CBSE Class 7 Science Revision Notes Chapter 5

Class 7 Science Chapter 5 Notes

CBSE Class 7 Science Revision Notes Chapter 5 – Acids, Bases And Salts

The CBSE Syllabus of Class 7 Science introduces students to acids, bases, and salts, which constitute an important part of chemistry. The chapter aims at inculcating interest in the students’ minds as well as developing a deep understanding of the topics for them to easily comprehend the advanced concepts taught in higher classes.

Students need the right guidance at this stage to build a strong foundation in science. Here, the notes prepared by Extramarks become vital. Class 7 Science Chapter 5 Notes provided by Extramarks are prepared by subject matter experts in a concise manner. These notes will help them understand and quickly revise all the concepts related to the chapter in-depth.

These comprehensive notes are aligned with the latest CBSE Syllabus. Students will be able to answer all the questions as the notes cover pointers for all the Important Questions asked in the board exams.

Class 7 Chapter 5 Science Notes provided by Extramarks are easily accessible from the website at any time. CBSE Revision Notes on Acids, Bases, And Salts to give an edge to students’ exam preparations.

Revision Notes For CBSE Class 7 Science Chapter 5

Access CBSE Class 7 Science Chapter 5 – Acids, Bases And Salts

There are three types of substances in nature: acids, bases, and salts.

  1. Acids: The pungent-smelling substance that gets corroded easily is called an acid. They are available in diluted form and concentrated form. Concentrated acids are extremely powerful. They can cut through clothes and wool. They can also cause severe burns on the skin. They are good conductors of electricity, as the electric current can pass through them easily. There are several types of acids discussed below.
  • Mineral acids are those acids that are prepared from the minerals available on the earth’s crust. For example hydrochloric acid (HCl), nitric acid (HNO3), etc.
  • Organic acids are prepared from organic matter like plants and animals. The only exception in this category is hydrochloric acid.
  • Strong acids are those acids that can dissociate completely in solutions. For example, sulphuric acid (H2SO4), hydrochloric acid (HCl), etc.
  • Weak acids do not dissociate completely in solution, unlike strong acids. Tartaric acid (C4H6O6) and lactic acid (C3H6O3) are instances of weak acids.

      2.Bases: The substances that are bitter in taste and soapy in appearance are called bases. Bases can be classified into two categories:

  • Strong Bases: These kinds of bases produce many hydroxide ions when dissolved in solutions. For example, sodium hydroxide (NaOH), potassium hydroxide (KOH), etc.
  • Weak Bases: These kinds of bases cannot produce a huge number of ions when dissolved in solutions. Magnesium hydroxide (Mg(OH)2) and ammonium hydroxide (NH4OH) fall into this category.

     3.Salts: When an acid and a base react with each other, they produce salt and water. These salts can be either acidic or basic in nature. Examples of salts include sodium chloride (NaCl), potassium chloride (KCl), etc.

     4.Natural Substances: These types of substances are neither acidic nor basic in nature.

     5.Naturalisation: This is a chemical process in which an acid and a base react with each other to produce salt and water. Acid + Base = Salt + Water. Some of the naturalisation reactions observed in our daily life are given below:

  • Indigestion: When too much acid is produced in our stomach, it causes indigestion. It can be relieved by taking milk of magnesia, which is basic in nature.
  • Ant Sting: When an ant stings on our skin, it injects formic acid that causes irritation. The effect of this acid can be neutralised by applying moist soda or calamine to the affected area.
  • Soil Treatment: In agricultural lands, quicklime or slaked lime is often added if the soil becomes acidic.

      6.Indicators: These are special types of chemicals that change the colour of solutions to indicate the presence of acidic or basic compounds in the solutions. They produce different colours when added to an acidic, basic or neutral solution. A more detailed discussion on indicators is given below.

Classification of Indicators is Given Below

  • Natural Indicators
    • Litmus: Litmus is prepared from lichen and comes in the form of a solution as well as paper strips. Litmus is widely used to detect acids and bases. When blue litmus is added to an acidic solution its colour changes to red. When red litmus is added to a basic solution it changes its colour to blue.
    • Turmeric: Turmeric, which can be easily found in the kitchens of Indian households, is used in chemistry labs as a natural indicator for the detection of acid and base. It retains its natural yellow colour in neutral and acidic solutions but turns red if an alkaline solution is added to it.
    • Chinese Rose: This flower is also a natural indicator used in labs for detecting acids and bases. When it is dipped into an acidic solution, the colour of the solution turns dark pink (magenta); but it gives a green colour when added to a basic solution.
    • Red Cabbage: Red cabbages are well known for turning acidic solutions into a red colour and basic solutions into a blue colour.
  • Other Chemical Indicators
    • Methyl Orange: It produces a pinkish-red colour in acidic solutions and a yellow colour in alkaline solutions.
    • Phenolphthalein: It turns pink when it comes into contact with basic solutions, but in acidic solutions it remains colourless.

About Acids, Bases, And Salts: Class 7 Science Chapter 5 Notes

The chapter imparts basic knowledge about chemical solutions and compounds. As this chapter is crucial for developing a basic understanding of acids, bases, and salts, students must have conceptual clarity to understand complex concepts covered in higher classes.

Class 7 Science Chapter 5 Notes cover the definitions of acids and bases, their nature, and the identification of acids and bases using indicators. The notes are well-structured and written in lucid language. Students can clear any queries related to the concepts by referring to these notes.

Acids are aqueous solutions of non-metallic oxides that release hydrogen ions during a chemical reaction. Acids are sour in taste and corrosive in nature. They can be found in substances commonly used in daily life. They are present in different types of fruits, curd, vinegar, etc.

Bases are the aqueous solutions of metallic oxides and produce hydroxyl ions in chemical reactions. The bases that can be dissolved in water are called alkalis. Bases are bitter in taste. Soaps, detergent powder, ammonia, bleach, etc., are basic in nature.

Salts are the byproducts of neutralisation reactions between acids and bases. They possess the properties of either acids or bases. They are neutral in nature. As the name suggests, they are salty in taste. Class 7 Science Chapter 5 Notes thoroughly explain the concepts of acids, bases, and salts.

These notes also explain how salts are produced and how the method is useful in day-to-day life. For example, the neutralising reaction is used to heal certain ailments and provide relief from inflammation after ant bites and many other problems. A neutralisation reaction is also used to restore the productivity of soil by applying acidic or basic compounds to the arable lands in the agricultural sector.

The notes further move on to discuss the various types of indicators used to detect acids and bases. Indicators are substances used to determine whether a solution is acidic,  basic, or neutral. The most commonly used natural indicators are litmus, turmeric, Chinese Rose, and red cabbage, whereas methyl orange and phenolphthalein are widely used chemical indicators.

Why Study Acid Bases And Salts Class 7 NCERT Notes?

Class 7 Science Chapter 5 Notes are extensive yet concise, which will help students revise the chapter quickly before the exam. Extramarks’ revision notes are prepared by subject matter experts.  Students can refer to Class 7 Chapter 5 Science Notes for a better understanding of the topic and secure better marks in the exams.

FAQs (Frequently Asked Questions)

1. What is the difference between acids and bases according to the Class 7 Science Chapter 5 Notes?

According to the CBSE Revision Notes provided by Extramarks, acids are corrosive aqueous solutions of non-metallic oxides that have a pungent taste. The bases, on the contrary, are produced by dissolving metallic oxides in water. Bases usually taste bitter.

2. How can acids and bases be detected?

Acids and bases can be distinguished by adding some indicators to their aqueous solutions. There are two types of indicators available on the market – natural indicators and chemical indicators.

China Rose, litmus, turmeric, and red cabbage are natural indicators. Methyl orange and phenolphthalein are chemical indicators.

To detect the acidic and basic solutions, add any one of the indicators to the solutions. Observe if the colours of the solutions change. Refer to the Class 7 Chapter 5 Science Notes provided by Extramarks to know which indicator gives which colour in what kind of solution.

3. What is meant by a neutralisation reaction?

When an acidic solution and a basic solution react with each other to produce salt and water, and the chemical properties of both solutions become last in the process, this type of reaction is called a neutralisation reaction. In this type of reaction, heat is often produced.

4. Why should one opt for Class 7 Science Chapter 5 Notes provided by Extramarks?

The Class 7 Science Chapter 5 Notes provided by Extramarks are meticulously designed by subject matter experts. These comprehensive notes are prepared in accordance with the latest CBSE Syllabus. With these notes, students will be able to excel in the subject and score more marks in the exams.

5. What are the fundamental concepts discussed in Chapter 5 Science Class 7 Notes?

Class 7 Science Chapter 5 Notes elaborately discuss several concepts related to acids and bases, such as:

  • The nature of acids and bases
  • Different types of indicators: natural and chemical
  • The neutralisation reaction and its significance in daily life.

6. What are some important equations mentioned in the Class 7 Science Chapter 5 Notes?

Chapter 5 Acids, Bases And Salts listed in the CBSE Syllabus of Class 7 Science introduces certain elementary concepts related to acids, bases, and salts. There are some equations that are important from the exam perspective as well as for understanding complex concepts taught in higher classes. They are listed below.

  • Acid + Base = Salt + Water + H (H stands for heat generated during the chemical reaction)
  • HCl + NaOH = NaCl + H2O
  • dil HCl + Ca(OH)2 = CaCl2 + H2O (dil stands for diluted)
  • NaHCO3 + HCOOH = HCOONa + CO2 + H2O
  • CaO + HCl =CaCl2 + H2O
  •  Ca(OH)2 + H2SO4 = CaSO4 + H2O
  • 2KOH + H2SO4 = K2SO4 + 2H2O