Introduction
Everything around us consists of different substances, some of which are acidic, some are basic, and some are neutral. The sour taste of lemons, the bitterness of soap, and the neutrality of common salt are all due to the chemical nature of these substances. This chapter will help us understand acids, bases, and salts, their properties, reactions, and importance in daily life.

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1. Acids – The Sour Substances
Definition of AcidsAcids are substances that have a sour taste and show specific reactions when tested with indicators. They release hydrogen ions (H?) when mixed with water, which is responsible for their acidic properties.

Examples of Acids

Natural Acids (found in food items):
Present in citrus fruits like oranges and lemons.
Found in curd, tamarind, vinegar, and tomatoes.

Mineral Acids (prepared in laboratories and used in industries):
Used in car batteries.
Found in stomach acid, helping in digestion.
Used in fertilizers and explosives.

Properties of Acids
They have a sour taste due to the presence of H? ions.
They react with metals, producing gas release.
They turn blue litmus paper red.
Strong acids are corrosive and can cause damage.
They conduct electricity in solution (electrolytes).
They react with bases to form salt and water (neutralization reaction).
They react with carbonates to produce gas, salt, and water.

2. Bases – The Bitter and Soapy Substances
Definition of BasesBases are substances that taste bitter and feel slippery and soapy to touch. They release hydroxide ions (OH?) when mixed with water, which gives them their basic properties.

Examples of Bases

Natural Bases (found in plants and minerals):
Found in substances like lime water.
Used in antacids to relieve stomach acidity.

Industrial Bases (used in cleaning and manufacturing):
Used in soap-making.
Found in cleaning agents like detergents and alkaline batteries.

Properties of Bases
They have a bitter taste.
They feel slippery when touched (soap contains bases).
They turn red litmus paper blue.
They conduct electricity in solution (electrolytes).
They react with acids to form salt and water (neutralization).

3. Salts – The Neutral Compounds
Definition of SaltsSalts are substances formed when acids and bases react with each other in a neutralization reaction. They can be neutral, slightly acidic, or slightly basic.

Examples of Salts

Table Salt: Used in food.
Chalk Powder: Used in blackboards.
Fertilizers: Help in crop growth.

Properties of Salts
Some are neutral, while others may be slightly acidic or basic.
They dissolve in water and conduct electricity.
Used in industries, food preparation, and agriculture.

4. Indicators – Identifying Acids and Bases
Since tasting a substance is unsafe, we use indicators to identify acids and bases.

Types of Indicators

Natural Indicators:
Litmus: Red in acid, blue in base.
Turmeric: Red in base, yellow in acid.
China Rose: Dark pink in acid, green in base.

Synthetic Indicators:
Phenolphthalein: Colorless in acid, pink in base.
Methyl Orange: Red in acid, yellow in base.

5. pH Scale – Measuring Acidity and Basicity

The pH scale helps measure the strength of acids and bases.
Acidic substances have a pH < 7.
Neutral substances have a pH = 7.
Basic substances have a pH > 7.

Importance of pH in Daily Life:
Stomach pH helps in digestion.
Soil pH affects crop growth.
Water pH ensures safe drinking water.

6. Important Reactions of Acids and Bases

(i) Reaction of Acids with MetalsAcids react with metals, releasing gas and forming salt. This reaction is responsible for corrosion.
(ii) Neutralization Reaction (Acid + Base → Salt + Water)This reaction occurs in medicine (antacids relieve acidity), agriculture (fertilizers), and industrial applications.
(iii) Reaction of Acids with CarbonatesAcids react with carbonates, producing gas, salt, and water. This reaction is used in baking.

7. Importance of Acids, Bases, and Salts in Daily Life

Digestion: Stomach acid helps break down food.
Antacids: Contain bases to neutralize acidity.
Table Salt: Essential for health.
Soaps and Detergents: Contain bases for cleaning.
Fertilizers: Enhance plant growth.
Rust Removal: Vinegar, an acid, helps remove rust.

Frequently Asked Questions (FAQs)

Q1: Why do acids taste sour?
Acids release H? ions, which interact with our taste buds, producing a sour taste.

Q2: Why should we not touch strong acids and bases?
Strong acids and bases are corrosive, which means they can cause burns.

Q3: Why does soap feel slippery?
Soap is a base and has a slippery feel due to its reaction with oils and fats.

Q4: What happens when we mix an acid and a base?
They undergo neutralization, forming salt and water.

Q5: Why is pH important in daily life?
pH plays a crucial role in digestion, agriculture, and cleaning.

Q6: Why does vinegar help remove rust?
Vinegar is an acid and reacts with rust, helping dissolve it.

Q7: How do antacids help with acidity?
Antacids contain mild bases that neutralize excess stomach acid, providing relief.