Class 7 Science - WEST-BENGAL
Exploring Substances: Acidic, Basic and Neutral
In the chapter 'Exploring Substances: Acidic, Basic and Neutral' for Class 7 West Bengal (WBBSE), students learn to identify different substances based on their chemical nature. The chapter covers natural indicators like litmus, turmeric, and china rose to test whether a solution is acidic, basic, or neutral. It also explains the crucial process of neutralization, where an acid and a base react to form salt and water, which has many daily life applications like treating indigestion and ant bites. This chapter is highly important for board exam preparation as it forms the fundamental base for higher chemistry concepts.
Start Learning FreeKey Concepts
Acids
Substances that taste sour and turn blue litmus paper red. Examples include hydrochloric acid and acetic acid found in vinegar.
Bases
Substances that are bitter in touch and taste, feel soapy, and turn red litmus paper blue. Examples include sodium hydroxide and baking soda.
Indicators
Special substances used to test whether a substance is acidic or basic by showing a change in color.
Neutral Substances
Substances that are neither acidic nor basic and show no change in the color of litmus paper, such as pure water and common salt.
Neutralisation
A chemical reaction between an acid and a base that produces salt, water, and heat.
Important Formulas
Board Exam Info
In West Bengal (WBBSE) Class 7 science examinations, this chapter typically carries around 6 to 8 marks. Common question types include short answer questions, identifying indicators and their color changes, defining neutralisation, and practical application-based questions like treating ant stings or soil treatment.
Frequently Asked Questions
What is the color of turmeric indicator in a basic solution?
Turmeric turns bright yellow to reddish-brown (or red) in a basic solution.
Why does an ant bite cause irritation?
An ant bite injects formic acid into the skin, which causes irritation and pain.
Are all substances either acidic or basic?
No, substances that are neither acidic nor basic are called neutral substances, such as distilled water.
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