Skip to content

Answer the following. (Science 2024 31/5/1 Q35b)

questionbuddy.in/q/cbse-10-science-2024-31-5-1-q35b

ScienceCBSE Class 10 · Board exam 2024, set 31/5/1 · 5 marks · Long answer

CBSE Class 10 Science 2024: question 35(b)

Set in the CBSE Class 10 board exam of 2024, paper 31/5/1, section D, question 35(b), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q35(b) · 5 marks · Long answerLife Processes

Answer the following.

  1. (i)

    In the experimental set-up shown above in diagram (I) atmospheric air is being passed into lime water with a syringe while in diagram (II) air is being exhaled into lime water. The time taken for the lime water to turn milky in both the test tubes is different. Give reason.

    2 marks
  2. (ii)

    Draw the diagram of an open stomatal pore and label (I) Guard cells, and (II) Chloroplast on it. Mention two functions performed by stomata.

    3 marks

Figure in the paper: Two labelled test tubes each containing lime water. Diagram (I): a syringe with its plunger at the top is fitted with a narrow tube whose outlet is immersed in the lime water, and air bubbles rise from the tip. Diagram (II): a person's mouth/tube is shown exhaling through a narrow tube whose outlet is immersed in the lime water, with bubbles rising. Both test tubes are labelled 'Lime water'. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/5/1.

Hints

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

Hint 1

Which gas turns lime water milky? Compare how much of it is in the air we breathe in and the air we breathe out.

Hint 2

For the stoma, picture two kidney-shaped cells around a pore. Think about which gases and which vapour pass through 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. (i) Lime water in set-up (I) takes more time to turn milky than in set-up (II).

    1 mark

  2. Reason: exhaled air contains a much higher percentage of (about 4%) than atmospheric air (about 0.03–0.04%). turns lime water milky: . So the exhaled air of (II) does it faster.

    1 mark

  3. (ii) Diagram (described): draw an open stoma as two bean-shaped (kidney-shaped) guard cells facing each other with their concave sides enclosing an elliptical gap, the stomatal pore. Show a nucleus and small oval chloroplasts in each guard cell, with epidermal cells around them. Title it 'Open stomatal pore'.

    1 mark

  4. Label (I) Guard cells: the two bean-shaped cells around the pore.

    ½ mark

  5. Label (II) Chloroplast: the small green bodies inside the guard cells.

    ½ mark

  6. Function 1: exchange of gases ( and ) for photosynthesis and respiration.

    ½ mark

  7. Function 2: loss of water vapour by transpiration.

    ½ mark

Answer: (i) Exhaled air has more than atmospheric air, so lime water in (II) turns milky faster and (I) takes longer. (ii) Diagram of an open stoma with guard cells and chloroplasts labelled; stomata carry out gaseous exchange and transpiration.

Where the marks are

  • States that set-up (I) takes longer / (II) turns milky faster (1 mark)
  • Gives the reason: exhaled air has a higher percentage of (1 mark)
  • Draws a correct diagram of an open stomatal pore (1 mark)
  • Labels the guard cells (½ mark)
  • Labels a chloroplast (½ mark)
  • States two functions: gaseous exchange and transpiration (½ + ½ marks)

Revise the chapter

  • Chapter: Life Processes (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Life Processes, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 31/5/1: 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.