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Political Science NCERT Solutions Class 8 Science - Curiosity Chapter 7 – Particulate Nature of Matter
Class 8 Science - Curiosity
Last Updated: 31 May 2026
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Important Points
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Practice MCQ Questions (59 questions)
Q1. What does grinding a piece of chalk into powder demonstrate?
✓ Correct Answer: A
Q2. In Activity 7.2, sugar disappears in water because it:
✓ Correct Answer: B
Q3. The tiny units that make up a substance are called its:
✓ Correct Answer: C
Q4. The spaces between particles of matter are called:
✓ Correct Answer: B
Q5. When sugar dissolves without stirring initially, the top layer tasting sweet shows:
✓ Correct Answer: C
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Frequently Asked Questions (FAQ)
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Tough Words (Glossary)
erosion
Meaning: Gradual wearing away of rock or soil by wind, water, or ice.
अर्थ: क्षय/कटाव – हवा, पानी या बर्फ़ से चट्टानों/मिट्टी का घिसना।
"Erosion turns big rocks into small pebbles and sand."
eroded
Meaning: Worn away or broken down by natural forces.
अर्थ: क्षित/घिसा हुआ – प्राकृतिक शक्तियों से घिसा-बिखरा।
"Eroded rocks are carried by rivers to the plains."
transport
Meaning: To carry something from one place to another.
अर्थ: ढोना/ले जाना।
"Rivers transport sand and pebbles to distant places."
plains
Meaning: Large flat areas of land.
अर्थ: मैदानी क्षेत्र।
"Rivers deposit sand in the plains."
grains
Meaning: Very small hard particles (like sand).
अर्थ: कण/दाने।
"Grains of sand can still be seen with the naked eye."
constituent
Meaning: Forming part of a whole; a component.
अर्थ: घटक – किसी संपूर्ण वस्तु का हिस्सा।
"Water and sugar are constituent parts of a solution."
constituent particle
Meaning: The smallest building unit that makes up a substance.
अर्थ: घटक कण – पदार्थ को बनाने वाली सबसे छोटी इकाई।
"Each grain of sugar has millions of constituent particles."
particle
Meaning: A very small piece of matter.
अर्थ: कण – पदार्थ का बहुत छोटा भाग।
"Particles in gases move freely in all directions."
interparticle
Meaning: Between particles; relating to the spacing/forces among particles.
अर्थ: अन्तरकणीय – कणों के बीच का।
"Interparticle spaces allow sugar to mix in water."
dissolution
Meaning: The process of a substance mixing completely in a liquid.
अर्थ: विघटन/विलेयन – पदार्थ का तरल में घुल जाना।
"Dissolution of salt in water makes a solution."
magnifying glass
Meaning: A curved glass that makes small things look bigger.
अर्थ: आवर्धक काँच – छोटी वस्तुओं को बड़ा दिखाने वाला काँच।
"Use a magnifying glass to see the chalk powder clearly."
mortar and pestle
Meaning: Tools used to crush or grind substances.
अर्थ: ओखली-मूसल – पीसने‑कूटने के औज़ार।
"We used a mortar and pestle to grind the chalk."
physical change
Meaning: A change in form or size without forming a new substance.
अर्थ: भौतिक परिवर्तन – रूप/आकार में बदलाव, नया पदार्थ नहीं बनता।
"Grinding chalk is a physical change."
chemical change
Meaning: A change that forms a new substance.
अर्थ: रासायनिक परिवर्तन – जिसमें नया पदार्थ बनता है।
"Rusting of iron is a chemical change."
occupy
Meaning: To take up space or be present in a place.
अर्थ: स्थान घेरना/घटना।
"Sugar particles occupy spaces between water particles."
microscope
Meaning: An instrument that makes tiny objects look larger.
अर्थ: सूक्ष्मदर्शी – बहुत छोटी वस्तुओं को बड़ा दिखाने वाला यंत्र।
"Cells can be seen clearly under a microscope."
attractive forces
Meaning: Pulling forces that bring particles or objects closer.
अर्थ: आकर्षी बल – जो कणों/वस्तुओं को पास लाते हैं।
"Attractive forces keep solid particles tightly packed."
interparticle attractions
Meaning: Attractive forces acting between particles.
अर्थ: अन्तरकणीय आकर्षण – कणों के बीच के आकर्षी बल।
"Interparticle attractions are strongest in solids."
Parmanu
Meaning: Ancient Indian idea of an indivisible particle (atom).
अर्थ: परमाणु – अविभाज्य सूक्ष्म कण की प्राचीन भारतीय धारणा।
"Acharya Kanad proposed the concept of Parmanu."
philosopher
Meaning: A thinker who studies ideas about knowledge and existence.
अर्थ: दार्शनिक – ज्ञान व अस्तित्व पर विचार करने वाला।
"An ancient philosopher wrote about atoms."
indivisible
Meaning: Unable to be divided further.
अर्थ: अविभाज्य – जिसे और नहीं बाँटा जा सके।
"He called the smallest particle indivisible."
eternal
Meaning: Existing forever; without end.
अर्थ: शाश्वत – सदैव रहने वाला।
"Parmanu was described as eternal."
Vaisheshika Sutras
Meaning: Ancient Indian text describing atoms and matter.
अर्थ: वैशेषिक सूत्र – पदार्थ व परमाणु पर प्राचीन ग्रंथ।
"The Vaisheshika Sutras discuss particles of matter."
definite shape
Meaning: A fixed and unchanging form.
अर्थ: निश्चित आकार – जो नहीं बदलता।
"Solids have a definite shape."
volume
Meaning: The amount of space an object or substance occupies.
अर्थ: आयतन – वस्तु/पदार्थ द्वारा घेरा गया स्थान।
"Liquids have a fixed volume."
vibrate
Meaning: To move back and forth rapidly around a position.
अर्थ: कम्पन करना – एक स्थान के आसपास तेज़ी से हिलना।
"Solid particles vibrate in fixed positions."
oscillate
Meaning: To swing or move in a regular back-and-forth motion.
अर्थ: दोलित होना – आगे‑पीछे नियमित रूप से हिलना।
"Particles oscillate faster when heated."
melting point
Meaning: Temperature at which a solid changes to a liquid.
अर्थ: गलनांक – ताप जिस पर ठोस तरल बनता है।
"Ice melts at its melting point."
boiling point
Meaning: Temperature at which a liquid changes to vapour.
अर्थ: क्वथनांक – ताप जिस पर तरल भाप बनता है।
"Water boils at its boiling point."
evaporation
Meaning: Slow change of a liquid to vapour at the surface.
अर्थ: वाष्पीकरण – सतह पर तरल का धीरे‑धीरे भाप बनना।
"Evaporation makes a wet floor dry."
vapour
Meaning: Gas form of a substance that is usually liquid or solid.
अर्थ: वाष्प – ऐसा गैसीय रूप जो सामान्यतः तरल/ठोस होता है।
"Water vapour rises from hot tea."
compress
Meaning: To press into a smaller space.
अर्थ: संपीड़ित करना – दबाकर जगह कम करना।
"Air can be compressed by pushing a syringe."
syringe
Meaning: A tube with a plunger used to push or pull fluids.
अर्थ: सीरिंज – द्रव खींचने/डालने का नलीदार औज़ार।
"We used a syringe to show air compression."
plunger
Meaning: The sliding part of a syringe that moves the fluid.
अर्थ: पिस्टन/धक्का‑दंड – सीरिंज का चलायमान हिस्सा।
"Push the plunger to reduce the air volume."
incompressible
Meaning: Not able to be squeezed into a smaller volume.
अर्थ: असंपीड्य – जिसे दबाकर छोटा नहीं किया जा सके।
"Water is almost incompressible."
soluble
Meaning: Able to dissolve in a liquid.
अर्थ: घुलनशील – जो तरल में घुल सके।
"Sugar is soluble in water."
insoluble
Meaning: Not able to dissolve in a liquid.
अर्थ: अघुलनशील – जो तरल में न घुले।
"Sand is insoluble in water."
diffusion
Meaning: Spreading of particles from high to low concentration.
अर्थ: प्रसरण – कणों का अधिक से कम घनत्व की ओर फैलना।
"The fragrance spread by diffusion in the room."
fragrance
Meaning: A pleasant smell.
अर्थ: सुगंध/खुशबू।
"The fragrance of incense filled the room."
incense stick
Meaning: A stick that burns to release fragrant smoke.
अर्थ: अगरबत्ती – जलने पर सुगंधित धुआँ देने वाली डंडी।
"An incense stick helped show air movement."
fluids
Meaning: Substances that can flow (liquids and gases).
अर्थ: तरल पदार्थ – जो बह सकते हैं (द्रव व गैसें)।
"Both liquids and gases are called fluids."
gaseous
Meaning: Relating to gas; in the form of gas.
अर्थ: गैसीय – गैस से संबंधित/गैस के रूप में।
"In the gaseous state, particles are far apart."
thermal energy
Meaning: Heat energy possessed by particles.
अर्थ: उष्मीय ऊर्जा – कणों में निहित ऊष्मा ऊर्जा।
"More thermal energy makes particles move faster."
interparticle spacing
Meaning: The space between particles of matter.
अर्थ: अन्तरकणीय दूरी/रिक्ति – कणों के बीच की जगह।
"Interparticle spacing is minimum in solids."
force of attraction
Meaning: Pulling force that holds particles together.
अर्थ: आकर्षण बल – जो कणों को बाँधे रखता है।
"The force of attraction is weaker in liquids."
dissolve
Meaning: To mix completely with a liquid to form a solution.
अर्थ: घुलना – तरल में पूर्णतः मिलकर घोल बनाना।
"Salt will dissolve faster in warm water."
uniform
Meaning: Same everywhere; even and consistent.
अर्थ: समान/एकरूप – हर जगह एक जैसा।
"After stirring, the solution became uniform."
vessel
Meaning: A container used to hold liquids.
अर्थ: बर्तन/पात्र – द्रव रखने का बर्तन।
"Pour the solution into a clean vessel."
suspended
Meaning: Hanging or floating in a fluid without settling quickly.
अर्थ: निलम्बित – द्रव में तैरता/लटका हुआ, जल्दी न बैठने वाला।
"Smoke has suspended tiny particles in air."
schematic
Meaning: Shown using a simple diagram to explain something.
अर्थ: रूपरेखात्मक – समझाने हेतु सरल आरेख में दिखाया हुआ।
"The book shows a schematic of melting."