Passage IV

Companies W-Z were suspected of diluting pure (100%) honey before packaging it for sale. Students investigated each company's product by using the process of osmosis. During osmosis, H₂O flows across a semipermeable membrane (such as dialysis tubing) from a solution having a lower solute concentration into one with a higher solute concentration. Smaller molecules (such as H₂O) can pass through tiny pores in the dialysis tubing, but larger molecules (such as sugars) cannot.

Experiment 1

Two mL of 100% honey was mixed with 8 mL of H₂O to form a 20% honey solution. A 40%, a 60%, and an 80% honey solution were also made. A sample of 1 of the 4 solutions, 100% honey, or pure H₂O was added to each of 6 bags made of dialysis tubing. Air was pressed out of the bags, the bags were sealed, and the initial mass of each bag plus its contents was measured. Each bag was fully submerged in a separate beaker of pure H₂O at 25°C for 2 hr. The bags were then removed and dried off, and the final mass of each bag plus its contents was measured (see Table 1).

Experiment 2

A sample of each company's product was added to a separate bag and tested as in Experiment 1 (see Table 2).

Experiment 3

A sample of Company Z's product was added to 5 bags. The samples were tested as in Experiment 1, except that the bags were submerged in separate beakers containing, respectively, 20%, 40%, 60%, 80%, or 100% honey. The mass of the bag plus its contents increased for 4 of the bags, but decreased for 1 of the bags.