Chemical Reactions and Equations Class 10 notes– A Simple Guide
Introduction
Chemical reactions happen all around us — when food is cooked, iron rusts, or candles burn. By learning how these reactions work, we can better understand the science behind many daily activities. This guide will help you learn what chemical reactions are, how to write them as equations, and why they’re important.
1. What is a Chemical Reaction?
A chemical reaction is when one or more substances (called reactants) change into new substances (called products) with different properties. (Chemical Reactions and Equations Class 10 notes)
It’s not like physical changes such as melting or freezing, where the substance stays the same. In chemical changes, the bonds between atoms break and new ones are formed.
Example:
When you burn a magnesium ribbon in air, it reacts with oxygen and forms a white powder called magnesium oxide.
2. Signs of a Chemical Reaction
You can often tell a chemical reaction is happening by these changes:
- A new state is formed (solid, liquid, or gas)
- Color changes
- A gas is released (bubbles/fizzing)
- Temperature goes up or down
- A precipitate (solid) is formed from two liquids
3. What is a Chemical Equation?
A chemical equation is a short and easy way to describe a chemical reaction using symbols and formulas for the substances involved.
Example:
When methane burns in oxygen:
CH₄ + 2O₂ → CO₂ + 2H₂O
This shows that methane and oxygen react to form carbon dioxide and water.
How to Write a Chemical Equation:
- Write reactants on the left
- Write products on the right
- Use an arrow (→) to show the flow of the reaction
- Use plus signs (+) to separate substances
4. Types of Chemical Reactions
4.1 Combination Reaction
More than one substance joins together to produce a single new product.
Example:
CaO + H₂O → Ca(OH)₂
(Hydrated lime is made when quicklime reacts with water)
4.2 Decomposition Reaction
One compound splits into two or more simpler substances, usually by heating, light, or electricity.
Example:
CaCO₃ → CaO + CO₂
(When heated, calcium carbonate splits into calcium oxide and carbon dioxide)
4.3 Exothermic and Endothermic Reactions
- Exothermic reactions give off heat
(Example: Burning wood) - Endothermic reactions absorb heat
(Example: Photosynthesis in plants)
4.4 Displacement Reaction
In these reactions, a stronger element pushes out a weaker one from its compound.
Example:
Zn + CuSO₄ → ZnSO₄ + Cu
(Zinc takes the place of copper in copper sulfate)
4.5 Double Displacement Reaction
Two compounds swap their ions to form two new compounds. Often, a precipitate is formed.
Example:
Na₂SO₄ + BaCl₂ → BaSO₄ ↓ + 2NaCl
(Barium sulfate forms as a white solid)
Chemical Reactions and Equations Class 10 notes
5. Redox Reactions (Oxidation and Reduction)
- Oxidation means gaining oxygen or losing hydrogen
- Reduction means gaining hydrogen or losing oxygen
These happen together in a redox reaction.
Example:
CuO + H₂ → Cu + H₂O
(Copper oxide is reduced to copper; hydrogen is oxidized to water)
6. Balanced Chemical Equations
A balanced chemical equation ensures that each type of atom appears equally on both sides, showing that no atoms are lost or created in the reaction.
Steps to Balance an Equation:
- Write the unbalanced (skeletal) equation
- Count atoms of each element
- Add numbers (coefficients) in front to balance
- Check again and adjust if needed
7. How to Make Chemical Equations More Informative
To make chemical equations clearer:
- Show physical states (s = solid, l = liquid, g = gas, aq = dissolved in water)
- Use arrows like ↑ (gas released) or ↓ (precipitate formed)
- Mention conditions (like heat, light, catalyst) above the arrow
8. Chemical Reactions in Daily Life
8.1 Corrosion
When metals slowly get damaged by air, water, or chemicals — it’s called corrosion. Rusting of iron is a common example.
8.2 Rancidity
When fats and oils spoil due to air (oxidation), it causes rancidity — giving a bad taste and smell.
8.3 How to Prevent Them
- Paint or galvanize metal objects to avoid rust
- Store food in airtight containers
- Use antioxidants and keep food refrigerated
(Chemical Reactions and Equations Class 10 notes)
Conclusion
Chemical reactions are happening all the time — in our bodies, in the kitchen, and in factories. Learning how they work, how to write their equations, and how to balance them helps us understand science better and apply it in real life. Whether you’re baking, cleaning, or studying science — chemistry is always around you!