Interactive Mind maps- Assessment -Chemical Equations

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Class 10 Physical Science

Chapter 2: Chemical Equations

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🗺️ Interactive Mind Map 1: Chemical Equations

Click any coloured branch to explore the concept and examples.

⚗️ CHEMICAL EQUATIONS

Start exploring!

Choose any coloured branch above. Its explanation and example will appear here.

🧠 Interactive Mind Map 2: Types of Reactions

CHEMICAL REACTIONS

Click a reaction type to see its pattern and example.

📚 Student-Ready Notes

1. What is a chemical reaction?

A chemical reaction is a process in which one or more substances change into new substances with different properties.

2. What is a chemical equation?

A chemical equation represents a chemical reaction using chemical symbols and formulae.

Hydrogen + Oxygen → Water

2H₂ + O₂ → 2H₂O

• Reactants: Substances that take part in a reaction; written on the left.
• Products: New substances formed; written on the right.
• Arrow (→): Indicates the direction of the reaction.
• Coefficients: Numbers placed before formulae to balance atoms.
• State symbols: (s) solid, (l) liquid, (g) gas, (aq) aqueous solution.

3. Balanced and unbalanced equations

A balanced equation has the same number of atoms of each element on both sides. It follows the law of conservation of mass.

Unbalanced: Mg + O₂ → MgO

Balanced: 2Mg + O₂ → 2MgO

Remember: Change coefficients to balance an equation. Never change subscripts in a chemical formula; doing so changes the substance.

4. Steps to balance a chemical equation

1. Write the correct formulae of all reactants and products.
2. Count atoms of every element on both sides.
3. Add suitable coefficients to balance the atoms.
4. Recount all atoms and reduce coefficients to the smallest whole-number ratio.
5. Include state symbols and reaction conditions where required.

5. Types of chemical reactions

Type	Example
Combination	CaO + H₂O → Ca(OH)₂
Decomposition	CaCO₃ → CaO + CO₂ (on heating)
Displacement	Zn + CuSO₄ → ZnSO₄ + Cu
Double displacement	AgNO₃ + NaCl → AgCl + NaNO₃
Combustion / oxidation	CH₄ + 2O₂ → CO₂ + 2H₂O

These equations are balanced. In the decomposition example, heating is required. Silver chloride forms a precipitate in the double-displacement example.

6. Exothermic and endothermic reactions

• Exothermic: Releases energy to the surroundings. Example: combustion of fuels.
• Endothermic: Absorbs energy from the surroundings. Example: thermal decomposition of calcium carbonate.

7. Oxidation and reduction

• Oxidation: In classical examples, gain of oxygen or loss of hydrogen; in electron terms, loss of electrons.
• Reduction: In classical examples, loss of oxygen or gain of hydrogen; in electron terms, gain of electrons.
• Redox reaction: Oxidation and reduction occur together.

CuO + H₂ → Cu + H₂O

CuO is reduced to Cu, while H₂ is oxidised to H₂O.

8. Corrosion and rancidity

• Corrosion: Gradual damage to a metal by its environment. Rusting of iron requires oxygen and moisture.
• Prevention: Painting, oiling, greasing, galvanising or suitable protective coatings.
• Rancidity: Oxidation of fats and oils that causes unpleasant smell and taste.
• Prevention: Airtight storage, refrigeration, antioxidants and limiting exposure to air.

9. Important observations

• Evolution of gas or formation of a precipitate may indicate a chemical reaction.
• Colour change and temperature change may also indicate a reaction.
• Symbols such as Δ above an arrow indicate heating; sunlight or electricity may be shown as reaction conditions.

Exam tip: Balance the equation first, identify the reaction type second, and explain the evidence or condition third.

📝 Assessment: Test Your Knowledge

Answer all 10 questions. Each correct answer carries 1 mark. No negative marking.

📊 Your Assessment Result

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🎯 Quick Revision Checklist

I can distinguish reactants and products.
I can balance chemical equations.
I can identify the major reaction types.
I can explain oxidation, reduction and redox.
I can explain corrosion and rancidity.

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