During the course of an experiment, 'to determine the percentage of water absorbed by raisins', raisins are weighed

Life Processes

Osmosis and Water Absorption in Raisins

Options

(A)every half an hour.

(B)every hour.

(C)once - only after completing the experiment.

(D)two times - before soaking and after soaking for three hours.

Official Answer

The correct option is D. In the experiment to determine the percentage of water absorbed by raisins, the raisins are weighed exactly two times: first in their dry state before soaking ( $W_1$ ), and second after soaking them in water for about three hours and wiping off the excess surface water ( $W_2$ ).

dry weightsoaked weighttwo timesosmosis

Marking Scheme

11 Mark for selecting the correct option D.

Hint

To find the percentage of water absorbed, you need the initial dry weight and the final wet weight of the raisins.

Quick Oral Answer

We weigh the raisins twice: once before soaking to get the initial dry mass ( $W_1$ ), and once after soaking and wiping to get the final mass ( $W_2$ ).

Analysis & Explanation

To calculate the percentage of water absorbed by raisins, we use the formula:

$\text{Percentage of water absorbed} = \frac{W_2 - W_1}{W_1} \times 100$

where $W_1$ is the initial weight of the dry raisins and $W_2$ is the final weight of the swollen (soaked) raisins. Therefore, weighing is required only twice: once before soaking to find $W_1$ , and once after soaking (typically for 2 to 3 hours) and wiping to find $W_2$ .

Option A is incorrect because weighing every half hour is unnecessary and would repeatedly disturb the osmosis process.
Option B is incorrect because hourly weighing is not required for calculating the final absorption percentage.
Option C is incorrect because without the initial dry weight, the amount of water absorbed cannot be calculated.

Common Mistakes

1Students sometimes forget to wipe the raisins before the second weighing, which leads to an overestimation of water absorption due to surface water.

Interesting Facts

Raisins act as a semi-permeable system. Water enters the dry raisins through the process of endosmosis because the concentration of water outside is higher than inside the raisin cells.

Spotted a mistake or something unclear?

Tell us — we fix reported answers fast.

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 and Water Absorption in Raisins" 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.