NCERT Solutions for Class 7th Science Chapter 2 Exploring Substances: Acidic, Basic, and Neutral
Updated on 2026-09-08
About this chapter
The chapter opens at a school science fair on National Science Day, where a sprayed liquid makes hidden writing appear on a white sheet of paper. The whole chapter is the explanation of that trick. Substances around us are of three kinds — acidic , basic and neutral . A substance that shows different colours in acidic and basic solutions is an acid-base indicator . Litmus , obtained from lichens , is the standard natural indicator. Acids turn blue litmus red ; bases turn red litmus blue ; neutral substances change neither. Red rose extract is another indicator — red in acid, green in base. Turmeric paper turns red only in a base, so it can spot bases but cannot tell an acid from a neutral substance. Acids taste sour (lemon, amla, tamarind, vinegar); bases feel soapy or slippery and general
- Litmus as an indicator
- What litmus is, and the Holistic Lens box
- Taste, touch and the acids in food
- Looking for other indicators
- Red rose as an indicator
- Testing samples with the red rose extract
- Fascinating Facts
- Turmeric as an indicator
- Onion as an olfactory indicator
- Neutralisation in Daily Life, and Let us wrap up!
Exercises
- Activity 2.1: Let us explore — Litmus as an indicator Page 8–9
- In-text Questions — What litmus is, and the Holistic Lens box Page 10
- Activity 2.2: Let us relate and explore — Taste, touch and the acids in food Page 11
- In-text Questions — Looking for other indicators Page 11
- Activity 2.3: Let us prepare — Red rose as an indicator Page 12
- Activity 2.4: Let us find out — Testing samples with the red rose extract Page 12–13
- Fascinating Facts — In-text Questions Page 14
- Activity 2.5: Let us prepare — Turmeric as an indicator Page 14–15
- Fascinating Facts, the Guru Purnima greeting card and olfactory indicators — In-text Questions Page 15–16
- Activity 2.6: Let us investigate — Onion as an olfactory indicator Page 16
- Activity 2.7: Let us experiment — What Happens When Acidic Substances Mix with Basic Substances? Page 17
- In-text Questions — Neutralisation in Daily Life, and Let us wrap up! Page 18–19
- End-of-chapter questions — Let Us Enhance Our Learning Page 20–21
- Thinking beyond the chapter — Dive Deeper Page 22
- Projects and further exploration — Exploratory Projects Page 22