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Write the essential function… (Class 10 Science 2025, Q33)

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ScienceCBSE Class 10 · Board exam 2025, set 31/2/1 · 3 marks · Short answer

CBSE Class 10 Science 2025: question 33

Set in the CBSE Class 10 board exam of 2025, paper 31/2/1, section C, question 33, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q33 · 3 marks · Short answerOur Environment

Write the essential function performed by ozone at the higher levels of the atmosphere. How is it formed in the upper atmosphere? Write the name of the group of chemicals mainly responsible for the depletion of ozone layer.

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

Which harmful radiation from the Sun does ozone block?

Hint 2

Ozone (O₃) is made from ordinary oxygen (O₂) with the help of that same radiation. Which chemicals in refrigerators harm it?

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. Function: the ozone layer in the upper atmosphere shields the Earth's surface from harmful ultraviolet (UV) radiation from the Sun. UV radiation damages living organisms (e.g. it can cause skin cancer).

    1 mark

  2. Formation: high-energy UV radiation splits some oxygen molecules into free oxygen atoms. Each free atom then combines with an oxygen molecule to form ozone.
    ;

    1 mark

  3. Chemicals responsible for depletion: chlorofluorocarbons (CFCs), also called freons, used as refrigerants and in fire extinguishers.

    1 mark

Answer: Ozone absorbs harmful UV radiation; it forms when UV splits O₂ into O atoms, which combine with O₂ to give O₃; CFCs deplete it.

Where the marks are

  • Function: protects from harmful UV radiation (1 mark)
  • Formation: UV splits O₂, and O + O₂ → O₃ (1 mark)
  • Names chlorofluorocarbons (CFCs) (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Our Environment, 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.