If solution Y is more concentrated than solution X, what will happen to the levels of X and Y when the thistle funnel is left for some time?

The diagram shows a thistle funnel containing solution X, inverted and placed in a beaker containing solution Y. The mouth of the thistle funnel is covered by a semi-permeable membrane, which separates solution X from solution Y.

Osmosis is the net movement of solvent molecules (typically water) from a region of higher solvent concentration (lower solute concentration) to a region of lower solvent concentration (higher solute concentration) across a semi-permeable membrane.

The question states that solution Y is more concentrated than solution X.

• This means solution Y has a higher solute concentration and thus a lower water concentration.
• This means solution X has a lower solute concentration and thus a higher water concentration.

According to the principle of osmosis, water will move from the region of higher water concentration (solution X) to the region of lower water concentration (solution Y) across the semi-permeable membrane.

• As water moves out of the thistle funnel (solution X) and into the beaker (solution Y), the level of solution X in the thistle funnel will fall.
• Conversely, as water moves into the beaker (solution Y), the level of solution Y in the beaker will rise.

The final answer is $\boxed{\text{D. The level of Y would rise, X would fall.}}$