Question

why is this called a selectively permeable membrane?

because it allows any molecule to selectively choose what side of the membrane to move toward.

because it allows small molecules, such as water, to pass through but not larger molecules, such as those in corn syrup.

Explanation:

Define selective permeability

Selective permeability refers to a membrane's physical property of allowing only certain substances to pass through while blocking others. This selection is typically based on molecular size, charge, or polarity.

Analyze the first option

The first option suggests that molecules themselves "selectively choose" which side of the membrane to move toward. This is scientifically incorrect because molecules move passively via random thermal motion (diffusion) rather than conscious choice.

Analyze the second option

The second option states that the membrane allows small molecules like water to pass through, but blocks larger molecules like those in corn syrup (such as complex sugars/polysaccharides). This accurately describes physical filtration based on pore size, which is how semipermeable membranes (like dialysis tubing) function.

Determine the correct choice

Since the second option correctly explains the physical mechanism of selective permeability based on molecular size, it is the correct answer.

Answer:

• Because it allows any molecule to selectively choose what side of the membrane to move toward.
• Because it allows small molecules, such as water, to pass through but not larger molecules, such as those in corn syrup. (Correct answer)