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Aluminium powder is used in… (Class 10 Science 2025, Q4)

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ScienceCBSE Class 10 · Board exam 2025, set 31/2/1 · 1 mark · MCQ

CBSE Class 10 Science 2025: question 4

Set in the CBSE Class 10 board exam of 2025, paper 31/2/1, section A, question 4, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q4 · 1 mark · MCQMetals and Non-metals

Aluminium powder is used in thermit welding because :

  1. (A)Its reaction with iron is highly exothermic.
  2. (B)When it is heated with iron (III) oxide, molten iron is obtained.
  3. (C)When it is heated with iron (III) oxide, molten aluminium oxide is obtained to join railway tracks.
  4. (D)Its melting point is low as compared to iron and a molten alloy of iron and aluminium is formed on heating which is used to join railway tracks.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/2/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Write the reaction of aluminium with .

Hint 2

Which product actually fills the gap between the rails?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Thermit reaction: .

  2. Aluminium is more reactive than iron, so it displaces iron from iron(III) oxide. So much heat is released that the iron formed is molten. This molten iron is used to join railway tracks and cracked machine parts.

  3. Aluminium does not react with iron itself, so (A) is wrong. Iron, not aluminium oxide, is the joining material, so (C) is wrong. No Fe–Al alloy is formed, so (D) is wrong. Answer: (B).

    1 mark

Answer: (B)

Where the marks are

  • Chooses (B): heating with iron(III) oxide gives molten iron (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Metals and Non-metals, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/2/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.