A semipermeable membrane allows

Answer

### Step-by-Step Text Solution:

1. **Definition of Semi-Permeable Membrane**:
A semi-permeable membrane is a type of barrier that selectively allows certain substances to pass through while blocking others. Specifically, it permits the passage of solvent molecules but not solute particles.

2. **Function of Semi-Permeable Membrane**:
The primary function of a semi-permeable membrane is to facilitate the process of osmosis. Osmosis is the movement of solvent molecules across the membrane from an area of lower solute concentration (more solvent) to an area of higher solute concentration (less solvent).

3. **Osmosis Process**:
In osmosis, solvent molecules move through the semi-permeable membrane. This movement occurs until equilibrium is reached, meaning the concentration of solute is balanced on both sides of the membrane.

4. **Separation of Solute and Solvent**:
Because the semi-permeable membrane allows only solvent molecules to pass, it effectively separates solute particles from solvent particles. As solvent moves to the side with higher solute concentration, the concentration of solute on that side increases while the concentration on the other side decreases.

5. **Conclusion**:
In summary, a semi-permeable membrane allows only solvent molecules to pass through it, facilitating the process of osmosis, which is essential for various biological and chemical processes.