CBSE Class 8 Science important questions (English Medium)
Physics (भौतिक विज्ञान)
Ch 8: Force and Pressure
- Define Pressure. Explain why school bags have wide straps. (दबाव की परिभाषा दें और बताएं कि स्कूल बैग की पट्टियां चौड़ी क्यों होती हैं?)
- Differentiate between Contact and Non-contact forces with examples.
- Why do deep-sea divers wear special suits? (Explain atmospheric/liquid pressure).
- Numerical: Calculate the pressure if a force of 100N is applied on an area of 2 m2.
Ch 9: Friction
- “Friction is a necessary evil.” Comment on this statement with examples. (घर्षण एक आवश्यक बुराई है – समझाइए).
- Differentiate between Sliding friction and Rolling friction. Which one is smaller?
- Explain Fluid Friction (Drag). How does the shape of an object (streamlined) affect it?
- List three methods to reduce friction and three methods to increase friction.
Ch 10: Sound
- Draw and explain the structure of the Human Ear.
- Differentiate between Noise and Music.
- Define the terms: Amplitude, Time Period, and Frequency. How are loudness and pitch related to them?
- What is Noise Pollution? List its harmful effects and measures to control it.
Ch 11: Chemical Effects of Electric Current
- What is Electroplating? Explain its uses with examples (e.g., Chromium plating).
- Why is it dangerous to handle electrical appliances with wet hands?
- Draw a simple circuit to show that distilled water is a poor conductor while salt water is a good conductor.
- What is the chemical effect of electric current? Give one example (Production of bubbles/change of color).
Ch 12: Some Natural Phenomena
- Explain the process of Lightning. How does a lightning conductor protect a building?
- What causes an Earthquake? Explain the terms: Focus, Epicenter, and Seismic waves.
- List three safety measures to take during a thunderstorm.
- Describe the working of an Electroscope with a diagram.
Ch 13: Light
- State the Laws of Reflection.
- Differentiate between Regular and Diffused reflection.
- Draw a well-labeled diagram of the Human Eye.
- What is a Kaleidoscope? On what principle is it based?
Biology (जीव विज्ञान)
Ch 1: Crop Production and Management
- Differentiate between Manure and Fertiliser. (खाद और उर्वरक में अंतर).
- Explain the modern methods of Irrigation (Sprinkler and Drip system) and their advantages.
- What are Weeds? How can we control them?
- Explain the process of harvesting and storage of grains (Silos/Granaries).
Ch 2: Microorganisms: Friend and Foe
- Explain the Nitrogen Cycle with a diagram.
- How are microorganisms useful in the food industry (Curd/Bread) and medicine (Antibiotics/Vaccines)?
- List three common plant diseases and three animal diseases caused by microorganisms.
- What is Food Preservation? Explain methods like Pasteurization and Salting.
Ch 5: Conservation of Plants and Animals
- Differentiate between Wildlife Sanctuary, National Park, and Biosphere Reserve.
- What is the Red Data Book?
- Explain the terms: Endemic Species, Extinct Species, and Endangered Species.
- What are the causes and consequences of Deforestation?
Ch 6: Reproduction in Animals
- Differentiate between Sexual and Asexual reproduction.
- Explain the process of Metamorphosis in frogs.
- Differentiate between Internal and External fertilization.
- Explain Binary Fission in Amoeba and Budding in Hydra with diagrams.
Ch 7: Reaching the Age of Adolescence
- List the physical changes that occur during Puberty.
- Explain the role of hormones like Insulin, Adrenaline, Thyroxine, and Testosterone/Estrogen.
- How is the sex of a baby determined in humans? (XX and XY chromosomes).
- Write short notes on: Menstruation and Adam’s Apple.
Chemistry (रसायन विज्ञान)
Ch 3: Coal and Petroleum
- Explain the formation of Coal and Petroleum.
- What is PCRA? List the tips suggested by them to save petrol/diesel.
- Define Carbonisation.
- List the constituents of petroleum (Petrol, Diesel, Kerosene, Paraffin wax) and their uses.
Ch 4: Combustion and Flame
- Draw a well-labeled diagram of a Candle Flame showing its three zones.
- What is Calorific Value? Unit of calorific value.
- Explain the conditions necessary for combustion (Fuel, Air, Heat).
- Why is Water not used to control fires involving electrical equipment or oil? What is used instead?
Pro Tips for Exam:
- Diagrams: Science में diagrams (Eye, Candle flame, Nitrogen cycle, Reproductive system) की practice जरूर करें। 3-5 marks के questions अक्सर यहीं से आते हैं।
- Keywords: Answers लिखते समय keywords (जैसे: Electroplating, Fermentation, Drag, Frequency) को highlight करें।
- Differences: “Difference between” वाले questions (जैसे Manure vs Fertilizer) को हमेशा table बनाकर लिखें।