10th Science - Quarterly Exam 2024 - Original Question Paper | Namakkal District
QUARTERLY EXAMINATION - 2024
10th Std - SCIENCE
Time: 3.00 Hours | MARKS: 75
Instructions:
- Write clearly and legibly without mistakes and overwriting utilising the maximum time allotted for the exam.
- Answer should be in your own style without changing the main core concept.
- Use only black or blue ink pen to write the exam.
PART I - Choose the correct answer (12 x 1 = 12)
- One kilogram force equals to ..........
- The value of universal gas constant
- Kilowatt hour is the unit of ..........
- 1 mole of any substance contains .......... Molecules.
- Which of the following have inert gases 2 electrons in the outermost shell.
- When pressure is increased at constant temperature the solubility of gases in liquid..........
- Which is formed during anaerobic respiration
- The wall of human heart is made of ..........
- Nerve cells do not possess
- Which organ act as both exocrine gland as well as endocrine gland
- Which one of the following is an IUCD.
- The region of the chromosome where the spindle fibers get attached during cell division.
PART II - Answer any 7 questions. (Question no: 22 Compulsory) (7 x 2 = 14)
- State Rayleigh's law of scattering.
Answer: Rayleigh's law of scattering states that the amount of scattering of light is inversely proportional to the fourth power of its wavelength (λ).
Scattering ∝ 1/λ4
- Distinguish between linear, aerial or superficial expansion.
Answer:
Linear Expansion Superficial/Aerial Expansion The expansion in the length of a solid when heated is called linear expansion. The expansion in the area of a solid when heated is called superficial or aerial expansion. It occurs in one dimension (length). It occurs in two dimensions (length and breadth). - Why is tungsten metal used in bulbs, but not in fuse wires?
Answer:
- Tungsten in Bulbs: Tungsten is used as a filament in incandescent bulbs because it has a very high melting point (3422°C) and high resistivity. This allows it to be heated to a very high temperature without melting, causing it to glow brightly (incandescence).
- Fuse Wires: Fuse wires are made of an alloy with a low melting point. Their purpose is to melt and break the circuit if the current exceeds a safe level, thus protecting the appliance. Tungsten's high melting point makes it unsuitable for this purpose.
- What is rust? Give the equation for formation of rust.
Answer: Rust is hydrated ferric oxide (Fe2O3·xH2O), a reddish-brown flaky substance formed when iron corrodes by reacting with oxygen and water (or moisture) in the air.
Equation: 4Fe + 3O2 + xH2O → 2Fe2O3·xH2O
- Why is the teeth of rabbit called heterodont?
Answer: The teeth of a rabbit are called heterodont because rabbits possess different types of teeth that are structurally different and perform different functions. They have incisors for gnawing and molars for grinding. This condition of having more than one type of tooth morphology is known as heterodont dentition.
- Match it:
Answer:
Column A Column B a) Symplastic pathway Plasmodesmata b) Transpiration Leaf c) Osmosis Pressure gradient d) Root pressure Pressure in Xylem - Why are thyroid hormones refered as personality hormone?
Answer: Thyroid hormones (thyroxine) are referred to as "personality hormones" because they regulate the Basal Metabolic Rate (BMR) of the body. Proper levels of these hormones are essential for maintaining normal physical, mental, and developmental functions. An imbalance can lead to changes in energy levels, mood, and alertness, thereby affecting an individual's overall personality.
- Identify the parts A,B,C and D
Answer: The image shows a chloroplast. The parts are:
- A: Stroma
- B: Granum (stack of thylakoids)
- C: Outer membrane
- D: Inner membrane
- What do you understands by the term phenotype and genotype?
Answer:
- Phenotype: The phenotype is the external, observable physical or biochemical characteristic of an organism, resulting from the interaction of its genotype with the environment. Example: Tallness or dwarfness of a plant.
- Genotype: The genotype is the genetic makeup of an organism, representing the complete set of genes it carries. Example: The genotype for a tall pea plant can be TT (homozygous tall) or Tt (heterozygous tall).
- (Compulsory) 3.5 litres of ethanol is present in 15 liters of aqueous solution of ethanol. Calculate volume precent of ethanol solution.
Answer:
Given:
- Volume of solute (ethanol) = 3.5 litres
- Volume of solution = 15 litres
Formula:
Volume % = (Volume of solute / Volume of solution) × 100
Calculation:
Volume % = (3.5 L / 15 L) × 100
Volume % = 0.2333... × 100
Volume % = 23.33 %
PART III - Answer any 7 Questions. (Question no: 32 Compulsory) (7 x 4 = 28)
- What is universal law? Write any 2 applications.
Answer: The "universal law" most likely refers to Newton's Law of Universal Gravitation.
Newton's Law of Universal Gravitation: It states that every particle in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. The formula is F = G(m₁m₂/r²).
Two Applications:
- Calculating Planetary Orbits: It helps to explain and calculate the motion of planets around the sun and moons around planets. It is the foundation of celestial mechanics.
- Artificial Satellites: The law is used to calculate the precise velocity and altitude required to place artificial satellites into stable orbits around the Earth for communication, weather forecasting, and navigation (GPS).
- Differentiate the eye defects: Myopia and Hypermetropia
Answer:
Feature Myopia (Near-sightedness) Hypermetropia (Far-sightedness) Vision Defect Can see nearby objects clearly, but distant objects appear blurry. Can see distant objects clearly, but nearby objects appear blurry. Cause Eyeball is too long, or the focal length of the eye lens is too short. Image is formed in front of the retina. Eyeball is too short, or the focal length of the eye lens is too long. Image is formed behind the retina. Correction Corrected using a concave lens, which diverges light rays before they enter the eye. Corrected using a convex lens, which converges light rays before they enter the eye. - Calculate the % of each element in calcium carbonate: (Atomic mass: C-12, O-16, Ca - 40)
Answer:
The chemical formula for calcium carbonate is CaCO3.
1. Calculate the molar mass of CaCO3:
Molar Mass = (Atomic mass of Ca) + (Atomic mass of C) + 3 × (Atomic mass of O)
Molar Mass = 40 + 12 + 3 × 16
Molar Mass = 40 + 12 + 48 = 100 g/mol
2. Calculate the percentage of each element:
- % of Calcium (Ca): (Mass of Ca / Molar Mass of CaCO3) × 100 = (40 / 100) × 100 = 40%
- % of Carbon (C): (Mass of C / Molar Mass of CaCO3) × 100 = (12 / 100) × 100 = 12%
- % of Oxygen (O): (Mass of O / Molar Mass of CaCO3) × 100 = (48 / 100) × 100 = 48%
- a) Identify the bond between H and F in HF molecule
b) What property forms the basis of identification?
c) How does the property vary in periods and in groups?Answer:
a) Bond in HF: The bond between Hydrogen (H) and Fluorine (F) in the HF molecule is a Polar Covalent Bond.
b) Basis of Identification: The basis for this identification is the difference in electronegativity between the two atoms. Fluorine is the most electronegative element, while hydrogen has a much lower electronegativity. This large difference causes the shared pair of electrons to be pulled closer to the fluorine atom, creating partial negative (δ-) and partial positive (δ+) charges on the F and H atoms respectively.
c) Variation of Electronegativity:
- In a Period (left to right): Electronegativity generally increases. This is because the nuclear charge increases while the atomic size decreases, leading to a stronger attraction for bonding electrons.
- In a Group (top to bottom): Electronegativity generally decreases. This is because the atomic size increases, and the shielding effect of inner electrons becomes more significant, reducing the nucleus's attraction for the bonding electrons.
- a) What is collateral vascular bundle?
b) Where does the carbon that is used in photosynthesis come from?
c) What is the common step in aerobic and anaerobic pathway?Answer:
a) Collateral Vascular Bundle: A collateral vascular bundle is one in which the xylem and phloem are located on the same radius, with the xylem situated towards the center (adaxial side) and the phloem towards the periphery (abaxial side). This is the most common type of vascular bundle found in the stems of dicots and gymnosperms.
b) Carbon Source for Photosynthesis: The carbon used in photosynthesis comes from carbon dioxide (CO2) present in the atmosphere. Plants take in CO2 through small pores on their leaves called stomata.
c) Common Step in Aerobic and Anaerobic Respiration: The common step for both aerobic and anaerobic respiration is Glycolysis. It is the initial pathway where a molecule of glucose is broken down into two molecules of pyruvic acid. This process occurs in the cytoplasm of the cell and does not require oxygen.
- How does locomotion take place in leech?
Answer: A leech has two primary modes of locomotion:
- Looping or Crawling Movement: This is the most common mode on a solid surface.
- The leech attaches its posterior sucker to the surface.
- It then extends its body forward.
- Next, it attaches its anterior sucker to the new position.
- It releases the posterior sucker and contracts its body, pulling the posterior end forward towards the anterior end, forming a loop.
- The cycle repeats, allowing the leech to "crawl" or "loop" forward.
- Swimming Movement: In water, the leech flattens its body and performs wave-like, undulating movements to swim.
- Looping or Crawling Movement: This is the most common mode on a solid surface.
- State whether True or False. If false write the correct statement
a) The phloem is responsible for the translocation of food
b) When guard cells lose water the stoma opens
c) What is cohesion?Answer:
a) The phloem is responsible for the translocation of food: True.
b) When guard cells lose water the stoma opens: False.
Correct Statement: When guard cells lose water, they become flaccid, and the stoma closes.
c) What is cohesion?: Cohesion is the force of attraction between molecules of the same substance. For example, in plants, the cohesion of water molecules helps to pull the water column up through the xylem vessels during transpiration.
- a) What are the structures involved in the protection of brain?
b) Define reflex arc.Answer:
a) Structures involved in the protection of the brain:
- Cranium (Skull): The hard, bony outer covering that encloses and protects the brain from physical injury.
- Meninges: Three protective membranes that lie between the skull and the brain. From outside to inside, they are the Dura mater, Arachnoid mater, and Pia mater.
- Cerebrospinal Fluid (CSF): A clear fluid found in the space between the meninges (subarachnoid space) and in the ventricles of the brain. It acts as a shock absorber, protecting the brain from jolts and impacts.
b) Reflex Arc: A reflex arc is the neural pathway that a nerve impulse follows to mediate a reflex action. It is an involuntary and rapid response to a stimulus. The components of a typical reflex arc are: a receptor, a sensory (afferent) neuron, an integration center (interneuron in the spinal cord), a motor (efferent) neuron, and an effector (muscle or gland).
- What is colostrum? How is milk production hormonally regulated?
Answer:
Colostrum: Colostrum is the first form of milk produced by the mammary glands of mammals immediately following delivery of the newborn. It is thick, yellowish, and rich in proteins, vitamins, and antibodies (especially IgA) that provide passive immunity to the baby, protecting it from infections.
Hormonal Regulation of Milk Production:
- Prolactin: This hormone, secreted by the anterior pituitary gland, is primarily responsible for the synthesis and production of milk in the mammary glands (lactation).
- Oxytocin: This hormone, released from the posterior pituitary gland, stimulates the ejection or "let-down" of milk from the alveoli of the mammary glands into the ducts so the baby can drink it. This is often triggered by the baby suckling.
- (Compulsory) The resistance of a wire of length 10 m is 2 ohm. If the area of cross section of the wire 2x10-7 m², determine its (i) resistivity (ii) Conductance.
Answer:
Given Data:
- Length (L) = 10 m
- Resistance (R) = 2 Ω
- Area of cross-section (A) = 2 × 10-7 m²
(i) Resistivity (ρ):
The formula for resistance is R = ρ (L/A).
Rearranging for resistivity (ρ): ρ = (R × A) / L
Substituting the values:
ρ = (2 Ω × 2 × 10-7 m²) / 10 m
ρ = (4 × 10-7) / 10 Ωm
ρ = 4 × 10-8 Ωm
(ii) Conductance (G):
Conductance is the reciprocal of resistance.
G = 1 / R
G = 1 / 2 Ω
G = 0.5 Siemens (S) or 0.5 mho
PART IV - Answer very briefly (3 x 7 = 21)
-
a) Deduce the equation of a force using Newton's second law of motion
Answer:
Newton's second law of motion states that 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.
- Let an object of mass 'm' be moving with an initial velocity 'u'.
- Let a force 'F' be applied on the object for a time 't', causing its velocity to change to 'v'.
- Initial momentum (pi) = m × u
- Final momentum (pf) = m × v
- Change in momentum (Δp) = pf - pi = mv - mu = m(v - u)
- Rate of change of momentum = Change in momentum / time = m(v - u) / t
- According to Newton's second law: Force (F) ∝ Rate of change of momentum
- F ∝ m(v - u) / t
- We know that acceleration (a) is the rate of change of velocity, so a = (v - u) / t.
- Substituting this in the equation, we get: F ∝ m × a
- To remove the proportionality, we introduce a constant, k: F = kma
- The value of the proportionality constant k is chosen to be 1 in SI units. One unit of force is defined as the force that produces one unit of acceleration in a body of unit mass.
- Therefore, F = ma. This is the equation for force.
(OR)b) Derive the ideal gas equation.
Answer:
The ideal gas equation can be derived by combining three fundamental 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 --- (Equation 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 --- (Equation 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 --- (Equation 3)
By combining these three equations, we get:
V ∝ (1/P) × T × n
or
V ∝ nT/P
We can rewrite this as: PV ∝ nT
To replace the proportionality sign with an equality sign, we introduce a constant of proportionality, R, which is called the Universal Gas Constant.
Therefore, the final equation is: PV = nRT
This is the Ideal Gas Equation.
-
a) Calcium carbonate is decomposed on heating in the following reaction.
CaCO3 → CaO + CO2
i) How many moles of calcium carbonate are involved in this reaction?
ii) Calculate the gram molecular mass of calcium carbonate involved in this reaction.
iii) How many moles of CO2 are there in this equation?Answer:
Given the balanced chemical equation: CaCO3 → CaO + CO2
i) How many moles of calcium carbonate are involved in this reaction?
Looking at the stoichiometric coefficient in front of CaCO3 in the balanced equation, we can see it is 1. Therefore, 1 mole of calcium carbonate is involved.
ii) Calculate the gram molecular mass of calcium carbonate involved in this reaction.
(Atomic masses: Ca=40, C=12, O=16)
Gram Molecular Mass of CaCO3 = (1 × Mass of Ca) + (1 × Mass of C) + (3 × Mass of O)
= (1 × 40) + (1 × 12) + (3 × 16)
= 40 + 12 + 48
= 100 g/mol
iii) How many moles of CO2 are there in this equation?
Looking at the stoichiometric coefficient in front of CO2 in the balanced equation, we can see it is 1. Therefore, 1 mole of CO2 is produced.
(OR)b) Write notes On various factors affecting solubility.
Answer:
Solubility is the maximum amount of a solute that can be dissolved in a given amount of solvent at a specific temperature. The main factors affecting solubility are:
-
Nature of the Solute and Solvent:
- This is governed by the principle "like dissolves like".
- Polar solutes (like common salt, NaCl) tend to dissolve in polar solvents (like water, H2O).
- Non-polar solutes (like grease, oil) tend to dissolve in non-polar solvents (like ether, benzene).
-
Temperature:
- Solids in Liquids: For most solid solutes, solubility increases as the temperature increases (e.g., sugar in water). The dissolution process is endothermic. However, for some substances like cerium sulfate (Ce2(SO4)3), solubility decreases with an increase in temperature as the dissolution is exothermic.
- Gases in Liquids: For all gaseous solutes, solubility decreases as the temperature increases. This is why boiled water has a "flat" taste (less dissolved oxygen) and why aquatic life is more comfortable in cold water.
-
Pressure:
- Solids and Liquids: Pressure has a negligible effect on the solubility of solid and liquid solutes.
- Gases in Liquids: The solubility of a gas in a liquid is directly proportional to the pressure of the gas over the liquid (Henry's Law). This is why carbonated drinks are bottled under high pressure to dissolve more CO2, and they fizz when opened as the pressure is released.
-
Nature of the Solute and Solvent:
-
a) i) Name the gaseous plant hormone. Describe its three different actions in plants.
ii) Which hormone is known as stress horomone in plants? Why ?
iii) What is Bolting?Answer:
a) i) Gaseous Plant Hormone and its Actions:
The gaseous plant hormone is Ethylene.
Three of its actions are:
- Fruit Ripening: Ethylene is widely used commercially to promote the ripening of fruits like bananas, mangoes, and tomatoes. It triggers a cascade of biochemical changes that lead to softening, color change, and aroma development.
- Promotion of Senescence and Abscission: It accelerates the aging (senescence) of leaves and flowers and promotes the shedding (abscission) of leaves, flowers, and fruits from the plant.
- Induction of Flowering: While it generally inhibits flowering in most plants, it promotes flowering in pineapple and its related plants.
ii) Stress Hormone in Plants:
Abscisic Acid (ABA) is known as the stress hormone in plants.
Why?: It is called a stress hormone because its production is stimulated by various environmental stresses, especially water stress (drought). In response to drought, ABA levels rise, causing the stomata on the leaves to close. This closure reduces water loss through transpiration, helping the plant to conserve water and survive the stressful condition.
iii) What is Bolting?:
Bolting is the premature production of a long flowering stem in biennial plants (like cabbage, beet) or rosette plants before the plant has reached its full vegetative size. It is often induced by specific environmental cues like changes in temperature or day length and is hormonally controlled, primarily by gibberellins.
(OR)b) What is the structure of DNA organized? What is the biological significance of DNA?
Answer:
Structure of DNA (Watson and Crick Model):
- DNA consists of two polynucleotide chains that are coiled around each other to form a double helix.
- Each polynucleotide chain is made up of repeating units called nucleotides.
- A nucleotide has three components: a deoxyribose sugar, a phosphate group, and a nitrogenous base.
- The "backbone" of each chain is formed by alternating sugar and phosphate groups.
- There are four types of nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).
- The two strands are held together by hydrogen bonds between the bases. This pairing is specific: Adenine always pairs with Thymine (A-T) with two hydrogen bonds, and Guanine always pairs with Cytosine (G-C) with three hydrogen bonds. This is called complementary base pairing.
- The two strands run in opposite directions, a property known as antiparallel.
Biological Significance of DNA:
- Repository of Genetic Information: DNA is the primary carrier of genetic information. The sequence of bases in DNA contains the instructions for building and maintaining an organism.
- Heredity: DNA is responsible for the transmission of genetic traits from one generation to the next. It can replicate itself accurately, ensuring that daughter cells receive a complete set of genetic instructions.
- Protein Synthesis: DNA holds the code (genes) for the synthesis of all proteins in a cell. Proteins carry out most of the cell's functions, including acting as enzymes, structural components, and signaling molecules.
- Control of Cell Activities: By controlling which proteins are made, when, and in what quantities, DNA regulates all metabolic activities and functions of the cell.
- Evolution: Changes or mutations in the DNA sequence can lead to variations within a species. Natural selection acts on these variations, driving the process of evolution over time.