Acids, Bases and Salts Class 7 Notes: CBSE Science Chapter 4

1. In Nature, Three Types of Substances are Found: 

a. Acids 

b. Bases

c. Salts

2. Acids: Acids are pungent in taste or acidic in nature. They get corroded easily. The concentrated form of acid can cut through clothes and destroy the wool away. On exposure to skin, it can cause severe burns. They act as good conductors of electricity thus allowing the electric current to pass through them. There are several types of Acids given below:

(i) Mineral Acids are acids that are prepared from minerals present in the earth’s crust.

(ii) Organic Acids are those acids that are produced by plants and animals (except hydrochloric acid).

(iii) Weak Acids are those that do not dissociate completely in solution. For example, tartaric acid, lactic acid etc.

(iv) Strong Acids have the ability to dissociate completely in solution. For example, sulphuric acid,  hydrochloric acid etc.

3. Neutralization: A reaction between an acid and a base that results in the formation of salt and water. Acid + Base gives Salt + Water.Neutralization reactions occur in our day to day life. Some of its examples are:

a. Indigestion: In this too much acid is formed in the stomach that causes indigestion. It is neutralized by taking an antacid like milk of magnesia that causes relief to the situation.

b. Ant Sting: When an ant bites, it injects formic acid inside the skin. This ant sting is then neutralized by rubbing moist baking soda (chemical name- sodium hydrogen carbonate) or by rubbing calamine (which contains zinc carbonate) over the affected area.

c. Soil Treatment: When the soil becomes too acidic, it is neutralized by adding quicklime (calcium oxide) or slaked lime (calcium hydroxide) to it.

4. Bases: Substances that are bitter in taste and soapy in appearance. Bases are classified into two:

a. Weak Bases: Those bases which produce fewer hydroxide ions in solution. For example, magnesium hydroxide, ammonium hydroxide etc.

b. Strong Bases: Those bases which produce many hydroxide ions when dissolved in water. For example, Sodium hydroxide(NaOH), Potassium hydroxide (KOH) etc.

Substances that are neither acidic nor basic are said to be neutral substances.

When an acid and a base react with each other they neutralise and forms a salt. Salt could be acidic, basic or neutral in nature.

5. Indicators are special chemicals that change their color to indicate the presence of a chemical substance. Solutions of substances show different colours in acidic, basic, and neutral solutions. Hence, It is widely used to confirm the presence of an acid, a base, or a neutral solution.

Classification of Indicators is Given Below:

1. Natural Indicators:

a. Litmus: It is obtained from lichens. It is generally available in the form of thin strips of paper or in the form of a solution.· When acid is added to blue litmus, its colour changes to red. When bases are added to red litmus paper, it changes its color to blue.

b. Turmeric: It is a natural indicator which remains yellow in neutral and acidic solutions but on coming in contact with alkaline solutions it turns red.

c. China Rose: Another naturally occuring indicator which turns acidic solutions to dark pink (magenta) and basic solution to green.

d. Red Cabbage: Turns acidic solutions to red and the basic solutions to blue.

2. Some Other Indicators:

a. Methyl Orange: In acidic solutions it gives pinkish-red colour whereas yellow colour with the bases.

b. Phenolphthalein: It acts as an acid-base indicator. It remains colourless in acidic solutions but turns pink in alkali solutions.

About Acids, Bases, and Salts: Class 7 Science Chapter 4 Notes

The chapter might sound intimidating to the students of Class7 but when the concepts are properly explained, it will become quite simpler to study. 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 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 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.

Acids are the aqueous solution of the non-metallic oxides that release hydrogen ions in the solution. They are sour and can be found in many common substances we find around us. You will find different acids in fruits, curd, vinegar, etc. Bases, on the other hand, are the aqueous solution of metallic oxides that release hydroxyl ions in the solution. The water-soluble bases are called alkalis. A base is bitter and can be found in different substances such as soap, washing soda, ammonia, bleach, etc. To understand deeply about the acids and bases, consider referring to the NCERT Class 7 Science Chapter 4 notes prepared by the best teachers.

Salts, on the other hand, are the product of a reaction between an acid and a base. These compounds are neutral. As the name suggests, they are salty. On progressing further, you will study the indicators in Class 7 Science Ch 5 notes. They are used to determine whether a compound is acidic, basic, or neutral.

The NCERT Solutions for Class 7 Science Chapter 4 will also describe what is a neutralization reaction to the students in a simpler language. You will be able to understand the mechanism of formation of salts by figuring out now a neutralization reaction occurs. Study the notes to find out how neutralization is used in everyday life to cure certain ailments and solve various problems.

As per the Acids, Bases and Salts notes for Class 7, neutralization is used to cure indigestion and provide relief to ant bites. It can be used to remove the acidity of soil by treating it with recommended bases or vice versa.

Important Topics of Class 7 Chapter 4 Science You Shouldn’t Miss!

Here are the important topics of Class 7 Chapter 4 Science that you shouldn’t miss:

• Properties of Acids and Bases: Learn the key characteristics that differentiate acids from bases, such as taste, pH level, and reactivity.

• Indicators: Understand how indicators like litmus paper, phenolphthalein, and turmeric can be used to identify acids and bases.

• Neutralization Reaction: Study how acids and bases react to form salts and water in a neutralization reaction.

• Common Examples of Acids and Bases: Explore everyday examples of acids and bases, such as vinegar, lemon juice, soap, and baking soda.

• Formation of Salts: Learn about the different types of salts and how they are formed through chemical reactions between acids and bases.

Importance of Chapter 4 Acids, Bases and Salts Class 7 Notes

• The Chapter 4 Acids, Bases, and Salts Class 7 Notes are important because they provide a solid foundation for understanding the basic chemistry concepts that are essential for higher studies.

• These notes explain how acids and bases behave, how to test and identify them, and the process of forming salts through chemical reactions.

• Understanding these concepts is crucial not only for exams but also for real-life applications, such as in cooking, cleaning, and even in the human body.

• By studying these notes, students can build a strong base in chemistry, which will be beneficial for their future studies.

Tips for Learning the Class 7 Science Chapter 4 Acids, Bases and Salts

Here are some tips for learning Class 7 Science Chapter 4, Acids, Bases, and Salts:

1. Understand the Basics: Start by grasping the fundamental properties of acids, bases, and salts. Knowing their characteristics will help you identify them in various contexts.

2. Use Visual Aids: Draw and label diagrams of pH scales, chemical reactions, and examples of indicators to reinforce your understanding.

3. Memorise Key Examples: Learn the common examples of acids, bases, and salts, such as vinegar (acid), soap (base), and table salt (salt), to better relate to everyday substances.

4. Experiment with Indicators: If possible, perform simple experiments with indicators like litmus paper or turmeric to see how they react with acids and bases.

5. Practice Neutralisation Reactions: Work through examples of neutralisation reactions, where acids and bases combine to form salts and water, to solidify your understanding.

Conclusion

Chapter 4 of Class 7 Science, Acids, Bases, and Salts, is fundamental for understanding basic chemistry concepts that have both academic and real-life applications. By learning about the properties of acids and bases, how to identify them using indicators, and the process of neutralization, students build a strong foundation in chemistry. These notes simplify complex ideas, making it easier to grasp essential concepts and prepare for exams. With this knowledge, students will be well-equipped to explore more advanced topics in future science studies.

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