Class 7 Science - TAMILNADU
Exploring Substances: Acidic, Basic and Neutral
In the Class 7 Science chapter 'Exploring Substances: Acidic, Basic and Neutral', students learn to classify everyday substances based on their chemical properties. The chapter covers the characteristics of acids (sour taste) and bases (bitter taste and soapy touch), introduces natural and synthetic indicators like litmus, turmeric, and china rose to test substances safely, and explains the crucial process of neutralization between acids and bases. This topic is essential for Tamil Nadu Samacheer Kalvi board exams as it forms the foundational building block for advanced chemistry in higher classes, frequently appearing in both objective and descriptive questions.
Start Learning FreeKey Concepts
Acids
Substances that taste sour and turn blue litmus paper to red. Examples include lemon juice, tamarind, and vinegar.
Bases
Substances that taste bitter, feel soapy to touch, and turn red litmus paper to blue. Examples include baking soda, soap, and lime water.
Indicators
Special chemical substances used to test whether a given substance is acidic, basic, or neutral by changing color.
Neutral Substances
Substances that are neither acidic nor basic and do not change the color of red or blue litmus. Distilled water is a common example.
Neutralisation
A chemical reaction between an acid and a base that results in the formation of salt and water, releasing heat.
Important Formulas
Board Exam Info
In the Tamil Nadu (Samacheer Kalvi) Class 7 Science examination, this chapter typically carries around 6 to 8 marks. Questions frequently include 1-mark objective questions (choose the best answer, fill in the blanks), 2-mark definitions, and 4-mark descriptive questions explaining neutralization reactions or practical uses of indicators.
Frequently Asked Questions
Why does turmeric stain turn red with soap?
Turmeric is a natural indicator. Soap is basic in nature, and basic substances turn yellow turmeric stains to a reddish-brown color.
What is the difference between an acid and a base?
Acids are sour in taste and turn blue litmus red, whereas bases are bitter, feel soapy, and turn red litmus blue.
How does neutralization help in curing a stomach ache?
When we have indigestion due to excess acid in the stomach, we take an antacid (a base) which neutralizes the excess acid and provides relief.
Learn Exploring Substances: Acidic, Basic and Neutral with Your AI Tutor
10 different ways to study this chapter. Free for 3 chapters per day.
Lecture
Key Points
Interactive
Quiz
Flashcards