states-of-matter-explained-by-particles MCQs for UPSC Prelims

29 practice questions on states-of-matter-explained-by-particles from the Particulate Nature of Matter section of the UPSC Prelims syllabus. 29 come with a written explanation. Try the sample set below - the answer stays hidden until you ask for it.

8 Easy 14 Medium 7 Hard

Sample questions

Q1
medium

Which pair of features together describes the particles of a solid?

  1. A Far apart and free to move anywhere
  2. B Closely packed and held in fixed positions
  3. C Closely packed and free to move anywhere
  4. D Far apart and held in fixed positions
Show answer and explanation

Correct answer: B - 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.

Q2
hard

A student claims that a liquid can be squeezed into a much smaller volume just as easily as a gas. Why is this claim wrong?

  1. A The particles of a liquid are already close together with very little space between them
  2. B The particles of a liquid do not move at all
  3. C A liquid contains no particles that could be pushed
  4. D A liquid turns into a solid as soon as it is pressed
Show answer and explanation

Correct answer: A - The particles of a liquid are already close together with very little space between them

There is hardly any space between liquid particles, so a squeeze has almost nothing to close up, unlike in a gas. Liquid particles do move, which is why a liquid flows. A liquid is made of particles like everything else, and pressing a liquid does not turn it into a solid.

Q3
easy

In a gas, the particles are

  1. A touching one another in a fixed pattern
  2. B very far apart and moving quickly in all directions
  3. C collected at the bottom of the container
  4. D close together but able to slide over one another
Show answer and explanation

Correct answer: B - very far apart and moving quickly in all directions

Wide spacing and rapid movement in every direction are what allow a gas to fill any container. A fixed pattern of touching particles describes a solid, and close sliding particles describe a liquid. Gas particles spread through the whole container instead of settling at the bottom.

Q4
hard

Assertion (A): A solid has a definite shape as well as a definite volume. Reason (R): The particles of a solid are far apart and move freely from place to place.

  1. A Both A and R are true, and R is the correct explanation of A
  2. B Both A and R are true, but R is not the correct explanation of A
  3. C A is true, but R is false
  4. D A is false, but R is true
Show answer and explanation

Correct answer: C - A is true, but R is false

The assertion is true, since a solid keeps both its shape and its volume. The reason is false: solid particles are close together and stay in fixed positions, which is exactly the opposite of what R claims. Only the assertion survives, so the choices that accept R are wrong.

Q5
easy

In a solid, the particles are

  1. A spread far apart with large gaps between them
  2. B close together but free to slide past one another
  3. C packed closely together in a regular fixed arrangement
  4. D joined end to end in one long single line
Show answer and explanation

Correct answer: C - packed closely together in a regular fixed arrangement

Solid particles sit close together in an orderly arrangement and stay in their own places, which is why a solid keeps its shape. Large gaps describe a gas, and sliding particles describe a liquid. Particles are not strung out in a single line; they fill the whole body of the solid.

Q6
hard

More air is pumped into a cycle tyre that already holds air. What happens to the air particles that were already inside?

  1. A They are pushed closer together and strike the walls of the tyre more often
  2. B They change into particles of a liquid
  3. C They each become smaller in size
  4. D They stop moving because there is no room left
Show answer and explanation

Correct answer: A - They are pushed closer together and strike the walls of the tyre more often

Adding air packs the particles closer, so more of them hit the tyre walls each second and the tyre feels harder. Particles never change size. Even in a tightly packed tyre the particles keep moving, and ordinary air does not become a liquid on being pumped.

Q7
easy

In a liquid, the particles are

  1. A close together but able to slide past one another
  2. B far apart and moving extremely fast
  3. C held rigidly in their places
  4. D locked in a fixed pattern that never changes
Show answer and explanation

Correct answer: A - close together but able to slide past one another

A liquid keeps its volume because its particles stay close, and it flows because they can slide over one another. Particles far apart and very fast describe a gas. Rigid positions and fixed patterns describe a solid, which cannot be poured.

Q8
medium

Two statements are made about a solid. (i) Its particles are very close to one another. (ii) Its particles can change places freely. Which of these is correct?

  1. A Both statements are correct
  2. B Only statement (i) is correct
  3. C Both statements are wrong
  4. D Only statement (ii) is correct
Show answer and explanation

Correct answer: B - Only statement (i) is correct

Solid particles are indeed very close together, so the first statement is right. They cannot change places freely; that is what makes a solid rigid, so the second statement is wrong. Since one statement is right and the other wrong, neither accepting both nor rejecting both can be correct.

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