To determine the percentage of water absorbed by raisins, raisins are soaked in water for:
To determine the percentage of water absorbed by raisins, raisins are soaked in water for:
Options
2 to 3 hours
Marking Scheme
- 11 Mark for selecting the correct option (C)
Hint
Consider the time required for water to diffuse through a semi-permeable membrane and fully swell a highly dehydrated cell.
Quick Oral Answer
We soak raisins for 2 to 3 hours to ensure that maximum endosmosis occurs and the cells reach a state of turgidity, allowing us to measure the maximum water-holding capacity of the cells.
Analysis & Explanation
To determine the percentage of water absorbed by raisins, they must be soaked in water for a sufficient period to allow endosmosis to reach equilibrium.
- Why '2 to 3 hours' is correct: This duration is optimal for water molecules to pass through the selectively permeable cell membranes of the dry, dehydrated raisin cells, making them fully turgid.
- Why other options are incorrect:
- 30 seconds and 10 minutes are far too short for any significant amount of water to diffuse through the thick, dry outer skin (exocarp) of the raisins.
- 24 hours is unnecessarily long and can lead to the initiation of decay, fermentation, or bursting of the cells due to excessive hydrostatic pressure.
Common Mistakes
- 1Choosing 24 hours thinking more time always leads to better absorption, which actually causes cell damage or fermentation.
- 2Choosing 10 minutes, which does not allow sufficient time for complete endosmosis.
Interesting Facts
Raisins swell up when placed in water because the water outside is hypotonic (higher water concentration) compared to the highly concentrated sugary cytoplasm inside the raisin cells (hypertonic medium).
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2011?
This question carries 1 mark in the CBSE Class 10 Science 2011 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Life Processes" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Osmosis in Raisins (Practical)" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2011 paper?
This is a MCQ question from Section B in the CBSE Class 10 Science 2011 paper.