Question

1. complete the table below by counting the molecules in model 1.

	inside the cell	outside the cell
number of water molecules
ratio of water to sugar

1. which solution in model 1 is more concentrated—the solution inside the cell or outside of the cell? explain your answer in terms of the ratio of solute to solvent particles.
2. consider the arrows indicating movement of water across the membrane.

a. in which direction are water molecules moving—into or out of the cell?
b. are more water molecules moving into or out of the cell?
c. is the net direction of water movement into or out of the cell?

1. bold or highlight the correct word below to indicate the change in the concentration of the sugar solution on each side of the membrane as water molecules move.

a. the solution inside the cell will become more/less concentrated with the net movement of water.
b. the solution outside the cell will become more/less concentrated with the net movement of water.
model 1 - movement of water in and out of cells
sugar molecules (solute)
water molecules (solvent)
selectively permeable membrane

Explanation:

Step1: Count molecules in Model 1

Since we don't have the actual counts from Model 1, assume there are $x$ sugar molecules inside the cell, $y$ sugar molecules outside the cell, $m$ water molecules inside the cell and $n$ water molecules outside the cell. The ratio of water to sugar inside the cell is $\frac{m}{x}$ and outside is $\frac{n}{y}$.

Step2: Determine more - concentrated solution

The more concentrated solution has a lower ratio of water (solvent) to sugar (solute). If $\frac{m}{x}>\frac{n}{y}$, the solution outside the cell is more concentrated and vice - versa.

Step3: Analyze water movement

Water moves from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration). If the outside solution is more concentrated, water moves out of the cell and vice - versa.

Step4: Determine net movement

The net movement is the overall direction of water movement. If more water molecules are moving in one direction, that is the net direction.

Step5: Analyze change in concentration

When water moves out of the cell, the inside solution becomes more concentrated (less water, same amount of sugar). When water moves into the cell, the inside solution becomes less concentrated. When water moves into the outside solution, it becomes less concentrated and when water moves out of the outside solution, it becomes more concentrated.

Answer:

1. Without actual counts from Model 1:

• Number of sugar molecules: [To be filled with counts from Model 1 for inside and outside]
• Number of water molecules: [To be filled with counts from Model 1 for inside and outside]
• Ratio of water to sugar: [To be calculated as $\frac{\text{number of water molecules}}{\text{number of sugar molecules}}$ for inside and outside]

1. Compare the ratios of water to sugar inside and outside the cell. The solution with the lower ratio of water to sugar is more concentrated.
2. a. Water moves from the area with a higher water - to - sugar ratio to the area with a lower water - to - sugar ratio.

b. Compare the number of water molecules moving in and out.
c. The net direction is the direction in which more water molecules are moving.

1. a. If water moves out of the cell, more; if water moves into the cell, less.

b. If water moves into the outside solution, less; if water moves out of the outside solution, more.