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Answer the following. (Class 10 Science 2025, Q28b)

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ScienceCBSE Class 10 · Board exam 2025, set 31/1/1 · 3 marks · Short answer

CBSE Class 10 Science 2025: question 28(b)

Set in the CBSE Class 10 board exam of 2025, paper 31/1/1, section C, question 28(b), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q28(b) · 3 marks · Short answerMetals and Non-metals

Answer the following.

  1. (i)

    Name two metals which react violently with cold water. List any three observations which a student notes when these metal are dropped in a beaker containing water.

    0 marks
  2. (ii)

    Write a test to identify the gas evolved (if any) during the reaction of these metals with water.

    0 marks

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

Hints

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

Hint 1

Which metals are stored under kerosene?

Hint 2

Think about what you see, feel and what happens to the gas formed.

Hint 3

What test identifies hydrogen gas?

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. (i) Two metals that react violently with cold water: sodium and potassium (lithium is also acceptable).

    1 mark

  2. (i) Observations: (1) the reaction is violent and vigorous, and the metal moves about on the water; (2) a large amount of heat is evolved (exothermic); (3) the hydrogen gas evolved catches fire. Reaction:

    1½ marks

  3. (ii) The gas evolved is hydrogen. Bring a burning matchstick or splinter near the gas: it burns with a pop sound, which confirms hydrogen.

    ½ mark

Answer: (i) Sodium, potassium; violent reaction, much heat evolved, gas catches fire; (ii) gas burns with a pop sound (hydrogen)

Where the marks are

  • Names two metals, e.g. Na and K (½ + ½ marks)
  • Three observations: violent reaction, heat evolved, gas catches fire (1½ marks)
  • Pop-sound test for hydrogen (½ 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 31/1/1: 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.