Passage III

Students performed 3 experiments to investigate the absorption of H₂O by dried chickpeas (a type of bean).

Experiment 1

A sample of 50 dried chickpeas with similar sizes and masse was selected. The total mass of the sample was measured, and the average initial mass per chickpea (CM_i) was calculated. The sample was immersed in 200 mL of distilled H₂O at 20°C. After 20 min, 5 chickpeas were removed from the distilled H₂O and gently patted dry with a paper towel, and their total mass was then measured. The average final mass per chickpea (CM_f) was calculated. At each of 6 different time thereafter, another 5 chickpeas were removed from the distilled H₂O and gently patted dry with a paper towel, and their CM_f was determined. The average moisture uptake per chickpea (CMU) was then calculated for each group of 5 chickpeas using the following equation:

The results are shown in Table 1.

Experiment 2

The students repeated the procedure from Experiment 1 at 4 other temperatures (see Table 2).

Experiment 3

The students repeated the procedure from Experiment 1, except that they replaced the distilled H₂O with aqueous solutions of NaCl at 3 different concentrations (see Table 3).

Tables adapted from Gabriel Pinto and All Esln, "Kinetics of the Osmotic Hydration of Chickpeas." ©2004 by Division of Chemical Educatlon, lnc., American Chemical Society.