In this Class 7 Science Curiosity chapter 2 Exploring Substances: Acidic, Basic, and Neutral, we will explore how to identify the nature of various substances. We will also learn how to use various indicators such as litmus paper, red rose extract, and turmeric paper.
We will also learn about neutralization reactions—how acids and bases react to form salt and water, and how these reactions are useful in real life, like treating ant bites or improving soil quality.
Have you ever wondered why lemon juice tastes sour or why soap feels slippery? These common experiences are linked to the chemical nature of substances around us. Every substance we use or consume—like fruits, cleaning liquids, or even drinking water—has a specific chemical nature. Some are acidic, some are basic, and some are neutral.
Class 7 Science Curiosity Chapter 2 Worksheet
Join us as we discover the colorful world of science where substances change colors and reveal their true nature. Download our Science Class 7 Curiosity Chapter 2 worksheet for extra practice and better understanding of the chapter.
Chapter 2 Exploring Substances: Acidic Basic and Neutral Notes
Nature — Our Science Laboratory
Indicators: Substances that show different colours in acidic and basic solutions.
Litmus: Natural indicator from lichens.
Acid turns blue litmus to red.
Base turns red litmus to blue.
Also download:
Class 7 Science Worksheet Curiosity
Class 7th Science NCERT Solutions Curiosity
Natural Indicators
Red Rose Extract: Turns red in acid, green in base.
Turmeric Paper: Turns red in basic substances, remains yellow in acid/neutral.
Olfactory Indicators: Substances like onion, whose smell changes with acids or bases.
Neutralisation
Reaction between acid and base forming salt, water, and heat.
Equation: Acid + Base → Salt + Water + Heat
Neutralisation in Daily Life
Ant bite → Baking soda (base) applied to neutralize formic acid.
Acidic soil → Treated with lime (base).
Factory acidic waste → Neutralised before releasing into water bodies.
Important Definitions:
- Acid: Substance that turns blue litmus red.
- Base: Substance that turns red litmus blue.
- Neutral Substances that do not affect litmus.
- Indicator: Substance that shows colour change in acids and bases.
- Neutralisation: Reaction between acid and base to form salt and water.
Class 7 Science Curiosity Chapter 2 Fill in the Blanks
Litmus is obtained from ________.
Substances that do not change litmus colour are ________ in nature.
The acid present in vinegar is ________.
Turmeric paper turns ________ in a basic solution.
Neutralisation reaction produces salt, water, and ________.
Class 7 Science Curiosity Chapter 2 Question – Answer
Q1. What are indicators? Give two examples.
Answer: Indicators are substances that show different colours in acidic and basic mediums.
Examples: Litmus, Red rose extract.
Q2. What happens to blue litmus paper when it is dipped in an acidic solution?
Answer: Blue litmus paper turns red when dipped in an acidic solution.
Q3. How can you prepare turmeric paper?
Answer: Mix turmeric powder with water to make a paste.
Dip filter paper in it and dry it.
Cut the dried paper into strips to use as turmeric paper.
Q4. What is neutralisation?
Answer: Neutralisation is the reaction between an acid and a base forming salt, water, and releasing heat.
Q5. Give an example of neutralisation in daily life.
Answer: When an ant bites, baking soda (a base) is applied to neutralise the effect of formic acid injected by the ant.
Science Class 7 Curiosity Chapter 2 MCQs
Q1. Which substance will turn blue litmus red?
a) Soap solution
b) Vinegar
c) Baking soda solution
d) Lime water
Q2. Which indicator turns yellow turmeric paper red?
a) Acid
b) Base
c) Neutral substance
d) None
Q3. Which is NOT an indicator?
a) Red rose extract
b) Turmeric
c) Sugar solution
d) Litmus
Q4. What is formed during a neutralisation reaction?
a) Only salt
b) Only water
c) Salt, water, and heat
d) Only heat