Fig. 1.1 shows apparatus used to investigate movement of molecules across Visking tubing: a tube of starch solution tied in Visking tubing, attached to a glass tube, standing in a beaker. The investigation was carried out three times using liquids of different concentrations. The level of the liquid in the glass tube was recorded at the start and at the end (after 40 minutes). The results are shown in Table 1.1.

1. aExplain the difference in the levels of liquids in the glass tubes of experiments 2 and 3. [4]

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