1. In the following experimental setup of electrolysis of water, if P and Q are the gases collected in the test tubes enclosing the electrodes R and S, then select the option/options in which the matching is correct:

(i) P-Oxygen gas, R-Anode

(ii) P-Hydrogen gas, R-Cathode

(iii) Q-Hydrogen gas, S-Cathode

(iv) Q-Oxygen gas, S-Anode

(A) (i) and (ii)

(B) (iii) and (iv)

(C) (i) and (iii)

(D) (ii) and (iv)

2. You have three aqueous solutions A, B and C as given below:

A - Potassium nitrate

B - Ammonium chloride

C - Sodium carbonate

The ascending order of the pH of these solutions is:

(A) A<B<C

(B) B<C<A

(C) C<A<B

(D) B<A<C

3 .Select from the following a statement which is not true about burning of magnesium ribbon in air:

(A) It burns with a dazzling white flame.

(B) A white powder is formed on burning.

(C) It is an endothermic reaction.

(D) It is an example of a combination reaction.

4.A Hydrocarbon which does not belong to the same homologous series of carbon compounds is

(A) C4H10

(B) C7H14

(C) C6H14

(D) C10H22

5.The colour of the solution observed after about 1 hour of placing iron nails in copper sulphate solution is

(A) Blue

(B) Pale green

(C) Yellow

(D) Reddish brown

6. Juice of tamarind turns blue litmus to red. It is because of the presence of a chemical compound called

(A) Acetic acid

(B) Methanoic acid

(C) Oxalic acid

(D) Tartaric acid

7. The water of crystallization is present in

(i) Bleaching Powder

(ii) Plaster of Paris

(iii) Washing Soda

(iv) Baking Soda

(A) (ii) and (iv)

(B) (ii) and (iii)

(C) (i) and (iii)

(D) (i) and (iv)

8.A tall pea plant with round seeds (TTRR) is crossed with a short pea plant with wrinkled seeds (ttrr). The F1 generation will be

(A) 25% tall with round seeds

(B) 50% tall with wrinkled seeds

(C) 75% tall with wrinkled seeds

(D) 100% tall with round seeds

9. A pair of endocrine glands located in the human brain is

(A) Parathyroid and Pituitary

(B) Pineal and Thymus

(C) Hypothalamus and Thymus

(D) Hypothalamus and Pineal

10. Select the option having correct matching of the organism given in Column I with the mode of reproduction in Column II:

(A) P-4, Q-2, R-1, S-3

(B) P-3, Q-4, R-5, S-2

(C) P-3, Q-4, R-1, S-2

(D) P-4, Q-3, R-2, S-1

11.The basic filtration unit of the excretory system in human beings is:

(A) Nephron

(C) Neuron

(B) Urethra

(D) Urinary bladder

12.In human alimentary canal, the digestive juice secreted by the gastric glands are

(A) Bile, Trypsin, Pepsin

(B) Hydrochloric acid, Pepsin, Mucus

(C) Lipase, Bile, Mucus

(D) Salivary amylase, Pepsin, Bile

13.Identify from the following the ray diagram which shows the correct path of the reflected ray for the ray incident on a concave mirror as shown:

14.The part of human eye which controls the amount of light entering into it.

(A) Iris

(B) Cornea

(C) Ciliary muscles

(D) Pupil

15.Consider the following food chain:

Grass → Grasshopper → Frog → Snake → Eagle

If the amount of energy available at third trophic level is 50 kJ, the available energy at the producer level was:

(A) 0.5 kJ

(B) 5 kJ

(C) 500 kJ

(D) 5000 kJ

16.The incorrect statement about ozone is

(A) It is a deadly poisonous gas.

(B) It shields the surface of the earth from UV radiation from sun.

(C) It is used as a refrigerant and in fire-extinguishers.

(D) It is formed by combining oxygen molecule with free oxygen atom.

Q.Nos. 17 to 20, two statements are given labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below:

(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

(B) Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of the Assertion (A).

(C) Assertion (A) is true, but Reason (R) is false

(D) Assertion (A) is false, but Reason (R) is true.

17.Assertion (A): Carbon and its compounds are our major sources of fuels.

Reason (R): Most of the carbon compounds on burning release a large amount of heat and light.

18.Assertion (A): Xylem tissue moves water and minerals obtained from the soil by the roots.

Reason (R): Xylem tissue is found only in the roots of a plant.

19.Assertion (A): In the common domestic circuits the earth wire is connected to a metallic plate buried deep inside the earth.

Reason (R): Earth wire ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, so the user may not get a severe electric shock.

20,Assertion (A): The food web is a network of several food chains operating in an ecosystem.

Reason (R): The food web decreases the stability of an ecosystem.

21 .A light green-coloured solution of the sulfate salt of metal ‘P’ is taken in a beaker, and a rod of another metal ‘Q’ is put in this solution, as shown in the following figures:

Identify the metals ‘P’ and ‘Q’ and write the chemical equation for the reaction that occurs. State the conclusion of this reaction in terms of the reactivity series of metals.

Metal 'P' is Iron (Fe)

Metal 'Q' is Zinc (Zn)

Reaction: FeSO4+ Zn→ZnSO4+Fe

22.(a) How is the brain protected in our body?

(b) A doctor finds in one of his patients that he is not maintaining a proper posture and balance of his body. State the region of the brain and also the part of the brain which is responsible for it.

a)The brain is protected by the skull (cranium) and three protective membranes called meninges. A fluid called cerebrospinal fluid (CSF) cushions the brain from shocks.

(b)The region of the brain responsible for maintaining posture and balance is the hindbrain. The specific part of the brain that controls body posture and balance is the cerebellum.

23.(a) "Proteins control the expression of various characters." Explain this statement by taking an example of "tallness" as a characteristic in plants.

OR

(b) Explain the mechanism of inheritance used by sexually reproducing organisms to ensure the stability of the DNA of the species.

 (a) Proteins are encoded by genes, which determine traits. In tall plants, the gene responsible for tallness produces a protein that influences plant height by regulating growth hormones like gibberellins.

OR

(b) Each gene is present on chromosomes, which are separate, independent pieces of DNA. Each cell in an organism contains two copies of each chromosome—one from the male parent and one from the female parent.

During gamete formation (in germ cells):

• Each gamete receives one chromosome from each pair, either maternal or paternal.
• When fertilization occurs, the two gametes combine, restoring the normal chromosome number in the progeny.

This process ensures the stability of DNA in a species and maintains genetic information across generations.

24.Study the figure in which the path of a ray of light going from Medium 1 to Medium 2 is shown.

(a) Out of the two Media – Medium 1 and Medium 2, in which is the speed of light more?

(b) State the reason for the bending of the refracted ray away from the normal.

(c) Express the refractive index of Medium 2 with respect to Medium 1 in terms of the speed of light in two media.

(a)Speed of light is more in Medium 1 because the ray bends away from the normal when entering Medium 2.

(b)The refracted ray bends away from the normal because Medium 2 is optically less dense than Medium 1.

(c)Refractive index of Medium 2 with respect to Medium 1 is given as,

n21=Speed of light in Medium 2/Speed of light in Medium 1

25.(a) Give reasons:

(i) The sky appears dark to passengers flying at a very high altitude.

(ii) 'Danger' signal lights are red in color.

OR

(b) What is a rainbow? "We see a rainbow in the sky only after the rainfall." Why?

(i)The sky appears dark at high altitudes due to the thin atmosphere and less scattering of light.

(ii)Danger signals are red because red light has the longest wavelength and is least scattered, making it visible from a distA rainbow is a natural spectrum of light appearing in the sky when sunlight passes through raindrops.

OR

(b)A rainbow forms when sunlight is refracted, internally reflected, and dispersed by water droplets in the air. Rainwater droplets act as prisms, breaking white light into its spectrum of colors.ance.

27. We do not clean natural ponds or lakes whereas an aquarium or a swimming pool needs to be cleaned regularly. Why?

Natural ponds or lakes do not require regular cleaning because they have a self-sustaining ecosystem. They contain microorganisms, plants, and aquatic animals that maintain a natural balance by decomposing organic waste and recycling nutrients.

In contrast, an aquarium or a swimming pool lacks such a natural ecosystem. 

28.Write balanced chemical equations for the reactions that occur when:
(a) Steam is passed over red-hot iron.
(b) Natural gas is burnt in air.
(c) Glucose reacts with oxygen in the cells of our body and provides energy.

(a) 3Fe+4H2O→Fe3O4 + 4H2

(b)CH4+2O2→CO2+2H2O

(c) C6H12O6+6O2→6CO2+6H2O

+Energy(ATP)

29.(a) State the chemical property in each case on which the following uses of baking soda are based:
(i) As an anti-acid
(ii) As a constituent in making baking powder
(iii) In soda-acid fire extinguishers

(i) As an antacid: It is weakly basic and neutralizes stomach acid.

(ii) In making baking powder: It releases CO₂ when heated,

making cakes fluffy.

(iii) In soda-acid fire extinguishers: It reacts with acid to produce CO₂,

which puts out the fire.

30.Name the blood vessel that brings

(i) oxygenated blood

(ii) deoxygenated blood, to the human heart.

Also, name the chamber of the heart which receives deoxygenated blood and state how deoxygenated blood from this chamber is sent to the lungs for oxygenation.

(i) Oxygenated blood vessel: Pulmonary vein

(ii) Deoxygenated blood vessel: Pulmonary artery

Heart chamber receiving deoxygenated blood is Right atrium.

The right ventricle pumps deoxygenated blood to the lungs 

via the pulmonary artery to.

31.The gene combination of purple-flowered pea plants is denoted as (WW) and that of white-flowered pea plants as (ww). When these two plants are crossed, F₂ generation is obtained.

(a) List two observations made by Mendel in F₂ generation plants.

(b) Give the 
(i) percentage of white-flowered plants and 
(ii) ratio of the gene combination, and in F₂ generation.

(c) Write one difference between dominant and recessive traits.

(a) Mendel’s observations in F₂ generation:

• Dominant traits appear in a 3:1 ratio in F₂ generation.
• Recessive traits reappear in 25% of offspring.

(b) (i) Percentage of white-flowered plants: 1/4x100=25%

(ii) Gene ratio in F₂: WW: Ww: ww = 1:2:1

(c) Difference between dominant and recessive traits:

• Dominant trait: Expressed even if one allele is present (e.g., Purple flower).
• Recessive trait: Expressed only if both alleles are recessive (e.g., White flower).

32.A student placed a candle flame at different distances from a convex lens and focused its image on a screen. He recorded his observation in tabular form as given below:

Analyse the observation table and, on the basis of your analysis only, answer the following questions (without doing any calculations):

(a) What is the focal length of the convex lens used? Give reason to justify your answer.

(b) Which one of the set of observations is not correct and why?

(c) Draw a ray diagram to show image formation for any correct set of observations.

(a) Focal length of the convex lens:

• The data suggests focal length = 30 cm.
• Reason: Image is inverted and magnified when the object is beyond 2F.

(b) Incorrect observation: 

• When object is at -12 cm, image should not be at +120 cm.
• A virtual, erect, and magnified image forms when the object is within focal length.

(c) Ray diagram for convex lens image formation:

Draw ray diagram for object beyond 2F, forming an image between F and 2F.

32.A person uses lenses of +2.0 D power in his spectacles for the correction of his vision.

(a) Name the defect of vision the person is suffering from.

(b) List two causes of this defect.

(c) Determine the focal length of the lenses used in the spectacles.

(a) Defect of vision: Hypermetropia (Far-sightedness)

(b) Causes:

• Eyeball too short
• Lens too weak to focus near objects
  (c) Focal length of +2.0 D lens: f= 1/d = ½ = 0.5m

33.(a) Explain the statement "Potential difference between two points is 1 volt."

(b) What do the symbols given below represent in an electric circuit? Write one function of each.

(Image contains two circuit symbols: one for an ammeter and another for a resistor.)

Potential difference of 1V Definition: 

1 volt is when 1 joule of work is done to move 1 coulomb of charge.

(b) Symbols and functions:

(i) Ammeter (A): Measures current in a circuit.

(ii) Resistor: Controls the flow of current.