Chemical Reactions and Equations — العلوم – الصف 10 (CBSE) بشرح مبسّط

ما ستتعلّمه

1. 1

   الدرس 1: Chemical reactions and equations

   5 دقائق
   • 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
2. 2

   الدرس 2: Types and effects of chemical reactions

   6 دقائق
   • 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?

المفاهيم الأساسية

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.

تركيز الامتحان

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).

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1. Very short answerدرجتان

   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.

   نقاط التصحيح

   • H₂O(g) indicates that water is used as steam, in the gaseous state.1
   • Fe₃O₄ is solid.0.5
   • Hydrogen is gaseous.0.5

2. Short answer3 درجات

   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.

   نقاط التصحيح

   • 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

الأسئلة الشائعة

فصول أخرى في العلوم – الصف 10

• الفصل 2Acids, Bases and Saltsالدروس: 4 · الدقائق: 23→
• الفصل 3Metals and Non-metalsالدروس: 4 · الدقائق: 25→
• الفصل 4Carbon and its Compoundsالدروس: 4 · الدقائق: 27→
• الفصل 5Life Processesالدروس: 5 · الدقائق: 31→

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