Class 7 Science - KERALA
Exploring Substances: Acidic, Basic and Neutral
In this chapter, Kerala SCERT Class 7 students explore the fascinating world of chemistry by identifying substances as acidic, basic, or neutral. Students learn about natural indicators like litmus, turmeric, and china rose that change color in different solutions to test substances safely. The chapter also introduces neutralization reactions, explaining how acids and bases cancel each other out, which has real-world applications in daily life such as treating acidity in the stomach and soil management. This chapter is vital for board exams as it forms the foundational building blocks for 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 red. Examples include lemon juice, vinegar, and tamarind.
Bases
Substances that taste bitter, feel soapy to touch, and turn red litmus paper blue. Examples include baking soda, soap, and lime water.
Indicators
Special substances used to test whether a substance is acidic or basic by changing their color in different mediums.
Neutral Substances
Substances that are neither acidic nor basic and do not change the color of red or blue litmus paper. Pure water is a common example.
Neutralization
A chemical reaction between an acid and a base that produces salt and water, releasing heat in the process.
Important Formulas
Board Exam Info
This chapter typically carries around 5 to 8 marks in the Kerala SCERT Class 7 Science examinations. Common question types include identifying the nature of given substances using indicators, explaining neutralization reactions with examples from daily life, and matching acids or bases with their natural sources.
Frequently Asked Questions
What is the color of turmeric indicator in a basic solution?
Turmeric indicator turns reddish-brown or red when added to a basic solution.
Why does an ant sting cause pain and how is it treated?
An ant sting injects formic acid into the skin, causing pain. It is treated by rubbing moist baking soda or calamine solution, which neutralizes the acid.
What is a neutral solution?
A neutral solution is one that is neither acidic nor basic. It does not show any color change with standard litmus indicators.
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