Changes Around Us: Physical and Chemical MCQs (Class 7 Science, NCERT)

120 practice questions on Changes Around Us: Physical and Chemical, a chapter in the NCERT Class 7 Science textbook, organised into 2 topics. Every question includes a written explanation. Pick a topic below, or try the samples first.

Practice by topic

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

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

Correct answer: D - 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 chemical nature of the paper
  2. B Only its shape and size, not the material
  3. C The material, from paper to plastic
  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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More Class 7 Science chapters

Exploring Substances: Acidic, Basic, and Neutral 116 Electricity: Circuits and their Components 110 The World of Metals and Non-metals 110 Heat Transfer in Nature 105 Measurement of Time and Motion 115 Life Processes in Animals 105 Life Processes in Plants 105 Light: Shadows and Reflections 120 Earth, Moon, and the Sun 100