Class 8 Science: Particulate Nature of Matter MCQs (NCERT)
100 practice questions on Particulate Nature of Matter, a chapter in the NCERT Class 8 Science textbook, organised into 2 topics. Every question includes a written explanation. Pick a topic below, or try the samples first.
A stick of chalk snaps easily, but an iron rod of the same thickness does not. This tells us that
Achalk particles move about much faster than iron particles inside the solid
Bthe attraction between iron particles is stronger than that between chalk particles
Cchalk has no particles inside it
Diron particles are much smaller than chalk particles, so they cannot be pulled out of place
Show answer and explanation
Correct answer: B - the attraction between iron particles is stronger than that between chalk particles
Breaking a solid means pulling its particles apart, so the harder material has the stronger attraction between its particles. Chalk is made of particles like everything else. Particle size does not decide strength here, and particles in both solids only vibrate in place.
Q2
easy
Sugar dissolves faster in hot milk than in cold milk mainly because
Asugar becomes lighter when the milk is hot and floats apart
Bcold milk has no spaces between its particles
Chot milk contains more particles than cold milk to push the sugar apart
Dthe particles in hot milk move faster and mix the sugar quickly
Show answer and explanation
Correct answer: D - the particles in hot milk move faster and mix the sugar quickly
Faster-moving particles carry the sugar away from the lump more quickly, so it dissolves sooner. Heating does not add extra milk particles. The sugar itself is unchanged in weight, and cold milk certainly has spaces between its particles.
Q3
medium
Which pair of features together describes the particles of a solid?
AFar apart and free to move anywhere
BClosely packed and free to move anywhere
CClosely packed and held in fixed positions
DFar apart and held in fixed positions
Show answer and explanation
Correct answer: C - Closely packed and held in fixed positions
Both close packing and fixed positions are needed to explain why a solid has a definite shape and a definite volume. Close packing with free movement would let the solid flow like a liquid. Particles far apart would leave large gaps, which a solid does not have, and the last pair describes a gas.
Q4
medium
A student wants to show diffusion to the class within one minute. Which set-up is most likely to work?
AOpening a bottle of a strong-smelling liquid at one end of the room
BPressing two metal blocks tightly against each other
CPlacing a drop of ink at the bottom of a tall jar of still water
DKeeping a sugar cube on a plate beside a glass of water
Show answer and explanation
Correct answer: A - Opening a bottle of a strong-smelling liquid at one end of the room
Diffusion through air is fast enough for the smell to reach the class in seconds. Ink in still water takes hours, which is far too slow for one minute. A sugar cube that never touches the water cannot dissolve, and diffusion between two solids is far slower still.
Q5
easy
A solid keeps its own shape because its particles
Ahave no attraction between them at all and simply rest in place
Bare held in fixed positions by a strong attraction
Cslide past one another very easily
Dare far apart and free to go anywhere
Show answer and explanation
Correct answer: B - are held in fixed positions by a strong attraction
Strong attraction keeps each particle in its own place, so the whole object holds its shape. Particles far apart and free to move describe a gas, which has no shape of its own. Easy sliding describes a liquid, and with no attraction the solid would simply fall apart.
Q6
medium
A steel plate is left in the sun for an hour and becomes hot to touch. What has happened to its particles?
AThey are vibrating faster about their positions
BThey have stopped vibrating
CThey have begun to move freely all over the plate
DThey have each become larger in size
Show answer and explanation
Correct answer: A - They are vibrating faster about their positions
Heating a solid speeds up the vibration of its particles while they stay in their places. Free movement through the whole plate would mean it had melted. Vibration increases rather than stops, and the particles themselves keep their size even though the plate as a whole expands slightly.
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