Class 10 Science Ch2 Notes Acids, Bases & Salts 2026 PDF

Chapter 2 of Class 10 Chemistry, Acids, Bases and Salts, is one of the most important and scoring chapters in the syllabus. These class 10 science chapter 2 notes explain how acids, bases and salts behave and why they are used in our daily life.

From the sour taste of lemon to the soap we use every day, this chapter connects chemistry with real-life examples. These acid base and salt class 10 notes help you understand definitions, properties, reactions, pH scale, indicators and common salts clearly, exactly as asked in board exams.

Class 10 Science Chapter 2 Notes PDF

Acids, bases and salts are chemicals that we use in our daily life without even realising it. The sour taste of lemon, the soap we use for bathing, the toothpaste that protects our teeth, and even the medicine for stomach pain are all examples of acids, bases or salts.

An acid is a substance that produces hydrogen ions (H⁺) in aqueous solution, a base feels bitter and soapy, and a salt is formed when an acid and a base react with each other.

This chapter explains why tooth decay happens, how antacids work, why soil needs treatment and how plaster of Paris is made. 

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How to get the latest Class 10 Science Ch 2 Acid, Bases, and Salts Notes 2025-26?

Below, we have provided the links to downloadable PDFs of class 10 chemistry chapter 2 notes Science and that too for different categories of marks.

<red> ➜   <red> Ch 2 Acid, Bases, and Salts Notes

What are Acids? - Ch 2 Science Class 10 Notes

Acids are chemical compounds that release hydrogen ions (H⁺) when dissolved in water. Acids are sour and can change blue litmus paper to red. Examples of acids are:

• Hydrochloric acid (HCl), which is present in the stomach.
• Sulfuric acid (H₂SO₄), which is used in industrial processes.
• Acetic acid (CH₃COOH), the main component of vinegar.
• Citric acid (C₆H₈O₇), which is present in citrus fruits such as lemons and oranges.

Properties of Acids

Every acid behaves differently but they have some specific properties that fit them into this category:

• Taste: Acids are sour in taste. Citric acid, for example, makes lemons sour.
• Effect on Litmus Paper: Blue litmus paper is changed to red by acids.
• Reaction with Metals: Acids react with metals like zinc and magnesium, and release hydrogen gas (H₂). Example: Zn + 2HCl → ZnCl₂ + H₂

• Reaction with Carbonates and Bicarbonates: When acids react with carbonates, for example, calcium carbonate, they release carbon dioxide gas (CO₂). Example: CaCO3 + 2HCl → CaCl₂ + H₂O + CO₂

• Electrical Conductivity: Acids are able to conduct electricity in water because they dissociate to form ions (H⁺ and their respective anions).

Strength of Acids

Acids are referred to as strong acids and weak acids based on how completely they dissociate in water:

• Strong Acids: These acids dissociate totally in water. Hydrochloric acid (HCl) and sulfuric acid (H₂SO₄) are examples.
• Weak Acids: These acids dissociate partially in water. Acetic acid (CH₃COOH) and citric acid (C₆H₈O₇) are examples.

What are Bases? - Chemistry Class 10 Chapter 2 Notes

Bases are substances that produce hydroxide ions (OH⁻) when they dissolve in water. When dissolved, they are often referred to as alkalis. Bases have a bitter taste and a slippery texture. Some common examples of bases are:

• Sodium hydroxide (NaOH), also known as caustic soda.
• Potassium hydroxide (KOH), used in soap making.
• Ammonium hydroxide (NH₄OH), used in most household cleaning products.

Properties of Bases

Bases show properties opposite to acids in many cases like, Take a look below to learn how:

• Taste: Bases generally have a bitter flavor. 
• Effect on Litmus Paper: Bases change red litmus paper to blue.
• Feel: Bases feel slippery or soapy to the touch, which is why they are often referred to as alkalis when dissolved in water.
• Reaction with Acids: Bases react with acids to form salt and water, a process known as neutralization. Example: NaOH + HCl → NaCl + H₂O

• Electrical Conductivity: Bases dissolved in water can conduct electricity because they dissociate to form hydroxide ions (OH⁻).

Strength of Bases

Similar to acids, bases are also strong or weak based on their dissociation in water:

• Strong Bases: These completely dissociate in water. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are examples.
• Weak Bases: These dissociate only partially in water. An example is ammonia (NH₃), that dissolves in water to give ammonium hydroxide (NH₄OH).

What are Salts? - Class 10 Ch 2 Science Notes

Salts are ionic compounds formed when an acid reacts with a base. A common example is the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH), which results in sodium chloride (NaCl), better known as table salt.

Formation of Salts

Salts are formed during a neutralization reaction between an acid and a base. In this process, the hydrogen ion (H⁺) from the acid combines with the hydroxide ion (OH⁻) from the base to form water (H₂O), and the remaining ions form the salt.

Example:

HCl + NaOH → NaCl + H₂O

• Salts can also be formed when acids react with various other substances, including metals, metal oxides, and metal carbonates.

Common Uses of Salts

When we hear the word “salts”, only table salt comes to mind. Or maybe black salt? Here is a list of some other salts and how they are used in daily life.

(a) Washing Soda Na₂CO₃·10H₂O

Preparation: NaCl → NaHCO₃ → Na₂CO₃

Uses:

• Cleaning agent
• Softening hard water
• Glass and soap industry

(b) Baking Soda NaHCO₃

Preparation: NaCl + NH₃ + H₂O + CO₂ → NaHCO₃

Uses:

• Baking cakes
• Antacid
• Fire extinguisher

(c) Bleaching powder (Calcium oxychloride, CaOCl₂)

Preparation: Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O

Uses:

• Bleaching cotton and linen
• Disinfecting water
• Oxidising agent

(d) Plaster of Paris CaSO₄·½H₂O

Preparation: CaSO₄·2H₂O → CaSO₄·½H₂O + 1½H₂O

Uses:

• Making casts
• Statues and toys
• False ceilings

(e) Gypsum CaSO₄·2H₂O

Uses:

• Cement
• Fertilisers

Water of Crystallisation - Acid Base and Salt Notes

Water of Crystallisation is the fixed number of water molecules present in one formula unit of a salt.

Examples:

• CuSO₄·5H₂O
• Na₂CO₃·10H₂O

What is pH Scale?

The pH scale is used to measure the acidity or basicity of a solution. The scale ranges from 0 to 14:

• pH = 7: Neutral (pure water)
• pH < 7: Acidic (lemon juice or vinegar)
• pH > 7: Basic or Alkaline (soap solution or baking soda solution)

pH value of a solution is based on the concentration of hydrogen ions (H⁺) it contains. A higher concentration of H⁺ ions indicates a more acidic solution, resulting in a lower pH value.

Importance of pH

pH (potential of Hydrogen) - pH stands for “potential of hydrogen” and indicates the acidity or basicity of a solution,

• In the Human Body: Blood pH is approximately 7.4, which is slightly alkaline. Any major change from this level may be a sign of health issues.
• In Soil: Soil pH is very important for plant growth. Most plants grow well in slightly acidic to neutral soil pH for optimal growth.
• In Industry: pH is an important factor in most industrial operations, including food processing, chemical production, and waste treatment.

How Indicators help? - Chemistry Class 10 Ch 2 notes

Indicators are substances that change color depending on the pH of a solution. They are useful in finding out whether a solution is acidic or basic. Some of the common indicators include:

• Litmus Paper: Red litmus paper turns blue in basic solutions, and blue litmus paper turns red in acidic solutions.
• Phenolphthalein: It is pink in basic solutions and colorless in acidic solutions.
• Methyl Orange: The indicator is yellow in alkaline solutions and red in acidic solutions.

Quick Revision – Acids, Bases and Salts Class 10

This section highlights the most important points from Acids, Bases and Salts that students should revise before examinations.

1. Acids produce hydrogen ions (H⁺) in aqueous solutions, bases produce hydroxide ions (OH⁻), and salts are formed through neutralisation reactions.

2. Acids and bases show their acidic or basic nature only when dissolved in water.

3. The pH scale ranges from 0 to 14 and is used to measure the strength of acids and bases:

• pH < 7 indicates an acidic solution
• pH = 7 indicates a neutral solution
• pH > 7 indicates a basic solution

4. Indicators help identify whether a solution is acidic or basic:

• Litmus: Turns red in acids and blue in bases
• Phenolphthalein: Colourless in acidic solutions and pink in basic solutions
• Methyl orange: Red in acidic solutions and yellow in basic solutions

5. Students should learn definitions clearly before memorising chemical reactions and uses.

6. Practising balanced chemical equations is essential for accuracy in board examinations.

7. Solving pH-based numericals helps in understanding acidity and basicity more effectively.

8. Revise the preparation and uses of common salts such as baking soda, washing soda, and plaster of Paris, as they are frequently asked in exams.

FAQs

Q1. What are the main properties of acids, bases, and salts?

Ans. Acids produce hydrogen ions (H⁺) when dissolved in water. They have a sour taste and turn blue litmus red. Bases produce hydroxide ions (OH⁻) in aqueous solutions, feel soapy in nature, and turn red litmus blue. Salts are formed by the neutralisation of acids and bases. Depending on their formation, salts can be acidic, basic, or neutral.

Q2. What is the difference between strong and weak acids and bases?

Ans. Strong acids and bases ionise completely in water, which means they produce a large number of ions. Weak acids and bases ionise only partially in water and therefore show less acidic or basic strength. For example, hydrochloric acid and sodium hydroxide are strong, while acetic acid and ammonia are weak.

Q3. What is the pH scale and why is it important in everyday life?

Ans. The pH scale is used to measure the acidity or basicity of a solution and ranges from 0 to 14. It is important in daily life because it helps explain problems like tooth decay, the working of antacids, and the need to maintain proper soil pH for crops.

Q4. Which natural indicators are used to test acids and bases?

Ans. Natural indicators are substances obtained from plants that show colour changes in acidic or basic solutions. Litmus, turmeric, and china rose are commonly used natural indicators to identify acids and bases.

Q5. Why should curd and sour substances not be stored in brass or copper vessels?

Ans. Curd and sour foods contain acids that react with copper or brass to form harmful salts. These salts can mix with food and may cause health problems, which is why such foods should be stored in non-reactive containers.

Q6. What happens when acids react with metals and carbonates?

Ans. When acids react with metals, they form a salt and release hydrogen gas. When acids react with carbonates or bicarbonates, salt, water, and carbon dioxide gas are produced.

Q7. What are some common examples of acids, bases, and salts used in daily life?

Ans. Citric acid in lemons and acetic acid in vinegar are common acids used daily. Sodium hydroxide and calcium hydroxide are common bases used in soap making and whitewashing. Examples of salts include sodium chloride (table salt), baking soda, and washing soda.