TEACHGYAN • CLASS 10 SCIENCE • NCERT 2026–27
Chapter 1: Chemical Reactions and Equations
Detailed Notes • Diagrams • Experiments • Competency • Board Practice
📖 Chapter Explanation
Chemical reactions transform reactants into new substances. This chapter develops how to recognise reactions, represent them with balanced equations and classify common reaction types. It also connects oxidation, reduction, corrosion and rancidity with everyday observations.
🧭 Concept Map
🔬 Core Science Concepts
A chemical equation must obey conservation of mass. In 2Mg + O₂ → 2MgO, the number of Mg and O atoms is the same on both sides. Combination, decomposition, displacement and double displacement are identified from the pattern of reactants and products.
💡 Worked Example / Observation
Magnesium ribbon burns with a bright light to form magnesium oxide. The equation 2Mg + O₂ → 2MgO is balanced and represents a combination reaction.
🖼️ Diagram & Visual Study
Draw and label: a key diagram/process from this chapter. Add arrows showing the sequence or relationships, then write one function/observation beside each labelled part. This page is designed to be paired with textbook figures for visual revision.
⚠️ Common Errors
Do not change subscripts while balancing. Coefficients are changed because changing a subscript changes the substance itself.
🧠 Concept-Based MCQs
- A balanced equation obeys: A) conservation of mass B) conservation of volume only C) conservation of temperature D) conservation of colour
- 2H₂+O₂→2H₂O is a: A) decomposition B) combination C) displacement D) neutralisation
- Oxidation can involve: A) gain of oxygen B) loss of oxygen only C) no chemical change D) melting
- Rancidity is associated with oxidation of: A) fats and oils B) water C) salts only D) metals only
Answer Key: 1-A, 2-B, 3-A, 4-A.
📊 Case-Based / Competency
A metal reacts with an acid and releases a gas. Students identify the evidence of reaction, write the word equation, predict the gas and explain the reaction type.
- Identify the scientific concept.
- Use the relevant equation, process or diagram.
- Explain the observation using scientific reasoning.
- State and justify the conclusion.
🔎 Extension Case
An iron object is left exposed to moist air. Students explain rusting as a chemical change, identify conditions that promote it and propose ways to reduce corrosion.
🔥 HOTS & Board Challenge
- Predict what would happen if one condition changed.
- Explain the observation at the particle/cellular/system level where appropriate.
- Correct a plausible misconception and justify your correction.
- Design a simple investigation to test a related idea.
✍️ Exam Practice
- Define the central scientific terms.
- Explain one process using a labelled diagram.
- Write and balance/interpret an equation where applicable.
- Solve a competency-based situation.
- Answer a 5-mark board-style question with reasoning.
🧪 Activity / Experiment Corner
- State the aim.
- List the key materials/conditions.
- Predict the observation.
- Record the result.
- Explain the scientific principle.
📄 Practice Worksheet
- 5 concept checks
- 5 application questions
- 3 diagram/process questions
- 2 case-based questions
- 2 HOTS questions
- 1 board-style challenge
🎯 One-Minute Revision
observation → reactants/products → word equation → balanced equation → reaction type → oxidation/reduction → everyday applications
🏆 Mastery Checklist
- ☐ I can explain the concept in my own words.
- ☐ I can draw/interpret the key diagram.
- ☐ I can explain observations scientifically.
- ☐ I can answer competency and case-based questions.
- ☐ I can apply the concept to a new situation.
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Original explanatory study material aligned to NCERT/CBSE topics; textbook passages are not reproduced verbatim.