hydrogen produced in the reaction to water.

Assertion (A) : In our actions of writing or talking, our nervous system communicates with the muscles.

Reason (R) : Cranial nerves and spinal nerves form the peripheral nervous system.

Assertion (A) : Use of jute bags for shopping reduces pollution.

Reason (R) : Jute is biodegradable and its bag may be reused as and when needed.

(a) Write the formula of the ions which (i) acids, and (ii) bases generate in water solutions.

(b) Dry HCl gas does not change the colour of dry litmus paper. Why ?

(a) Explain how the proteins control the ‘characteristics’ in an organism with the help of an example of ‘tallness’ trait in pea plant.

(b) Name the section of DNA that controls the ‘characteristics’ in an organism.

(a) What is a reactivity series of elements ? How is it developed ? Arrange the following elements as they are arranged in the reactivity series : Aluminum, Calcium, Copper, Lead

(b) Write balanced chemical equation to show the reaction of iron (III) oxide (Fe₂O₃)with aluminium.

On the basis of the characteristics of the processes given in the brackets in each case, differentiate between the following:

(a) Products of breakdown of pyruvate in aerobic and anaerobic respiration in human beings (product(s) of the processes)

(b) Respiration and photosynthesis in plants (gas released)

(c) Respiration in terrestrial animals and fishes (organs involved)

A pure pea plant having round (R), yellow (Y) seeds is crossed with another pure pea plant having wrinkled (r), green (y) seeds. Subsequently F₁ progeny is self-pollinated to obtain F₂ progeny.

(a) What do the seeds of F₁ generation look like?

(b) Give the possible combinations of traits in seeds of F₂ generation. Also give their ratio.

(c) State the reason of obtaining seeds of new combination of traits in F₂ generation.

Consider a rectangular cardboard having two holes P and Q through which a current carrying circular loop has been inserted as shown in the diagram.

(a) Make this diagram on your answer sheet and draw three magnetic field lines, one each passing through the points 1 (near P), 2 (at the centre of the loop) and 3 (near Q).

(b) List two factors on which the intensity of the magnetic field produced at the centre of the loop depends.

(c) Name the rule you will apply to determine the direction of magnetic field produced due to a current carrying straight conductor.

(a) ‘‘In a food chain energy flow is unidirectional.’’ Give two reasons for the given statement.

(b) If 10,000 J energy is available at the producer level, how much energy will be available to the secondary consumers ? Give reason to justify your answer.

Design an experimental set-up to demonstrate that ‘‘Alcohol and glucose contain hydrogen but are not categorised as acids’’. Also give the reason to justify this fact.

(i) Consider the following metals : K, Ca, Al, Cu, Ag, Fe Select from the above metals, a metal which

I. does not react with oxygen even at high temperature.

II. reacts with oxygen at ordinary temperature and forms a protective oxide layer which prevents the metal from further oxidation.

III. catches fire when kept in the open.

IV. does not burn in oxygen but the hot metal is coated with a black coloured oxide layer.

(ii) What are amphoteric oxides ? With the help of balanced chemical equations show that aluminium oxide is an amphoteric oxide.

(iii) What are alkalis ? Give one example.

(i) Identify the parts ‘X’ and ‘Y’ in the figure given below :

(ii) Name the yellowish coloured structures produced by the part labelled as ‘Y’.

(iii) Write the name of the process by which these are transferred to the part labelled as ‘X’.

(iv) Explain the process of seed formation in a flowering plant.

(i) ‘‘In refraction of light through a rectangular glass slab, the emergent ray is always parallel to the direction of the incident ray.’’ Why ? Explain with the help of a ray diagram. What happens when a ray of light falls normally on one of the faces of a rectangular glass prism ? Draw diagram.

(ii) An object is placed at a distance of 30 cm from the optical centre of a concave lens of focal length 20 cm. Use Lens formula to determine the position of the image formed in this case.

(i) Name the type of asexual mode of reproduction shown in the given figure.

(ii) Identify the unicellular organism in the diagram.

(iii) List any two advantages of asexual reproduction over sexual reproduction.

(iv) Name and explain any one mode of asexual reproduction observed in Hydra.

(i) A student wishes to study the image formation by a concave mirror using candle flame as object. State the type of the image formed by the mirror and mention the change in the image formed, if any, that he observes when the candle flame is gradually moved away from the pole of the mirror. Draw a ray diagram to show the image formation when the object distance is nearly equal to the radius of curvature of the mirror.

(ii) A convex mirror used for rear-view on an automobile has a focal length of 3∙0 m. If a bus is located at 6∙0 m from this mirror, use mirror formula to find the position of the image of the bus as seen in the mirror.