Changes Around Us: Physical and Chemical MCQs for UPSC Prelims

120 practice questions covering Changes Around Us: Physical and Chemical, organised into 2 topics. 120 questions include a written explanation. Pick a topic below, or try the samples first.

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chemical-changes

30 questions with answers

physical-changes

28 questions with answers

Sample questions

Q1
easy

A potter shapes wet clay into a pot and then bakes it in a hot kiln. Why is this change made on purpose?

  1. A To make the pot dissolve away in water
  2. B To help the clay rust when it is left in the rain
  3. C To get a hard, useful pot that keeps its shape and holds water
  4. D To spoil the clay so that it can no longer be used
Show answer and explanation

Correct answer: C - To get a hard, useful pot that keeps its shape and holds water

Baking hardens the clay so that the pot keeps its shape and holds water, which is exactly why the potter does it. Nobody bakes clay in order to spoil it. Rusting happens to iron, not clay, and a baked pot is meant to resist water rather than dissolve in it.

Q2
medium

Which observation best shows that rust is a different substance from the iron it forms on?

  1. A Rust forms on the outer surface of the iron object
  2. B Rust appears only after the object has been left for many days
  3. C Rust makes the iron object look old and neglected
  4. D Rust is a brown, flaky powder that is neither shiny nor strong like iron
Show answer and explanation

Correct answer: D - Rust is a brown, flaky powder that is neither shiny nor strong like iron

Different properties mean a different substance, and rust differs from iron in colour, strength and shine. Forming on the surface, taking time to appear and looking untidy are all true of rust but say nothing about whether the material itself has changed.

Q3
medium

An aluminium sheet is cut and pressed into a lunch box. Which statement best describes this change?

  1. A A chemical change, because a useful new object is made
  2. B A change of state from solid to liquid
  3. C A change of state from liquid to solid
  4. D A change of shape and size only, as the metal is still aluminium
Show answer and explanation

Correct answer: D - A change of shape and size only, as the metal is still aluminium

Cutting and pressing alter the form of the sheet, but every property of the metal remains that of aluminium. The metal stays solid throughout, so neither of the change-of-state options can apply. Making a new object is not the same as making a new substance, which is what a chemical change requires.

Q4
hard

Assertion (A): A change in which one or more new substances are formed is called a chemical change. Reason (R): Chemical changes are often accompanied by a rise or fall in temperature.

  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: B - Both A and R are true, but R is not the correct explanation of A

A states the correct definition of a chemical change, so it is true. Many chemical changes do give out or take in heat, so R is true as well. But a temperature change is only a common sign, not the reason for the definition, and it happens in some physical changes too, so R does not explain A.

Q5
hard

Which reasoning correctly explains why a rusted iron gate cannot be made as good as new simply by drying it in the Sun?

  1. A Rust must be cooled rather than dried in order to become iron again
  2. B Rust is a new substance, and drying only removes water without turning rust back into iron
  3. C Drying will reverse the change if the gate is left in the Sun for long enough
  4. D Drying works only on changes that were caused by heat in the first place
Show answer and explanation

Correct answer: B - Rust is a new substance, and drying only removes water without turning rust back into iron

Rusting produced a new substance on the surface, and removing moisture does nothing to change rust back into iron. It only slows down further rusting. Cooling has no such power either, and no length of drying will undo a chemical change, so waiting longer will not help.

Q6
easy

A sheet of paper is folded several times to make a paper boat. What has changed?

  1. A The material, from paper to plastic
  2. B Only its shape and size, not the material
  3. C The chemical nature of the paper
  4. D Nothing at all
Show answer and explanation

Correct answer: B - Only its shape and size, not the material

Folding rearranges the sheet but leaves it as the same piece of paper, so only the shape and the space it takes up have changed. Paper cannot turn into plastic by folding, and its chemical nature is untouched. Saying nothing changed ignores the obvious change of shape.

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