Question

1. make a claim about the water potential of the potato. provide evidence and reasoning to support your claim.

graph 1 title
% change in mass (%)

Explanation:

1. Claim: The potato cells have a negative water potential, and the solute potential of the potato is equivalent to the solute potential of a solution where the potato's mass does not change (the x-intercept of the linear fit line, ~-2% change in mass, corresponding to an external solution solute potential that matches the potato's).
2. Evidence: The linear fit line of % change in mass crosses the x-axis (0% change in mass) at a negative x-value (between 0 and -5). When the potato is in a solution with a higher water potential (lower solute concentration), it gains mass (positive % change, e.g., +15% at the right data point). When in a solution with lower water potential (higher solute concentration), it loses mass (negative % change, e.g., leftmost data point with large negative % change).
3. Reasoning: Water moves from an area of higher water potential to lower water potential via osmosis. A 0% change in mass means no net water movement, so the potato's water potential equals the external solution's water potential. The positive mass gain in dilute solutions shows the potato has lower (more negative) water potential than those solutions, while mass loss in concentrated solutions shows the potato has higher water potential than those solutions.

Answer:

Claim:

The potato has a negative water potential, and its solute potential is equal to that of the external solution where the potato experiences 0% change in mass (the x-intercept of the linear fit, ~-2% mass change).

Evidence:

• The linear fit line for % change in mass intersects the 0% change axis at a negative value.
• The potato gains mass (positive % change) in dilute external solutions and loses mass (negative % change) in concentrated external solutions.

Reasoning:

Osmosis drives water from higher to lower water potential. 0% mass change means the potato and external solution have equal water potential. Positive mass gain shows the potato has lower (more negative) water potential than dilute solutions; negative mass gain shows it has higher water potential than concentrated solutions, confirming its water potential is negative.