CBSE · Class 10 · Science · Chapter 1
Chemical Reactions and Equations — Class 10 Science (CBSE) explained
- Board exam 2026-27
- 2 lessons
- 13 scenes
- About 11 min
- Updated
Quick answer
Chemical Reactions and Equations is Chapter 1 of CBSE Class 10 Science. It covers meaning of a chemical reaction, chemical equation structure, balancing equations, combination and exothermic reactions, decomposition reactions and double displacement and precipitation. AI Lessons teaches it in 2 narrated lessons (about 11 minutes) with an AI tutor and board-pattern practice.
What you’ll learn
Lesson 1: Chemical reactions and equations
5 min- Chemical reactions are already happening around you
- Burning magnesium: a reaction you can see
- Four clues that a chemical reaction has taken place
- From words to symbolic chemical equations
- Balance equations without changing chemical formulae
- Make chemical equations more informative
Lesson 2: Types and effects of chemical reactions
6 min- Combination reactions and exothermic change
- Decomposition can be driven by heat, electricity or light
- A more reactive element can displace another
- Double displacement can create a precipitate
- Oxidation and reduction happen together
- Corrosion and rancidity are oxidation in daily life
- Can you classify, balance and explain?
Key concepts
- Meaning of a chemical reaction
- Chemical reactions are not something that only happens inside a laboratory.
- Chemical equation structure
- The substances that react are called reactants and they are written on the left-hand side. The new substances that are formed are called products and they are written on the right-hand side.
- Balancing equations
- The golden rule is simple: change coefficients in front of formulae, never the subscripts inside a formula.
- Combination and exothermic reactions
- A reaction that releases heat along with its products is called exothermic. One reaction can therefore have a structural label, combination, and an energy label, exothermic, at the same time.
- Decomposition reactions
- A decomposition reaction is the opposite pattern. One reactant breaks down into two or more simpler products.
- Double displacement and precipitation
- A precipitate is an insoluble solid formed during a reaction in solution, and any reaction that produces one can be called a precipitation reaction.
Exam focus
- Board exam
- CBSE assesses this chapter in the 2026-27 year-end board examination.
- Syllabus
- Chemical Reactions and Equations: Chemical reactions, Chemical equation, Balanced chemical equation, types of chemical reactions: combination, decomposition, displacement, double displacement, precipitation, endothermic exothermic reactions, oxidation and reduction.
- Paper pattern
- 80 marks, 3 hours, 39 questions in three sections (A Biology, B Chemistry, C Physics); internal assessment 20. Units: I Chemical Substances 25, II World of Living 25, III Natural Phenomena 12, IV Effects of Current 13, V Natural Resources 5.
- Question style
- About 50% of board questions are competency-focused: case-based, source-based, integrated, data interpretation, situational and application-oriented.
- Practice in the app
- 44 board-pattern questions with marking schemes: 10 multiple choice (1 mark), 7 assertion–reason (1 mark), 12 very short answer (2 marks), 8 short answer (3 marks), 2 long answer (5 marks) and 5 case-based (4 marks).
Sample questions with marking points
Board-pattern questions from the AI Lessons practice set for this chapter. The marking points show what an examiner looks for; full model answers are in the app.
Very short answer2 marks
Read the equation 3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g). Explain why water is marked (g), and identify the physical state of each product.
Marking points
- H₂O(g) indicates that water is used as steam, in the gaseous state.1
- Fe₃O₄ is solid.0.5
- Hydrogen is gaseous.0.5
Short answer3 marks
An oil-rich snack develops an unpleasant smell and a changed taste after being left open for a long time. Name the process and explain its cause. State two measures, other than nitrogen flushing, that can slow or prevent it, explaining how each helps.
Marking points
- Names the process as rancidity.0.5
- Explains that fats and oils are oxidised.0.5
- Identifies airtight storage.0.5
- Explains that airtight storage helps slow oxidation.0.5
- Identifies addition of antioxidants.0.5
- Explains that antioxidants help prevent oxidation.0.5
Frequently asked questions
What does Chemical Reactions and Equations cover in Class 10 Science?
It covers meaning of a chemical reaction, chemical equation structure, balancing equations, combination and exothermic reactions, decomposition reactions and double displacement and precipitation. AI Lessons teaches it in 2 lessons: Chemical reactions and equations and Types and effects of chemical reactions.
Is Chemical Reactions and Equations in the CBSE Class 10 board exam?
Yes. CBSE assesses Chemical Reactions and Equations in the 2026-27 year-end board examination.
Which feature is essential for a change to be classified as a chemical reaction?
Formation of substances with a different nature and identity. A chemical reaction changes the nature and identity of the starting substances and forms new substances.
What does the arrow convey in the word equation Magnesium + Oxygen → Magnesium oxide?
Magnesium and oxygen react to produce magnesium oxide. The arrow points from the reactants towards the product and shows the direction of the reaction.
What does exothermic mean?
A reaction that releases heat along with its products is called exothermic. One reaction can therefore have a structural label, combination, and an energy label, exothermic, at the same time.
What is a decomposition reaction?
A decomposition reaction is the opposite pattern. One reactant breaks down into two or more simpler products.
What is a precipitate?
A precipitate is an insoluble solid formed during a reaction in solution, and any reaction that produces one can be called a precipitation reaction.
How does AI Lessons teach Chemical Reactions and Equations?
As 2 narrated, animated lessons (13 scenes, about 11 minutes in all), with an AI tutor that knows the step you are on and board-pattern practice with marking schemes. The full lessons open after sign-in on an AI Lessons account.
Watch the full lesson
Chemical Reactions and Equations, as a narrated, animated lesson
2 lessons · 13 animated scenes · about 11 minutes, with an AI tutor that knows the step you are on and 44 board-pattern questions with marking schemes.
Lessons open after sign-in. A parent or guardian holds the account and adds each child.