Neutralisation in Daily Life
Class 7 Science · Chapter 2: Exploring Substances: Acidic, Basic, and Neutral · NCERT Curiosity section 2.3
Learn
Ant bite: Zoya leans on a tree and a red ant bites her. The ant injects an acid (formic acid), which stings. Her brother rubs moist baking soda, a base, on the spot, and the pain eases: the acid is neutralised.
Soil: too much chemical fertiliser can make soil acidic, and plants grow poorly. Farmers add lime (a base). If soil is too basic, they add manure or composted leaves, which release acids. Sometimes neutral soil still gives weak plants because it lacks nutrients.
Factories: fish in a lake near a factory are dying. If the factory waste is acidic, it should be neutralised with a basic substance before it is released, to keep the water safe for living things.
The mystery solved: at the fair, the white sheets had been coated with turmeric, and the message was written with soap solution. Or the spray held turmeric and the words were in soap. Where soap touched turmeric, the letters turned red!
Explore: acidic, basic or neutral?
- Sort each substance by its nature.
Remember
- Bases soothe acidic stings; lime treats acidic soil, compost treats basic soil.
- Acidic factory waste must be neutralised before release.
Quick check
What should be added to soil that is too acidic?
- lime
- vinegar
- lemon juice
- more fertiliser
Answer
lime. Lime is a base and neutralises acidic soil.
Think about it
Neel is blindfolded and given two unknown solutions. Which indicator should he use to find out if they are acidic or basic?
One answer
An olfactory indicator such as onion-soaked cloth: its smell changes in a base, so he can tell by smell instead of colour.
Practice
Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.