Exercise 2.3
Why is it important to cut the two potato pieces in roughly equal size and measure their initial weight before placing them in different liquids? membrane, In addition to the nucleus, the cytoplasm contains several sub-cellular Vacuole Chloroplast Cell wall Ribosome cell (Fig. 2.10a, b and c). A bacterial cell lacks a well-defined nucleus and membrane-bound
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
Because the two pieces must differ in only one thing — the liquid they are placed in.
Roughly equal size means roughly equal surface area of cell membrane exposed to the liquid, so water enters or leaves at comparable rates. A large piece and a small piece would change by different amounts for reasons that have nothing to do with the solution.
The initial weight is the baseline. The whole result of the activity is the change, \(\displaystyle \text{change} = \text{final weight} - \text{initial weight} \), and with no initial value there is no change to calculate.
It turns "the potato looks a little swollen" into a measured number, so the gain in Beaker A and the loss in Beaker B can be shown rather than claimed.
This is what makes it a fair test: one variable changed, everything else held the same.