Opening the Class 10 NCERT Science book and feeling unsure about which chapters to focus on first is a situation most students can relate to. The good news is that not all chapters carry the same weightage. Some of the most important chapters for CBSE Class 10 Science 2027, such as Life Processes, Light—Reflection & Refraction, Chemical Reactions, Metals & Non-Metals, Carbon & Its Compounds, Electricity, and more, together account for nearly 50 out of the 80 marks in the theory paper. You need to focus on these chapters to score 95+ in the Science exam. Along with syllabus pressure, they go through a lot of emotions, and we totally understand that. It is a year filled with new challenges, higher expectations, countless revision sessions, and the excitement of preparing for the first major board examination.
Considering both the academic demands and emotional journey of Class 10 students, this guide is designed to simplify your preparation by breaking down the CBSE Class 10 Science syllabus chapter by chapter, highlighting important topics, expected weightage, and practical strategies to help you approach the 2027 board exam with confidence. 
How CBSE Distributes Marks in CBSE Class 10 Science
The CBSE Class 10 Science theory paper is 80 marks over 3 hours. Additional 20 marks can be gained from internal assessment, which includes practicals, periodic tests, and notebooks. Together, they make the total of 100 marks.
Here we are attaching the breakdown of the 80-mark theory paper, which is divided across five units:
|
Unit |
Topic Covered |
Marks |
|
Unit I |
Chemical Substances–Nature & Behaviour |
25 marks |
|
Unit II |
World of Living (Biology) |
25 marks |
|
Unit III |
Natural Phenomena (Physics–Light) |
12 marks |
|
Unit IV |
Effects of Current (Electricity & Magnetism) |
13 marks |
|
Unit V |
Natural Resources |
5 marks |
Chemistry and Biology each carry 25 marks, together contributing to 62.5% of the entire theory paper.
Read More - Best Books for CBSE Class 10 2027 Board Exam Preparation
Chapter-Wise Breakdown of CBSE Class 10 Science
We are giving the detailed chapter-wise breakdown and the important topics within, which will give you direction where to focus more.
Chapter 1: Chemical Reactions & Equations
Unit: Chemistry | Approximate Weightage: 6–7 marks
This chapter is not conceptually difficult; it includes deep knowledge of balancing equations, identifying types of reactions, observations from chemical reactions, and writing chemical equations from word descriptions. To excel in this portion of the course, you can take the help of Oswaal CBSE Class 10 Science question banks, which are perfect for extensive practice questions, previous year trends, detailed explanations, and exam-oriented exercises.
Chapter 2: Acids, Bases, & Salts
Unit: Chemistry | Approximate Weightage: 7 marks
In this chapter, the pH concept is a particular favourite of CBSE question setters. This chapter combines theory, reactions, indicators, pH, and real-life applications, which sets the ground for every question type CBSE asks. Memorise the key reactions with their equations. Understand the why behind indicators changing colour. Alongside this, learn the preparation and uses of sodium hydroxide, baking soda, washing soda, and bleaching powder.
Chapter 3: Metals & Non-Metals
Unit: Chemistry | Approximate Weightage: 7 marks
This is one of the high-scoring chapters, including most-important topics such as reactivity series, physical properties, extraction of metals, and corrosion. From the reactivity series, you can expect questions based on displacement reactions–will metal X displace metal Y from its salt solution? The extraction of metals — ore to metal via reduction, electrolytic refining — is another favourite for long-answer questions carrying 3–5 marks. The electrolytic refining diagram appears frequently. Practice drawing and labelling it until it takes you under two minutes.
Chapter 4: Carbon & Its Compounds
Unit: Chemistry | Approximate Weightage: 5-6 marks
This chapter is often mistaken as the chapter of memorisation. Instead, ist it is built around a few simple rules, the binding properties of carbon, the naming of organic compounds, and the characteristic reactions of different functional groups. Within this chapter, CBSE Class 10 students need to prepare well for electron dot structures of organic compounds, homologous series, naming of carbon compounds, properties of ethanol & ethanoic acid, and more. Also, topics such as saponification and cleansing action of soaps & detergents, students can expect long-answer questions and case-based questions, respectively.
Chapter 5: Life Processes
Unit: Biology | Approximate Weightage: 10-12 marks
Life Processes is the single most important chapter in CBSE Class 10 Science. It carries the highest marks of any individual chapter, and it tests the widest variety of question types: MCQs, short answers, diagrams, case-based questions, and long answers. The chapter covers nutrition, respiration, transportation, and excretion — four complete systems of the human body, plus plant equivalents for each. Related to the human body, students need to prepare in depth, like concepts + diagrams of the digestive system, human heart, and excretion. Alongside this, prepare the nephron structure, double circulation, and a clear-cut difference between aerobic & anaerobic respiration.
Chapter 6: Control & Coordination
Unit: Biology | Approximate Weightage: 8 marks
The reflex arc diagram is a consistent board exam feature. Draw it, label it, understand the direction of impulse travel. Questions asking students to "describe what happens when you touch a hot object" are essentially asking you to narrate the reflex arc — if you know the diagram, you know the answer.
For the endocrine system, focus on the functions of key hormones: insulin (blood sugar), adrenaline (fight-or-flight), thyroxine (metabolism), growth hormone. CBSE loves asking what happens when these hormones are over-secreted or under-secreted.
"Compare nervous and hormonal coordination" is a 3-mark question that appears across multiple years in slightly different forms. Prepare a clear 3-point comparison table.
Chapter 7: Heredity & Evolution
Unit: Biology | Approximate Weightage: 8 marks
In this chapter, the important topics to be cared about–Mendel’s laws, dominant & recessive traits, and more. Of these, Mendelian genetics crosses attract the maximum marks. A monohybrid cross and a dihybrid cross using a Punnett square are not optional — it is almost certain to appear. Practise drawing and completing Punnett squares until you can do them correctly under timed conditions. To get a better idea of how questions are framed from this section, what's best you can do is pick the Oswaal Class 10 PYQ book can be highly beneficial.
Chapter 8: Light–Reflection & Refraction
Unit: Physics | Approximate Weightage: 10-12 marks
Physics is the portion where students mostly struggle with derivations, formulas, and numericals. This chapter itself is numerically heavy, like the mirror formula, lens formula, magnification, and more. Also, the ray diagrams for concave/convex mirrors and lenses under different object positions, which carry 2-3 marks, make it further challenging. But don’t worry; we can make things easy for you by letting you practice with the Oswaal CBSE Class 10 Science question bank. It will not only help you with the mentioned topics but also with other rigorous ones such as refraction, the human eye and its defects, with properly explained solutions and diagrams.
Chapter 9: Electricity
Unit: Physics | Approximate Weightage: 10-12 marks
The concepts — Ohm's Law, resistance, series and parallel circuits, power and energy — are not complicated. But applying them correctly under exam pressure requires repeated practice. Circuit problems are the most common long-answer question type in this chapter. A circuit with mixed series-parallel combinations, asking for total resistance, current through each component, and power dissipated, this format appears in almost every paper. Students who have practised 15+ circuit problems from the Oswaal Class 10 PYQ book before the exam handle them in 8–10 minutes.
The structure of the Oswaal Science Question Bank reflects the actual priority of the paper: more questions from Life Processes, Electricity, and Light — fewer from Natural Resources. That proportion itself is a preparation guide.
A Note of Encouragement for Students
The CBSE Class 10 Science board exam rewards students who are strategic, not just hardworking. Eighty marks across five units and thirteen chapters means every hour of preparation has a different return depending on where it is invested.
Life Processes, Electricity, Light, Metals and Non-Metals, and Acids, Bases and Salts, master these five chapters and you have covered the ground where the majority of marks live. Add Control and Coordination and Heredity and Evolution, and you are in genuinely strong territory.
Then practise not from your textbook, but from varied, exam-format questions that mirror what CBSE actually asks. The Oswaal CBSE Class 10 Science Question Bank 2026–27 is built precisely for this: chapter-wise, format-wise, difficulty-wise giving every student, from average to topper, the structured practice that the difference between knowing a chapter and performing it in an exam actually requires.
Know the chapters. Know the formats. Practise under time pressure. The marks will follow.
FAQs
Life Processes carries the highest individual chapter weightage — approximately 10–12 marks — making it the single most important chapter to master. Electricity and Light each carry comparable weightage, and together these three chapters account for roughly 35–40% of the theory paper.
Mastering seven chapters deeply — Life Processes, Electricity, Light, Chemical Reactions, Acids, Bases & Salts, Metals and Non-Metals, and Control & Coordination — and revising the remaining chapters for basic coverage gives most students a strong path to 85–90+ marks. The key is depth in high-weightage chapters, not superficial coverage of all thirteen.
Yes — and they are among the easiest marks to earn with practice. Diagrams from Life Processes (alimentary canal, heart, nephron), Light (ray diagrams), and Electricity (circuit diagrams) appear in almost every paper. A student who has practised these 10–15 times each can draw a correct, labelled diagram in 2–3 minutes during the exam.
Natural Resources carries only 5 marks. Spend enough time to understand the core concepts and answer basic questions — not more. This is a low-return chapter relative to time invested. Use that time on Life Processes or Electricity instead.
The core chapter structure remains stable. However, the exam pattern under NEP 2020 increasingly emphasises competency-based and case-based questions. To have an idea about competency based questions class 10, practice through Oswaal question banks for sure-shot success.
