Chapter-Chapter 2. Exploring Substances – Acidic, Basic and Neutral Science Curiosity class 7 in english Medium CBSE Notes

Chapter 2: Exploring Substances – Acidic, Basic and Neutral

Definitions:

Acid: Acids are substances that have a sour taste and turn blue litmus paper red.

Base: Bases are substances that have a bitter taste and feel soapy to touch.

Neutral Substance: A neutral substance is neither acidic nor basic in nature.

Indicator (संसूचक): An indicator is a substance that shows different colours in acidic and basic solutions.

Natural Indicator: Indicators obtained from natural sources like plants are called natural indicators.

Artificial Indicator: Indicators prepared in laboratories are called artificial indicators.

Litmus: Litmus is a natural indicator that turns red in acids and blue in bases.

Neutralization: Neutralization is the process in which an acid reacts with a base to form salt and water.

Salt: Salt is the substance formed as a result of a neutralization reaction.

Quick Revision Points:

• Acids are sour and turn blue litmus red.
• Bases are bitter and turn red litmus blue.
• Neutral substances do not change indicator colour.
• Indicators help identify substances safely.
• Litmus is the most commonly used indicator.
• Turmeric turns reddish-brown in bases.
• Phenolphthalein turns pink in bases.
• Neutralization produces salt and water.
• Acids and bases are widely used in daily life.
• Tasting chemicals is unsafe and should be avoided.
• Neutralization helps in indigestion and soil treatment.
• Acids and bases may be strong or weak.

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