Solvation with water as a solvent

Solvent: A liquid in which substances dissolve; water is the “universal” solvent because it is able to dissolve more substances than other liquids can

Solute: The substance that is being dissolved, for example, sugar in tea

Solution: The final mixture of solvent + solution

Water is a good solvent because of its dipolarity

Dipolarity: hydrogen side of the molecule is slightly positive, oxygen side is slightly negative; can therefore form H bonds with other polar molecules and ions

Solvation: The interaction between a solvent and a solute

Why is water able to dissolve charged and polar molecules?

Water is polar (slightly positively charged hydrogen atoms, slightly negatively charged oxygen atoms), allowing water to attract to other charged or polar substances. Positive H ions are attracted to negative oxygen in water, and vice versa. In polar molecules, water can form hydrogen bonds, (weak electrostatic attractions that help integrate these molecules together in environments with water). Therefore, water can dissolve a wide range of substances.

Solvation of hydrophilic substances: Hydrophilic substances dissolve in water because they are polar and charged

- Polar because of its positively charged H atoms and negatively charged O atoms

Hydrophilic Substances dissolve in water e.g. polar molecules and ions, for example, sugars and salts. Due to their polarity, water molecules can form hydrogen bonds with the polar or charged parts of hydrophilic molecules, in this case dissolving them effectively. Solvation in this context is the process of hydrophilic molecules being surrounded by water molecules.

Solvation of hydrophobic substances: Hydrophobic substances cannot form hydrogen bonds with water molecules because they do not contain polar/charged regions, so instead of dissolving, water molecules form a cage-like structure (clathrate) around hydrophobic substances, minimizing their contact with water

Hydrophobic Substances do not dissolve in water e.g. non-polar molecules (fats, oils) do not have polar or charged regions that form hydrogen bonds with water molecules,  therefore repelling water. In solvation, they form a clathrate ("hydrophobic effect"). 

Water movement from less concentrated to more concentrated solutions

*osmoles: 1 mole of any fully dissolved substance in water

Osmolarity - measure of solute concentration defined by the number of osmoles* of a solute per liter of solution (osmol/L)

Isotonic solution -  has the same solute concentration as the cell

Hypotonic solution - has a lower concentration of solute compared to the cell

Hypertonic solution - has a higher concentration of solute compared to the cell

View count: 26