CBSE Science Chapter 5 Acids, Bases and Salts Class 7 Notes [Free PDF Download]: The class 7 Science Syllabus aims to build a solid foundation for students so that they can study and understand their advanced science syllabuses in the following classes. They can develop their knowledge in a better way in the higher classes if they have a clear understanding of the new concepts. ‘Acids, Bases, and Salts’ is one of the most important chapters in the Class 7 Science syllabus. In this chapter, we learn what acids, bases, and salts are and how they are formed.

Here, students will benefit from SpeEdLabs‘ Class 7 Science Chapter 5 notes prepared by the best Chemistry experts. They can use these notes later on to answer questions in the exercises and exams using the new concepts they have learned. You can access these notes anywhere, anytime, and use them to prepare for an exam. Students can access free study materials and CBSE Solutions (NCERT) through SpeEdLabs. Those students looking for the best solutions can download Class 7 Science NCERT Solutions to help them revise the complete syllabus and do well in their examinations.

Acids, Bases and Salts Revision Notes of Class 7 Science – Chapter 5

Acids and Bases

Acids

Acids are substances that taste sour and are corrosive in nature.
It turns blue litmus paper to red.
These substances are chemically acidic in nature. E.g.: orange juice, curd, vinegar, hydrochloric acid etc.

Bases

Bases are substances that, in aqueous solution, are slippery to the touch and bitter in taste.
It turns red litmus paper to blue.
These substances are chemically basic in nature. E.g.: soap, ammonium hydroxide, calcium hydroxide, etc.

Neutralisation Reaction

When an acid and base react with each other to form a salt, water and heat then such reaction is known as neutralisation reaction.
In this reaction, the acidic and basic nature of the acid and base respectively are destroyed.
The reaction between hydrochloric acid and sodium hydroxide is a classic neutralisation reaction where sodium chloride is formed.

HCl+NaOH→NaCl(salt)+H2O

Salts

Salt is the product formed from the neutralisation reaction of acids and bases.
In the reaction between hydrochloric acid and sodium hydroxide the salt formed is sodium chloride.

HCl+NaOH→NaCl+H2O

Salt can be acidic, basic or neutral in nature.

Visual Indicators

Indicators

Substances, which are used to test whether a substance is acidic or basic, are called indicators.

	Acidic Solution	Basic Solution
Red litmus	No change	Turns blue
Blue litmus	Turns red	No change

Natural Indicators

Plants or plant parts contain useful chemicals that are used for testing an acidic or basic property of a solution are termed as natural indicators. China Rose and turmeric are examples of natural indicators.

Litmus

Litmus is a naturally occurring purple indicator, which is extracted from lichens.
When added to an acidic solution, it turns red and when added to a basic solution, it turns blue.
It is available in the form of a solution or as strips of paper known as litmus paper.

(A) Red litmus turns blue indicating a basic solution

(B) Blue litmus turns red indicating an acidic solution

Phenolphthalein

Phenolphthalein is an acid-base indicator which is colourless in acid solution but turns pink to red as the solution becomes alkaline.
It is a synthetic indicator and is used for the neutralisation experiment.

Olfactory Indicators

Olfactory indicators are substances whose smell changes whether they are mixed with an acidic or a basic solution.
Onion, clove oil and vanilla extract are examples of such indicators.

Visual Indicators

Visual Indicators are substances used to show visually (as by a change in colour) the condition of a solution with respect to the presence of a particular material (as a free acid or base).
Common examples are litmus, red cabbage, phenolphthalein, etc.

Neutralisation in Daily Life

During indigestion, taking milk of magnesia (magnesium hydroxide) gives us relief as it neutralises the effect of excess acid produced inside the stomach.
The effect of ant sting which is caused by formic acid can be neutralised by rubbing moist baking soda (basic in nature).
To ensure that plants can grow well, the soil is treated with either acids or bases depending if it’s basic or acidic in nature.
Factory wastes, generally being acidic in nature can cause environmental damage, are treated with basic substances before discharge.

Safety Measures While Using Acids

When diluting acids pour the acid into the water, NOT water into acid as this may cause spattering of the acid.
Safety gloves are to be worn whenever working with acids or bases.

Uses and Applications

pH of Soil

Excessive use of chemical fertilisers changes the pH of the soil.
Plants do not grow well when the soil is either too acidic or too basic.
Hence substances are added to bring the pH at a neutral level.

Uses of Acids and Bases

Food preservation – Citric acid.
Aerated drinks – Carbonic acid.
Baking powder – Tartaric acid.
Cooking – Acetic acid(vinegar)
Manufacture of soaps – Sodium hydroxide.
Manufacture of bleaching powder – Calcium hydroxide
As a foaming agent in fire extinguishers – Aluminium hydroxide.

Acids, Bases, and Salts: Class 7 Science Chapter 5 Overview

Class 7 students may find the chapter intimidating, but once the concepts are explained properly, it becomes quite easy to understand. In Acids Bases and Salts Class 7 notes, you will find the basic definitions and explanations of the terminologies used. Every section of the chapter has been aptly covered by the experts of SpeEdLabs so that the students can proceed in a methodical way and understand what it is all about. Let us delve a little deeper and find out what these notes are all about.

The Acid, Base and Salt Class 7 Science notes will describe what are acids and bases. After studying the chapter, you will get an idea of these chemical compounds. You will discover how the words ‘acid’ and base’ have been derived and used for everyone’s understanding. By comparing the features and characteristics of these compounds, you will be able to identify and distinguish between them. To understand deeply about the acids and bases, consider referring to the NCERT Class 7 Science Chapter 5 notes prepared by the best teachers.

The NCERT Solutions for Class 7 Science Chapter 5 will also describe what a neutralisation reaction is to the students in a simpler language. You will be able to understand the mechanism of formation of salts by figuring out how a neutralisation reaction occurs. Study the notes to find out how neutralisation is used in everyday life to cure certain ailments and solve various problems.

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Acids, Bases, and Salts: Class 7 Chapter 5 Science Notes