CBSE Class 7 Science Chapter 02 Exploring Substances Acidic, Basic, And Neutral MCQs Set 02

Download CBSE MCQs for Class 7 Science: Chapter 02 Exploring Substances Acidic, Basic, And Neutral

Access targeted multiple-choice questions for Chapter 02 Exploring Substances Acidic, Basic, And Neutral designed to align with the latest CBSE academic syllabus for Class 7 Science. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.

Chapter-wise Objective Questions: Chapter 02 Exploring Substances Acidic, Basic, And Neutral

Access the complete set of multiple-choice questions for Chapter 02 Exploring Substances Acidic, Basic, And Neutral below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.

Question: The chapter opens with a school science fair held on a specific date to mark National Science Day. Which date is mentioned?
A. 28 February
B. 2 October
C. 15 August
D. 5 September
Show Answer & Explanation

Answer: (A) 28 February

Explanation:
The chapter begins by describing the fair happening on 28 February, which is when National Science Day is observed.

Question: While preparing red rose extract in Activity 2.3, what does the term 'filtrate' refer to?
A. The liquid obtained after straining out the crushed petal residue
B. The solid mash left behind after crushing the petals
C. The water used only to wash the petals beforehand
D. The glass tumbler used to hold the mixture
Show Answer & Explanation

Answer: (A) The liquid obtained after straining out the crushed petal residue

Explanation:
Filtrate simply means the clear liquid that passes through after filtering out solid bits, and that filtered liquid is what becomes the usable flower extract.

Question: Based on Fig. 2.4 in the chapter, which acid is mainly associated with mangoes?
A. Tartaric acid
B. Citric acid alone
C. Oxalic acid alone
D. Ascorbic acid alone
Show Answer & Explanation

Answer: (A) Tartaric acid

Explanation:
Among the edible substances shown in the figure, mango is linked with tartaric acid, unlike citrus fruits or tomatoes, which are linked to different acids.

Question: Arrange the correct order of steps followed while preparing red rose extract in Activity 2.3.
A. Crush the petals, soak them in hot water, then filter the liquid
B. Filter the liquid first, then crush the petals, then soak in water
C. Soak the petals in hot water first, then crush them, then filter
D. Crush the petals, filter immediately, then soak in hot water
Show Answer & Explanation

Answer: (A) Crush the petals, soak them in hot water, then filter the liquid

Explanation:
The activity instructs students to crush washed petals, immerse them in hot water for several minutes, and only then filter out the coloured liquid to obtain the extract.

Question: What was the main purpose of the 'Colourful World of Substances' stall that Ashwin and Keerthi visited at the fair?
A. To show how mixing substances produces colour changes revealing their acidic or basic nature
B. To display fertilisers used by farmers across India
C. To demonstrate how industrial waste is treated before disposal
D. To narrate the biography of Acharya Prafulla Chandra Ray
Show Answer & Explanation

Answer: (A) To show how mixing substances produces colour changes revealing their acidic or basic nature

Explanation:
This stall was where the siblings first saw colour-changing reactions, sparking their interest in exploring acids, bases, and indicators throughout the chapter.

Question: Why does the chapter include real-life situations such as an ant bite, acidic farm soil, and factory waste in a lake?
A. To show practical, everyday uses of the neutralisation reaction
B. To warn students against eating sour fruits
C. To explain how synthetic indicators are manufactured
D. To describe the life cycle of lichens
Show Answer & Explanation

Answer: (A) To show practical, everyday uses of the neutralisation reaction

Explanation:
Each of these situations demonstrates neutralisation solving a real problem — pain relief, soil health, or protecting fish — tying the chemistry concept to daily life.

Question: When a drop of soap solution is placed on red litmus paper, the paper turns blue. What explains this change?
A. Soap solution is basic in nature
B. Soap solution is strongly acidic
C. Soap solution is a neutral cleaning agent
D. Soap solution contains citric acid
Show Answer & Explanation

Answer: (A) Soap solution is basic in nature

Explanation:
Turning red litmus blue is the defining test for a basic substance, and soap solution behaves exactly this way in the chapter's activity.

Question: Which group of substances did the chapter identify as turning red litmus paper blue during classification?
A. Soap solution, baking soda solution, lime water, and washing powder solution
B. Lemon juice, amla juice, tamarind water, and vinegar
C. Tap water, sugar solution, and salt solution
D. Turmeric paste, onion strips, and rose petals
Show Answer & Explanation

Answer: (A) Soap solution, baking soda solution, lime water, and washing powder solution

Explanation:
These four samples formed Group B in the chapter's table, all sharing the basic property of turning red litmus paper blue.

Question: How does the chapter describe the meaning of 'neutralisation'?
A. An acid and a base combine to form salt and water, cancelling each other's effect
B. A liquid slowly evaporates, leaving behind a solid residue
C. A coloured substance is filtered until it becomes colourless
D. A basic solution is diluted with plain tap water
Show Answer & Explanation

Answer: (A) An acid and a base combine to form salt and water, cancelling each other's effect

Explanation:
• Acid reacts with base
• Salt and water are formed
• Heat is released during the reaction
This combination of outcomes is what the chapter calls neutralisation.

Question: Into how many broad groups did the chapter sort the tested samples based on their litmus reactions?
A. Three
B. Two
C. Four
D. Five
Show Answer & Explanation

Answer: (A) Three

Explanation:
The samples were divided into Group A (acidic), Group B (basic), and Group C (neutral) — three categories in total.

Question: Olfactory indicators, as introduced in the chapter's onion activity, detect acids and bases through which sense?
A. Smell
B. Taste
C. Touch
D. Sight
Show Answer & Explanation

Answer: (A) Smell

Explanation:
Unlike litmus or turmeric, these substances work by changing odour rather than colour when exposed to acidic or basic samples.

Question: In which country did Acharya Prafulla Chandra Ray complete his doctorate before returning to India?
A. United Kingdom
B. United States
C. Germany
D. France
Show Answer & Explanation

Answer: (A) United Kingdom

Explanation:
The chapter's profile notes he earned his chemistry doctorate in the UK, after which he came back to India and pushed forward scientific research here.

Question: Where are synthetic acid-base indicators typically produced?
A. In laboratories
B. On farms
C. In kitchens
D. In soap factories
Show Answer & Explanation

Answer: (A) In laboratories

Explanation:
Unlike natural indicators such as litmus or rose extract, synthetic ones are manufactured in laboratories, a topic the chapter says will be explored more in later grades.

Question: How does the chapter explain the preparation of lime water for classroom testing?
A. Calcium oxide is mixed with water, left undisturbed, and then the liquid is filtered
B. Calcium carbonate is boiled directly in water for an hour
C. Baking soda is dissolved in vinegar and then filtered
D. Limestone is crushed and dissolved in lemon juice
Show Answer & Explanation

Answer: (A) Calcium oxide is mixed with water, left undisturbed, and then the liquid is filtered

Explanation:
The chapter's note clarifies that lime (chuna) is stirred into water, allowed to settle for about an hour, and the clear liquid is then filtered off to use as lime water — distinct from the fruit called lime.

Question: Why does litmus paper come in two separate colours, blue and red, for testing purposes?
A. So that both acidic and basic substances can be detected through opposite colour changes
B. Because blue paper detects only liquids and red paper detects only solids
C. Because red litmus works only with fruit juices
D. To help distinguish neutral substances from synthetic ones
Show Answer & Explanation

Answer: (A) So that both acidic and basic substances can be detected through opposite colour changes

Explanation:
Blue litmus reveals acids by turning red, while red litmus reveals bases by turning blue — together the pair covers both possibilities, which is why litmus is called an acid-base indicator.

Question: As per the chart in Fig. 2.4, which acids does the chapter list as being present in amla?
A. Ascorbic acid (Vitamin C) and Citric acid
B. Tartaric acid only
C. Citric acid and Oxalic acid
D. Formic acid and Citric acid
Show Answer & Explanation

Answer: (A) Ascorbic acid (Vitamin C) and Citric acid

Explanation:
Amla is shown in the chart as containing both Vitamin C, chemically known as ascorbic acid, and citric acid together.

Question: In which year did Acharya Prafulla Chandra Ray set up India's first pharmaceutical company, as mentioned in the chapter?
A. 1901
B. 1920
C. 1895
D. 1911
Show Answer & Explanation

Answer: (A) 1901

Explanation:
The chapter credits P.C. Ray with founding the company in 1901, alongside his broader contributions to advancing chemical research in India.

Question: Activity 2.2 asks students to recall the taste of substances like lemon juice, amla juice, tamarind water, and vinegar. What common taste links them all?
A. Sour
B. Bitter
C. Salty
D. Sweet
Show Answer & Explanation

Answer: (A) Sour

Explanation:
All these Group A substances share a sour taste, which the chapter uses to draw the conclusion that acidic substances generally taste sour.

Question: The 'Fascinating Facts' box describing turmeric as a golden spice places it within which plant family?
A. Ginger family
B. Mint family
C. Citrus family
D. Legume family
Show Answer & Explanation

Answer: (A) Ginger family

Explanation:
Turmeric, or haldi, is identified in the chapter as belonging to the ginger family, grown widely in India and valued both as a spice and in Ayurvedic remedies.

Question: A gardener finds that her soil is basic, not acidic, and her plants are struggling. What remedy does the chapter suggest for this situation?
A. Mixing in organic matter such as manure and composted leaves
B. Spraying the soil with lime water
C. Adding more chemical fertiliser
D. Watering with baking soda solution
Show Answer & Explanation

Answer: (A) Mixing in organic matter such as manure and composted leaves

Explanation:
• Basic soil needs something that counteracts its alkalinity, not another base.
• Organic matter like manure and composted leaves naturally releases acids as it breaks down.
• These acids neutralise the excess basicity, helping restore healthier soil conditions for plants.

Question: Which sequence correctly reflects the steps followed in Activity 2.5 to make turmeric indicator paper?
A. Make a turmeric paste with water, dip filter paper until yellow, dry it, then cut into strips
B. Cut filter paper into strips, dip in water, add turmeric powder, dry it
C. Dry filter paper first, then dip it in turmeric paste, and grind it
D. Grind turmeric with oil, soak paper overnight, then boil the strips
Show Answer & Explanation

Answer: (A) Make a turmeric paste with water, dip filter paper until yellow, dry it, then cut into strips

Explanation:
The activity begins with preparing a turmeric-water paste, soaking filter paper in it until coloured yellow, letting it dry, and finally cutting the dried sheet into thin strips for testing.

Question: A gardener notices her hydrangea shrub is blooming in shades of pink and red. Going by the chapter's fact box, what does this suggest about her soil?
A. The soil is basic
B. The soil is acidic
C. The soil is neutral
D. The soil is oversalted
Show Answer & Explanation

Answer: (A) The soil is basic

Explanation:
Pink or red hydrangea blooms appear when the surrounding soil is basic, whereas acidic soil produces blue flowers instead.

Question: Among the exploratory project ideas listed at the end of the chapter, which one is actually suggested?
A. Creating rangoli using acidic or basic substances and natural indicators
B. Building a baking-soda volcano model
C. Growing salt crystals overnight
D. Measuring the pH of human blood
Show Answer & Explanation

Answer: (A) Creating rangoli using acidic or basic substances and natural indicators

Explanation:
The chapter proposes making rangoli patterns using acids, bases, and natural indicators as one of its hands-on exploratory projects, alongside testing water and soil samples.

Question: What overall idea ties together the litmus, red rose extract, and turmeric paper activities in this chapter?
A. Certain natural substances can reveal whether a solution is acidic, basic, or neutral
B. Only synthetic chemicals can reliably detect acids and bases
C. Every plant extract behaves identically as an indicator
D. Litmus paper is the sole trustworthy indicator available
Show Answer & Explanation

Answer: (A) Certain natural substances can reveal whether a solution is acidic, basic, or neutral

Explanation:
Each activity demonstrates a different natural material acting as an acid-base indicator, showing students that colour-changing substances from lichens, flowers, and spices can all classify solutions by their chemical nature.

Question: Why does the chapter insert a caution against tasting unknown samples right before discussing the sour taste of acidic substances?
A. To prevent students from accidentally harming themselves by tasting unsafe or unidentified liquids
B. Because sour substances damage tooth enamel instantly
C. Because tasting interferes with litmus paper results
D. Because only teachers are permitted to identify tastes
Show Answer & Explanation

Answer: (A) To prevent students from accidentally harming themselves by tasting unsafe or unidentified liquids

Explanation:
Tasting is used here only as a classroom observation tool for known, safe samples; the caution exists so learners do not extend this curiosity to unknown or potentially harmful substances outside the activity.

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