If you are searching for Class 10 Science Chapter 1 Chemical Reactions and Equations Notes, you’re in the right place! These CBSE Class 10 Science Notes are designed for quick revision and to help students score high marks in the board exams. Here you can easily download the NCERT Class 10 Science Notes PDF for Chapter 1: Chemical Reactions and Equations, completely free of cost. The notes cover all important definitions, equations, and examples from the chapter to strengthen your understanding of chemical reactions. According to the latest CBSE Exam Pattern 2025, MCQ Questions for Class 10 Science now carry 20 marks, making these notes and practice questions highly valuable for your exam preparation.
CBSE Class 10 Science Notes Chapter 1 — Chemical Reactions and Equations (PDF Free Download)
Topic: According to the latest NCERT and CBSE 2025 syllabus, Chapter-1 Chemical Reactions and Equations covers all the key topics essential for board exam preparation. Students will learn about the types of chemical reactions, balancing equations, and their applications in everyday life.
Here’s a complete list of important topics covered in this chapter:
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These Class 10 Science Notes follow the new NCERT exam pattern, making them perfect for quick revision, homework help, and board exam preparation.
⚗️ What is a Chemical Reaction? – Class 10 Science Chapter 1 Explanation
A chemical reaction is a process in which one or more substances (called reactants) are transformed into new substances (called products) with different properties. In simple words, it is the transformation of one chemical substance into another.
- Chemical reaction
- The transformation of a chemical substance into another chemical substance is known as a Chemical Reaction.
🔹 Examples of Chemical Reactions in Everyday Life
Chemical reactions are fundamental processes that occur all around us. Here are common examples you encounter daily:
Rusting of Iron
A redox reaction where iron reacts with oxygen in the presence of water/moisture to form hydrated iron(III) oxide (rust).
4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O
Setting of Milk into Curd
A fermentation process where Lactobacillus bacteria convert lactose (milk sugar) into lactic acid, causing milk proteins to coagulate.
Digestion of Food
Enzymatic hydrolysis reactions where complex carbohydrates, proteins, and fats break down into simpler absorbable molecules.
- Carbohydrates → Glucose
- Proteins → Amino acids
- Fats → Fatty acids + Glycerol
Respiration Process
Aerobic cellular respiration where glucose is oxidized to produce ATP energy, carbon dioxide, and water.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)
During a chemical reaction, the new substance formed has completely different physical and chemical properties compared to the original substance. This indicates that a chemical change has taken place.
It is important to note that in every chemical reaction, only the rearrangement of atoms occurs — no new atoms are created or destroyed. The law of conservation of mass is always followed in such reactions.
Chemical Reactions: Understanding Reactants and Products
🔬 Basic Concepts of Chemical Reactions
- Reactants
- The substances which take part in a chemical reaction are called reactants.
- Products
- The new substances produced as a result of a chemical reaction are called products.
🧪 Practical Example: Burning of Magnesium
Example: The burning of magnesium in the air to form magnesium oxide is an example of a chemical reaction.
2Mg(s) + O₂(g)
△
→
2MgO(s)
- Reactants
- Substances which take part in a chemical reaction
- Examples: Mg and O₂
- Products
- New substance formed after a chemical reaction
- Example: MgO
Characteristics of Chemical Reactions
Chemical reactions exhibit specific characteristics that help identify when a chemical change occurs. Here are the five main characteristics with detailed examples.
(i) Evolution of Gas
The chemical reaction between zinc and dilute sulphuric acid is characterised by the evolution of hydrogen gas.
Zn(s) + H₂SO₄(aq)
△→
ZnSO₄(aq) + H₂(g) ↑
Observation: Bubbles of hydrogen gas are evolved, indicated by the upward arrow (↑).
(ii) Change in Colour
Some chemical reactions are characterized by a distinct color change in the reactants.
The chemical reaction between citric acid and purple coloured potassium permanganate solution is characterised by a change in colour from purple to colourless.
The chemical reaction between sulphur dioxide gas and acidified potassium dichromate solution is characterized by a change in colour from orange to green.
(iii) Change in State of Substance
The combustion reaction of candle wax is characterised by a change in state from solid to liquid and gas.
Candle Wax Combustion:
- Wax: Solid (initial state)
- Water formed: Liquid at room temperature
- Carbon dioxide produced: Gas
Note: Some chemical reactions can show more than one characteristic.
(iv) Change in Temperature
Some reactions release or absorb heat energy, resulting in temperature changes.
The chemical reaction between quick lime and water to form slaked lime is characterized by a change in temperature (rise in temperature).
Type: Exothermic reaction (heat released)
The chemical reaction between zinc granules and dilute sulphuric acid is also characterised by a change in temperature (rise in temperature).
Observation: The reaction mixture becomes warm.
(v) Formation of Precipitate
The chemical reaction between sulphuric acid and barium chloride solution is characterised by the formation of a white precipitate of barium sulphate.
BaCl₂(aq) + H₂SO₄(aq)
△→
BaSO₄(s) ↓ + 2HCl(aq)
Precipitate: BaSO₄(s) - White precipitate indicated by downward arrow (↓)