Class 9 Science Important Questions – Chapter Wise (CBSE/NCERT)
Important Questions for Class 9 Science lay the foundation for the concepts that return, in a deeper form, in Class 10 and beyond. A large share of exam marks comes from a small set of ideas that repeat every year in different wording, so revising chapter by chapter with the right formulas and question patterns is the fastest way to build confidence before a test. ThisImportant questions page from MyClass24 lists chapter-wise important questions for CBSE Class 9 Science, along with the key concepts and formulas students most often forget. Use it alongside your NCERT textbook as a quick revision sheet, not a replacement for practice.
Find a chapter-wise PDF of Class 9 Science Important Questions
Why Chapter-wise Revision Works
Class 9 Science has three sections — Physics, Chemistry, and Biology — and each behaves differently in an exam. Physics chapters test whether you can apply a formula correctly under a given condition, so numerical practice matters more than reading speed. Chemistry chapters test precise definitions and the ability to explain "why" in one or two lines, which is why the tables below focus on terms that are easy to mix up. Biology chapters reward labelled diagrams and comparisons, so a short table often does more for your score than a paragraph of text. Keeping this difference in mind while revising saves time, because you stop treating every chapter the same way. The list below follows the order of the NCERT textbook, so you can revise alongside your school syllabus without jumping around.
Chapter-wise Important Questions for Class 9 Science
Chapter 1: Matter in Our Surroundings
This chapter explains why matter exists as solids, liquids, and gases, and how temperature and pressure change one state into another.
Key Terms and Concepts
Term | Meaning |
Evaporation | Surface-level change of liquid to vapour below boiling point |
Sublimation | Solid changes directly into gas without becoming liquid |
Latent heat of fusion | Heat needed to melt 1 kg of solid at its melting point |
Latent heat of vaporisation | Heat needed to convert 1 kg of liquid into vapour at boiling point |
Important Questions
Why does a desert cooler work poorly on a humid day?
Explain why we feel cold after a bath even on a warm day.
Give two differences between boiling and evaporation.
Chapter 2: Is Matter Around Us Pure
Here you classify matter into pure substances and mixtures, and learn separation techniques used for each type of mixture.
Types of Mixtures
Type | Feature |
True solution | Particle size below 1 nm; does not scatter light |
Colloid | Particle size 1–1000 nm; shows Tyndall effect |
Suspension | Particle size above 1000 nm; settles on standing |
Important Questions
Why does a colloidal solution show the Tyndall effect but a true solution does not?
How would you separate a mixture of salt, sand, and ammonium chloride?
State one difference between homogeneous and heterogeneous mixtures with an example.
Chapter 3: Atoms and Molecules
This chapter introduces the laws of chemical combination and the mole concept, which students often lose marks on due to formula slips.
Important Formulas
Quantity | Formula |
Number of moles | n = Given mass ÷ Molar mass |
Number of particles | N = n × 6.022 × 10²³ (Avogadro number) |
Molar mass of a compound | Sum of atomic masses of all atoms in the formula |
Important Questions
State the law of conservation of mass with a suitable example.
Calculate the number of moles in 22 g of carbon dioxide.
Differentiate between an atom and a molecule with one example each.
Chapter 4: Structure of the Atom
This chapter covers subatomic particles, atomic models, and how electrons are arranged in shells around the nucleus.
Subatomic Particles
Particle | Charge / Location |
Proton | Positive charge, inside nucleus |
Neutron | No charge, inside nucleus |
Electron | Negative charge, revolves in shells |
Important Questions
What is the maximum number of electrons that can be placed in the M shell, and why?
Define valency and find the valency of an atom having atomic number 17.
Distinguish between isotopes and isobars with one example each.
Chapter 5: The Fundamental Unit of Life
This is a diagram-heavy chapter, so pair every organelle with its function while revising, not just the name.
Cell Organelles and Their Function
Organelle | Function |
Mitochondria | Site of respiration; releases energy as ATP |
Ribosomes | Site of protein synthesis |
Golgi apparatus | Packaging and dispatch of cell products |
Nucleus | Controls cell activity; carries genetic material |
Important Questions
Why is the mitochondrion called the powerhouse of the cell?
Give two differences between plant cells and animal cells.
Explain why the cell is called the structural and functional unit of life.
Chapter 6: Tissues
This chapter asks students to identify tissue types from their location and function, which is best learnt through a comparison table.
Types of Plant Tissue
Tissue | Main Function |
Meristematic | Actively dividing tissue found at growing tips |
Parenchyma | Storage of food; fills spaces between other tissues |
Xylem | Transport of water and minerals upward |
Phloem | Transport of food made during photosynthesis |
Important Questions
Differentiate between xylem and phloem on the basis of function.
Why are our elbow joints more flexible due to cartilage rather than bone?
Name the tissue responsible for growth in the length of a plant.
Chapter 7: Diversity in Living Organisms
This chapter is about classifying organisms scientifically; focus on the basis used at each level rather than memorising names alone.
Five Kingdom Classification
Kingdom | Key Feature |
Monera | Prokaryotic, unicellular organisms such as bacteria |
Protista | Eukaryotic, mostly unicellular, e.g. amoeba |
Fungi | Eukaryotic, cell wall of chitin, absorb nutrition |
Plantae | Multicellular, prepare their own food |
Animalia | Multicellular, depend on other organisms for food |
Important Questions
What is the basis for classifying organisms into five kingdoms?
Why are viruses not placed in any of the five kingdoms?
Give the hierarchy of classification from kingdom to species.
Chapter 8: Motion
This chapter is largely numerical, and most marks depend on correctly applying the three equations of motion.
Equations of Motion
Equation | Use |
v = u + at | Finds final velocity |
s = ut + ½at² | Finds distance covered |
v² = u² + 2as | Relates velocity and distance without time |
Important Questions
A car increases its speed from 20 m/s to 30 m/s in 5 seconds. Find its acceleration.
Distinguish between uniform and non-uniform motion with one example each.
Derive the equation v = u + at using a velocity-time graph.
Chapter 9: Force and Laws of Motion
Newton's three laws are conceptual, but numericals on momentum and force are equally common in exams.
Important Formulas
Quantity | Formula |
Momentum | p = mass × velocity |
Newton's second law | F = mass × acceleration |
Force | F = rate of change of momentum |
Important Questions
State Newton's first law of motion and explain why it is called the law of inertia.
Why does a passenger fall forward when a moving bus stops suddenly?
A bullet of mass 20 g moving at 300 m/s hits a wall. Find its momentum.
Chapter 10: Gravitation
This chapter connects the universal law of gravitation with everyday ideas like weight, free fall, and buoyancy.
Important Formulas
Quantity | Formula |
Universal law of gravitation | F = G(m1m2)/r² |
Weight | W = mass × g |
Acceleration due to gravity | g ≈ 9.8 m/s² near Earth's surface |
Important Questions
State the universal law of gravitation and write its formula.
Why does a body weigh less on the Moon than on the Earth?
Explain why an object thrown upward returns to the ground with the same speed it was thrown, ignoring air resistance.
Chapter 11: Work and Energy
This chapter defines work, energy, and power precisely, and students should be careful about when work is actually zero.
Important Formulas
Quantity | Formula |
Work done | W = Force × displacement in the direction of force |
Kinetic energy | KE = ½mv² |
Potential energy | PE = mgh |
Power | P = Work done ÷ time |
Important Questions
Why is the work done by a person holding a heavy bag while standing still equal to zero?
State the law of conservation of energy with an example of a falling object.
A 2 kg object moving at 5 m/s has how much kinetic energy?
Chapter 12: Sound
Sound as a wave, its reflection, and the conditions needed to hear an echo are frequently tested from this chapter.
Key Terms
Term | Meaning |
Frequency | Number of vibrations per second; unit hertz |
Amplitude | Maximum displacement of a vibrating particle; decides loudness |
Speed of sound in air | About 346 m/s at room temperature |
Important Questions
What is the minimum distance required to hear an echo distinctly, and why?
Explain why sound cannot travel through vacuum.
Differentiate between loudness and pitch of sound.
Chapter 13: Why Do We Fall Ill
This chapter separates health from disease and explains the difference between acute and chronic conditions.
Acute vs Chronic Disease
Type | Feature |
Acute disease | Sudden onset, lasts a short time, e.g. common cold |
Chronic disease | Long-lasting, develops slowly, e.g. tuberculosis |
Important Questions
Why does a chronic disease affect a person's nutritional status more than an acute one?
List any two personal and two community-level measures for preventing infectious disease.
Chapter 14: Natural Resources
This chapter covers the atmosphere, water, and soil cycles that keep resources renewable on Earth.
Layers of the Atmosphere
Layer | Feature |
Troposphere | Lowest layer; where weather occurs |
Stratosphere | Contains the ozone layer that absorbs UV rays |
Important Questions
Why is the ozone layer important for life on Earth?
Explain briefly how the nitrogen cycle maintains nitrogen balance in nature.
Chapter 15: Improvement in Food Resources
This applied chapter links crop production and animal husbandry to India's food security, and is a scoring, easy-to-revise section.
Key Concepts
Term | Meaning |
Mixed cropping | Growing two or more crops together to reduce risk of failure |
Composite fish culture | Rearing several fish species together to use all pond levels |
Important Questions
What is the difference between mixed cropping and intercropping?
Why is crop rotation with legumes beneficial for soil fertility?
Quick Revision Tips
Physics, Chemistry, and Biology each reward a different style of revision. For Physics chapters like Motion, Force and Laws of Motion, Gravitation, and Work and Energy, keep the formula table open while solving numericals so units and signs become automatic. For Chemistry chapters such as Matter in Our Surroundings, Is Matter Around Us Pure, Atoms and Molecules, and Structure of the Atom, focus on definitions and diagrams, since many board questions ask for reasons rather than calculations. For Biology chapters like The Fundamental Unit of Life, Tissues, Diversity in Living Organisms, Why Do We Fall Ill, Natural Resources, and Improvement in Food Resources, labelled diagrams and comparison tables carry easy marks. Go through each chapter section on this page, attempt the important questions from memory first, and only then check your textbook. Repeating this cycle a week before the exam is usually enough to move a shaky chapter into a confident one.