Water

Properties of Water

• Water is a polar molecule, all emergent properties of H2O are explained by hydrogen bonding.

• Emergent properties:

  • Cohesion (water likes water - creates surface tension)

  • Adhesion (water likes non water - polar things)

  • High heat absorption

  • Excellent solvent

  • Ice formation and floating

Cohesion and Adhesion

• Cohesion: Water molecules stick together, creating surface tension.

• Adhesion: Water molecules stick to other surfaces; polar surfaces interact well, nonpolar surfaces minimize contact.

Heat Absorption

• Water absorbs a lot of heat with minimal temperature change (high specific heat).

• High heat of vaporization; evaporative cooling is a homeostatic mechanism.

• It takes a lot heat to break up hydrogen bonds to raise temperature and separate H2o molecules.

Water as a Solvent

• Interacts with hydrophilic substances due to electrostatic attractions.

• Breaks ionic bonds, dissolving compounds.

• Evaporative cooling is an important homeostatic mechanism that helps regulate temperature in living organisms, preventing overheating by allowing heat release during the phase change from liquid to vapor.

• Key Terms

• Solute: Substance being dissolved.

• Solvent: Dissolving agent.

• Solution: Homogeneous mixture of solute and solvent.

• Aqueous solution: Water as the solvent.

Molarity

• Molarity: Moles of solute per liter of solution.

Hydrophilic vs. Hydrophobic

• Hydrophilic: Water-loving; polar molecules.

• Hydrophobic: Water-fearing; nonpolar molecules clump to minimize water contact.

Ice Formation

• Ice is less dense than liquid water due to stable hydrogen bonds spacing molecules apart.

• Ice floats, insulating aquatic environments in winter.

Importance of Ice Floatation

• Allows aquatic life to survive winters, preventing freezing from the bottom up.