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Political Science NCERT Solutions Class 7 Science Chapter 2 – Exploring Substances: Acidic, Basic, and Neutral
Class 7 Science
Last Updated: 31 May 2026
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Important Points
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Practice MCQ Questions (50 questions)
Q1. What appeared on Ashwin and Keerthi's paper when sprayed at the science fair?
✓ Correct Answer: B
Q2. What natural substance is litmus obtained from?
✓ Correct Answer: B
Q3. What color does blue litmus turn in acidic substances?
✓ Correct Answer: B
Q4. Which of these is NOT a natural indicator?
✓ Correct Answer: D
Q5. What happens when lime water is added to lemon juice?
✓ Correct Answer: B
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Frequently Asked Questions (FAQ)
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Tough Words (Glossary)
Indicator
Meaning: A substance that shows a visible change (like color) to reveal the nature of another substance
अर्थ: सूचक – वह पदार्थ जो किसी दूसरी वस्तु का स्वभाव दिखाने के लिए रंग/आकृति में बदलाव दिखाए
"Red litmus is an indicator that turns blue in a base."
Litmus
Meaning: A natural dye from lichens used to test acids and bases
अर्थ: लिटमस – लाइकेन से प्राप्त प्राकृतिक रंजक, अम्ल‑क्षार की जाँच के लिए
"Litmus paper changed color when lemon juice was added."
Lichens
Meaning: Organisms made of a fungus and an alga living together
अर्थ: लाइकेन – कवक और शैवाल का सहजीवी संघटन
"Litmus is obtained from certain lichens."
Acidic
Meaning: Having the properties of an acid; turns blue litmus red
अर्थ: अम्लीय – अम्ल का स्वभाव रखने वाला; नीले लिटमस को लाल करता है
"Vinegar is acidic in nature."
Basic
Meaning: Having the properties of a base; turns red litmus blue
अर्थ: क्षारीय – क्षार का स्वभाव रखने वाला; लाल लिटमस को नीला करता है
"Soap solution is basic."
Neutral
Meaning: Neither acidic nor basic
अर्थ: उदासीन – न अम्लीय, न क्षारीय
"Pure water is neutral."
Lime water
Meaning: A solution of calcium hydroxide in water
अर्थ: चूने का पानी – कैल्शियम हाइड्रॉक्साइड का जलीय घोल
"Lime water neutralised the acid in the test tube."
Filtrate
Meaning: The liquid that passes through a filter during filtration
अर्थ: फिल्ट्रेट – छनन के बाद छननी/फ़िल्टर से होकर निकला द्रव
"Collect the filtrate in a clean beaker."
Extract
Meaning: A concentrated solution obtained by drawing out substances, often from plants
अर्थ: सार/निर्गत – किसी पदार्थ (अक्सर पौधों) से निकाला गया घना द्रव
"We used rose petal extract as an indicator."
Turmeric
Meaning: A yellow spice that can act as a natural indicator
अर्थ: हल्दी – पीला मसाला, प्राकृतिक सूचक का काम करता है
"Turmeric paper turned red with soap."
Olfactory
Meaning: Related to the sense of smell
अर्थ: घ्राण-संबंधी – सूँघने की इंद्रिय से जुड़ा
"Onion strips act as an olfactory indicator."
Neutralisation
Meaning: A reaction where an acid and a base react to form salt and water
अर्थ: उदासीनीकरण – अम्ल व क्षार की प्रतिक्रिया जिससे लवण व जल बनते हैं
"Baking soda gave relief by neutralisation of the ant acid."
Synthetic
Meaning: Made by chemical processes; artificial
अर्थ: संश्लिष्ट/कृत्रिम – रसायनिक विधि से बनाया गया
"Phenolphthalein is a synthetic indicator."
Edible
Meaning: Safe and suitable for eating
अर्थ: खाद्य – खाने योग्य
"Lemon and curd are edible acidic substances."
Slippery
Meaning: Smooth and difficult to hold due to low friction
अर्थ: फिसलनदार – पकड़ना कठिन, घर्षण कम होने के कारण
"Bases often feel slippery to touch."
Immersed
Meaning: Completely covered by a liquid
अर्थ: डुबोया हुआ/डूबा – द्रव में पूरी तरह ढँका
"Rose petals were immersed in hot water."
Mortar and pestle
Meaning: Tools used to crush or grind substances
अर्थ: ओखली और मूसल – पीसने‑कूटने के औज़ार
"Crush the petals with a mortar and pestle."
Compost
Meaning: Decayed organic material used to enrich soil
अर्थ: खाद/कम्पोस्ट – सड़ी‑गली जैविक सामग्री, मिट्टी को उपजाऊ बनाती है
"Compost is added to basic soil to improve it."
Deficiency
Meaning: A lack or shortage of something needed
अर्थ: कमी/अभाव – आवश्यक वस्तु का अभाव
"Poor plant health may be due to nutrient deficiency."
Abundant
Meaning: Existing in large quantities; plentiful
अर्थ: प्रचुर – बहुत मात्रा में उपलब्ध
"Lichens grow in areas with abundant clean air."