CBSE Class 7 Science Chapter 2: Exploring Substances: Acidic, Basic, and Neutral — Assertion & Reason
CBSE Class 7 Science Assertion & Reason
Expert crafted · Instant PDF download · 2026-27
The following Assertion and Reason questions are based on Chapter 2: Exploring Substances: Acidic, Basic, and Neutral from the NCERT Class 7 Science textbook Curiosity. Each question has four options — read both the Assertion (A) and Reason (R) carefully before selecting your answer.
How to attempt Assertion & Reason questions:
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Assertion & Reason Questions
1
Assertion (A): Lemon juice tastes sour because it contains acid.
Reason (R): Substances that taste sour tend to contain acids and are acidic in nature.
Reason (R): Substances that taste sour tend to contain acids and are acidic in nature.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The sour taste of certain edible substances, like lemon, amla, or vinegar, is a direct result of their acidic nature.
2
Assertion (A): Baking soda solution feels soapy or slippery to touch.
Reason (R): Basic substances are generally slippery to touch.
Reason (R): Basic substances are generally slippery to touch.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Bases generally have a soapy and slippery feel when rubbed between the fingers, which is a key physical property of basic substances like baking soda.
3
Assertion (A): Every edible substance that tastes bitter contains a base.
Reason (R): Bitter gourd (karela) possesses a bitter taste but is not basic in nature.
Reason (R): Bitter gourd (karela) possesses a bitter taste but is not basic in nature.
Answer: (d)
A is false, but R is true. While bases generally taste bitter, not everything with a bitter taste is basic. Bitter gourd is a perfect example of a substance that is bitter but not basic.
4
Assertion (A): Litmus is a natural acid-base indicator.
Reason (R): Litmus is obtained from lichens and shows different colours in acidic and basic solutions.
Reason (R): Litmus is obtained from lichens and shows different colours in acidic and basic solutions.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Litmus serves as a natural indicator precisely because it is extracted from a natural organism (lichen) and changes colour based on the nature of the solution.
5
Assertion (A): A piece of blue litmus paper turns red when dipped in vinegar.
Reason (R): Vinegar is acidic in nature, and acids turn blue litmus to red.
Reason (R): Vinegar is acidic in nature, and acids turn blue litmus to red.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Because vinegar contains acid, it causes the standard colour change of turning blue litmus paper red.
6
Assertion (A): Sugar solution changes the colour of red litmus paper to blue.
Reason (R): Sugar solution is neutral in nature and does not affect the colour of either red or blue litmus paper.
Reason (R): Sugar solution is neutral in nature and does not affect the colour of either red or blue litmus paper.
Answer: (d)
A is false, but R is true. Sugar solution is neutral, so it will not change the colour of red litmus paper to blue, nor will it change blue litmus to red.
7
Assertion (A): Red rose extract is an example of a synthetic acid-base indicator.
Reason (R): Red rose extract gives a green colour in basic solutions.
Reason (R): Red rose extract gives a green colour in basic solutions.
Answer: (d)
A is false, but R is true. Red rose extract is a natural indicator, not a synthetic one, because it is derived directly from flower petals.
8
Assertion (A): Lemon juice turns red rose extract to a green colour.
Reason (R): Lemon juice is acidic, and acidic solutions give a red colour with red rose extract.
Reason (R): Lemon juice is acidic, and acidic solutions give a red colour with red rose extract.
Answer: (d)
A is false, but R is true. Lemon juice is acidic, so it will keep or turn the red rose extract red, not green. Green is the colour produced by basic solutions.
9
Assertion (A): Turmeric paper can be used to easily distinguish between acidic and neutral substances.
Reason (R): Turmeric paper changes colour from yellow to red only in basic solutions.
Reason (R): Turmeric paper changes colour from yellow to red only in basic solutions.
Answer: (d)
A is false, but R is true. Turmeric paper remains yellow in both acidic and neutral solutions, making it impossible to distinguish between the two using only turmeric.
10
Assertion (A): A turmeric (curry) stain on a white shirt turns red when washed with soap.
Reason (R): Soap is basic in nature and changes the yellow colour of turmeric to red.
Reason (R): Soap is basic in nature and changes the yellow colour of turmeric to red.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The base in the soap reacts with the natural turmeric indicator in the curry stain, causing the distinctive colour change from yellow to red.
11
Assertion (A): The odour of finely chopped onions changes when mixed with certain acidic or basic substances.
Reason (R): Substances whose odours change in an acidic or basic medium are called olfactory indicators.
Reason (R): Substances whose odours change in an acidic or basic medium are called olfactory indicators.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Onion is an olfactory indicator, meaning its characteristic smell reacts and changes depending on the acidic or basic nature of the medium it is exposed to.
12
Assertion (A): When an acidic solution is mixed with a basic solution in sufficient quantity, the resulting solution is neither acidic nor basic.
Reason (R): The acid and base neutralise each other's effect to form salt and water.
Reason (R): The acid and base neutralise each other's effect to form salt and water.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. This is the definition of a neutralisation reaction, where the opposing properties cancel each other out, leaving a neutral solution.
13
Assertion (A): In a neutralisation reaction, heat is always absorbed from the surroundings, making the test tube feel cold.
Reason (R): Neutralisation reactions form salt and water with the evolution (release) of heat.
Reason (R): Neutralisation reactions form salt and water with the evolution (release) of heat.
Answer: (d)
A is false, but R is true. Neutralisation reactions always evolve (release) heat, causing the reaction mixture and the container to become warm, not cold.
14
Assertion (A): The pain from a red ant bite can be relieved by rubbing moist baking soda on it.
Reason (R): An ant bite injects formic acid into the skin, which is neutralised by the basic baking soda.
Reason (R): An ant bite injects formic acid into the skin, which is neutralised by the basic baking soda.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The basic nature of baking soda counteracts the acidic venom from the ant, providing relief through a neutralisation reaction.
15
Assertion (A): If the soil in a field is too acidic, farmers should treat it by adding lime.
Reason (R): Lime is basic in nature and neutralises the excessive acid in the soil to help plants grow well.
Reason (R): Lime is basic in nature and neutralises the excessive acid in the soil to help plants grow well.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Since highly acidic soil hinders plant growth, adding a basic substance like lime restores the soil to a neutral, healthy state.
16
Assertion (A): Basic soil can be neutralised by adding organic matter like manure and compost.
Reason (R): Organic matter releases acids that neutralise the basic nature of the soil.
Reason (R): Organic matter releases acids that neutralise the basic nature of the soil.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. As organic matter decomposes, it releases natural acids that balance out excessively basic soil, improving its fertility.
17
Assertion (A): Acidic factory waste should be directly released into lakes and rivers without any treatment.
Reason (R): Acidic waste can kill fish and other aquatic organisms in water bodies.
Reason (R): Acidic waste can kill fish and other aquatic organisms in water bodies.
Answer: (d)
A is false, but R is true. Factory waste must be neutralised by adding basic substances before being released, precisely because its untreated acidic nature would harm aquatic life.
18
Assertion (A): The colour of Hydrangea flowers depends on the acidic or basic nature of the soil they grow in.
Reason (R): Hydrangea produces blue flowers in acidic soil and pink or red flowers in basic soil.
Reason (R): Hydrangea produces blue flowers in acidic soil and pink or red flowers in basic soil.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Hydrangea plants act as natural soil indicators, changing the pigmentation of their blooms based on the chemical makeup of their environment.
19
Assertion (A): Lime water is prepared by dissolving lime fruit juice (lemon) in water.
Reason (R): Lime water is a solution of calcium hydroxide in water, which is basic in nature.
Reason (R): Lime water is a solution of calcium hydroxide in water, which is basic in nature.
Answer: (d)
A is false, but R is true. Lime water is not made from the citrus fruit 'lime'; it is prepared by mixing chuna (calcium oxide/hydroxide) in water.
20
Assertion (A): Litmus, turmeric, and red rose extract are classified as natural indicators.
Reason (R): These indicators are obtained from natural sources like lichens, plant roots, and flower petals rather than being made in laboratories.
Reason (R): These indicators are obtained from natural sources like lichens, plant roots, and flower petals rather than being made in laboratories.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Their classification as 'natural' stems directly from the fact that they are derived from plants and organisms found in nature.
❓ Frequently Asked Questions
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 Assertion & Reason useful for CBSE board exams?
Yes, designed for CBSE Class 7 board exam preparation covering the complete syllabus.
Are these CBSE Class 7 Science Assertion & Reason 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 Assertion & Reason for each chapter.
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