Question

part a: which of the following statements best describes the result of the experiment? a the bag decreased in mass because the solution in the beaker is hypertonic. b the bag decreased in mass because the solution in the beaker is hypotonic. c the bag decreased in mass because the solution in the bag is hypertonic. d the bag decreased in mass because the solution in the bag is hypotonic. part b: how could students modify their experiment so that the mass of the bag increases? a they could increase the concentration of solute in the bag so that water enters it. b they could increase the concentration of water in the bag so that water enters it. c they could decrease the concentration of water in the bag so that water enters it. d they could decrease the concentration of solute in the bag so that water enters it.

Explanation:

Part A

To determine the change in the bag's mass, we analyze osmosis. If the solution in the beaker is hypertonic (higher solute concentration) relative to the bag's solution, water leaves the bag, decreasing its mass. Option A says the bag increases in mass (wrong, as water would leave if beaker is hypertonic). Option B: If the bag's solution is hypertonic, water enters the bag, increasing mass (but the question's context likely has the beaker as hypertonic? Wait, no—wait, the options: Let's re - evaluate. Wait, the key is osmosis: water moves from low solute (high water) to high solute (low water) concentration. If the bag decreases in mass, water is leaving the bag, meaning the beaker's solution is hypertonic (higher solute) than the bag's. Now, let's check the options:

• Option A: Says bag increases in mass (water enters) → beaker is hypotonic to bag. But the question is about why the bag decreased. So A is wrong.
• Option B: Bag decreased in mass because solution in beaker is hypertonic (water leaves bag to beaker) → correct.
• Option C: Bag decreased in mass because bag is hypertonic (then water would enter bag, increasing mass) → wrong.
• Option D: Bag decreased in mass because bag is hypertonic (same as C, wrong).

So the correct answer for Part A is B. The bag decreased in mass because the solution in the beaker is hypertonic (water moves out of the bag to the beaker via osmosis).

To increase the rate of water entering the bag (so that the mass of the bag increases), we need to create a greater osmotic gradient. Osmosis depends on solute concentration difference. If we increase the solute concentration in the bag (so the bag's solution is more hypertonic relative to the beaker's solution), more water will enter the bag. Let's analyze the options:

• Option A: Increase solute concentration in the bag so that more water enters it. This creates a larger concentration difference (bag has more solute, beaker has less), so water moves into the bag faster. Correct.
• Option B: Increase water concentration in the bag (which is equivalent to decreasing solute concentration). Then the osmotic gradient is reduced, and less water would enter (or maybe leave). Wrong.
• Option C: Decrease water concentration in the bag (increase solute? No, decreasing water while keeping solute same? Wait, no—if we decrease water concentration in the bag (by adding solute? No, the option says "decrease the concentration of water in the bag so that water enters it"—wait, decreasing water concentration in the bag means the bag has more solute (since concentration of water = 1 - solute concentration). Wait, maybe misphrased. But compared to A, A is more direct. Also, if we decrease water concentration in the bag (increase solute), but the option says "so that water enters it"—but if we increase solute in the bag (decrease water concentration in the bag), water enters. But Option A is "increase the concentration of solute in the bag so that more water enters it"—which is the same as decreasing water concentration in the bag (since solute + water = 100% in terms of concentration). But Option A is more clearly stated. Also, Option D: Decrease solute concentration in the bag (increase water concentration in the bag) → osmotic gradient is reduced, water would enter less or leave. Wrong.

So the correct answer for Part B is A. By increasing the solute concentration in the bag, the osmotic gradient between the bag and the beaker (assuming beaker has lower solute concentration) is increased, leading to more water entering the bag.

Answer:

B. The bag decreased in mass because the solution in the beaker is hypertonic.

Part B