🔬 9th Science - 1st Mid Term Test 2025 - Original Question Paper | Tirunelveli District- (English Medium) Answer Key

Standard 9 Science - First Mid Term Test 2025 - Solved Paper

Tirunelveli District

Common First Mid Term Test - 2025

Standard 9 - SCIENCE

Time: 1.30 Hrs. | Marks: 50

Question Paper

PART - I 10 x 1 = 10
I. Choose the correct answer:
1) 1 Metric ton is equal to.
  1. 100 quintals
  2. 10 quintals
  3. 1/10 quintals
  4. 1/100 quintals
2) Rulers, measuring tapes and metre scales are used to measure
  1. mass
  2. weight
  3. time
  4. length
3) The centrifugal force is
  1. a real force
  2. the force of reaction of centripetal force
  3. a virtual force
  4. directed towards the centre
4) ________ is essential to perform separation by solvent extraction method.
  1. Separating funnel
  2. Filter paper
  3. Centrifuge machine
  4. Sieve
5) The separation of denser particles from lighter particles done by rotation at high speed is called
  1. filtration
  2. sedimentation
  3. decantation
  4. centrifugation
6) The term nucleons refer to
  1. protons and electrons
  2. only neutrons
  3. electrons and neutrons
  4. protons and neutrons
7) The correct electronic configuration of potassium is
  1. 2, 8, 9
  2. 2, 8, 1
  3. 2, 8, 8, 1
  4. 2, 8, 8, 3
8) Mesoglea is present in
  1. Porifera
  2. Coelenterata
  3. Annelida
  4. Arthropoda
9) Excretory organ of tape worm is
  1. flame cells
  2. nephridia
  3. body surface
  4. solenocytes
10) The animal without skull is
  1. Acrania
  2. Acephalia
  3. Apteria
  4. Acoelomate
PART - II 7 x 2 = 14
Write any seven of the following:
11) Define least count of any device.
12) Differentiate mass and weight.
13) Define velocity.
14) What is meant by uniform circular motion? Give two examples of uniform circular motion.
15) A few drops of 'Dettol' when added to water the mixture turns turbid - why?
16) True or False. If false correct the statement:
  1. Liquid - Liquid colloids are called gel.
  2. Buttermilk is an example of heterogeneous mixture.
17) Define taxonomy.
18) Why are frogs said to be amphibians?
19) Match the following:
  1. Coelenterata - Snail
  2. Platyhelminthus - Starfish
  3. Echinodermata - Tapeworm
  4. Mollusca - Hydra
20) Write the electronic configuration of K and Cl.
PART - III 3 x 4 = 12
Answer any three of the following:
21) Write the rules that are followed in writing the symbols of units in SI system.
22) A racing car has a uniform acceleration of 4ms⁻². What distance it covers in 10s after the start?
23) How are Homogeneous solutions different from Heterogeneous solutions? Explain with examples.
24) Draw the structure of oxygen and sulphur atoms.
25) Outline the flow charts of Phylum Chordata.
PART - IV 2 x 7 = 14
Answer in detail:
26) How will you find the thickness of a one rupee coin?
(OR)
Explain different types of motion.
27) Explain Tyndall effect and Brownian movement with suitable diagram.
(OR)
Give an account on Phylum Arthropoda.

Solutions

PART - I: Solutions 10 x 1 = 10
  1. Answer: b) 10 quintals
    Explanation: 1 Metric ton = 1000 kg, and 1 quintal = 100 kg. Therefore, 1 Metric ton = 1000 kg / 100 kg/quintal = 10 quintals.
  2. Answer: d) length
    Explanation: Rulers, measuring tapes, and metre scales are standard instruments designed to measure distance or length.
  3. Answer: c) a virtual force
    Explanation: Centrifugal force is an apparent or "pseudo" force that is perceived in a rotating frame of reference. It is not a real force resulting from an interaction but a consequence of inertia.
  4. Answer: a) Separating funnel
    Explanation: A separating funnel is used in solvent extraction to separate immiscible liquids (liquids that do not mix, like oil and water) based on their different densities.
  5. Answer: d) centrifugation
    Explanation: Centrifugation is a technique that uses centrifugal force (generated by high-speed rotation) to separate components of a mixture with different densities, such as separating cream from milk.
  6. Answer: d) protons and neutrons
    Explanation: Nucleons are the subatomic particles found in the atomic nucleus. These are the protons and neutrons.
  7. Answer: c) 2, 8, 8, 1
    Explanation: Potassium (K) has an atomic number of 19. The electrons fill the shells according to the rules: K-shell (2), L-shell (8), M-shell (8), N-shell (1).
  8. Answer: b) Coelenterata
    Explanation: Mesoglea is the non-cellular, jelly-like substance found between the two epithelial cell layers (ectoderm and endoderm) in the bodies of coelenterates (like jellyfish and hydra).
  9. Answer: a) flame cells
    Explanation: Flame cells are specialized excretory cells found in the simplest freshwater invertebrates, including flatworms (Phylum Platyhelminthes) like the tapeworm.
  10. Answer: a) Acrania
    Explanation: Acrania is a group of chordates that lack a true skull or cranium. Cephalochordates (like Amphioxus) are examples.
PART - II: Solutions 7 x 2 = 14
11) Define least count of any device.
Answer: The least count of a measuring instrument is the smallest and most accurate value that can be measured by that instrument. For example, the least count of a standard metre scale is 1 mm.
12) Differentiate mass and weight.
Answer:
Mass Weight
It is the amount of matter contained in a body. It is the gravitational force exerted on a body.
It is a scalar quantity. It is a vector quantity.
Its SI unit is kilogram (kg). Its SI unit is newton (N).
It is constant everywhere. It varies from place to place depending on gravity.
13) Define velocity.
Answer: Velocity is defined as the rate of change of displacement of an object. It is a vector quantity, meaning it has both magnitude (speed) and direction.

Formula: Velocity = Displacement / Time

The SI unit for velocity is metres per second (m/s).
14) What is meant by uniform circular motion? Give two examples of uniform circular motion.
Answer:

Uniform Circular Motion: When an object moves in a circular path with a constant speed, its motion is called uniform circular motion. Although the speed is constant, the direction of velocity changes continuously, which means the object is constantly accelerating (this is called centripetal acceleration).

Examples:

  1. The revolution of the Earth around the Sun (approximately).
  2. The motion of the tip of the second's hand of a clock.
15) A few drops of 'Dettol' when added to water the mixture turns turbid - why?
Answer: Dettol is an antiseptic liquid which is an emulsion of oil (chloroxylenol) in a soap-water base. When Dettol is added to water, the soap base dissolves and the oil droplets disperse throughout the water, forming a colloidal solution. These tiny oil droplets are large enough to scatter light, causing the mixture to appear cloudy or turbid. This light-scattering phenomenon is known as the Tyndall effect.
16) True or False. If false correct the statement:
  1. Liquid - Liquid colloids are called gel.
  2. Buttermilk is an example of heterogeneous mixture.
Answer:
  1. False.
    Correct Statement: Liquid-Liquid colloids are called emulsions. (A gel is a colloid where a liquid is dispersed in a solid medium).
  2. True.
    Buttermilk is a colloid, which is a type of heterogeneous mixture where fat globules are dispersed in water. The components are not uniformly distributed.
17) Define taxonomy.
Answer: Taxonomy is the branch of biology that deals with the principles and procedures of identification, classification, and nomenclature (naming) of organisms. It provides a systematic framework for organizing the diversity of life on Earth.
18) Why are frogs said to be amphibians?
Answer: Frogs are called amphibians (from Greek 'amphi' meaning dual and 'bios' meaning life) because they lead a dual life.
  • They live in water during their larval stage (as tadpoles), respiring through gills.
  • As adults, they live on land and respire using lungs, but they must return to water for breeding. Their skin is also moist and helps in cutaneous respiration.
19) Match the following:
Answer:
  • a) Coelenterata   -   Hydra
  • b) Platyhelminthus   -   Tapeworm
  • c) Echinodermata   -   Starfish
  • d) Mollusca   -   Snail
20) Write the electronic configuration of K and Cl.
Answer:
  • Potassium (K): Atomic number is 19.
    • Electronic configuration: 2, 8, 8, 1
    • (K-shell: 2, L-shell: 8, M-shell: 8, N-shell: 1)
  • Chlorine (Cl): Atomic number is 17.
    • Electronic configuration: 2, 8, 7
    • (K-shell: 2, L-shell: 8, M-shell: 7)
PART - III: Solutions 3 x 4 = 12
21) Write the rules that are followed in writing the symbols of units in SI system.
Answer: The rules for writing symbols of units in the SI system are:
  1. Case of Letters: Symbols for units are written in lowercase letters (e.g., m for metre, kg for kilogram, s for second). However, if the unit is named after a person, the symbol is an uppercase letter (e.g., N for newton, Pa for pascal, W for watt).
  2. No Plurals: Symbols are never written in plural form. For example, we write '10 kg', not '10 kgs'.
  3. No Full Stops: Symbols are not followed by a full stop or other punctuation marks, unless it is at the end of a sentence.
  4. Spacing: A space is always left between the numerical value and the unit symbol (e.g., '25 m', not '25m').
  5. Division of Units: For compound units formed by division, a solidus (/) or a negative exponent is used (e.g., m/s or ms⁻¹).
22) A racing car has a uniform acceleration of 4ms⁻². What distance it covers in 10s after the start?
Answer: We can solve this using the second equation of motion.

Given:

  • Initial velocity (u) = 0 m/s (since the car starts from rest)
  • Acceleration (a) = 4 ms⁻²
  • Time (t) = 10 s

To find: Distance (s)

Formula:

$$ s = ut + \frac{1}{2}at^2 $$

Calculation:

$$ s = (0 \times 10) + \frac{1}{2} \times 4 \times (10)^2 $$ $$ s = 0 + \frac{1}{2} \times 4 \times 100 $$ $$ s = 2 \times 100 $$ $$ s = 200 \, \text{m} $$ The racing car covers a distance of 200 metres in 10 seconds.
23) How are Homogeneous solutions different from Heterogeneous solutions? Explain with examples.
Answer:
Feature Homogeneous Mixture Heterogeneous Mixture
Composition Has a uniform composition and properties throughout the mixture. Has a non-uniform composition and varying properties.
Visibility of Particles The individual components are not visible to the naked eye. The individual components can often be seen with the naked eye.
Phases Consists of only one phase (e.g., solid, liquid, or gas). Consists of two or more distinct phases.
Boundary of Separation There is no visible boundary of separation between components. There are visible boundaries of separation between components.
Light Scattering Does not scatter a beam of light (does not show Tyndall effect). Usually scatters a beam of light (shows Tyndall effect). Eg: colloids and suspensions.
Examples Salt dissolved in water, sugar solution, air, alloys like brass. Sand in water, oil and water, mixture of salt and pepper, buttermilk.
24) Draw the structure of oxygen and sulphur atoms.
Answer:

The structure of atoms is represented by the Bohr model, showing the nucleus and electron shells.

1. Oxygen (O) Atom:

  • Atomic Number (Z) = 8
  • Number of Protons = 8
  • Number of Electrons = 8
  • Number of Neutrons = Mass Number - Atomic Number = 16 - 8 = 8
  • Electronic Configuration: 2, 6
Bohr Model of Oxygen Atom

Structure of Oxygen Atom

2. Sulphur (S) Atom:

  • Atomic Number (Z) = 16
  • Number of Protons = 16
  • Number of Electrons = 16
  • Number of Neutrons = Mass Number - Atomic Number = 32 - 16 = 16
  • Electronic Configuration: 2, 8, 6
Bohr Model of Sulphur Atom

Structure of Sulphur Atom

25) Outline the flow charts of Phylum Chordata.
Answer:

Phylum Chordata is classified based on the presence or absence of a cranium (skull) and vertebral column.

Phylum Chordata
└─┬─ Subphylum: Urochordata (Tunicates)
  ├─ Subphylum: Cephalochordata (Lancelets)
  └─ Subphylum: Vertebrata (Craniata)
     └─┬─ Division: Agnatha (Jawless vertebrates)
       │  └─ Class: Cyclostomata (Lampreys, Hagfish)
       └─ Division: Gnathostomata (Jawed vertebrates)
          └─┬─ Superclass: Pisces (Fishes)
            │  ├─ Class: Chondrichthyes (Cartilaginous fish)
            │  └─ Class: Osteichthyes (Bony fish)
            └─ Superclass: Tetrapoda (Four-limbed vertebrates)
                ├─ Class: Amphibia (Frogs, Salamanders)
                ├─ Class: Reptilia (Lizards, Snakes, Turtles)
                ├─ Class: Aves (Birds)
                └─ Class: Mammalia (Mammals)
PART - IV: Solutions 2 x 7 = 14
26) How will you find the thickness of a one rupee coin?
Answer: The thickness of a single coin is too small to be measured accurately with a standard metre scale. We can find it using an indirect method by measuring a stack of coins.

Aim: To find the thickness of a one rupee coin.

Apparatus Required: A set of identical one rupee coins (e.g., 10 or 20 coins) and a metre scale.

Procedure:

  1. Collect about 10 or 20 identical one rupee coins. Let the number of coins be 'n'. For this example, let's take n = 10.
  2. Stack the coins one on top of the other to form a neat, vertical cylinder on a flat surface.
  3. Place a metre scale vertically next to the stack of coins. Ensure the zero mark of the scale aligns with the base of the stack.
  4. Measure the total height of the stack of coins. Let this height be 'h'. Record the reading carefully.
  5. To ensure accuracy, repeat the measurement at least three times and calculate the average height.
  6. Calculate the thickness of a single coin using the formula:

    Thickness of one coin = Total height (h) / Number of coins (n)

Example Calculation:

  • Number of coins (n) = 10
  • Let the measured total height of the stack (h) be 1.5 cm (or 15 mm).
  • Thickness of one coin = 1.5 cm / 10 = 0.15 cm.
  • Or, Thickness = 15 mm / 10 = 1.5 mm.

By measuring a larger quantity and then dividing, we can significantly reduce the measurement error and obtain a more accurate value for a small dimension.

(OR)
Explain different types of motion.
Answer: Motion is the change in the position of an object with respect to its surroundings over time. Based on the path taken by the object, motion can be classified into several types:
  1. Linear Motion (or Rectilinear Motion):

    This is the motion of an object along a straight line. All parts of the body move the same distance in the same interval of time.

    • Example: A car moving on a straight road, an apple falling from a tree.
  2. Circular Motion:

    This is the motion of an object along a circular path. The distance of the object from the center of the circle remains constant.

    • Example: The revolution of the Earth around the Sun, a stone tied to a string being whirled in a circle.
  3. Rotatory Motion:

    This is the motion of a body about a fixed axis passing through the body itself. Different particles of the body move different distances in the same interval of time.

    • Example: A spinning top, the rotation of the Earth on its axis, a rotating fan.
  4. Oscillatory Motion:

    This is the repetitive to-and-fro motion of an object about a mean or equilibrium position.

    • Example: The swinging of a pendulum, the vibration of a guitar string.
  5. Random Motion:

    This is a type of motion that is irregular and unpredictable. The object moves without any specific path or direction.

    • Example: The movement of a dust particle in the air, the flight of a housefly.
27) Explain Tyndall effect and Brownian movement with suitable diagram.
Answer:

Tyndall Effect:

The Tyndall effect is the phenomenon in which a beam of light is scattered by particles in a colloid or a very fine suspension, making the path of the light beam visible. True solutions do not exhibit the Tyndall effect because their constituent particles are too small to scatter light.

  • Explanation: When a beam of light passes through a colloidal solution, the colloidal particles, which are larger than the particles of a true solution, scatter the light in all directions. This scattered light enters our eyes, and we can see the path of the beam.
  • Examples: The path of sunlight becoming visible through a dusty room or a forest canopy; the visibility of a projector beam in a dark cinema hall.
Diagram of Tyndall Effect

Tyndall Effect: Light path is invisible in a true solution but visible in a colloid.

Brownian Movement:

Brownian movement is the random, erratic, zigzag motion of microscopic particles suspended in a fluid (a liquid or a gas). This movement is caused by the continuous and random collisions of the suspended particles with the fast-moving molecules of the surrounding fluid.

  • Explanation: The molecules of the liquid or gas are in constant, random motion. They bombard the larger suspended particles from all sides. The bombardment is uneven at any given instant, resulting in a net force that pushes the particle in a random direction. This process repeats continuously, causing the particle to move in a jerky, unpredictable path.
  • Significance: It provides direct evidence for the existence and random motion of atoms and molecules (Kinetic Theory of Matter).
Diagram of Brownian Movement

Brownian Movement: A suspended particle moving in a random, zigzag path.

(OR)
Give an account on Phylum Arthropoda.
Answer:

Phylum Arthropoda (from Greek, 'arthron' = joint, 'podos' = foot) is the largest phylum in the animal kingdom, including insects, spiders, crabs, and centipedes. They are characterized by their jointed limbs and a hard exoskeleton.

General Characteristics of Phylum Arthropoda:

  1. Symmetry and Body Organization: They are bilaterally symmetrical, triploblastic (have three germ layers), and have an organ-system level of organization.
  2. Body Segmentation: The body is segmented and typically divided into three distinct regions: a head, a thorax, and an abdomen. In some cases, the head and thorax are fused to form a cephalothorax (e.g., in prawns and spiders).
  3. Exoskeleton: The entire body is covered by a tough, non-living, chitinous exoskeleton. This provides protection and support but must be shed periodically through a process called moulting or ecdysis to allow for growth.
  4. Jointed Appendages: They possess paired, jointed appendages (legs, antennae, mouthparts) that are modified for various functions like locomotion, feeding, and sensory reception.
  5. Circulatory System: They have an open circulatory system. The blood, called haemolymph, is pumped by a dorsal heart into the body cavity (haemocoel), where it directly bathes the tissues.
  6. Respiratory System: Respiration occurs through various organs depending on the habitat:
    • Gills: in aquatic arthropods (e.g., prawns).
    • Book lungs: in terrestrial forms like scorpions and spiders.
    • Tracheal system: a network of air tubes in insects and myriapods.
  7. Excretory System: Excretion is carried out by Malpighian tubules (in insects) or green glands / coxal glands (in crustaceans like prawns).
  8. Nervous System: A well-developed nervous system is present, consisting of a brain and a ventral nerve cord. They have sensory organs like antennae, simple or compound eyes, and statocysts (for balance).
  9. Reproduction: They are mostly dioecious (sexes are separate) and exhibit internal fertilization. Development can be direct or indirect (involving a larval stage).
  10. Examples: Prawn, Crab, Cockroach, Butterfly, Millipede, Centipede, Spider, Scorpion.