To Determine the Percentage of Water Absorbed by Raisins (Class 9 Biology Practical)
To measure the increase in mass of raisins when soaked in water and calculate the percentage of water absorbed.
TL;DR: To measure the increase in mass of raisins when soaked in water and calculate the percentage of water absorbed.
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
Aim: To measure the increase in mass of raisins when soaked in water and calculate the percentage of water absorbed.
Materials Required
- Dried raisins
- Distilled water
- Beaker
- Electronic balance
- Paper towel
- Measuring cylinder
Theory
When raisins (dried grapes) are soaked in water, water enters by osmosis through the semi-permeable cell membrane. The mass increases due to water uptake. The percentage increase in mass indicates the amount of water absorbed. This demonstrates osmosis and the importance of water in plant cells.
Procedure
- Weigh a known number of dry raisins (about 10-15 grams) using an electronic balance and record the initial mass
- Place the raisins in a beaker and add distilled water, covering them completely
- Allow the raisins to soak for 30 minutes to 1 hour
- Remove the raisins and gently pat them dry with a paper towel to remove excess water
- Weigh the soaked raisins immediately and record the final mass
- Calculate the mass of water absorbed: Water mass = Final mass - Initial mass
- Calculate percentage of water absorbed: Percentage = (Mass of water absorbed / Initial mass) x 100
- Repeat the experiment 2-3 times and calculate the average percentage
Observation
The dried raisins initially have a wrinkled appearance and low mass. After soaking, they become plump, smooth, and significantly heavier. The mass increases by [value] grams, corresponding to [value]% water absorption.
Result
The percentage of water absorbed by raisins is approximately [value]%, confirming that raisins absorb substantial water when soaked. The plump appearance after soaking indicates significant cell turgor due to water uptake.
Precautions
- Use distilled water to maintain consistency and avoid dissolved salts
- Pat raisins gently with paper towel to remove surface water but not squeeze out absorbed water
- Weigh raisins immediately after drying to avoid further water loss
- Use an accurate electronic balance for precise measurements
- Repeat the experiment multiple times for reliable average result
Viva Questions
Why do raisins absorb water when soaked?
Raisins absorb water by osmosis because the cell membrane is semi-permeable and water moves toward higher solute concentration inside the cells.
What changes occur in raisins after soaking?
The raisins become plump, smooth, and their mass increases due to water absorption and cell turgor.
Why is distilled water used instead of tap water?
Distilled water maintains consistent osmotic potential, while tap water with dissolved minerals may give variable results.
What does high percentage of water absorption indicate?
High water absorption indicates that a significant portion of the raisin's mass was water that was removed during drying.
More Class 9 Biology Practicals
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