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Seema took a small amount of… (Class 10 Science 2026, Q27)

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ScienceCBSE Class 10 · Board exam 2026, set 31/2/1 · 3 marks · Short answer

CBSE Class 10 Science 2026: question 27

Set in the CBSE Class 10 board exam of 2026, paper 31/2/1, section B, question 27, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27 · 3 marks · Short answerChemical Reactions and Equations

Seema took a small amount of copper powder in a china dish and heated it. What changes will she observe on heating ? When gas is passed over this heated substance, what visible changes will be seen in it ? Give the chemical equations of the reactions involved, along with the names and colours of the products in each case.

Figure in the paper: Apparatus: a china dish containing copper powder placed on a wire gauze over a tripod stand, heated by a burner below. Labels: China dish containing copper powder, Wire gauze, Tripod stand, Burner. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/2/1.

Hints

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

Hint 1

Copper reacts with oxygen of air when heated; what is the colour of the product?

Hint 2

Hydrogen removes oxygen from the oxide. What is regenerated?

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. On heating, the brown copper powder turns black as it gets coated with copper(II) oxide.

    ½ mark

  2. When gas is passed over the heated black substance, the black coating turns brown again as copper is regenerated.

    ½ mark

  3. Reaction 1 (oxidation):

    ½ mark

  4. Product: copper(II) oxide, black in colour.

    ½ mark

  5. Reaction 2 (reduction of CuO):

    ½ mark

  6. Products: copper, brown in colour, and water (as vapour).

    ½ mark

Answer: Brown Cu turns black (2Cu + O₂ → 2CuO, copper oxide, black); with H₂ the black turns brown (CuO + H₂ → Cu + H₂O, copper, brown).

Where the marks are

  • Observation: brown turns black on heating (½ mark)
  • Observation: black turns brown on passing H₂ (½ mark)
  • Equation 2Cu + O₂ → 2CuO (½ mark)
  • Name and colour: copper oxide, black (½ mark)
  • Equation CuO + H₂ → Cu + H₂O (½ mark)
  • Name and colour: copper, brown (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Chemical Reactions and Equations, one at a time, marked against the answer key and marking points.Back to the full paper2026 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.