Class 7 Science - ODISHA
Exploring Substances: Acidic, Basic and Neutral
In this chapter, Class 7 students of Odisha (BSE) will explore the fascinating world of substances around us by classifying them into acids, bases, and salts. You will learn how to identify these substances using natural indicators like turmeric, litmus, and China rose petals. The chapter also covers the crucial process of neutralization, explaining how acids and bases react to form salt and water, and how neutralization applies to our daily lives, such as treating ant bites, indigestion, and acidic soil. Mastering these concepts is essential for scoring well in your Board examinations.
Start Learning FreeKey Concepts
Acids
Substances that taste sour and turn blue litmus red. They are found in citrus fruits like lemons and oranges.
Bases
Substances that taste bitter, feel soapy to touch, and turn red litmus blue. Examples include baking soda and soap.
Indicators
Special substances used to test whether a substance is acidic or basic by changing their color in different solutions.
Neutral Substances
Substances that are neither acidic nor basic and do not change the color of red or blue litmus paper, such as pure water.
Neutralization
A chemical reaction between an acid and a base that results in the formation of salt, water, and heat.
Important Formulas
Board Exam Info
This chapter typically carries around 5 to 8 marks in the Odisha (BSE) Class 7 Science examination. Common question types include defining neutralization, giving examples of natural indicators, identifying the color changes of litmus in acidic and basic solutions, and explaining daily life applications like treating ant bites or soil treatment.
Frequently Asked Questions
What is the color of phenolphthalein in an acidic solution?
Phenolphthalein remains colorless in an acidic solution, but turns pink in a basic solution.
Why does a turmeric stain on a white shirt turn reddish-brown when soap is applied?
Soap is basic in nature. Turmeric is a natural indicator that changes its yellow color to reddish-brown when it comes in contact with a base.
How is indigestion cured using milk of magnesia?
Our stomach contains hydrochloric acid which causes indigestion when produced in excess. Milk of magnesia contains magnesium hydroxide, which is a base; it neutralizes the excess acid and provides relief.
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