Overview
This lecture explains the unique properties of water due to hydrogen bonds, focusing on their significance in nature and daily life.
Properties of Water
- Water is a universal solvent, meaning it dissolves many substances.
- Water exhibits cohesion (sticks to itself) and adhesion (sticks to other surfaces).
- Surface tension, created by hydrogen bonds, allows water to form bubbles and supports small insects walking on water.
- Water has a high heat capacity, absorbing and retaining heat to stay stable in temperature.
- Water has a high heat of vaporization, requiring a lot of energy to evaporate, which enables cooling through sweat evaporation.
- Frozen water (ice) is less dense than liquid water, so it floats.
- Water freezes from the surface downward, allowing aquatic life to survive under ice.
Examples & Applications
- Spit removes stains due to water’s solvent property.
- Water on hair takes time to evaporate because of cohesion and adhesion.
- Swimming water feels warm in the afternoon due to high heat capacity.
- Sweat cools the body by removing heat as it evaporates; animals that can't sweat pant to cool down.
- Ice floating enables activities like ice skating and ice fishing without harming aquatic life.
Key Terms & Definitions
- Solvent — a substance that dissolves other substances.
- Cohesion — attraction between molecules of the same substance.
- Adhesion — attraction between molecules of different substances.
- Surface Tension — the tightness of the surface layer of water due to hydrogen bonding.
- Heat Capacity — the amount of heat needed to raise the temperature of a substance.
- Heat of Vaporization — the energy required to turn a liquid into vapor.
- Density — mass per unit volume; ice is less dense than liquid water.
Action Items / Next Steps
- Learn and be able to explain the six main properties of water: solvent, cohesion, adhesion, surface tension, heat capacity, and density differences between ice and water.