Complete Guide For Class 7 Science Chapter 4: Acids Bases and Salts

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Understanding the acids bases and salts of Class 7 Chapter 4 is fundamental to comprehending basic chemistry. This chapter provides insights into the tastes and properties of various substances and their classifications as acids or bases. It also explores natural indicators and the phenomenon of neutralization in everyday life.

Tastes of Edible Substances

While understanding the concepts of acids bases and salts, let’s recall the tastes of some edible substances:

What is an Acid?

Within the chapter Acids bases and salts, we first start with understanding what is an Acid. What do lemon, tamarind (imli), curd, and vinegar have in common? They all taste sour because they contain acids. The term “acid” comes from the Latin word “acere,” meaning sour. Naturally occurring acids in these substances are called neutral acids.

Now, Let’s take a look at some common acids present in substances around us.

Common Acids in Substances

What is a Base?

Within the chapter Acids bases and salts, we’ll further discuss what is a base. Have you ever tasted baking soda, the one used in cakes? If you have, you know it’s bitter. Substances like detergent, which are bitter and feel soapy to touch, are known as bases. These substances are said to have a basic nature.

Now, since we already know about acids and bases. Let’s explore the different indicators used to test them.

Indicators

Within the chapter Acids bases and salts, we’ll further discuss indicators. Indicators are substances used to identify whether a substance is an acid or a base. Solutions of these substances show different colors in acidic, basic, and neutral solutions. Examples include litmus paper, turmeric, and China rose.

There are various natural indicators present around us. Come, let’s explore them only one by one.

Natural Indicators Around Us

Litmus: Extracted from lichens, it is a commonly used indicator that turns red in acidic solutions and blue in basic solutions. It is available as a solution or in strips of red and blue paper.

Turmeric: Another natural indicator that changes color in the presence of a base but not in an acidic solution.

China Rose: To prepare this indicator, collect some Chinese rose petals and place them in warm water until the water becomes colored.

Let’s observe some experiments to learn more about indicators and their functions.

Experiments and Observations

Within the chapter Acids bases and salts, we’ll now have a look at some experiments and observations about acids bases and salts. Perform the following experiments and record your remarks:

Now that we have a good understanding of acids, bases, and indicators in class 7 Science chapter 4, let’s move on to an important concept: acid rain.

Acid Rain

Acid rain contains excess acids formed from carbon dioxide, sulfur dioxide, and nitrogen dioxide in the air, which dissolve in raindrops to create carbonic acid, sulfuric acid, and nitric acid. Acid rain can damage historical monuments, buildings, plants, and animals.

Let’s learn about a very important reaction that takes place between an acid and a base. 

Neutralization

When an acidic solution is mixed with a basic solution, they neutralize each other, forming salt and water and releasing heat. This reaction is called neutralization.

Reaction: Acid  + Base → Salt + Water + Heat

Neutralization reactions can be seen in various day-to-day phenomena. Let’s understand a few practical examples of neutralization in our lives.

Neutralization in Everyday Life

• Indigestion: Antacids like milk of magnesia relieve indigestion.
• Ant Sting: Formic acid from ant stings can be neutralized by rubbing a moist baking soda solution on the affected area.
• Bee Sting: Honey-bee stings, which inject acid, can be treated with baking soda.
• Agriculture: Plants require a specific pH range for growth. Acidic soil is treated with quicklime, slaked lime, or calcium carbonate to lower its acidity.
• Nettle Plant Sting: The methanoic acid injected by nettle plants can be neutralized with baking soda.
• Factory Wastes: Factory wastes containing acids must be treated before disposal to prevent harm to aquatic life.

Understanding the properties and interactions of acids bases and salts is crucial for both scientific knowledge and practical applications in daily life.

In conclusion, the chapter Acids Bases and Salts for Class 7 Science provides a comprehensive understanding of the fundamental concepts related to acids, bases, and salts. By exploring the tastes of edible substances, identifying common acids and bases, and learning about various indicators, students gain essential insights into these chemical principles. The chapter’s focus on natural indicators, experiments, and real-life applications such as neutralization reactions enriches the learning experience.

Through engaging with the chapter Acids Bases and Salts, students not only prepare for their exams but also acquire knowledge that is applicable in everyday scenarios. From identifying acids and bases in household items to understanding the impact of acid rain and the importance of neutralization in various contexts, the chapter equips students with valuable skills and knowledge.

So, as you navigate through the chapter Acids Bases and Salts, remember that mastering these concepts lays the groundwork for more advanced studies in chemistry and helps in appreciating the chemistry present in our daily lives.