🔬 Science 1st Mid Term Test 2024 - Original Question Paper | English Medium | Vellore

Science Mid Term Test - 2024 (Solved) | Standard X

FIRST MID TERM TEST - 2024

Standard X - SCIENCE (Solved Paper)

Original Question Paper & Solutions

Part - I: Choose the correct answer 10 x 1 = 10 Marks
1. The unit of 'g' is ms⁻², it can be also expressed as _______.
  1. cms⁻¹
  2. N kg⁻¹
  3. Nm² Kg⁻¹
  4. cm² s⁻²
Answer: b) N kg⁻¹ Explanation: The acceleration due to gravity is 'g'. According to Newton's second law of motion, Force (F) = mass (m) × acceleration (a). For an object near the Earth's surface, the force is weight (W), and acceleration is 'g'. So, W = m × g. Rearranging the formula for 'g', we get: $g = \frac{W}{m}$. The SI unit of force (Weight) is Newton (N) and the SI unit of mass is kilogram (kg). Therefore, the unit of 'g' can be expressed as N/kg or N kg⁻¹.
2. Power of lens is -4D, then its focal length is _______.
  1. 4 m
  2. -40 m
  3. -0.25 m
  4. -2.5 m
Answer: c) -0.25 m Explanation: The relationship between the power of a lens (P) and its focal length (f) is given by the formula: $P = \frac{1}{f(\text{in meters})}$. Given, Power (P) = -4 Dioptre (D). So, $f = \frac{1}{P} = \frac{1}{-4} = -0.25 \text{ m}$. The negative sign indicates that the lens is a concave lens.
3. 1 mole of any substance contains _______ molecules.
  1. 6.023 x 10²³
  2. 6.023 x 10⁻²³
  3. 3.0115 x 10²³
  4. 12.046 x 10²³
Answer: a) 6.023 x 10²³ Explanation: According to Avogadro's hypothesis, one mole of any substance (element or compound) contains a fixed number of particles (atoms, molecules, or ions). This number is known as Avogadro's number, which is approximately $6.023 \times 10^{23}$.
4. Neon shows zero electron affinity due to _______.
  1. stable arrangement of neutrons
  2. stable configurations of electrons
  3. reduced size
  4. Increased density
Answer: b) stable configurations of electrons Explanation: Neon (Ne) is a noble gas with the electronic configuration 1s²2s²2p⁶. Its outermost shell (n=2) is completely filled with 8 electrons (a stable octet). Due to this highly stable electron configuration, Neon has no tendency to accept an additional electron. Therefore, its electron affinity is zero.
5. Oxygen is produced at what point during photosynthesis?
  1. when ATP is converted to ADP
  2. when CO₂ is fixed
  3. when H₂O is split
  4. all of these
Answer: c) when H₂O is split Explanation: Oxygen is released as a byproduct during the light-dependent reactions of photosynthesis. This occurs through a process called photolysis, where light energy is used to split water molecules ($H_2O$) into hydrogen ions (H+), electrons (e-), and oxygen atoms ($O$). The oxygen atoms then combine to form molecular oxygen ($O_2$).
6. In Leech, locomotion is performed by _______.
  1. Anterior sucker
  2. Parapodia
  3. Setae
  4. Contraction and Relaxation of muscle
Answer: d) Contraction and Relaxation of muscle Explanation: While leeches use their anterior and posterior suckers for attachment, the actual movement is achieved by the coordinated contraction and relaxation of longitudinal and circular muscles in their body wall. This allows them to perform looping or crawling movements. Parapodia are found in Nereis (a polychaete worm) and Setae are found in earthworms.
7. Atrioventricular bundle was discovered by _______.
  1. William Harvey
  2. His
  3. Edward Jenner
  4. None of the above
Answer: b) His Explanation: The atrioventricular bundle, a crucial part of the heart's electrical conduction system, was discovered in 1893 by the Swiss cardiologist Wilhelm His Jr. It is often referred to as the "Bundle of His".
8. The wall of the human heart is made of _______.
  1. endocardium
  2. epicardium
  3. myocardium
  4. all the above
Answer: d) all the above Explanation: The wall of the human heart is composed of three distinct layers:
  • Epicardium: The outermost protective layer.
  • Myocardium: The middle, muscular layer responsible for pumping blood.
  • Endocardium: The innermost layer that lines the heart chambers and valves.
Therefore, all the listed options are components of the heart wall.
9. In Reflex action, the reflex arc is formed by _______.
  1. brain, spinal cord, muscle
  2. receptor, muscle, spinal cord
  3. muscle, receptor, brain
  4. receptor, spinal cord, muscle
Answer: d) receptor, spinal cord, muscle Explanation: A reflex arc is the neural pathway that a nerve impulse follows during a reflex action. The typical components in order are: Receptor (senses stimulus) → Sensory Neuron → Integration Center (e.g., Spinal Cord) → Motor Neuron → Effector (e.g., Muscle or Gland). Option (d) provides the most accurate simplified sequence: Receptor (start), Spinal Cord (processing), and Muscle (effector/end).
10. The eye defect "Presbyopia" can be corrected by _______.
  1. convex lens
  2. concave lens
  3. convex mirror
  4. bifocal lenses
Answer: d) bifocal lenses Explanation: Presbyopia is an age-related condition where the eye's lens loses its elasticity, making it difficult to focus on near objects. Often, people with presbyopia also have a pre-existing refractive error like myopia (nearsightedness) or hypermetropia (farsightedness). Bifocal lenses are used for correction. They have two different powers: the upper part for distant vision and the lower part (typically a convex segment) for near vision.
Part - II: Answer any 5 questions (Q.No.18 is compulsory) 5 x 2 = 10 Marks
11. Define Inertia. Give its classification.
Answer:

Inertia: It is the inherent property of a body to resist any change in its state of rest or state of uniform motion, unless it is acted upon by an external unbalanced force.

Classification of Inertia:
  • Inertia of Rest: The inability of a body to change its state of rest by itself. (e.g., When a bus starts suddenly, passengers tend to lean backward).
  • Inertia of Motion: The inability of a body to change its state of uniform motion by itself. (e.g., When a bus stops suddenly, passengers tend to lean forward).
  • Inertia of Direction: The inability of a body to change its direction of motion by itself. (e.g., When a car takes a sharp turn, passengers are pushed outwards).
12. State Snell's Law.
Answer:

Snell's Law (also known as the second law of refraction) states that:

"The ratio of the sine of the angle of incidence (i) to the sine of the angle of refraction (r) is constant for a given pair of media."

This constant is called the refractive index of the second medium with respect to the first medium ($\mu_2 / \mu_1$ or $n_{21}$).

Mathematically, it is expressed as: $$ \frac{\sin i}{\sin r} = \text{constant} = \mu $$ or $$ n_1 \sin i = n_2 \sin r $$ Where $n_1$ and $n_2$ are the refractive indices of the first and second media, respectively.
13. Differentiate Convex lens and Concave lens.
Answer:
Feature Convex Lens Concave Lens
Shape Thicker at the center and thinner at the edges. Thinner at the center and thicker at the edges.
Action on Light Converges a parallel beam of light to a point (focus). Also called a converging lens. Diverges a parallel beam of light, making it appear to come from a point (focus). Also called a diverging lens.
Focal Length Positive. Negative.
Image Formed Forms real, inverted images (mostly) and a virtual, erect image (in one case). Always forms a virtual, erect, and diminished image.
14. Give any two examples for hetero diatomic molecules.
Answer:

A hetero diatomic molecule is a molecule consisting of two different atoms chemically bonded together.

Two examples are:
  1. Hydrogen Chloride (HCl): Consists of one Hydrogen atom and one Chlorine atom.
  2. Carbon Monoxide (CO): Consists of one Carbon atom and one Oxygen atom.
15. Why should the light-dependent reaction occur before the light-independent reaction?
Answer: The light-dependent reaction must occur first because it produces the necessary energy and reducing power for the light-independent reaction.
  • During the light-dependent reaction, light energy is captured and used to produce ATP (energy currency) and NADPH (reducing power).
  • The light-independent reaction (Calvin Cycle) uses the ATP and NADPH generated in the first stage to fix carbon dioxide ($CO_2$) and synthesize glucose.
Without the products of the light-dependent reaction, the light-independent reaction cannot proceed.
16. State whether the statements are True or False. (Correct the false statement)
  1. Anaerobic respiration produces more ATP than Aerobic respiration.
  2. Plants lose water by the process of transpiration.
Answer:
  1. False.
    Correct statement: Aerobic respiration produces significantly more ATP (approximately 36-38 ATP molecules per glucose) than Anaerobic respiration (only 2 ATP molecules per glucose).
  2. True.
    (The original text has a typo "mater", which should be "water"). Plants lose water vapour from their surfaces, mainly through stomata on the leaves, in a process called transpiration.
17. Fill in the blanks.
  1. Water enters into the root hair cell through ______ membrane.
  2. _______ is the longest cell in our body.
Answer:
  1. Water enters into the root hair cell through the cell membrane. (The process is osmosis).
  2. Nerve cell (or Neuron) is the longest cell in our body.
18. (Compulsory) Calculate the velocity of a moving body of mass 5 kg whose linear momentum is 2.5 kg ms⁻¹.
Answer:

Given:

  • Mass (m) = 5 kg
  • Linear Momentum (p) = 2.5 kg ms⁻¹

Formula:

Linear momentum (p) is the product of mass (m) and velocity (v). $$ p = m \times v $$

Calculation:

To find the velocity (v), we rearrange the formula: $$ v = \frac{p}{m} $$ $$ v = \frac{2.5 \text{ kg ms}^{-1}}{5 \text{ kg}} $$ $$ v = 0.5 \text{ ms}^{-1} $$ The velocity of the moving body is 0.5 ms⁻¹.
Part - III: Answer briefly any 4 questions (Q.No.25 is compulsory) 4 x 4 = 16 Marks
19. List out any five properties of light.
Answer: Five properties of light are:
  1. Rectilinear Propagation: Light travels in a straight line in a homogenous medium.
  2. Reflection: Light bounces back when it strikes a polished surface (like a mirror).
  3. Refraction: Light bends when it passes from one medium to another.
  4. Dispersion: White light splits into its constituent colors (VIBGYOR) when it passes through a prism.
  5. Scattering: Light is deflected in various directions when it strikes very fine particles. This is why the sky appears blue.
20. A is a silvery white metal. A combines with O₂ to form B at 800°C. The alloy of A is used in making the aircraft. Find A and B. What is Rust?
Answer:

a) Finding A and B:

  • The clue "silvery white metal" whose "alloy... is used in making the aircraft" points to Aluminium (Al) due to its low density and high strength when alloyed.
  • Therefore, Metal A is Aluminium (Al).
  • Aluminium combines with Oxygen ($O_2$) at high temperatures to form Aluminium Oxide.
  • The balanced chemical reaction is: $4Al + 3O_2 \xrightarrow{800^\circ C} 2Al_2O_3$
  • Therefore, Compound B is Aluminium Oxide ($Al_2O_3$).

b) What is Rust?

Rust is the common term for a reddish-brown flaky substance that forms on iron or its alloys when they are exposed to oxygen and moisture for a prolonged period. Chemically, rust is hydrated iron(III) oxide.
The chemical formula for rust is Fe₂O₃·nH₂O.

21. Match the following:
  1. Amphicribal
  2. Cambium
  3. Amphivasal
  4. Xylem
  • Dracaena
  • Conduction of water
  • Fern
  • Secondary growth
Answer:
  1. Amphicribal - c) Fern (A vascular bundle where xylem is surrounded by phloem).
  2. Cambium - d) Secondary growth (A layer of meristematic tissue responsible for increase in girth).
  3. Amphivasal - a) Dracaena (A vascular bundle where phloem is surrounded by xylem).
  4. Xylem - b) Conduction of water (The water-conducting tissue in vascular plants).
22.
  1. Why is the Sinoatrial node called the pacemaker of heart?
  2. Draw the structure of a neuron and label the parts. (2 marks)
  3. Write the reaction of photosynthesis.
Answer:

a) Why is the Sinoatrial node called the pacemaker of the heart?

The Sinoatrial (SA) node is called the natural pacemaker of the heart because it has the unique ability to spontaneously generate electrical impulses at the fastest rate in the heart's conduction system. These impulses spread through the atria, causing them to contract, and then travel to the rest of the heart, setting the normal rhythm and rate of the heartbeat.

b) Structure of a neuron:

(A diagram of a neuron should be drawn here).

The key parts to be labeled are:
  • Dendrites: Branch-like extensions that receive signals from other neurons.
  • Cell Body (or Cyton/Soma): Contains the nucleus and other organelles.
  • Nucleus: Controls the cell's activities.
  • Axon: A long, slender projection that transmits electrical impulses away from the cell body.
  • Myelin Sheath: An insulating layer that covers the axon and speeds up signal transmission.
  • Nodes of Ranvier: Gaps in the myelin sheath.
  • Axon Terminal: The end of the axon, where signals are passed to other neurons or effector cells.

c) Reaction of photosynthesis:

The overall balanced chemical equation for photosynthesis is:

$$ 6CO_2 + 6H_2O \xrightarrow{\text{Sunlight, Chlorophyll}} C_6H_{12}O_6 + 6O_2 $$

Carbon Dioxide + Water $\xrightarrow{\text{Sunlight, Chlorophyll}}$ Glucose + Oxygen

23. Enumerate the functions of blood.
Answer: The main functions of blood can be categorized into three groups:
  1. Transport:
    • Transports oxygen from the lungs to the body tissues.
    • Transports carbon dioxide from the tissues back to the lungs.
    • Carries digested food (nutrients) from the small intestine to all body cells.
    • Transports metabolic wastes (like urea) to the kidneys for excretion.
    • Distributes hormones from endocrine glands to their target organs.
  2. Regulation:
    • Regulates body temperature by distributing heat throughout the body.
    • Maintains the body's pH balance (acid-base balance).
    • Regulates water balance by controlling the exchange of water between blood and tissues.
  3. Protection:
    • White blood cells (leukocytes) defend the body against pathogens (bacteria, viruses).
    • Platelets (thrombocytes) and clotting factors help in the coagulation of blood to prevent excessive blood loss from injuries.
24. Differentiate between Aerobic and Anaerobic respiration.
Answer:
Feature Aerobic Respiration Anaerobic Respiration
Oxygen Requirement Requires oxygen. Does not require oxygen.
Location in Cell Occurs in the cytoplasm and mitochondria. Occurs only in the cytoplasm.
Breakdown of Glucose Complete breakdown of glucose. Incomplete breakdown of glucose.
End Products Carbon dioxide ($CO_2$), water ($H_2O$), and ATP. Lactic acid (in animals) or ethanol and $CO_2$ (in yeast), and ATP.
Energy Yield (ATP) High (approx. 36-38 ATP per glucose molecule). Low (only 2 ATP per glucose molecule).
25. (Compulsory) Calculate the number of moles in:
  1. 27 g of Al
  2. 1.5 x 10²³ molecules of NH₄Cl
Answer:

i) 27 g of Al

  • Given mass = 27 g
  • Molar mass of Aluminium (Al) = 27 g/mol
  • Formula: Number of moles = $\frac{\text{Given mass}}{\text{Molar mass}}$
  • Calculation: Number of moles = $\frac{27 \text{ g}}{27 \text{ g/mol}}$ = 1 mole

ii) 1.5 x 10²³ molecules of NH₄Cl

  • Given number of molecules = $1.5 \times 10^{23}$
  • Avogadro's number ($N_A$) = $6.023 \times 10^{23}$ molecules/mol
  • Formula: Number of moles = $\frac{\text{Given number of molecules}}{\text{Avogadro's number}}$
  • Calculation: Number of moles = $\frac{1.5 \times 10^{23}}{6.023 \times 10^{23}}$ ≈ 0.249 moles (or approx. 0.25 moles)
Part - IV: Answer in detailed 2 x 7 = 14 Marks
26. 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 linear momentum of a body is directly proportional to the external force applied on the body, and this change takes place in the direction of the applied force."

Derivation of F = ma:

  1. Let 'm' be the mass of a moving body and 'u' be its initial velocity.
  2. Its initial momentum is $p_i = mu$.
  3. Let an external force 'F' act on the body for a time 't'. This changes the velocity of the body to 'v'.
  4. Its final momentum is $p_f = mv$.
  5. The change in momentum is $\Delta p = p_f - p_i = mv - mu = m(v-u)$.
  6. The rate of change of momentum is the change in momentum divided by time: $$ \text{Rate of change of momentum} = \frac{\Delta p}{t} = \frac{m(v-u)}{t} $$
  7. We know that acceleration (a) is the rate of change of velocity, so $a = \frac{v-u}{t}$.
  8. Substituting this into the previous equation, we get: $$ \text{Rate of change of momentum} = m \times a $$
  9. According to Newton's second law, the applied force (F) is directly proportional to the rate of change of momentum: $$ F \propto \text{Rate of change of momentum} $$ $$ F \propto ma $$
  10. To change the proportionality into an equation, we introduce a constant of proportionality, 'k': $$ F = kma $$
  11. The value of the constant 'k' is made equal to 1 by choosing the units of force appropriately. In the SI system, one unit of force (1 Newton) is defined as the force that produces an acceleration of 1 m/s² in a body of mass 1 kg.
    So, $1 \text{ N} = k \times (1 \text{ kg}) \times (1 \text{ m/s}^2)$. This gives $k=1$.
  12. Therefore, the equation for force becomes:
$$ \mathbf{F = ma} $$

This is the mathematical expression for force derived from Newton's second law of motion.

(OR)
i) Give the salient features of modern atomic theory. (5 marks)
ii) Assertion and Reason - (2 marks)
Assertion: An uncleaned copper vessel is covered with greenish layer.
Reason: Copper is not attacked by Alkali.
  1. A is wrong, R is correct
  2. A and R are correct, R does not explain A
Answer:

i) Salient Features of Modern Atomic Theory:

  1. Atom is no longer indivisible: The atom is composed of subatomic particles: protons, neutrons, and electrons.
  2. Isotopes and Isobars: Atoms of the same element may have different atomic masses (isotopes, e.g., ¹²C, ¹⁴C). Atoms of different elements may have the same mass number (isobars, e.g., ⁴⁰Ar, ⁴⁰K, ⁴⁰Ca).
  3. Mass-Energy Equivalence: Matter can be converted into energy and vice-versa, according to Einstein's equation, $E = mc²$. The mass of an atom can be converted into energy.
  4. Dual Nature of Electron: Electrons have both particle-like and wave-like properties.
  5. Quantization of Energy: The energy of electrons in an atom is quantized. They can only exist in specific energy levels or orbitals, not in between them.
  6. Orbitals: The modern theory replaces the concept of fixed orbits with orbitals, which are three-dimensional regions around the nucleus where the probability of finding an electron is maximum.
  7. Atoms are not always conserved: In nuclear reactions (like fission and fusion), atoms of one element can be transformed into atoms of another element.

ii) Assertion and Reason:

  • Analysis of Assertion (A): "An uncleaned copper vessel is covered with greenish layer." This statement is True. Copper reacts slowly with carbon dioxide, water, and oxygen in the air to form a green layer of basic copper carbonate ($CuCO_3 \cdot Cu(OH)_2$).
  • Analysis of Reason (R): "Copper is not attacked by Alkali." This statement is also True. Copper is a relatively unreactive metal and does not react with alkalis like sodium hydroxide.
  • Evaluating the link: Does the reason explain the assertion? No. The green layer is formed due to a reaction with acidic gases and moisture in the air, not because of its non-reactivity with alkalis. The reason is a correct fact about copper, but it is not the explanation for the assertion.
Correct Option: b) A and R are correct, R does not explain A
27. Describe and name three stages of cellular respiration that aerobic organisms use to obtain energy from glucose.
Answer:

Aerobic cellular respiration is the process by which organisms use oxygen to break down glucose completely to produce a large amount of ATP. It occurs in three main stages:

1. Glycolysis

  • Location: Cytoplasm of the cell.
  • Process: This is an anaerobic stage (does not require oxygen). One molecule of glucose (a 6-carbon sugar) is broken down into two molecules of pyruvic acid (a 3-carbon compound).
  • Products:
    • 2 molecules of Pyruvic Acid
    • A net gain of 2 ATP molecules
    • 2 molecules of NADH (an electron carrier)

2. Krebs Cycle (or Citric Acid Cycle)

  • Location: Mitochondrial matrix.
  • Process: This is an aerobic stage. Before entering the cycle, each pyruvic acid molecule is converted into Acetyl-CoA, releasing one molecule of $CO_2$. The Acetyl-CoA then enters the Krebs Cycle, a series of enzyme-catalyzed reactions that completely oxidizes it.
  • Products (per two turns of the cycle, from one glucose molecule):
    • 4 molecules of Carbon Dioxide ($CO_2$)
    • 2 molecules of ATP
    • 6 molecules of NADH
    • 2 molecules of FADH₂ (another electron carrier)

3. Electron Transport Chain (ETC) and Oxidative Phosphorylation

  • Location: Inner mitochondrial membrane.
  • Process: This is the final and highest ATP-yielding stage. The high-energy electrons from NADH and FADH₂ (produced in glycolysis and the Krebs cycle) are passed down a series of protein complexes (the electron transport chain). As electrons move, energy is released and used to pump protons (H⁺) across the membrane, creating a proton gradient. Oxygen acts as the final electron acceptor, combining with protons and electrons to form water ($H_2O$). The flow of protons back across the membrane through an enzyme called ATP synthase drives the synthesis of a large amount of ATP (Oxidative Phosphorylation).
  • Products:
    • Approximately 32-34 molecules of ATP
    • Water ($H_2O$)
(OR)
i) List out the parasitic adaptations in Leech. (5 marks)
ii) Define 'Reflex arc'.
Answer:

i) Parasitic Adaptations in Leech:

Leeches exhibit several adaptations for their parasitic (sanguivorous or blood-sucking) mode of life:

  1. Suckers for Attachment: They have an anterior and a posterior sucker. The posterior sucker is used for strong attachment to the host, while the anterior sucker surrounds the mouth and helps in feeding.
  2. Painless Bite: The saliva of the leech contains an anaesthetic substance, which makes the bite painless. This prevents the host from noticing the leech and removing it.
  3. Anticoagulant Secretion: The salivary glands secrete a powerful anticoagulant called hirudin. Hirudin prevents the host's blood from clotting, ensuring a continuous flow of blood for the leech to feed on.
  4. Jaws and Teeth: The mouth, located in the anterior sucker, is equipped with three jaws bearing tiny, sharp teeth. These create a characteristic Y-shaped incision on the host's skin.
  5. Large Crop for Blood Storage: The alimentary canal has a very large crop with many diverticula (pouches). This allows the leech to store a large volume of blood, often several times its own body weight, from a single meal. This stored blood is digested very slowly, enabling the leech to survive for many months without another meal.
  6. Body Shape: The dorso-ventrally flattened and elongated body is suited for crawling and swimming to find a host.

ii) Define 'Reflex arc':

A reflex arc is the neural pathway that mediates a reflex action. It includes a sensory receptor, a sensory neuron, an integration center (like the spinal cord), a motor neuron, and an effector (a muscle or gland). It is the path along which nerve impulses are carried from a stimulus at a receptor to the response at an effector, typically bypassing conscious thought for a rapid, involuntary response.