CBSE Important Questions Class 10 Science PDF for 2026

We all know that Class 10 Science can feel like a never-ending mix of formulas, reactions, and diagrams. And with the 2026 board exams coming up, everyone’s on the hunt for that one-stop list of CBSE Important Questions Class 10 Science PDF 2026 that actually helps in last-minute prep.

That’s exactly what this blog is for. We’ve pulled together the most expected and important questions straight from chapters like Physics, Chemistry, and Biology - so you don’t waste time guessing what to study. Think of this as your quick revision buddy: simple, sorted, and exam-focused.

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Chapter-wise CBSE Class 10 Science Important Questions 2026

Instead of cramming the whole book, the smart way is to go chapter by chapter. Below is a ready-made list of the most expected Class 10 Science Important Questions 2026 from Physics, Chemistry, and Biology. 

<red> → <red>Class 10  Chemical Reactions and Equations Important Questions

<red> → <red>Class 10  Acids Bases and Salts Important Questions

<red> → <red>Class 10  Metals and Non-Metals Important Questions

<red> → <red>Class 10  Carbon and its Compounds Important Questions

<red> → <red>Class 10  Life Processes Important Questions

<red> → <red>Class 10  Control and Coordination Important Questions

<red> → <red>Class 10  How do Organisms Reproduce Important Questions

<red> → <red>Class 10  Heredity and Evolution Important Questions

<red> → <red>Class 10  Light Reflection and Refraction Important Questions

<red> → <red>Class 10  Human Eye and The Colorful World Important Questions

<red> → <red>Class 10  Electricity Important Questions

<red> → <red>Class 10  Magnetic Effects of Electric Current Important Questions

<red> → <red>Class 10  Our Environment Important Questions

If you cover these, you’ll be exam-ready without wasting time on the extra stuff.

Why Solving Important Questions for Class 10 Science Matters

If you’re aiming to score well in CBSE Class 10 Science 2026, solving important questions is honestly a game-changer. Here’s why:

• Helps You Understand the Exam Pattern

Most of these questions are picked directly from sample papers, past year boards, and NCERT-based exercises. By practicing them, you get familiar with the exact type of questions CBSE repeats, whether it’s MCQs, case studies, or long-answer questions.

• Boosts Concept Clarity

Science is not just about memorizing; it’s about applying concepts. When you solve Class 10 Science important questions, you realize which topics are strong and which ones need a quick revision. This clears up confusion and builds a stronger foundation.

• Improves Speed & Accuracy

Board exams are all about time management. Practicing with chapter-wise important questions makes you faster at writing answers and reduces silly mistakes that usually cost marks.

• Prepares You for High-Weightage Topics

Many important questions are directly linked to chapters that carry more marks in the exam. So, instead of wasting time on less important content, you know where to focus.

• Builds Exam Confidence

By the time you’ve solved these questions a couple of times, the actual board exam will feel like just another practice test. That’s the kind of confidence you need on exam day.

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Tips to use this Science Important Questions list effectively

So you’ve got the Class 10 Science Important Questions 2026 in your hands, but how do you actually use them smartly! Think of it like a game plan.

Step 1: Start Early

Don’t wait until the last 10 days. Begin solving these important questions for Class 10 Science at least 2–3 months before exams. This way, you’ll understand which topics need extra revision.

Step 2: Go Chapter-Wise

Use the chapter-wise CBSE Class 10 Science Important Questions 2026 list to cover one chapter at a time. This keeps your prep organized and avoids last-minute chaos.

Step 3: Cross-Check with NCERT

Keep your NCERT Class 10 Science textbook open while solving. Many questions are framed directly from NCERT, so you’ll quickly notice patterns.

Step 4: Practice Writing, Not Just Reading

Treat these like an actual exam. Write down answers - this helps improve speed, accuracy, and presentation for the real CBSE Class 10 Science Board Exam 2026.

Step 5: Mix with Sample Papers

After solving a chapter, test yourself with a Class 10 Science Sample Paper 2026. This shows how these questions actually fit into board-style papers.

Step 6: Revise with Notes

Cross-check tricky topics using your Class 10 Science Notes and Questions. This double layer of practice makes sure nothing slips from your memory.

Pro move: Don’t memorize word-to-word. Understand concepts, then frame answers in your own words - CBSE loves that.

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Benefits of practising Class 10 Science Important Questions

When you keep solving a well-picked set of Class 10 Science Important Questions, you’re not just revising - you’re building exam skills. Here’s how:

• Confidence Booster: The fear of “what if a new question comes?” goes away because you’ve already tackled the most expected ones. You walk into the exam knowing you’re prepared.
  
• Spotting Patterns: CBSE often repeats questions with slight twists. Practising these gives you a sharp eye to identify those patterns instantly.
  
• Concept Clarity: Science isn’t about memorising; it’s about applying. Writing out answers helps you understand why a reaction happens or how a diagram works.
  
• Speed & Time Management: Exams are all about finishing on time. Regular practice trains your brain to think faster and write cleaner answers under pressure.
  
• Higher Accuracy - More Marks: Since these questions are closely linked to NCERT and sample papers, you reduce silly mistakes and score better in both theory and numericals.
  
• Quick Revision Tool: Instead of re-reading the entire book, this list acts like a shortcut - covering Physics, Chemistry, and Biology in one place.
  
• Better Exam Strategy: Knowing which questions matter most helps you prioritise and focus energy on high-scoring areas.
  

In short: Practising these important questions is like playing the previous season before the final match - you already know the moves, so nothing feels new in the exam hall.

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Class 10 Science Important Questions with Answers

Here's your handy list of Class 10 Science Important Questions with Answers. Go through these, and you’ll get a solid grip on all the must-know stuff for your exams without wasting time.

Q1. Define the power of a lens. Write its SI unit.
Ans. The power of a lens is the degree of convergence or divergence of light rays by the lens. It is equal to the reciprocal of its focal length (in meters).
SI unit = Dioptre (D).

Q2. What is meant by the term ‘refraction of light’? State Snell’s law.
Ans. Refraction is the bending of light when it passes from one medium to another due to a change in its speed.
Snell’s Law: The ratio of sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.

Q3. Why is the colour of the clear sky blue?
Ans. The blue colour of the sky is due to scattering of light. Shorter wavelengths like blue scatter more by atmospheric particles compared to red, hence the sky appears blue to us.

Q4. Draw a ray diagram to show the formation of image by a concave mirror when the object is placed between focus (F) and pole (P). Describe the nature of the image.
Ans. Ray diagram shows that when an object is placed between F and P, the image formed is virtual, erect, magnified, and appears behind the mirror. This is why concave mirrors are used in makeup/shaving mirrors.

Q5. A student needs a lens of focal length 20 cm for studying the image of a small insect. Which type of lens should he use and why?
Ans. He should use a convex lens of 20 cm focal length because convex lenses converge light rays and form a magnified image when the object is placed between the focus and the optical centre.

Q6. What is the role of the fuse in a domestic circuit? Why is it always connected in the live wire?
Ans. A fuse is a safety device that protects electrical appliances from damage due to excessive current. It melts and breaks the circuit when current exceeds the safe limit. It is always connected in the live wire so that when it melts, it disconnects the appliance from the high voltage supply.

Q7. Two resistors of 6 ohm and 12 ohm are connected in parallel. Find the equivalent resistance of the combination.
Ans.
1/Req = 1/6 + 1/12
= (2 + 1)/12 = 3/12 = 1/4
So, Req = 4 ohm.

Q8. What is the difference between a short circuit and an overload in a domestic electric circuit?
Ans.

• Short circuit: Occurs when live wire and neutral wire come in direct contact, causing sudden flow of high current.
• Overload: Happens when too many appliances are connected to a single socket, drawing more current than the safe limit.
  Both are dangerous and can cause fire hazards.
  

Q9. Explain with the help of a diagram the phenomenon of dispersion of white light by a glass prism.
Ans. When a narrow beam of white light passes through a prism, it splits into seven colours (VIBGYOR). This happens because different colours bend by different amounts - violet bends the most, red the least. This separation of colours is called dispersion of light.

Q10. An electric iron draws a current of 5 A from a 220 V supply. What is the power consumed? Also calculate the energy consumed in 2 hours.
Ans.
Power = V × I = 220 × 5 = 1100 W.
Energy consumed = Power × Time = 1100 × 2 = 2200 Wh = 2.2 kWh.

Q11. Define homologous series in carbon compounds. Give one example.

Ans. A homologous series is a group of organic compounds having the same functional group, similar chemical properties, and successive members differing by a –CH₂ group.
Example: Alkanes – CH₄ (Methane), C₂H₆ (Ethane), C₃H₈ (Propane), etc.

Q12. Explain the role of the diaphragm in the process of breathing in humans.

Ans. The diaphragm is a dome-shaped muscular partition between the chest and abdominal cavity.

• During inhalation: It contracts and flattens, increasing the chest cavity volume, which allows air to enter the lungs.
• During exhalation: It relaxes and moves upward, decreasing the chest cavity volume, pushing air out of the lungs.

Q13. State the law of conservation of mass with an example.

Ans. The Law of Conservation of Mass states that mass can neither be created nor destroyed in a chemical reaction; it remains constant.
Example: In the reaction:
H₂ + Cl₂ → 2HCl
The mass of hydrogen and chlorine before the reaction equals the mass of HCl formed after the reaction.

Q14. What is the function of platelets in our blood?

Ans. Platelets (thrombocytes) are small cell fragments in the blood that help in clotting. When a blood vessel is injured, platelets collect at the site, release clotting factors, and help form a fibrin clot to stop blood loss. Without platelets, even a small cut could cause excessive bleeding.

Q15. What are ionic compounds? Mention their two general properties.

Ans. Ionic compounds are formed by the transfer of electrons from metals to non-metals, creating strong electrostatic forces between ions.
Properties:

1. High melting and boiling points.
2. Generally soluble in water and conducts electricity in aqueous solution.

Q16. Explain the difference between biodegradable and non-biodegradable substances with examples.

Ans.

• Biodegradable substances: Can be broken down by natural agents like bacteria, fungi, etc. (e.g., paper, vegetable waste).
• Non-biodegradable substances: Cannot be decomposed easily and persist in the environment, causing pollution (e.g., plastic, glass).

Q17. State two advantages of connecting electrical devices in parallel in a household circuit.

Ans.

1. Each device gets the same potential difference (220 V).
2. If one device stops working, the others continue to operate.
3. Devices can be operated independently without affecting others.

Q18. Why is it dangerous to connect electrical appliances with the earth wire?

Ans. The earth wire is meant only for safety - it provides a low resistance path to ground in case of leakage of current. If appliances are directly connected to the earth wire, a high current may flow through the circuit, leading to short circuits or damage.

Q19. Explain why forests are called the ‘green lungs’ of the earth.

Ans. Forests are called the green lungs because they release oxygen during photosynthesis, which is essential for the survival of most living organisms. They also absorb carbon dioxide, helping to maintain the balance of gases in the atmosphere. 

Q20. What is the difference between an element, compound, and mixture?

Ans.

• Element: A pure substance made of only one type of atom. Example: Oxygen (O₂)
• Compound: A pure substance formed by chemically combining two or more elements in a fixed ratio. Example: Water (H₂O)
• Mixture: A physical combination of two or more substances where each retains its identity. Example: Sand + Salt

Q21. Explain the process of rusting of iron.

Ans. Rusting is the corrosion of iron due to its reaction with oxygen and moisture in the environment, forming hydrated iron oxide (Fe₂O₃·xH₂O).

• Conditions required: Presence of water, oxygen, and electrolytes (like salt).
• Rust weakens the metal and causes it to crumble over time.

Q22. Define velocity. How is it different from speed?

Ans.

• Velocity: The rate of change of displacement of an object in a given direction.
• Difference from speed: Speed is scalar (only magnitude), while velocity is vector (magnitude + direction).

Q23. What is the role of stomata in plants?

Ans. Stomata are tiny pores on the leaf surface that regulate gas exchange:

• Absorb carbon dioxide for photosynthesis.
• Release oxygen and water vapor during transpiration.

Q24. Explain how acids and bases are classified according to the pH scale.

Ans.

• pH < 7 → Acidic (e.g., HCl, lemon juice)
• pH = 7 → Neutral (e.g., pure water)
• pH > 7 → Basic (e.g., NaOH, soap solution)
  The lower the pH, the stronger the acid; the higher the pH, the stronger the base.

Q25. Define power of a lens. How is it related to focal length?

Ans. Power (P) of a lens is the ability to converge or diverge light.

• Formula: P (in diopters) = 100 / f (in cm)
• Focal length (f) and power are inversely related: smaller the focal length, higher the power.

Q26. Explain the difference between exothermic and endothermic reactions with examples.

Ans.

• Exothermic: Release energy as heat or light. Example: Combustion of wood.
• Endothermic: Absorb energy from surroundings. Example: Photosynthesis.
  Exothermic reactions feel hot; endothermic reactions feel cold.

Q27. What is the function of the human skeleton?

Ans. The skeleton provides:

1. Support: Holds the body upright.
2. Protection: Shields vital organs (e.g., skull protects the brain).
3. Movement: Works with muscles to facilitate motion.
4. Blood formation: Bone marrow produces RBCs and WBCs.

Q28. A student mixes baking soda in water. What will happen? Write the chemical reaction.

Ans. Baking soda (NaHCO₃) dissolves in water to form a mildly basic solution.

• Reaction with acid (e.g., vinegar, CH₃COOH):
  NaHCO₃ + CH₃COOH → CO₂ + H₂O + CH₃COONa
• CO₂ gas bubbles are released, which can be observed easily.

Q29. Explain the phenomenon of refraction of light.

Ans. Refraction is the bending of light when it passes from one medium to another due to a change in speed.

• Example: A pencil appears bent when partially immersed in water.
• Applications: Lenses, spectacles, microscopes, and optical instruments rely on refraction to focus light.

FAQs

Q1. What are the most important chapters for Class 10 Science board exams?

Ans: some chapters just pop up more often in exams. Focus on Chemical Reactions and Equations, Acids, Bases and Salts, Electricity, Light, and Life Processes. Nail these, and you cover a big chunk of likely questions.

Q2. Are there any sample papers available for Class 10 Science 2026?

Ans: Yes, Official sample papers are out there. Practising them helps you understand the exam pattern, manage time, and avoid surprises on the big day.

Q3. What types of questions are commonly asked in Class 10 Science exams?

Ans: The papers are a mix: short answers, long answers, MCQs, and case-based questions. So you gotta be ready for both quick definitions and detailed explanations.

Q4. How can I improve my problem-solving skills for numerical questions in Science?

Ans: Practice is everything. Solve numericals regularly, understand the formulas instead of just memorizing, and check your mistakes to get faster and more accurate.