About Important Questions for CBSE Class 8 Science Chapter-wise
If you opened this page while juggling a school diary, a half-marked NCERT book, and a phone full of half-finished notes, you are exactly the person this guide is for. CBSE has rolled out a new Class 8 Science textbook called Curiosity under the NEP 2020 framework, and it has quietly changed how the subject is taught — and how it is examined. The chapter count dropped from 18 to 13, several topics were merged or renamed, and the emphasis has shifted from "memorise and reproduce" to "understand and apply." This Page cuts through that noise. Read the NCERT textbooks and solve questions with the help of NCERT solutions for NCERT solutions for class 8 and NCERT solutions for class 8 Exemplar check the respective pages.
Find the PDF of Important Questions for Class 8 Science – Chapter-wise
That shift matters more than most students realise. A question on Coal and Petroleum used to ask you to define a term. A question from the new Pressure, Winds, Storms and Cyclones chapter is more likely to ask you to explain why a cyclone forms, using two or three linked ideas at once. This guide walks through every chapter of the current syllabus, flags the question types your school is actually likely to set, and gives you tables you can revise from on a phone screen between classes — not a wall of text you'll skip.
A quick note before we start: a number of schools are still completing the transition and may be following the older 18-chapter NCERT Science book for this session. If your school hasn't switched yet, the topics largely map onto each other (for instance, the old "Force and Pressure" and "Friction" chapters now sit inside "Exploring Forces"), so the question patterns below will still be broadly useful — just check with your teacher which book your exam is based on.
How CBSE Is Actually Testing Class 8 Science Now
Before chapter-wise prep, important questions for class 8 helps to know what's changed in the exam pattern itself. The New framework leans harder into competency-based questions — ones that test whether you can use a concept, not just recall it.
Question Type | What It Actually Looks Like | How to Prepare |
|---|---|---|
Assertion-Reason | Two statements; you judge if both are true and if the second explains the first | Don't just learn facts — learn why one fact leads to another |
Case-based/Source-based | A short passage or data table, followed by 3–4 questions | Practice reading unfamiliar data quickly; the science is usually simple once you decode the setup |
Diagram-based | Label, complete, or interpret a diagram (eye, electric circuit, food chain) | Draw every important diagram by hand at least five times before the exam |
Application/HOTS | "Why does X happen in situation Y?" rather than "Define X" | Connect chapter concepts to daily-life examples your teacher used in class |
Very Short Answer (1 mark) | Definitions, units, simple differences | Keep a one-line definition ready for every bold term in the chapter |
Internal assessment — periodic tests, practicals, and projects — typically carries a significant chunk of your final score and is entirely controlled by consistent classwork, so don't treat "important questions" as a substitute for finishing your activity-based tasks on time.
Chapter 1: Exploring the Investigative World of Science
This opening chapter sets up how scientists think rather than teaching a fixed body of facts, which is exactly why students underestimate it — and then lose easy marks on terminology.
Most-asked question types:
Differentiate between observation, hypothesis, and experiment (a perennial 2–3 marker)
Identify the independent and dependent variable in a given experimental setup
Why is a "fair test" important in an experiment? Name one variable that must be kept constant in a stated example
Case-based question describing a simple experiment, asking you to identify the question being investigated
Key Term | One-Line Meaning You Should Memorise |
|---|---|
Hypothesis | An educated guess that can be tested through experiment |
Variable | Any factor that can change or be changed in an investigation |
Controlled variable | A factor deliberately kept constant so results stay reliable |
Inference | A conclusion drawn from observed evidence |
Chapter 2: The Invisible Living World — Beyond Our Naked Eye
This is the microbiology chapter, and it remains one of the highest-yield chapters for short-answer questions because the content is fact-dense and easy to frame as "name two" or "give one example" questions.
Most-asked questions:
Classify microorganisms into the four/five major groups with one example each
Explain the role of Rhizobium in nitrogen fixation (frequently asked as a 3-marker)
How does food preservation through salting, drying, or refrigeration prevent microbial spoilage?
Differentiate between a vaccine and an antibiotic
Case study: a passage about food poisoning or a disease outbreak, followed by application questions
Group of Microorganism | Example | One Use or Effect |
|---|---|---|
Bacteria | Lactobacillus | Converts milk to curd |
Fungi | Yeast | Used in bread-making (fermentation) |
Protozoa | Plasmodium | Causes malaria |
Algae | Spirogyra | Produces oxygen, base of aquatic food chains |
Virus | Influenza virus | Causes flu; cannot reproduce outside a host cell |
Chapter 3: Health — The Ultimate Treasure
Expect a mix of biology and applied life-skills questions here. CBSE has been framing more questions around balanced diets, deficiency diseases, and the difference between communicable and non-communicable disease — areas students often confuse under exam pressure.
Most-asked questions:
Tabulate three deficiency diseases with the missing nutrient and one symptom each
What is the difference between communicable and non-communicable diseases? Give one example of each
Explain any two ways of preventing the spread of communicable diseases
Why is it important to complete a full course of antibiotics even after symptoms disappear?
Deficiency Disease | Missing Nutrient | One Visible Symptom |
|---|---|---|
Scurvy | Vitamin C | Bleeding gums |
Night blindness | Vitamin A | Difficulty seeing in dim light |
Rickets | Vitamin D | Bone deformity in children |
Goitre | Iodine | Swelling in the neck |
Anaemia | Iron | Fatigue, pale skin |
Chapter 4: Electricity — Magnetic and Heating Effects
This chapter merges what used to be spread across "chemical effects of electric current" and basic circuit work, and it is now tested heavily through circuit diagrams and real-life heating-effect examples (fuses, electric iron, bulb filament).
Most-asked questions:
Explain the heating effect of electric current with one practical application
Why does an electromagnet lose its magnetism when the current is switched off, unlike a permanent magnet?
Draw and label a simple electromagnet using a coil, iron nail, and battery
A fuse wire melts and breaks the circuit during a short circuit — explain why this is a safety feature, not a fault
Numerical-style reasoning: which material among a given list would make the best fuse wire, and why?
Effect of Current | Real-Life Device | Underlying Principle |
|---|---|---|
Heating effect | Electric iron, room heater, fuse | Current flowing through resistance produces heat |
Magnetic effect | Electric bell, electromagnet, electric motor | Current-carrying conductor generates a magnetic field |
Chemical effect | Electroplating | Current causes a chemical change at the electrodes |
Chapter 5: Exploring Forces
Force, pressure, and friction — three previously separate chapters — have been integrated here, so cross-topic questions (e.g., "how does pressure relate to the force exerted by a sharp object?") are now common rather than rare.
Most-asked questions:
Define thrust and pressure. Why does a sharp knife cut more easily than a blunt one for the same applied force?
Differentiate between balanced and unbalanced forces with one example each
List two methods to increase and two methods to decrease friction, with real-life examples
Why does a ball rolling on a rough surface stop sooner than one rolling on a smooth, polished floor?
Case-based: a diagram showing forces acting on an object from different directions — identify the net effect
Force Type | Example | Contact or Non-Contact |
|---|---|---|
Muscular force | Pushing a door | Contact |
Frictional force | Brakes stopping a cycle | Contact |
Magnetic force | Compass needle pointing north | Non-contact |
Gravitational force | An apple falling from a tree | Non-contact |
Electrostatic force | Comb attracting paper bits after rubbing on hair | Non-contact |
Chapter 6: Pressure, Winds, Storms and Cyclones
This chapter rewards students who can connect atmospheric pressure to weather events rather than memorise definitions in isolation — it's a favourite for case-based questions describing a cyclone warning or weather report.
Most-asked questions:
Explain why areas of low air pressure are associated with stormy weather
Describe how uneven heating of land and water gives rise to sea breeze and land breeze
What precautions should be taken during a cyclone warning? (Listed answer, frequently 3–5 marks)
Why do roofs sometimes get lifted off during very strong winds? (Applies Bernoulli's-type reasoning in simple terms)
Phenomenon | Cause | Result |
|---|---|---|
Sea breeze | Land heats faster than sea in daytime | Cool air from sea moves toward land |
Land breeze | Sea retains heat longer at night | Cool air from land moves toward sea |
Cyclone | Very low pressure over warm ocean water | Strong rotating winds, heavy rainfall |
High-speed wind over a roof | Lower pressure created above the roof | Roof may lift due to pressure difference |
Chapter 7: Particulate Nature of Matter
A conceptually heavy chapter testing whether students truly understand particle movement, not just states of matter. Diagram-based and reasoning questions dominate here.
Most-asked questions:
Explain diffusion using the movement of particles, with one everyday example
Why does a gas fill the entire volume of its container while a solid does not?
Using the particle model, explain why ice melts faster in a warm room than in a refrigerator
Differentiate between evaporation and boiling in terms of particle behaviour
State of Matter | Particle Arrangement | Particle Movement |
|---|---|---|
Solid | Tightly packed, fixed positions | Vibrate in place only |
Liquid | Close but able to move past each other | Slide and move freely within the liquid |
Gas | Widely spaced | Move rapidly in all directions |
Chapter 8: Nature of Matter — Elements, Compounds and Mixtures
This is the foundation chapter for Class 9–10 chemistry, and CBSE tests it through classification-based questions more than anything else.
Most-asked questions:
Classify the following into elements, compounds, and mixtures: [a given list — practice this with random examples]
Why is water called a compound and not a mixture, even though it contains two elements?
Differentiate between homogeneous and heterogeneous mixtures with two examples each
Give two properties that distinguish a metal from a non-metal
Category | Example | Key Identifying Feature |
|---|---|---|
Element | Oxygen, Iron | Made of only one type of atom |
Compound | Water (H₂O), Salt (NaCl) | Two or more elements chemically combined in fixed ratio |
Homogeneous mixture | Salt solution, air | Uniform composition throughout |
Heterogeneous mixture | Sand and water, oil and water | Components remain visibly separate |
Chapter 9: The Amazing World of Solutes, Solvents and Solutions
Closely linked to Chapter 8, this chapter is where numerical-style concentration questions start appearing, even at this level — keep formulas for mass percentage handy.
Most-asked questions:
Define solute, solvent, and solution with one example
What is a saturated solution? How can you make a saturated solution unsaturated again?
Calculate the concentration of a solution given the mass of solute and solvent (simple numerical)
Why does sugar dissolve faster in hot water than in cold water?
Differentiate between a true solution and a suspension
Term | Meaning | Example |
|---|---|---|
Solute | Substance that dissolves | Salt in salt water |
Solvent | Substance that dissolves the solute | Water in salt water |
Saturated solution | No more solute can dissolve at that temperature | Sugar syrup at maximum sweetness |
Suspension | Particles do not dissolve, settle on standing | Chalk powder in water |
Chapter 10: Light — Mirrors and Lenses
A high-weightage chapter with the most diagram-based questions in the entire syllabus. Ray diagrams are non-negotiable practice here.
Most-asked questions:
State and explain the laws of reflection of light
Draw a ray diagram showing image formation by a plane mirror, and list two characteristics of the image
Differentiate between a real image and a virtual image
Why does a doctor use a concave mirror to examine the throat or ear?
Explain lateral inversion with a real-life example (e.g., reading text in a mirror)
Mirror/Lens Type | Common Use | Nature of Image Formed |
|---|---|---|
Plane mirror | Regular looking glass | Virtual, erect, same size |
Concave mirror | Shaving mirror, headlights, dentist's mirror | Can be real or virtual depending on object distance |
Convex mirror | Vehicle rear-view mirror | Virtual, smaller, wider field of view |
Convex lens | Magnifying glass, camera | Can form real, inverted images |
Concave lens | Used to correct short-sightedness (myopia) | Always virtual, diminished |
Chapter 11: Keeping Time with the Skies
A newer-style chapter blending astronomy with the history of timekeeping. Expect conceptual questions about calendars and the Moon's phases rather than pure fact recall.
Most-asked questions:
Explain why the Moon's phases are not caused by Earth's shadow
What is the difference between a lunar calendar, a solar calendar, and a luni-solar calendar?
Why doesn't a birthday that falls on a full moon day repeat on the full moon every year?
What are artificial satellites used for, and what is "space debris"?
Calendar Type | Based On | Example in Use |
|---|---|---|
Solar calendar | Earth's revolution around the Sun (~365.25 days) | Gregorian calendar |
Lunar calendar | Moon's phase cycle (~29.5 days) | Islamic Hijri calendar |
Luni-solar calendar | Combines both lunar months and solar year | Hindu and Hebrew calendars |
Chapter 12: How Nature Works in Harmony
This is the ecology chapter, and CBSE tends to test food chains, food webs, and decomposer roles through diagram-completion and case-based formats.
Most-asked questions:
Construct a food chain for a given habitat (pond, forest, grassland) and identify the trophic levels
Why are decomposers essential to an ecosystem? What would happen if they were removed?
Differentiate between a food chain and a food web
Explain one example of a symbiotic relationship and one example of a harmful human impact on an ecosystem
Trophic Level | Role | Example |
|---|---|---|
Producer | Makes its own food via photosynthesis | Grass, algae |
Primary consumer | Eats producers | Grasshopper, deer |
Secondary consumer | Eats primary consumers | Frog, fox |
Decomposer | Breaks down dead matter, recycles nutrients | Fungi, bacteria |
Chapter 13: Our Home — Earth, A Unique Life-Sustaining Planet
The concluding chapter ties together atmosphere, biodiversity, and climate change, and it is increasingly tested through long-answer, opinion-based questions on environmental responsibility.
Most-asked questions:
What is the "Goldilocks zone," and why does Earth's position in it matter for life?
Explain the greenhouse effect and how human activity is intensifying it
How does Earth's magnetic field protect life on the planet?
List three major threats to biodiversity and one possible solution for each
Long-answer/HOTS: "Earth is the only planet known to sustain life — justify this statement using at least three scientific reasons."
Earth Feature | Why It Matters for Life |
|---|---|
Position in the Goldilocks zone | Allows liquid water to exist — neither too hot nor too cold |
Atmosphere with ozone layer | Filters harmful UV radiation from the Sun |
Magnetic field | Deflects harmful solar wind and cosmic radiation |
Presence of liquid water | Essential medium for biochemical reactions in living cells |
A Smarter Way to Revise: Weightage-Based Prioritisation
Not every chapter carries equal exam weight, and burning equal hours on all 13 is rarely the smartest strategy this close to a test. Based on how CBSE has structured recent question papers and sample papers, here's a rough sense of where marks concentrate:
Subject Area | Chapters Involved | Typical Question Focus |
|---|---|---|
Physics | Electricity, Exploring Forces, Pressure & Winds, Light, Keeping Time | Diagrams, applied reasoning, numericals |
Chemistry | Particulate Nature of Matter, Elements/Compounds/Mixtures, Solutions | Classification, particle-model explanations |
Biology | Invisible Living World, Health, How Nature Works in Harmony | Tables, examples, case-based passages |
Earth & Environment | Our Home: Earth | Long-answer, opinion-based, HOTS |
If your exam is approaching fast, prioritise Light, Exploring Forces, and Our Home: Earth first — these three consistently generate the highest number of diagram-based and long-answer marks across CBSE schools, closely followed by Electricity and How Nature Works in Harmony.
Final Revision Habits That Actually Move Your Score
A few habits separate students who merely "cover" the syllabus from those who score well in it:
Redraw every diagram from memory — ray diagrams, electromagnets, food chains — rather than just reading them. Recognition and recall are different skills, and CBSE tests recall.
Convert each chapter's bold terms into a one-line glossary in your own words. If you can't explain a term in one sentence, you don't know it well enough yet.
Practice classification questions out of order. Mixing up examples from Chapter 8 forces real understanding instead of memorised sequence.
Time yourself on case-based passages. These are new to many students and cost more time than they should if you haven't practised reading unfamiliar data under a clock.
Don't skip the "why" behind every "what." Almost every most-asked question above is really asking you to explain a mechanism — not just name a fact.
Science at this stage isn't really about cramming definitions; it's the first real test of whether you can connect an idea to a reason. Get comfortable doing that chapter by chapter, and the exam stops feeling like 13 separate subjects and starts feeling like one connected way of thinking.