The following 20 Multiple Choice Questions (MCQ) are based on
Chapter 2: Exploring Substances: Acidic, Basic, and Neutral from the NCERT Class 7
Science textbook Curiosity. Each question has four options - select the
best answer and click to check.
Instructions: Read each question carefully. Choose the most
appropriate option from (a), (b), (c), or (d). Click
Show Answer to reveal the correct answer with explanation.
Multiple Choice Questions
1An acid turns blue litmus:
(a) Red
(b) Green
(c) Yellow
(d) Blue
(a) is correct
Blue litmus changes to red in an acidic solution.
2A base turns red litmus:
(a) Red
(b) Colourless
(c) Orange
(d) Blue
(d) is correct
Red litmus changes to blue in a basic solution.
3Which substance is acidic?
(a) Lime water
(b) Baking soda solution
(c) Lemon juice
(d) Soap solution
(c) is correct
Lemon juice contains acids and changes blue litmus to red.
4Which substance is basic?
(a) Tamarind water
(b) Soap solution
(c) Vinegar
(d) Amla juice
(b) is correct
Soap solution shows basic behaviour with indicators.
5A neutral solution generally changes red and blue litmus by:
(a) Producing no colour change
(b) Turning both green
(c) Turning both red
(d) Turning both blue
(a) is correct
Neutral substances do not show the characteristic litmus changes of acids or bases.
6An acid-base indicator is a substance that:
(a) Always remains colourless
(b) Measures mass
(c) Produces electricity
(d) Shows different colours in acidic and basic media
(d) is correct
Indicators reveal the nature of a solution through a visible colour response.
7Litmus is obtained from:
(a) Table salt
(b) Plastic
(c) Lichens
(d) Iron
(c) is correct
Litmus is a natural dye traditionally extracted from lichens.
8Red rose extract becomes which colour in an acidic solution?
(a) Black
(b) Red
(c) Green
(d) Blue
(b) is correct
The chapter reports a red colour in acidic solutions.
9Red rose extract becomes which colour in a basic solution?
(a) Green
(b) Red
(c) Yellow
(d) Colourless
(a) is correct
Its basic-medium colour is green.
10Yellow turmeric turns red in:
(a) An acidic solution
(b) A neutral solution
(c) Pure water only
(d) A basic solution
(d) is correct
Turmeric is unchanged by acids and neutral substances but turns red with bases.
11Why can turmeric paper not by itself distinguish an acid from a neutral solution?
(a) It dissolves in both
(b) It is not an indicator
(c) Both usually leave it yellow
(d) Both turn it red
(c) is correct
Turmeric responds clearly to bases, but remains yellow in acid and neutral media.
12Neutralisation occurs when:
(a) Water freezes
(b) An acid reacts with a base
(c) Two acids are mixed only
(d) A metal is hammered
(b) is correct
Sufficient acid and base cancel their characteristic effects.
13The products of an acid-base neutralisation are mainly:
(a) Salt, water and heat
(b) Only oxygen
(c) Metal and hydrogen
(d) Sugar and water
(a) is correct
The general reaction is acid + base -> salt + water, with heat released.
14Moist baking soda can relieve an ant bite because it:
(a) Adds more acid
(b) Freezes the skin
(c) Acts as litmus
(d) Neutralises the injected formic acid
(d) is correct
Baking soda is basic and reduces the effect of the acidic sting.
15Acidic soil can be treated with:
(a) Lemon juice
(b) Amla juice
(c) Lime
(d) Vinegar
(c) is correct
Lime is basic and neutralises excess soil acidity.
16Basic soil may be improved by adding:
(a) Soap solution
(b) Compost or organic matter
(c) More lime
(d) Baking soda
(b) is correct
Decaying organic matter releases acids that reduce excess basicity.
17Acidic industrial waste should be treated before release by:
(a) Neutralising it with a suitable base
(b) Adding more acid
(c) Adding only colour
(d) Heating it without testing
(a) is correct
Neutralisation helps reduce harm to aquatic organisms and ecosystems.
18Vinegar on eggshell produces bubbles because acid reacts with:
(a) Pure iron
(b) Plastic
(c) Sugar
(d) Calcium carbonate
(d) is correct
The reaction releases carbon dioxide gas.
19A solution turns red litmus blue. It is most likely:
(a) Always neutral
(b) A metal
(c) Basic
(d) Acidic
(c) is correct
Changing red litmus to blue is the standard test for a base.
20Adding excess vinegar to a basic solution would eventually make it:
(a) Unable to affect indicators
(b) Acidic after passing through neutralisation
(c) More basic forever
(d) A metal
(b) is correct
Once enough acid has neutralised the base, additional acid makes the mixture acidic.
What is covered in CBSE Class 7 Science Chapter 2 Exploring Substances: Acidic, Basic, and Neutral?
This chapter covers all key topics from Exploring Substances: Acidic, Basic, and Neutral as per CBSE 2026-27 syllabus.
Is this MCQ Test useful for CBSE board exams?
Yes, designed for CBSE Class 7 board exam preparation covering the complete syllabus.
Are these CBSE Class 7 Science MCQ Test updated for 2026-27?
Yes, all content at eBookPublisher is updated as per the latest 2026-27 CBSE syllabus.
How many chapters are in CBSE Class 7 Science?
All chapters of CBSE Class 7 Science are covered at eBookPublisher with free MCQ Test for each chapter.
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