D2.3.1 — Solvation with Water as the Solvent
Key Definitions:
- Solvent: A substance that dissolves other substances (solutes) to form a solution.
- Solute: The substance dissolved in a solvent.
- Solvation: The process in which solvent molecules surround and interact with solute molecules or ions.
Why Water Is an Effective Solvent:
- Water is a polar molecule, with partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms.
- Water can form hydrogen bonds with polar or charged substances.
- Ionic compounds dissociate in water, with cations surrounded by the partially negative oxygen and anions by the partially positive hydrogens.
Solvation of Hydrophilic vs. Hydrophobic Substances:
- Hydrophilic substances (e.g., sugars, salts, proteins) dissolve easily in water due to their polar or charged nature.
- Hydrophobic substances (e.g., lipids, oils) do not interact favorably with water and tend to clump together to minimize water contact (hydrophobic effect).
D2.3.2 — Water Movement from Less Concentrated to More Concentrated Solutions
Key Definitions:
- Osmolarity: The total concentration of solute particles in a solution, measured in osmoles per liter (Osm/L).
- Isotonic solution: Equal solute concentration as the cell → no net water movement.
- Hypotonic solution: Lower solute concentration than the cell → water moves into the cell.
- Hypertonic solution: Higher solute concentration than the cell → water moves out of the cell.
Water Movement: