Chapter 5 – Acids, bases and salts

These NCERT Class 7 Science Chapter 5 notes explain the nature of acids, bases, and salts that we commonly use in daily life. The chapter helps students identify acidic and basic substances using indicators like litmus and turmeric.

Acids, Bases and Salts also explains neutralisation reactions and their importance in daily life, such as treatment of indigestion, soil improvement, and waste management. This chapter builds a basic understanding of chemistry around us.

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1. Introduction: why acids, bases and salts are studied

•  Many daily-use substances are acids, bases, or salts.
•  Taste, cleaning action, and many reactions depend on them.
•  This chapter helps to identify and classify these substances.
•  Lemon’s sour taste and soap’s soapy feel come from chemistry.

2. Acids

•  Acids are substances that taste sour and turn blue litmus red.
•  Common acids are found in daily foods and liquids.
•  Lemon juice contains citric acid.
•  Vinegar contains acetic acid.
•  Curd contains lactic acid.

3. Bases

•  Bases taste bitter, feel soapy, and turn red litmus blue.
•  Soap solution is a common base.
•  Baking soda solution shows basic nature.
•  Lime water is also a base.

4. Salts

•  Salts are formed when an acid reacts with a base.
•  This reaction is called neutralisation.
•  Salt used in food is sodium chloride.

5. Natural acids in daily life

•  Citric acid is found in lemon and orange.
•  Lactic acid is found in curd.
•  Acetic acid is found in vinegar.
•  Tartaric acid is found in tamarind and grapes.

6. Indicators

•  Indicators show whether a solution is acidic or basic.
•  Litmus, turmeric, and china rose are natural indicators.
•  Phenolphthalein and methyl orange are synthetic indicators.

7. Litmus test

•  Blue litmus turns red in an acid.
•  Red litmus turns blue in a base.
•  Neutral substances show no colour change.

8. Turmeric as indicator

•  Turmeric turns red in a base.
•  Turmeric shows no change in an acid.
•  Soap solution changes turmeric colour.

9. Neutralisation reaction

•  Neutralisation is the reaction between an acid and a base.
•  It produces salt and water.
•  General form is acid + base → salt + water.
•  Ant sting is treated with calamine using neutralisation.

10. Uses of neutralisation in daily life

•  Indigestion occurs due to excess acid, and antacids neutralise it.
•  Acidic soil is treated with quick lime or slaked lime to improve crops.
•  Factory waste is neutralised before release to protect aquatic life.

11. Acids and bases are dangerous

•  Strong acids and bases can cause skin burns.
•  They must be handled with care and safety measures.

12. Importance of salts

•  Salts are used in food.
•  Salts help in food preservation.
•  Salts are widely used in industries.

13. Important keywords with simple definitions

•  Acid – substance that tastes sour and turns blue litmus red.
•  Base – substance that tastes bitter and turns red litmus blue.
•  Salt – substance formed by reaction of acid and base.
•  Indicator – substance that shows acidic or basic nature.
•  Litmus – natural indicator obtained from lichen.
•  Neutralisation – reaction of acid and base forming salt and water.

Understanding NCERT Class 7 Science Chapter 5 – Acids, Bases and Salts is important to learn how substances behave and react with each other. The chapter clearly explains indicators, neutralisation, and safe handling of acids and bases.

These ideas are very useful for school examinations and foundation-level science preparation. Students should next read Chapter 6: Physical and Chemical Changes to understand different types of changes in matter.

FAQs

Q1. What is explained in NCERT Class 7 Science Chapter 5?
The chapter explains acids, bases, salts, indicators, and neutralisation reactions.

Q2. What are indicators?
Indicators are substances that show whether a solution is acidic or basic.

Q3. What is neutralisation?
Neutralisation is a reaction between an acid and a base that forms salt and water.

Q4. Give one daily-life example of neutralisation.
Antacids neutralising excess stomach acid is a common example.

Q5. Why is NCERT Class 7 Science Chapter 5 important for exams?
It covers basic chemistry concepts frequently asked in school and foundation-level exams.

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