Class 8 Science Half Yearly Exam Paper 2025 With Answer

Preparing for exams becomes easier when you have access to solved question papers. Here we provide the Class 8 Science Half Yearly Exam Paper 2025 with complete answers, designed according to the latest NCERT syllabus. The solved paper includes Section A (2 marks questions), Section B (3 marks questions) and Section C (4 marks long answers) with neat explanations.

Class 8 Science Half Yearly Exam Paper 2025 With Answer

This resource will help students:

  • Revise important concepts from Physics, Chemistry and Biology.
  • Practice exam-style questions with stepwise answers.
  • Improve writing skills for short and long answer questions.
  • Score better in their Half Yearly and Final exams.

Whether you are looking for All Class NCERT Solutions or focused help with Class 8 Science, this solved paper is a reliable guide for exam preparation.

Class 8 Science Half Yearly Exam Paper 2025 — Solved Paper

Class 8 Science Half Yearly Exam Paper 2025

SECTION A (2 × 10 = 20 marks)

(Short, 2-mark answers)

1. Define force. Give one example.
A force is a push or a pull that can change the state of motion or shape of an object.
Example: A person pushing a box to move it.

2. Why is friction called a necessary evil?
Friction is called a necessary evil because:

  • Necessary: it helps walking, writing, and braking (gives traction).
  • Evil: it causes wear and tear and wastes energy as heat.

3. Write the laws of reflection of light.
Laws of reflection:

  1. The incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.
  2. The angle of incidence equals the angle of reflection (∠i = ∠r).

4. Write four characteristics of a plane mirror.

  1. Produces virtual images.
  2. Image is erect.
  3. Image size = object size (magnification = 1).
  4. Image distance = object distance (behind the mirror).

OR — Distinguish between real and virtual image
Real image: formed by actual convergence of rays, can be obtained on a screen, inverted.
Virtual image: formed by apparent divergence, cannot be obtained on a screen, erect.

5. Name two endangered and extinct species of animals.
Endangered: Tiger, One-horned rhinoceros.
Extinct: Dodo, Passenger pigeon.

6. What is deforestation? Mention two effects.
Deforestation: Large-scale removal of forests/trees.
Effects: Soil erosion; loss of habitat leading to species extinction; increase in atmospheric CO₂.

7. What are plastids? Name their types.
Plastids are cell organelles involved in synthesis and storage of food. Types: Chloroplasts, Chromoplasts, Leucoplasts (amyloplasts).

8. Differentiate between prokaryotic and eukaryotic cells (any two points).

  1. Nucleus: Prokaryotes — no true nucleus; Eukaryotes — true nucleus present.
  2. Organelles: Prokaryotes — lack membrane-bound organelles; Eukaryotes — have membrane-bound organelles.

9. Mention two differences between metals and non-metals based on chemical properties.
Ans: Differences between metals and non-metals (based on chemical properties):

  1. Metals react with oxygen to form basic oxides.
    Example: 2Mg + O2 → 2MgO (Magnesium oxide is basic)

Non-metals react with oxygen to form acidic oxides.
Example: S + O2 → SO2 (Sulphur dioxide is acidic)

  • Metals react with acids to produce hydrogen gas.
    Example: Zn + 2HCl → ZnCl2 + H2

Non-metals generally do not react with acids to give hydrogen gas.

10. What is dispersion? Explain with the help of a simple diagram of a prism.
Dispersion: Splitting of white light into its constituent colors due to different refraction for different wavelengths.

dispersion of light

OR — What is Myopia? Write its causes and correction with diagram.

Ans:

myopia


Myopia, or nearsightedness, is a vision condition where you can see close objects clearly, but distant objects appear blurry.

  • Cause: It is most often caused by the eyeball being too long or the cornea (the front surface of the eye) being too curved, which causes light to focus in front of the retina instead of on it.
  • Correction: Myopia is corrected using a concave (diverging) lens. This lens spreads out the light rays before they enter the eye, allowing them to focus directly on the retina.

SECTION B (3 × 8 = 24 marks)

(Answers ~3 marks each — include steps/points; for diagram answers, describe key labels)

11. With the help of an activity show that frictional force is dependent on the nature of the two surfaces. Explain advantages and disadvantages of friction.

Activity:

  • Place a wooden block on a table. Measure force needed to pull it with a spring balance.
  • Put sandpaper under the block (rough surface) and measure force again — greater force.
  • Now put a smooth plastic sheet (smoother surface) and measure — less force.
    Conclusion: Friction depends on nature of surfaces (rougher → more friction).

Advantages of friction (3 points):

  1. Enables walking — prevents slipping.
  2. Helps braking of vehicles.
  3. Allows writing with a pen/pencil.

Disadvantages of friction (3 points):

  1. Causes wear and tear of machine parts.
  2. Wastes energy as heat (reduces efficiency).
  3. Increases fuel consumption in vehicles.

12. How to draw Ray diagrams for Reflection of light explain with construction.

Ans:

reflection of light in plane mirror

Construction steps (plane mirror):

  1. Draw the object (e.g., an arrow) and the plane mirror.
  2. From the tip of the object, draw two light rays (incident rays) that strike the mirror at different points.
  3. For each incident ray, draw the normal (a line perpendicular to the mirror’s surface) at the point of incidence.
  4. Draw the reflected rays, ensuring that the angle of reflection equals the angle of incidence for each ray.
  5. Extend the reflected rays backward (as dashed lines) behind the mirror. The point where these dashed lines meet is the location of the virtual image.

13. Explain how wildlife sanctuaries help in conservation of animals.
Ways sanctuaries help:

  1. Provide protected habitat where animals are safe from hunting and habitat loss.
  2. Promote breeding and recovery of endangered species.
  3. Help maintain ecological balance by protecting predator–prey relationships.
  4. Serve as research and education centers to raise awareness.
  5. Restrict human activities (logging, poaching) ensuring biodiversity conservation.

14. Write short notes on:
a) Endangered species — Species with populations declining to levels that risk extinction if threats continue (e.g., tiger). Conservation measures: protected areas, breeding programs, legal protection.
b) Biosphere reserves — Large protected areas with core (strict protection), buffer (limited activities) and transition zones (sustainable use); aim to conserve biodiversity and permit research, education and sustainable development.

15. Draw a labelled diagram of an animal cell and plant cell for comparison.


 
Animal cell: cell membrane, nucleus, cytoplasm, mitochondria, ribosomes, vacuole (small), lysosomes.
Plant cell: cell wall (outer), cell membrane, large central vacuole, chloroplasts, nucleus, mitochondria.
Key difference: cell wall and chloroplasts present in plant cell; large central vacuole in plant cell.

16. Explain the chemical properties of metals and non-metals (any three each).

Metals (three properties):

  1. React with oxygen to form basic oxides (e.g., 2Mg + O₂ → 2MgO).
  2. React with water (some) to form hydroxides and hydrogen (e.g., 2Na + 2H₂O → 2NaOH + H₂).
  3. React with acids to produce salt and hydrogen (e.g., Zn + 2HCl → ZnCl₂ + H₂).

Non-metals (three properties):

  1. React with oxygen to form acidic oxides (e.g., S + O₂ → SO₂).
  2. Do not generally react with acids to give hydrogen.
  3. Gain electrons to form anions; react with metals to form ionic compounds (e.g., Na + Cl → NaCl).

17. Describe the role of microorganisms in food industry with examples.
Roles:

  1. Fermentation: Yeast in bread making (CO₂ makes dough rise) and in alcohol production (ethanol).
  2. Dairy products: Bacteria (Lactobacillus) in curd, yogurt, cheese formation.
  3. Food processing: Molds and bacteria used in production of soy sauce, vinegar.
  4. Probiotics: Microbes beneficial for gut health in fermented foods.

18. Give reasons:
a) Friction produces heat.
Rubbing causes microscopic rough surfaces to interlock and move, converting kinetic energy into thermal energy due to molecular interactions — observed as heat.

b) Concave mirror is used by dentists.
Concave mirrors produce magnified, erect images of nearby objects when object is within focal length — helps dentists see a magnified view of teeth.

SECTION C (4 × 4 = 16 marks)

(4-mark answers — more detailed with steps/diagrams described)

19. Explain with examples the different types of friction.

Types of friction: (define and give example for each)

  1. Static friction — friction that acts on objects at rest relative to each other; it prevents motion up to a limiting value.
    • Example: A stationary book on a table does not move until a sufficient push overcomes static friction.
  2. Sliding (kinetic) friction — friction when two surfaces slide over each other; usually lower than static friction.
    • Example: A block sliding down an inclined plane.
  3. Rolling friction — friction when an object rolls over a surface; much smaller than sliding friction.
    • Example: Wheels of a bicycle on road.
  4. Fluid friction (viscous drag) — friction experienced by objects moving through fluids (liquids/gases).
    • Example: A swimmer moving through water or a skydiver falling through air.

Explain briefly why values differ: due to contact area, interlocking of asperities, and relative motion; lubrication reduces sliding friction to rolling or fluid type.

OR — Draw a labelled diagram of Human eye and explain its different parts.

Ans: The human eye is like a camera, using light to create images that the brain interprets. Its main parts are:

  • Cornea: The clear front window that first focuses light.
  • Iris: The colored part that controls the size of the pupil.
  • Pupil: The black opening that lets light into the eye.
  • Lens: A flexible part behind the iris that fine-tunes focus.
  • Retina: The light-sensitive tissue at the back of the eye that contains photoreceptors (rods for low-light vision and cones for color vision).
  • Optic Nerve: The “cable” that transmits the signals from the retina to the brain.
Human eye anatomy

20. Define Conservation. Explain the role of NGOs in conservation of biodiversity in India.

Conservation: Protection, preservation and wise management of natural resources and biodiversity to maintain ecological balance and ensure sustainable use.

Role of NGOs:

  1. Awareness & education: Conduct campaigns, workshops, and school programs to sensitize people about conservation.
  2. On-ground conservation: Run projects for habitat restoration, anti-poaching patrols, rescue and rehabilitation of wildlife.
  3. Community involvement: Work with local communities to develop eco-friendly livelihoods, reducing dependence on destructive practices.
  4. Policy & advocacy: Lobby for stronger conservation laws, protected area designations, and better enforcement.
  5. Research & monitoring: Carry out biodiversity surveys, long-term monitoring and scientific research to guide conservation actions.
  6. Fundraising & partnerships: Mobilize funds and collaborate with governments, international bodies and local stakeholders.

Example: NGOs help run reserve management programs, create community reserves, and operate rescue centers for injured wildlife.

21. Explain the role of microorganisms in:
a) Medicine

  • Production of antibiotics: Penicillium fungus produces penicillin.
  • Vaccines: Some vaccines use weakened microbes or their components.
  • Production of enzymes and drugs by fermentation (e.g., insulin via genetically engineered bacteria).
    b) Agriculture
  • Nitrogen fixation: Rhizobium bacteria in legume root nodules convert atmospheric N₂ into usable forms for plants.
  • Decomposition: Microbes decompose organic matter to form humus, improving soil fertility.
  • Biofertilisers and biopesticides: Use of beneficial microbes to enhance crop yield and control pests (e.g., Bacillus thuringiensis).

22. Describe with the help of a diagram an instrument which can be used to detect a charged body.

Electroscope (gold leaf or pith ball):
Construction & diagram (describe): A metal rod passes through an insulated stopper into a jar; at the lower end two thin metal leaves (gold leaves) are attached. The rod and leaves are connected; the whole conductor can get charged.

Working / Detection:

  • Bring a charged body near the metal cap of the electroscope (without touching): induced charge causes leaves to diverge slightly.
  • If the charged body is touched to the electroscope, same type of charge is transferred, leaves diverge strongly due to like charges repelling.
  • If the charge is removed (grounding), leaves collapse. The divergence indicates presence and polarity (with further tests) of charge.

Uses: Detect presence of electric charge; demonstrate charging by induction and conduction.

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