10th Science Quarterly Exam 2024 - Dindigul District (Solutions)
Part I: Choose the correct answer (12 x 1 = 12)
1. One kilogram force equals to ..........
Answer: b) 9.8 N. (Note: 1 kgf = 9.8 N. There might be a typo in the provided options. 9.8 N is the standard conversion. If we must choose, none seem correct as written, but 9.8 N is the physical value.)
2. The value of universal gas constant
Answer: d) 8.31 Jmol⁻¹ K⁻¹
3. Kilowatt hour is the unit of ..........
Answer: c) Electrical energy
4. 1 mole of any substance contains .......... Molecules.
Answer: a) 6.023x10²³
5. Which of the following have inert gases 2 electrons in the outermost shell.
Answer: a) He (Helium completes its duplet in the K-shell)
6. When pressure is increased at constant temperature the solubility of gases in liquid..........
Answer: b) increases (According to Henry's Law)
7. Which is formed during anaerobic respiration
Answer: b) Ethyl alcohol (in yeast) or Lactic acid (in muscles)
8. The wall of human heart is made of ..........
Answer: d) All of the above
9. Nerve cells do not possess
Answer: b) Sarcolemma (It is the plasma membrane of a muscle fiber).
10. Which organ act as both exocrine gland as well as endocrine gland
Answer: a) Pancreas
11. Which one of the following is an IUCD.
Answer: a) Copper-T (Intra-Uterine Contraceptive Device)
12. The region of the chromosome where the spindle fibers get attached during cell division.
Answer: c) Centromere
Part II: Answer any 7 questions. Q.No: 22 is Compulsory. (7 x 2 = 14)
13. State Rayleigh's law of scattering
Rayleigh's Law of Scattering: It states that "The amount of scattering of light is inversely proportional to the fourth power of its wavelength".
Mathematically, Amount of Scattering (S) ∝ 1/λ⁴
14. Distinguish between linear, arial or superficial expansion.
| Linear Expansion | Superficial (Areal) Expansion |
|---|---|
| When a solid is heated, the expansion in its length is called linear expansion. | When a solid is heated, the expansion in its area is called superficial or areal expansion. |
| It occurs in one dimension (length). | It occurs in two dimensions (length and breadth). |
| Coefficient of linear expansion (αL) is defined as the ratio of increase in length per degree rise in temperature to its unit length. | Coefficient of superficial expansion (αA) is defined as the ratio of increase in area per degree rise in temperature to its unit area. |
15. Why is tungsten metal used in bulbs, but not in fuse wires?
- Tungsten in Bulbs: Tungsten is used as the 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 (incandescence) to produce light without melting.
- Not in Fuse Wires: Fuse wires are safety devices designed to melt and break the circuit when an excessive current flows. Therefore, they must have a very low melting point. Using high-melting-point tungsten would defeat the purpose of a fuse.
16. What is rust? Give the equation for formation of rust.
Rust: Rust is a reddish-brown flaky substance formed on the surface of iron when it is exposed to moist air. Chemically, it is hydrated ferric oxide.
Equation for Rust Formation:
4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O
(Iron + Oxygen + Water → Hydrated Ferric Oxide (Rust))
17. Why is the teeth of rabbit called heterodont?
The teeth of a rabbit are called heterodont because they are of different types, each adapted for a specific function. Rabbits have four types of teeth: incisors, canines (absent in rabbits, creating a gap called diastema), premolars, and molars. This condition of having different kinds of teeth is known as heterodont dentition.
18. Match it:
| Column A | Column B |
|---|---|
| a) Symplastic pathway | Plasmodesmata |
| B) Transpiration | Leaf |
| c) Osmosis | Pressure gradient |
| d) Root pressure | Pressure in Xylem |
19. Why are thyroid hormones refered as personality hormone?
Thyroid hormones (thyroxine) are referred to as "personality hormones" because they regulate the Basal Metabolic Rate (BMR) of the body. They are essential for normal physical, mental, and personality development. A deficiency (hypothyroidism) or excess (hyperthyroidism) of these hormones can lead to significant changes in a person's energy levels, mood, weight, and overall physical and mental well-being, thereby affecting their personality.
20. Identify the parts A,B,C and D
The given diagram is a chloroplast.
- A: Outer membrane
- B: Inner membrane
- C: Stroma
- D: Thylakoid / Granum (stack of thylakoids)
21. What do you understands by the term phenotype and genotype?
- Phenotype: The phenotype refers to the observable physical or biochemical characteristics of an organism, such as its appearance, development, and behavior. It is determined by the genotype and environmental factors. Example: Tall or dwarf plant.
- Genotype: The genotype is the genetic makeup of an organism. It describes an organism's complete set of genes. Example: TT (homozygous tall), Tt (heterozygous tall), or tt (homozygous dwarf).
22. (Compulsory) 3.5 litres of ethanol is present in 15 liters of aqueous solution of ethanol. Calculate volume precent of ethanol solution.
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 / 15) × 100
Volume % = 0.2333 × 100
Volume % = 23.33 %
The volume percentage of the ethanol solution is 23.33%.
Part III: Answer any 7 Questions. Q.No: 32 is Compulsory. (7 x 4 = 28)
23. What is universal law? Write any 2 applications
Newton's Universal Law of Gravitation: It states that every particle of matter in this 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.
Force (F) = G (m₁m₂ / r²)
Applications:
- It helps in determining the dimensions of heavenly bodies like the mass of the Earth, radius of the Earth, and acceleration due to gravity.
- It explains the motion of the planets around the Sun and the motion of the moon around the Earth.
- It helps in discovering new stars and planets.
- It helps to explain the formation of tides and the shape of the Earth.
24. Differentiate the eye defects: Myopia and Hypermetropia
| Feature | Myopia (Near-sightedness) | Hypermetropia (Far-sightedness) |
|---|---|---|
| Vision | Can see nearby objects clearly, but distant objects appear blurry. | Can see distant objects clearly, but nearby objects appear blurry. |
| Cause | The eyeball is too long, or the lens has too much converging power. | The eyeball is too short, or the lens has too little converging power. |
| Image Formation | The image of a distant object is formed in front of the retina. | The image of a nearby object is formed behind the retina. |
| Correction | Corrected using a concave lens (diverging lens). | Corrected using a convex lens (converging lens). |
25. Calculate the % of each element in calcium carbonate: (Atomic mass: C-12, O-16, Ca - 40 )
Step 1: Calculate the molar mass of Calcium Carbonate (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
Step 2: Calculate the percentage composition of each element.
% of Calcium (Ca):
% Ca = (Mass of Ca / Molar mass of CaCO₃) × 100 = (40 / 100) × 100 = 40%
% of Carbon (C):
% C = (Mass of C / Molar mass of CaCO₃) × 100 = (12 / 100) × 100 = 12%
% of Oxygen (O):
% O = (Mass of O / Molar mass of CaCO₃) × 100 = (48 / 100) × 100 = 48%
26. 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?
a) Bond in HF molecule: 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, and 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 positive (δ+) charges on F and H respectively.
c) Variation of Electronegativity:
- In a Period (from left to right): Electronegativity generally increases because the nuclear charge increases while the atomic size decreases, leading to a stronger attraction for electrons.
- In a Group (from top to bottom): Electronegativity generally decreases because the atomic size increases and the shielding effect of inner electrons becomes more significant, reducing the nucleus's attraction for valence electrons.
27. 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 annerobic pathway?
a) Collateral Vascular Bundle: A collateral vascular bundle is one in which the xylem and phloem are present on the same radius, with the phloem located towards the periphery (outside) and the xylem located towards the center (inside).
b) Source of Carbon in Photosynthesis: The carbon used in photosynthesis comes from carbon dioxide (CO₂) present in the atmosphere.
c) Common step in Aerobic and Anaerobic pathway: The common step for both aerobic and anaerobic respiration is Glycolysis. It is the process where one molecule of glucose is broken down into two molecules of pyruvate, occurring in the cytoplasm of the cell.
28. How does locomotion take place in leech?
Locomotion in leech occurs in two ways:
- Looping or Crawling Movement: This is done on a solid surface. The leech fixes its posterior sucker and contracts its circular muscles, causing the body to extend forward. It then fixes its anterior sucker, releases the posterior sucker, and contracts its longitudinal muscles to shorten the body and bring the posterior end forward. This cycle is repeated.
- Swimming Movement: In water, the leech flattens its body and performs active undulatory (wave-like) movements to swim gracefully.
29. 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?
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 (stomatal pore) closes. The stoma opens when guard cells gain water and become turgid.
c) What is cohesion?
Cohesion is the force of attraction between molecules of the same substance. For example, the attraction between water molecules is cohesion.
30. a) What are the structures involved in the protection of brain?
b) Define reflex arc
a) Structures protecting 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 cranium and the brain. They are:
- Dura mater: The tough, outermost layer.
- Arachnoid mater: The web-like middle layer.
- Pia mater: The delicate innermost layer that adheres to the surface of the brain.
- Cerebrospinal Fluid (CSF): A clear fluid found in the subarachnoid space (between arachnoid and pia mater) and ventricles of the brain. It acts as a shock absorber, protecting the brain from mechanical shocks.
b) Reflex Arc: A reflex arc is the neural pathway that a nerve impulse follows during a reflex action. It begins with a stimulus at a receptor organ and ends with a response by an effector organ, without involving conscious thought from the brain. The pathway includes: Receptor → Sensory Neuron → Interneuron (in spinal cord) → Motor Neuron → Effector (muscle or gland).
31. What is colostrum? How is milk production hormonally regulated?
Colostrum: Colostrum is the first form of milk produced by the mammary glands of mammals immediately following delivery of the newborn. It is a yellowish, sticky fluid rich in proteins, vitamins, minerals, and most importantly, antibodies (especially IgA) that provide passive immunity to the baby.
Hormonal Regulation of Milk Production:
- Prolactin: Secreted by the anterior pituitary gland, prolactin is the primary hormone responsible for stimulating the mammary glands to produce milk (lactogenesis).
- Oxytocin: Secreted by the posterior pituitary gland, oxytocin is responsible for the ejection of milk (the "let-down" reflex). The suckling of the baby stimulates the release of oxytocin, which causes the contraction of myoepithelial cells around the alveoli in the mammary glands, pushing the milk out.
32. (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.
Given:
- Resistance (R) = 2 Ω
- Length (L) = 10 m
- 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 = (R × A) / L
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 mho (or Siemens, S)
Part IV: Answer very briefly (3 x 7 = 21)
33. a) Deduce the equation of a force using Newton's second law of motion
Newton's second law of motion states that "the force acting on a body is directly proportional to the rate of change of its linear momentum and the change in momentum takes place in the direction of the force."
Let 'm' be the mass of a moving body, moving with an initial velocity 'u'.
The initial momentum of the body, Pᵢ = m × u
Suppose a force 'F' is applied on the body for a time 't', which changes its velocity to 'v'.
The final momentum of the body, Pƒ = m × v
Now, the change in momentum, Δp = Pƒ - Pᵢ = mv - mu = m(v - u)
The rate of change of momentum = Change in momentum / time = m(v - u) / t
According to Newton's second law,
F ∝ Rate of change of momentum
F ∝ m(v - u) / t
We know that acceleration (a) = change in velocity / time = (v - u) / t.
Substituting this, we get:
F ∝ m × a
To replace the proportionality sign, we introduce a constant of proportionality, k:
F = k × m × a
The value of the constant k is chosen to be 1 in all systems of units. Therefore,
F = m × a
Thus, the equation for force is derived. Force = mass × acceleration.
b) Derive the ideal gas equation.
The ideal gas equation is 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 (at constant T and n) --- (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 (at constant P and n) --- (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 (at constant T and P) --- (Equation 3)
By combining these three equations (1, 2, and 3), we get:
V ∝ (1/P) × T × n
V ∝ nT/P
We can replace the proportionality sign with a constant, called the universal gas constant (R).
V = R (nT/P)
Rearranging the equation, we get the Ideal Gas Equation:
PV = nRT
Where:
- P = Pressure of the gas
- V = Volume of the gas
- n = Number of moles of the gas
- R = Universal gas constant (8.31 Jmol⁻¹K⁻¹)
- T = Absolute temperature of the gas
34. 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?
Given the balanced chemical equation: CaCO₃ → CaO + CO₂
i) How many moles of calcium carbonate are involved in this reaction?
Based on the stoichiometry of the balanced equation, the coefficient in front of CaCO₃ is 1. Therefore, 1 mole of calcium carbonate is involved.
ii) Calculate the gram molecular mass of calcium carbonate involved in this reaction.
Gram molecular mass of CaCO₃ = (Atomic mass of Ca) + (Atomic mass of C) + 3 × (Atomic mass of O)
= 40 + 12 + 3 × 16
= 40 + 12 + 48
= 100 g/mol.
The mass of 1 mole of calcium carbonate is 100 grams.
iii) How many moles of CO₂ are there in this equation?
Based on the stoichiometry of the balanced equation, the coefficient in front of CO₂ is 1. Therefore, 1 mole of carbon dioxide is produced.
b) Write notes On various factors affecting solubility.
The solubility of a solute in a solvent is affected by several factors:
1. Nature of the Solute and Solvent
The principle "like dissolves like" is fundamental.
- Polar Solutes: Polar compounds (like salt, sugar) are soluble in polar solvents (like water).
- Non-polar Solutes: Non-polar compounds (like grease, oil) are soluble in non-polar solvents (like ether, benzene).
2. Temperature
The effect of temperature depends on the state of the solute and the nature of the dissolution process.
- Solubility of Solids in Liquids: For most solids, solubility increases with an increase in temperature (e.g., dissolving sugar in hot water). For some substances like cerium sulphate (Ce₂(SO₄)₃), solubility decreases with an increase in temperature.
- Solubility of Gases in Liquids: The solubility of gases in liquids generally decreases with an increase in temperature. This is why boiled water has a "flat" taste (dissolved oxygen has escaped) and why fish prefer colder water.
3. Pressure
Pressure has a significant effect only on the solubility of gases in liquids.
- Henry's Law: It states that the solubility of a gas in a liquid is directly proportional to the pressure of the gas over the surface of the solution.
- This is why carbonated drinks are bottled under high pressure to increase the solubility of CO₂ gas. When the bottle is opened, the pressure decreases, and the gas fizzes out.
- Pressure has a negligible effect on the solubility of solids and liquids.
35. 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?
i) Gaseous Plant Hormone and its Actions:
The gaseous plant hormone is Ethylene (C₂H₄).
Three actions of Ethylene:
- Fruit Ripening: Ethylene is widely used commercially to promote the ripening of fruits like bananas, mangoes, and tomatoes. It enhances the rate of respiration during ripening, known as the respiratory climacteric.
- Senescence and Abscission: It promotes the aging (senescence) of leaves and flowers. It also accelerates the shedding (abscission) of leaves, flowers, and fruits from the plant.
- Inhibition of Stem Elongation: Ethylene generally inhibits the elongation of stems and roots, but promotes the transverse (horizontal) growth, leading to a shorter and thicker plant axis.
ii) Stress Hormone:
Abscisic Acid (ABA) is known as the stress hormone in plants.
Reason: It is called a stress hormone because its production is stimulated by various environmental stresses like drought (water scarcity), high salinity, and extreme temperatures. ABA helps the plant cope with these conditions, primarily by inducing the closure of stomata to reduce water loss through transpiration.
iii) Bolting:
Bolting is the rapid elongation of the internodes of a plant's stem just before flowering. This phenomenon is particularly noticeable in rosette plants like cabbage and beets. It can be induced artificially by the application of Gibberellins.
b) What is the structure of DNA organized? What is the biological significance of DNA?
Structure of DNA (Watson and Crick Model)
DNA (Deoxyribonucleic Acid) is a double-stranded helical molecule. Its key structural features are:
- Double Helix: It consists of two polynucleotide chains that are wound around each other to form a right-handed double helix, resembling a twisted ladder.
- Sugar-Phosphate Backbone: The "sides" of the ladder are made of alternating deoxyribose sugar and phosphate groups, connected by phosphodiester bonds. This backbone provides structural support.
- Nitrogenous Bases: The "rungs" of the ladder are formed by 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 of the helix run in opposite directions, referred to as antiparallel. One strand runs in the 5' to 3' direction, while the other runs in the 3' to 5' direction.
Biological Significance of DNA
DNA is fundamentally important for all living organisms. Its significance lies in:
- Carrier of Genetic Information: DNA is the "blueprint of life." It carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses.
- Heredity: DNA is responsible for the transmission of genetic traits from parents to offspring. The process of DNA replication ensures that each new cell receives an identical copy of the genetic material.
- Control of Cell Activities: The sequence of bases in DNA codes for the synthesis of proteins and RNA molecules. These proteins (including enzymes) control all metabolic activities within the cell.
- Mutation and Evolution: Changes in the DNA sequence (mutations) are the ultimate source of genetic variation. This variation is the raw material upon which natural selection acts, driving the process of evolution.