1. When 2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc in a test tube and then warmed, the reaction that occurs can be written in the form of a balanced chemical equation as:

(a) NaOH + Zn  → NaZnO2 + H20

(b) 2NaOH + Zn  → Na2ZnO2 + H2

(c) 2NaOH + Zn  → NaZnO2 + H2

(d) 2NaOH + Zn  → Na2ZnO2 + H2O

2. Select from the following a decomposition reaction in which source of energy for decomposition is light:

(a) 2FeSO4  → Fe203+ SO2+ SO3

(b) 2H2O  → 2H2+ O2

(c) 2AgBr  → 2Ag + Br2

(d) CaCO3  → CaO + CO2

3. A metal and a non-metal that exists in liquid state at the room temperature are respectively :

(a) Bromine and Mercury

(b) Mercury and lodine

(c) Mercury and Bromine

(d) Iodine and Mercury

4. Carbon compounds:

(i) are good conductors of electricity.

(ii) are bad conductors of electricity.

(iii) have strong forces of attraction between their molecules. 

(iv) have weak forces of attraction between their molecules.

The correct statements are:

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (ii) and (iv)

(d) (i) and (iii)

5. Consider the following compounds :

FeSO4; CuSO4; CaSO4; Na2CO3

The compound having maximum number of water of crystallisation in its crystalline form in one molecule is :

(a) FeSO4

(b) CuSO4

(c) CaSO4

(d) Na2CO3

6. Oxides of aluminium and zine are :

(a) acidic

(b) basic

(c) amphoteric

(d) neutral

7. MnO2 + 4HCI → MnCl2 + 2H2O + Cl2

The reaction given above is a redox reaction because in this case

(a) MnO2 is oxidised and HCI is reduced.

(b) HCI is oxidised.

(c) MnO2 is reduced.

(d) MnO2 is reduced and HCI is oxidised.

8. Consider the following statements

(i) The sex of a child is determined by what it inherits from the mother. 

(ii) The sex of a child is determined by what it inherits from the father. 

(iii) The probability of having a male child is more than that of a female child.

(iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote.

The correct statements are :

(a) (i) and (iii)

(b) (ii) and (iv)

(c) (iii) and (iv)

(d) i), (iii) and (iv)

Answer: (b) (ii) and (iv)

9. Chromosomes :

(i) carry hereditary information from parents to the next generation. 

(ii) are thread like structures located inside the nucleus of an animal cell. 

(iii) always exist in pairs in human reproductive cells. 

(iv) are involved in the process of cell division.

The correct statements are :

(a) (i) and (ii)

(b) (iii) and (iv)

(a) (i), (ii) and (iv)

(d) (i) and (iv)

10. In a nerve cell, the site where the electrical impulse is converted into a chemical signal is known as :

(a) Axon

(b) Dendrites

(c) Neuromuscular junction

(d) Cell body

c) Neuromuscular junction; a neuromuscular junction

 (or myoneural junction) is a chemical synapse between

 a motor neuron and a muscle fiber. 

11. A stomata closes when:

(i) it needs carbon dioxide for photosynthesis.

(ii) it does not need carbon dioxide for photosynthesis. 

(iii) water flows out of the guard cells. 

(iv) water flows into the guard cells.

The correct reason(s) in this process is/are :

(a) (i) only

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (ii) and (iv)

12. At what distance from a convex lens should an object be placed to get an image of the same size as that of the object on a screen?

(a) Beyond twice the focal length of the lens.

(b) At the principal focus of the lens.

(c) At twice the focal length of the lens.

(d) Between the optical centre of the lens and its principal focus.

13. The lens system of human eye forms an image on a light sensitive screen, which is called as:

(a) Cornea

(b) Ciliary muscles

(c) Optic nerves

(d) Retina

14. The pattern of the magnetic field produced inside a current carrying solenoid is:

a) The field lines inside the solenoid are 

in the form of parallel straight lines. 

15. Identify the food chain in which the organisms of the second trophic level are missing :

(a) Grass, goat, lion

(b) Zooplankton, Phytoplankton, small fish, large fish

(c) Tiger, grass, snake, frog

(d) Grasshopper, grass, snake, frog, eagle

16. In which of the following organisms, multiple fission is a means of asexual reproduction?

(a) Yeast

(b) Leishmania

(c) Paramoecium

(d) Plasmodium

For Q. Nos. 17 to 20, two statements are given - One 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, but 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): Hydrogen gas is not evolved when zinc reacts with nitric acid.

Reason (R): Nitric acid oxidises the hydrogen gas produced to water and itself gets reduced.

a) Both Assertion (A) and Reason (R) are true and 

Reason (R) is the correct explanation of the Assertion (A).

18. Assertion (A): Accumulation of harmful chemicals is maximum in the organisms at the highest trophic level of a food chain.

Reason (R): Harmful chemicals are sprayed on the crops to protect them from diseases and pests.

b) Both Assertion (A) and Reason (R) are true, but 

Reason (R) is not the correct explanation of the Assertion (A).

19. Assertion (A): The rate of breathing in aquatic organisms is much faster than in terrestrial organisms.

Reason (R): The amount of oxygen dissolved in water is very high as compared to the amount of oxygen in air.

20. Assertion (A): The rainbow is a natural spectrum of sunlight in the sky.

Reason (R): Rainbow is formed in the sky when the sun is overhead and water droplets are also present in air.

a) Both Assertion (A) and Reason (R) are true 

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

Section B

21. Name the type of chemical reaction in which calcium oxide reacts with water. Justify your answer by giving balanced chemical equation for the chemical reaction.

The type of chemical reaction is an {exothermic combination reaction}.

 When calcium oxide (quicklime) reacts with water, 

calcium hydroxide (slaked lime) is formed, 

and heat is released: CaO +H2O Ca(OH)2 + Heat

22. State one role of each of the following in human digestive system:

(i) Hydrochloric acid

(ii) Villi

(iii) Anal Sphincter

(iv) Lipase

1) Hydrochloric acid- It kills the microbes present in the stomach lining and creates an acidic environment in which the enzyme pepsin is activated and able to work.

2)Villi- Villi are small finger like projections on the surface of the small intestine. They have very thin walls and are one cell thick. The villi increase the surface area in the small intestine which helps in absorbing the nutrients.

3)Anal sphincter: It regulates the release of the undigested waste from the rectum through the anus.

4) Lipase: Lipase is an enzyme which helps the breakdown of fats so that it could be absorbed properly by the intestine.

23. 

(A) How is the movement of leaves of a sensitive plant different from the downward movement of the roots?

OR

The movement of leaves in a sensitive plant (Mimosa pudica) is a nastic movement, which is non-directional and occurs in response to touch (thigmonasty). It is a rapid movement caused by changes in turgor pressure in the leaf cells.

In contrast, the downward movement of roots is a tropic movement, specifically gravitropism (geotropism), which is directional and occurs in response to gravity. The roots grow downward due to the influence of gravity and the differential distribution of auxin hormone.

The hormone that regulates carbohydrate, protein, and fat metabolism in our body is insulin. It is secreted by the pancreas.

It is important to have iodised salt in our diet because iodine is essential for the production of thyroid hormones (thyroxine and triiodothyronine) by the thyroid gland. These hormones regulate metabolism, growth, and development. A deficiency of iodine can lead to goitre and other thyroid-related disorders.

25. (A) Show how you would connect three resistors each of resistance 6 Ω, so that the combination has a resistance of 9 Ω. Also justify your answer

B) In the given circuit calculate the power consumed in watts in the resistor of 2Ω

25 B) In the given circuit calculate the power consumed in watts in the resistor of 2Ω

26. (i) Two magnetic field lines do not intersect each other. Why?

(i) Magnetic field lines are imaginary lines that represent the direction and strength of a magnetic field. If two magnetic field lines were to intersect, it would mean that a single point would have two different directions of the magnetic field, which is impossible. 

(ii) A uniform magnetic field is represented by parallel and equally spaced magnetic field lines. This indicates that the strength and direction of the magnetic field are the same at all points in the region

27. Write one chemical equation each for the chemical reaction in which the following have taken place:

(i) Change in colour

(ii) Change in temperature

(iii) Formation of precipitate

Mention colour change/temperature change (rise/fall)/compound precipitated along with equation.

28.

(i) The pH of a sample of tomato juice is 4.6. How is this juice likely to be in taste ? Give reason to justify your answer.

(ii) How do we differentiate between a strong acid and a weak base in terms of ion-formation in aqueous solutions ?

(iii) The acid rain can make the survival of aquatic animals difficult. How?

(i) The tomato juice is likely to be sour in taste because its pH is 4.6, indicating it is acidic.

ii) Strong acids completely ionize in aqueous solutions, while weak bases only partially ionize.

Acid rain is acidic due to the presence of strong acids like sulfuric acid (H2SO4) and nitric acid (HNO3)

When acid rain falls into water bodies, it increases the acidity of the water, lowering its pH.

Aquatic animals are adapted to live in a specific pH range. A drastic change in pH can disrupt their physiological processes, making it difficult for them to survive.

(iii) Acid rain increases the acidity of water bodies, lowering their pH. This change in pH can disrupt the physiological processes of aquatic animals, making their survival difficult.

29.

(i) Why is respiratory pigment needed in multicellular organisms with large body size ?

(ii) Give reasons for the following:

(a) Rings of cartilage are present in the throat.

(b) Lungs always contain a residual volume of air.

(c) The diaphragm flattens and ribs are lifted up when we breathe in.

(d) Walls of alveoli contain an extensive network of blood vessels.

 i)Respiratory pigments, like hemoglobin in vertebrates, are needed in large multicellular organisms with large body sizes because they facilitate the efficient transport of oxygen throughout the body. With a greater volume of cells, there is a higher demand for oxygen, and respiratory pigments help increase the oxygen-carrying capacity of the blood, ensuring that all cells receive an adequate oxygen supply.

 (a) Rings of cartilage are present in the throat. Cartilage rings provide support and prevent the trachea from collapsing, maintaining an open airway for the passage of air during breathing.

(b) Lungs always contain a residual volume of air. The residual volume of air in the lungs ensures that the alveoli remain partially inflated, preventing their collapse and maintaining the surface area available for gas exchange even during exhalation.

(c) The diaphragm flattens and ribs are lifted up when we breathe in.

The flattening of the diaphragm and the lifting of the ribs increase the volume of the thoracic cavity, causing a decrease in air pressure inside the lungs compared to the atmospheric pressure, allowing air to flow into the lungs during inhalation.

(d) Walls of alveoli contain an extensive network of blood vessels.

The extensive network of blood vessels in the walls of alveoli allows for efficient gas exchange between the respiratory gases in the alveoli and the bloodstream, facilitating the exchange of oxygen and carbon dioxide during respiration.

Reflex actions are sudden responses that do not involve thinking. It is an involuntary action that takes place in response to the stimulus made by reflex arcs.

31. Study the diagram given below and answer the questions that follow :

(i) Name the defect of vision represented in the diagram. Give reason for your answer.

(ii) List two causes of this defect.

(iii) With the help of a diagram show how this defect of vision is corrected.

i) The diagram represents hypermetropia, commonly known as farsightedness. This refractive defect allows for clearer vision of distant objects than nearby ones. This issue arises when the eyeball is too short, or the cornea has insufficient curvature, leading light to focus behind the retina instead of directly on it. Individuals with hypermetropia can easily see distant things but struggle with close-range vision. A hypermetropic person's near point is farther away from the eye than the standard 25 cm distance.

ii. Two causes of the defects are:

1. The focal length of the eye lens is too long.

2. The eyeball has become too small.

 32.

Name and state the rule to determine the direction of a

(i) magnetic field produced around a current carrying straight conductor.

(ii) force experienced by a current carry ing straight conductor placed in a magnetic field which is perpendicular to it.

33.

(A) Plants  → Deer → Lion

In the giver food chain, what will be the impact of removing all the organisms of second trophic level on the first and third trophic level? Will the impact be the same for the organisms of the third trophic level in the above food chain if they were present in a food web? Justify.

OR

(B) A gas 'X' which is a deadly poison is found at the higher levels of atmosphere and performs an essential function.

Name the gas and write the function performed by this gas in the atmosphere. Which chemical is linked to the decrease in the level of this gas? What measures have been taken by an international organization to check the depletion of the layer containing this gas