CBSE Class 10 Science carries 80 marks in theory. The paper covers Physics, Chemistry, and Biology in one 3-hour exam. Knowing which chapters carry the most marks and which question types repeat every year gives you a clear edge.

This guide breaks down the most important questions from each section based on the 2027 exam pattern.

Mark Distribution by Unit

Unit	Topics	Marks
Chemical Substances	Chemical Reactions, Acids-Bases-Salts, Metals and Non-Metals, Carbon Compounds, Periodic Classification	25
World of Living	Life Processes, Control and Coordination, Reproduction, Heredity and Evolution	25
Natural Phenomena	Light - Reflection and Refraction, Human Eye	12
Effects of Current	Electricity, Magnetic Effects of Electric Current	13
Natural Resources	Our Environment, Management of Natural Resources	5

Key insight: Chemistry (25 marks) and Biology (25 marks) together carry 50 out of 80 marks. Physics carries 25 marks. Environment carries only 5 marks.

Chemistry: Most Important Questions

Chapter 1: Chemical Reactions and Equations

This chapter is the foundation. Questions appear in every section of the paper.

Write balanced chemical equations for: (a) burning of magnesium ribbon, (b) reaction of zinc with dilute sulphuric acid, (c) decomposition of ferrous sulphate. (3 marks — asked almost every year)
What is a combination reaction? Give an example. (2 marks)
What are the differences between exothermic and endothermic reactions? Give two examples of each. (3 marks)
What is rancidity? How can it be prevented? (2 marks)

Tip: Balancing equations is a guaranteed question. Practice at least 20 different equations.

Chapter 2: Acids, Bases, and Salts

What happens when an acid reacts with a metal? Write the general equation and give one example. (2 marks)
How is Plaster of Paris prepared? Write the chemical equation. (3 marks)
What is a pH scale? What happens to the pH of a solution when you add an acid to it? (2 marks)
Why does dry HCl gas not show acidic behavior? (1 mark MCQ — very frequently asked)

Chapter 3: Metals and Non-Metals

What is the reactivity series? Arrange the following metals in decreasing order of reactivity: Cu, Fe, Zn, Na, Au. (2 marks)
Explain the extraction of metals of medium reactivity from their sulphide ores. (5 marks)
What is corrosion? How can iron be protected from corrosion? (3 marks)
Why are ionic compounds generally solid at room temperature? (1 mark)

Chapter 4: Carbon and Its Compounds

What is a homologous series? Give any two characteristics. (2 marks)
Draw the structure of ethanol and ethanoic acid. (2 marks)
What are the differences between soap and detergent? (3 marks)
Write the chemical equation for the saponification reaction. (2 marks)

Biology: Most Important Questions

Chapter 6: Life Processes

This chapter alone carries 8-10 marks typically.

Draw a well-labeled diagram of the human digestive system. (5 marks)
Describe the process of nutrition in Amoeba. (3 marks)
What is the role of saliva in the digestion of food? (2 marks)
Explain the mechanism of breathing in human beings. (3 marks)
Draw a diagram of the human heart and label: left ventricle, right atrium, aorta, pulmonary artery. (3 marks)

Tip: The digestive system and heart diagrams are asked in alternate years. Learn both perfectly.

Chapter 7: Control and Coordination

What is the difference between a reflex action and walking? (2 marks)
Draw a labeled diagram of a neuron. (3 marks)
What are plant hormones? Name any two and state their functions. (3 marks)

Chapter 8: How Do Organisms Reproduce?

What are the advantages of vegetative propagation? (2 marks)
Draw a well-labeled diagram of the longitudinal section of a flower. (3 marks)
What is the significance of DNA copying in reproduction? (3 marks)

Physics: Most Important Questions

Chapter 10: Light - Reflection and Refraction

State Snell's law of refraction. A light ray passes from air to glass. If the angle of incidence is 45 degrees and the refractive index of glass is 1.5, find the angle of refraction. (3 marks)
An object is placed at 15 cm from a convex mirror of focal length 10 cm. Find the position, nature, and size of the image. (3 marks)
Draw a ray diagram to show the image formed when an object is placed between the focus and centre of curvature of a concave mirror. (2 marks)

Tip: Mirror formula and lens formula numericals carry 3-5 marks. Practice at least 10 numericals from each.

Chapter 12: Electricity

State Ohm's law. Draw the circuit diagram used to verify it. (3 marks)
Three resistors of 2 ohm, 3 ohm, and 6 ohm are connected in parallel. Find the equivalent resistance. (3 marks)
What is the difference between resistance and resistivity? (2 marks)
An electric heater of resistance 8 ohm draws 15 A from the supply. Calculate the rate at which energy is dissipated. (2 marks)

Chapter 13: Magnetic Effects of Electric Current

What is electromagnetic induction? State Faraday's law. (3 marks)
Draw the pattern of magnetic field lines around a current-carrying solenoid. (2 marks)
What is the function of a fuse in an electric circuit? (1 mark)

Scoring Strategy for Science

Do the MCQ section first (20 marks in 15-20 minutes). These test direct recall.
Biology questions next — draw neat, labeled diagrams. Diagrams carry 2-3 marks each and are the easiest marks in the paper.
Chemistry equations — always balance. An unbalanced equation gets zero marks.
Physics numericals last — these take the most time. Show every step and include units.
Never leave the Environment chapter — it is only 5 marks but the questions are very simple. Free marks.

Practice on Padhaao

Every CBSE Class 10 Science chapter is available with solved examples, board-exam style questions, and 10 different learning modes.

Quiz mode: 10 MCQs per topic for Section A practice
Exam Practice: Board-style paper with model answers
Important Questions: Most likely board exam questions with marks distribution

3 free chapters every day.

CBSE Class 10 Science Important Questions 2027 - Chapter Wise