OMTEX CLASSES: 10th Science Quarterly Exam 2024 Question Paper with Solutions

10th Science Quarterly Exam 2024 Question Paper with Solutions | Coimbatore District

Solutions

PART I

NOTE: (i) Answer all the questions. (ii) Choose the most appropriate answer from the given four alternatives and write the option code and the corresponding Answer. (12 × 1 = 12)

1. Newton's III law is applicable .........

(a) for a body is at rest
(b) for a body is in motion
(c) both a & b
(d) only for the bodies with equal masses

2. In a myopic eye, the image of the object is formed

(a) behind the retina
(b) On the retina
(c) infront of the retina
(d) On the blind spot

3. If a Substance is heated or cooled, the change in mass of that substance is ..........

(a) Positive
(b) Negative
(c) zero
(d) none of the above

4. Which of the following is a triatomic molecule?

(a) Glucose
(b) Helium
(c) Carbondioxide
(d) Hydrogen

5. The process of coating the surface of Metal with a thin layer of zinc is called ..........

(a) Painting
(b) thinning
(c) galvanization
(d) electroplating.

6. Which of the following is the universal solvent

(a) Acetone
(b) Benzene
(c) water
(d) Alcohol

7. Oxygen is produced at what point during photosynthesis?.

(a) When ATP is converted to ADP
(b) when CO₂ is fixed
(c) when H₂O is splitted
(d) all of these

8. During transpiration there is loss of

(a) Carbon dioxide
(b) Oxygen
(c) water
(d) none of the above

9. Identify the exocrine gland

(a) Pituitary gland
(b) Adrenal gland
(c) Salivary gland
(d) Thyroid gland

10. Syngamy results in the formation of

(a) zoospores
(b) Conidia
(c) Zygote
(d) chlamydospores

11. The loss of one or more chromosome in a ploidy is called

(a) Tetraploidy
(b) Aneuploidy
(c) Euploidy
(d) Polyploidy

12. Vomiting centre is located in

(a) medulla oblongata
(b) stomach
(c) Cerebrum
(d) the hypothalamus

PART II

NOTE: (i) Answer any Seven questions. (ii) Question No: 22 is compulsory. (7 × 2 = 14)

13. Differentiate mass and weight

Mass	Weight
It is the amount of matter contained in a body.	It is the gravitational force exerted on a body.
It is a fundamental quantity.	It is a derived quantity.
It is a scalar quantity.	It is a vector quantity.
Its SI unit is kilogram (kg).	Its SI unit is newton (N).
It remains constant everywhere.	It varies from place to place.

14. State the law of volume

Charles's Law (The Law of Volume) states that when the pressure of a gas is kept constant, the volume of a gas is directly proportional to the absolute temperature of the gas.

Mathematically, V ∝ T

15. Define the unit of current ?

The SI unit of electric current is the Ampere (A). One Ampere is defined as the flow of one coulomb of charge through a conductor in one second (1 A = 1 C/s).

16. What is molar volume of gas ?.

The volume occupied by one mole of any gas at Standard Temperature and Pressure (STP) is called molar volume. Its value is 22.4 litres/mol.

17. Define the term solutions.

A solution is a homogeneous mixture of two or more substances. It consists of a solute (the substance being dissolved) and a solvent (the substance in which the solute is dissolved).

18. What is photosynthesis? where in a cell does it occur?

Photosynthesis is the process used by green plants and some other organisms to convert light energy into chemical energy, through a process that converts carbon dioxide and water into glucose (sugar) and oxygen. In plant cells, this process occurs in the chloroplasts.

19. What is bolting? How can it be induced artificially?

Bolting is the elongation of the internodes in a plant just before flowering. It is the premature production of a flowering stem. Bolting can be induced artificially by the application of Gibberellins.

20. What are the structures involved in the protection of brain?

The brain is protected by:

1. Cranium (Skull): The bony box that encloses the brain.
2. Meninges: Three protective membranes - Dura mater (outer), Arachnoid mater (middle), and Pia mater (inner).
3. Cerebrospinal Fluid (CSF): A fluid that acts as a shock absorber and provides nutrients.

21. Draw the structure of Adrenal gland and label its parts?

[A neat, labelled diagram of the Adrenal Gland should be drawn here, showing the outer Adrenal Cortex and the inner Adrenal Medulla.]

22. An object is placed at a distance 20cm from a convex lens of focal length 10cm. Find the image distance and nature of the image. (Compulsory)

Given:

Object distance (u) = -20 cm (by sign convention)
Focal length (f) = +10 cm (for a convex lens)

To find: Image distance (v) and Nature of the image.

Formula: Using the lens formula, 1/f = 1/v - 1/u

Calculation:

1/10 = 1/v - 1/(-20)

1/10 = 1/v + 1/20

1/v = 1/10 - 1/20

1/v = (2 - 1) / 20

1/v = 1/20

v = +20 cm

Result:

The image distance is 20 cm.
Nature of the image: Since 'v' is positive, the image is real. Since the object is placed at 2F (2 x 10cm = 20cm), the image is formed at 2F on the other side. The image is real, inverted, and of the same size as the object.

PART III

NOTE: (i) Answer any Seven questions. (ii) Question No: 32 is compulsory. (7 × 4 = 28)

23. (i) Differentiate convex lens and concave lens

Convex Lens	Concave Lens
It is thicker in the middle and thinner at the edges.	It is thinner in the middle and thicker at the edges.
It is a converging lens.	It is a diverging lens.
It produces mostly real and inverted images.	It produces virtual, erect, and diminished images.
It is used to correct hypermetropia (long-sightedness).	It is used to correct myopia (short-sightedness).

(ii) Why does the sky appear in blue colour?

The sky appears blue due to a phenomenon called Rayleigh scattering. When sunlight enters the Earth's atmosphere, it is scattered in all directions by the gas molecules and other fine particles in the air. Blue light has a shorter wavelength compared to other colours in the visible spectrum (like red and yellow). According to Rayleigh's law, shorter wavelengths are scattered more effectively than longer wavelengths. As a result, the blue light is scattered more than the other colours, and our eyes perceive the sky as blue.

24. Derive ideal gas equation.

The ideal gas equation is derived by combining three gas laws:

Boyle's Law: At constant temperature (T) and number of moles (n), the volume (V) of a gas is inversely proportional to its pressure (P).
V ∝ 1/P ..........(1)
Charles's Law: At constant pressure (P) and number of moles (n), the volume (V) of a gas is directly proportional to its absolute temperature (T).
V ∝ T ..........(2)
Avogadro's Law: At constant temperature (T) and pressure (P), the volume (V) of a gas is directly proportional to the number of moles (n).
V ∝ n ..........(3)

Combining equations (1), (2), and (3):

V ∝ (1/P) × T × n

V ∝ nT/P

PV ∝ nT

To replace the proportionality sign with an equality sign, we introduce a constant 'R', known as the Universal Gas Constant.

PV = nRT

This is the ideal gas equation.

25. Give the salient features of "Modern atomic Theory"

The salient features of Modern Atomic Theory are:

An atom is no longer considered indivisible. It is composed of subatomic particles like protons, neutrons, and electrons.
Atoms of the same element may not be identical in all respects. They can have different masses, as seen in isotopes (e.g., ¹²C, ¹³C, ¹⁴C).
Atoms of different elements may have the same mass, as seen in isobars (e.g., ⁴⁰Ar, ⁴⁰K, ⁴⁰Ca).
The ratio in which atoms combine to form molecules may not always be a simple whole-number ratio (e.g., in non-stoichiometric compounds).
The atom is the smallest particle that takes part in a chemical reaction.
The mass of an atom can be converted into energy according to Einstein's equation, E = mc².

26. In what way hygroscopic substances differ from deliquescent substance.

Hygroscopic Substances	Deliquescent Substances
They absorb moisture from the atmosphere without changing their physical state.	They absorb enough moisture from the atmosphere to dissolve in it and form a solution.
They may be amorphous solids or liquids.	They are crystalline solids.
They do not form a solution.	They form a solution.
Example: Concentrated Sulphuric acid (H₂SO₄), Silica gel, Quicklime (CaO).	Example: Calcium chloride (CaCl₂), Sodium hydroxide (NaOH), Ferric chloride (FeCl₃).

27. Differentiate Aerobic and Anaerobic respiration.

Feature	Aerobic Respiration	Anaerobic Respiration
Oxygen	Occurs in the presence of oxygen.	Occurs in the absence of oxygen.
Location	Cytoplasm and Mitochondria.	Only in Cytoplasm.
End Products	Carbon dioxide (CO₂), water (H₂O), and ATP.	Ethanol and CO₂ (in yeast) or Lactic acid (in muscles), and ATP.
Energy Yield	High (36-38 ATP molecules per glucose molecule).	Low (2 ATP molecules per glucose molecule).
Breakdown of Glucose	Complete breakdown.	Incomplete breakdown.

28. (i) Define triple fusion?

Triple fusion is a process that occurs during double fertilization in flowering plants. It is the fusion of the second male gamete with the diploid secondary nucleus (or central cell) inside the embryo sac. This fusion results in the formation of a triploid (3n) primary endosperm nucleus (PEN), which develops into the endosperm, a nutritive tissue for the developing embryo.

(ii) what are the characteristics of insect pollinated flowers.

Characteristics of insect-pollinated flowers (Entomophily):

Flowers are generally large and conspicuous.
They are brightly coloured to attract insects.
They often possess a scent or fragrance.
They produce nectar, a sugary fluid that serves as a reward for pollinators.
Pollen grains are often sticky or spiny to adhere to the insect's body.
The stigma is typically sticky to receive the pollen grains.

29. List out the parasitic adaptation in Leech.

Parasitic adaptations in Leech (sanguivorous or blood-sucking nature):

Suckers: Possesses an anterior and a posterior sucker for strong attachment to the host.
Jaws: The mouth is equipped with three jaws that make a painless, Y-shaped incision in the host's skin.
Hirudin: Salivary glands secrete hirudin, an anticoagulant, which prevents blood from clotting, ensuring a continuous supply of blood.
Pharynx: The muscular pharynx helps in sucking the blood from the host.
Crop: The crop is a large chamber in the alimentary canal that can store a large amount of blood, allowing the leech to survive for months between meals.

30. (i) Why are thyroid hormones referred as personality hormone?.

Thyroid hormones (thyroxine and triiodothyronine) are called 'personality hormones' because they play a crucial role in regulating the body's Basal Metabolic Rate (BMR). They are essential for normal physical growth, mental development, and overall personality. An imbalance (hypothyroidism or hyperthyroidism) can significantly affect a person's energy levels, mood, weight, and cognitive functions, thereby altering their personality.

(ii) What are allosomes?

Allosomes are the sex chromosomes that determine the gender of an individual. In humans and many other species, there are two types of allosomes: the X chromosome and the Y chromosome. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

31. Enumerate the functions of blood?

The main functions of blood are:

Transport: It transports oxygen from the lungs to the tissues, carbon dioxide from tissues to the lungs, digested food from the intestine to all body cells, hormones from endocrine glands to target organs, and waste products like urea to the kidneys for excretion.
Protection: White blood cells (leukocytes) defend the body against pathogens. Platelets (thrombocytes) help in blood clotting to prevent excessive blood loss from injuries.
Regulation: It helps in regulating body temperature by distributing heat. It also maintains the water balance and pH of the body fluids.

32. (i) What happens when MgSO₄.7H₂O is heated?. Write the appropriate equations.

When magnesium sulphate heptahydrate (MgSO₄·7H₂O), also known as Epsom salt, is heated, it loses its water of crystallization and becomes anhydrous magnesium sulphate, a white powder.

The equation for the reaction is:

MgSO₄·7H₂O(s) → MgSO₄(s) + 7H₂O(g)

(Hydrated Magnesium Sulphate) → (Anhydrous Magnesium Sulphate) + (Water Vapour)

(ii) A solution was prepared by dissolving 25g of sugar in 100 g of water. Calculate the mass percentage of solute? (Compulsory)

Given:

Mass of solute (sugar) = 25 g
Mass of solvent (water) = 100 g

Calculation:

First, find the total mass of the solution:

Mass of solution = Mass of solute + Mass of solvent

Mass of solution = 25 g + 100 g = 125 g

Now, calculate the mass percentage of the solute:

Mass % of solute = (Mass of solute / Mass of solution) × 100

Mass % of solute = (25 / 125) × 100

Mass % of solute = (1 / 5) × 100

Mass % of solute = 20 %

Result: The mass percentage of sugar in the solution is 20%.

PART IV

NOTE: (i) Answer all the questions. (ii) Draw diagram wherever necessary. (3 × 7 = 21)

33. (a) Deduce the equation of a force using Newtons second law of motion.

Statement of Newton's Second Law: The rate of change of momentum of a body is directly proportional to the external force applied on it, and the change takes place in the direction of the force.

Derivation:

Let 'm' be the mass of a body.
Let 'u' be its initial velocity.
Initial momentum of the body (p₁) = m × u
Let a force 'F' act on the body for a time 't', causing its velocity to change to 'v'.
Final momentum of the body (p₂) = m × v
Change in momentum (Δp) = p₂ - p₁ = mv - mu = m(v - u)
Rate of change of momentum = Change in momentum / time taken = m(v - u) / t
We know that acceleration (a) = (v - u) / t (rate of change of velocity).
Therefore, the rate of change of momentum = m × a.
According to Newton's second law, Force (F) ∝ Rate of change of momentum.
F ∝ ma
To make this an equation, we introduce a proportionality constant, k: F = k * ma
The unit of force is chosen such that the value of k becomes 1. One newton is defined as the force that produces an acceleration of 1 m/s² in a body of mass 1 kg.
So, F = 1 × ma
F = ma

This is the equation for force derived from Newton's second law.

(b) (i) State Joule's law of heating

Joule's law of heating states that the heat (H) produced in a conductor is directly proportional to:

The square of the current (I²) flowing through the conductor.
The resistance (R) of the conductor.
The time (t) for which the current flows through it.

Mathematically, it is expressed as: H = I²Rt Joules.

(ii) An alloy of nickel and chromium is used as the heating element - why?

An alloy of nickel and chromium (Nichrome) is used as a heating element because it has:

High Resistivity: It offers high resistance to the flow of current, which leads to greater heat production (as H ∝ R).
High Melting Point: It can withstand very high temperatures without melting.
High Resistance to Oxidation: It does not get oxidized (or burn) easily even when it is red-hot, ensuring a long life for the heating element.

(iii) How does a fuse wire protect electrical appliances?

A fuse wire protects electrical appliances by acting as a safety device. It is made of an alloy with a low melting point and is connected in series with the appliance. When an excessive current flows through the circuit (due to overloading or a short circuit), the fuse wire heats up rapidly (H = I²Rt). Because of its low melting point, it melts and breaks the circuit, stopping the flow of current. This prevents the high current from reaching and damaging the expensive electrical appliance.

34. (a) Derive the relationship between Relative molecular mass and vapour density.

Vapour Density (V.D.): It is defined as the ratio of the mass of a certain volume of a gas or vapour to the mass of the same volume of hydrogen gas, measured under the same conditions of temperature and pressure.

V.D. = (Mass of a given volume of a gas) / (Mass of the same volume of H₂)

According to Avogadro's Law, equal volumes of all gases under the same conditions of temperature and pressure contain an equal number of molecules. Let this number be 'n'.

So, V.D. = (Mass of 'n' molecules of the gas) / (Mass of 'n' molecules of H₂)

Cancelling 'n' from the numerator and denominator:

V.D. = (Mass of 1 molecule of the gas) / (Mass of 1 molecule of H₂)

The mass of one molecule is its molecular mass.

V.D. = (Molecular mass of the gas) / (Molecular mass of H₂)

The molecular mass of hydrogen (H₂) is 2 (since atomic mass of H ≈ 1).

V.D. = (Molecular mass of the gas) / 2

Rearranging the equation:

Relative Molecular Mass = 2 × Vapour Density

(b) (i) Write notes on Saturated solution and unsaturated solution

Saturated Solution: A saturated solution is one that contains the maximum amount of solute that can be dissolved in a given amount of solvent at a specific temperature. In a saturated solution, no more solute will dissolve if added.

Unsaturated Solution: An unsaturated solution is one that contains less solute than the maximum amount that can be dissolved in a given amount of solvent at a specific temperature. If more solute is added to an unsaturated solution, it will dissolve.

(ii) Classify the following substances into deliquescent, hygroscopic, Conc. Sulphuric acid, Copper Sulphate pentahydrate, Silica gel, Calcium chloride and Gypsum salt.

Deliquescent: Calcium chloride
Hygroscopic: Conc. Sulphuric acid, Silica gel
Hydrated Salts (Neither): Copper Sulphate pentahydrate, Gypsum salt

(Note: The question's wording is slightly ambiguous, but this is the most accurate classification based on the properties of the substances listed.)

35. (a) (i) What is transpiration?. Give the importance of transpiration

Transpiration: It is the biological process of water loss in the form of water vapour from the aerial parts of a plant, mainly through small pores called stomata located on the leaves.

Importance of Transpiration:

Transpiration Pull: It creates a suction force, known as the transpiration pull, which is essential for the upward movement of water and minerals (ascent of sap) from the roots to the leaves.
Cooling Effect: The evaporation of water from the leaf surface helps to cool the plant, protecting it from heat damage caused by intense sunlight.
Maintains Turgidity: It regulates the water content within plant cells, helping to maintain their shape and turgidity.

(ii) What are synthetic auxins? Give examples.

Synthetic Auxins: These are man-made chemicals that mimic the effects of natural auxins (plant hormones) and are widely used in agriculture and horticulture to control plant growth.

Examples:

2, 4-D (2, 4-Dichlorophenoxyacetic acid) - used as a weedicide.
NAA (Naphthalene Acetic Acid) - used to induce rooting and prevent fruit drop.

(iii) Which hormone induces parthenocarpy in tomatoes?

Auxin is the hormone that is commonly used to induce parthenocarpy (the development of fruit without fertilization) in tomatoes.

(b) How is the structure of DNA organised? What is the biological significance of DNA?.

Structure of DNA:

The structure of DNA is organized according to the Watson and Crick double helix model:

Double Helix: DNA consists of two long polynucleotide chains coiled around a central axis to form a right-handed double helix, resembling a twisted ladder.
Backbone: The "sides" of the ladder are made of a sugar-phosphate backbone, formed by alternating deoxyribose sugar and phosphate groups.
Nitrogenous Bases: The "rungs" of the ladder consist of pairs of nitrogenous bases. There are four bases: Adenine (A), Guanine (G) (which are purines), and Cytosine (C), Thymine (T) (which are pyrimidines).
Complementary Base Pairing: The bases pair in a specific way due to hydrogen bonds: Adenine always pairs with Thymine (A=T) with two hydrogen bonds, and Guanine always pairs with Cytosine (G≡C) with three hydrogen bonds.
Antiparallel Strands: The two strands run in opposite directions, which is described as being antiparallel (one strand runs 5' to 3', and the other runs 3' to 5').

Biological Significance of DNA:

Carrier of Genetic Information: DNA is the hereditary material in most organisms. It carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses.
Controls Cellular Activities: It controls all the metabolic activities of the cell by directing the synthesis of specific proteins and enzymes.
Replication: DNA has the unique ability to make exact copies of itself through a process called replication. This ensures that genetic information is accurately passed down from one generation to the next during cell division.
Mutation and Evolution: Changes or errors in the DNA sequence (mutations) can lead to variations within a species. These variations are the raw material for natural selection and evolution.