Chapter 2: Exploring Substances: Acidic, Basic, and Neutral
Why are some fruits sour and why does a curry stain turn red with soap? In this chapter we test substances with natural indicators like litmus, red rose and turmeric, sort them as acidic, basic or neutral, and see how acids and bases neutralise each other in daily life.
In this chapter you will
- test substances with litmus and natural indicators
- sort substances as acidic, basic or neutral
- explain neutralisation
- use neutralisation to solve everyday problems
Topics
- Litmus as an Indicator NCERT 2.1–2.1.1
Acids turn blue litmus red; bases turn red litmus blue; neutral substances change neither.
- Red Rose, Turmeric and Smell Indicators NCERT 2.1.2–2.1.3
Red rose extract is red in acids and green in bases; turmeric turns red only in bases.
- When Acids Meet Bases NCERT 2.2
An acid and a base neutralise each other.
- Neutralisation in Daily Life NCERT 2.3
Bases soothe acidic stings; lime treats acidic soil, compost treats basic soil.
Key words
- Acidic
- turns blue litmus red; often tastes sour
- Basic
- turns red litmus blue; feels soapy
- Neutral
- neither acidic nor basic
- Indicator
- a substance that shows different colours (or smells) in acids and bases
- Neutralisation
- an acid and a base reacting to form salt and water, with heat
- Lichen
- a fungus and an alga living together; litmus comes from it
Summary
- Acids turn blue litmus red; bases turn red litmus blue; neutral substances change neither.
- Red rose extract: red in acids, green in bases. Turmeric turns red only in bases.
- Acid + base → salt + water + heat (neutralisation).
- Neutralisation helps with ant bites, soil treatment and factory waste.