Class 7 Science - GUJARAT
Exploring Substances: Acidic, Basic and Neutral
In this chapter, Class 7 Gujarat Board students explore the fascinating world of chemicals around us by classifying them into acidic, basic, and neutral substances. You will learn how to identify these substances using natural indicators like turmeric, litmus, and China rose. The chapter covers the fundamental concept of neutralization reactions, explaining how acids and bases cancel each other out, which is not only crucial for scoring high marks in your GSEB science exams but also helps you understand everyday practical chemistry, such as treating ant bites and managing soil acidity for farming.
Start Learning FreeKey Concepts
Acids
Substances that taste sour and turn blue litmus red. Examples include vinegar, lemon juice, and hydrochloric acid.
Bases
Substances that taste bitter, feel soapy to touch, and turn red litmus blue. Examples include baking soda, soap, and lime water.
Indicators
Special substances used to test whether a substance is acidic or basic by changing color. Litmus, turmeric, and China rose are common natural indicators.
Neutral Substances
Substances that are neither acidic nor basic and do not change the color of red or blue litmus paper, such as distilled water and common salt.
Neutralization Reaction
A chemical reaction between an acid and a base that produces salt, water, and heat.
Important Formulas
Board Exam Info
In the Gujarat (GSEB) Class 7 Science examinations, this chapter typically carries around 5 to 7 marks. Questions frequently include fill-in-the-blanks, true or false, matching columns based on indicator color changes, and short descriptive questions explaining neutralization reactions in everyday life or reasons for using antacids.
Frequently Asked Questions
Why does turmeric stain on clothes turn reddish-brown when washed with soap?
Soap is basic in nature. Turmeric acts as a natural indicator that turns red or reddish-brown when it comes in contact with a basic substance.
What is the color of phenolphthalein in acidic and basic solutions?
Phenolphthalein remains colorless in acidic solutions, but turns pink in basic solutions.
Why do farmers add basic substances like quicklime to their soil?
If the soil becomes too acidic due to excessive fertilizer use or natural conditions, farmers add bases like quicklime or slaked lime to neutralize the acidity and make the soil suitable for crop growth.
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