Schooling · Class 7 · Science · Exploring Substances: Acidic, Basic, and Neutral · Chapter on a page
CBSE Class 7 · Science · NCERT Curiosity
Exploring Substances: Acidic, Basic, and Neutral: chapter on a page
A cut of Shishya's notes for this chapter: the first paragraph of the introduction and the key ideas, formulas and facts, common mistakes and quick revision lists, word for word. Nothing is added or reworded; the worked examples are left out (they are on the chapter page).
About the notes: Written by Shishya's AI on 26 Sept 2026 from the chapter's title and class level, in Shishya's own words — not a copy or summary of the textbook. Read the official chapter for the book's own text, activities and exercises.
This note's current text has no applied fact-check on record.
Mind map
Drawn from the same notes by a fixed rule (no AI): each label is the item's own words — its bold term, its label before a colon, a short formula as written, or its first words.
The mind map as a list
- Key ideas
- Acids
- Bases
- Neutral substances
- Indicators
- Litmus
- Turmeric
- China rose
- Formulas and facts
- Blue litmus + Acid
- Red litmus + Base
- Turmeric + Base
- China rose solution + Acid
- Acid + Base
- Rainwater is slightly acidic because…
- Our stomach produces hydrochloric…
- Watch out for
- Thinking all sour things are…
- Believing bases are the opposite of…
- Assuming neutral means the substance…
- Using the same strip of litmus for…
- Forgetting that turmeric does not…
What this chapter is about
This chapter teaches you how to group substances based on their chemical nature. You will learn that the things around us can be acidic, basic, or neutral. Acids taste sour, bases taste bitter and feel slippery, and neutral substances are neither acidic nor basic.
Key ideas
- Acids are substances that taste sour and turn blue litmus paper red. Examples: lemon juice, vinegar, curd, orange juice.
- Bases are substances that taste bitter, feel soapy or slippery, and turn red litmus paper blue. Examples: baking soda solution, soap water, lime water.
- Neutral substances are neither acidic nor basic. They do not change the colour of litmus paper. Example: pure water, common salt solution.
- Indicators are substances that show different colours in acidic and basic solutions. They help us test without tasting.
- Litmus comes from a plant called lichen. Blue litmus turns red in acid; red litmus turns blue in base.
- Turmeric is a natural indicator. It stays yellow in acids but turns red or brown in bases.
- China rose (hibiscus) solution turns dark pink or magenta in acids and green in bases.
- Mixing an acid and a base can produce a neutral substance; this reaction is called neutralisation.
Formulas and facts to remember
- Blue litmus + Acid → turns red.
- Red litmus + Base → turns blue.
- Turmeric + Base → turns reddish-brown.
- China rose solution + Acid → dark pink; + Base → green.
- Acid + Base → Salt + Water (neutralisation).
- Rainwater is slightly acidic because it dissolves gases like carbon dioxide from the air.
- Our stomach produces hydrochloric acid to help digest food.
- Ant sting and bee sting contain acids; applying a mild base like baking soda paste can give relief.
Common mistakes
- Thinking all sour things are dangerous acids → Many safe foods like lemon and tamarind are acidic; the word acid does not always mean harmful.
- Believing bases are the opposite of acids in taste (so they must be sweet) → Bases taste bitter, not sweet.
- Assuming neutral means the substance has no chemicals → Neutral only means it is neither acidic nor basic; salt solution is neutral but still contains dissolved salt.
- Using the same strip of litmus for several tests → Always use a fresh strip for each test; leftover colour can give wrong results.
- Forgetting that turmeric does not change colour in acids → Turmeric stays yellow in acids; it changes only in bases.
Quick revision
- Acids turn blue litmus red; bases turn red litmus blue.
- Neutral substances do not change either litmus.
- Indicators like litmus, turmeric, and China rose help test without tasting.
- Neutralisation happens when an acid and a base react to form salt and water.
- Turmeric turns reddish-brown only in bases.
- Many kitchen items (lemon, curd, soap, baking soda) can be grouped as acidic or basic.