Types of Bonds

1. Covalent (strongest): shared valence electrons; polar or nonpolar
2. Ionic: transfer of electrons
3. Hydrogen Bonds (weakest): This is not really a bond but rather the attraction between the positive and negative parts of polar molecules, such as the attraction between the positive hydrogen and the negative oxygen in a water molecules.
   • Keep in mind that this force is between molecules, not atoms.
   • responsible for water's amazing and unique properties
   • Van der Waals interactions (very weak): asymmetrical distribution of electrons within molecules, which contribute to the 3D structure of a complex molecule

Water's Main Properties

1. Cohesion: water molecules stick to each other
   • causes surface tension
2. Adhesion: water molecules sticking to other materials
   • Transpiration: water is transported up the walls of a plant xylem and out of the leaves due to adhesion
3. High Specific Heat: the needed amount of heat to raise, or change, the temperature of water (by 1 degree Celsius) is high
   • water's temperature changes less when it absorbs the same amount of heat as another substance
   • Due to this, oceans' temperatures are stable. (but not anymore cuz of global warming)
4. Less Dense When Frozen: floats on water and supports other ecosystems by keeping heat in
5. Important Universal Solvent: water dissolves a whole lot of things
6. High Heat Vaporization: needs to absorb a lot of heat before it phase changes from liquid to gas

Stuff About pH

• pH measures the acidity of a substance on a scale of 0-14.
  • 0-6 is acidic
  • 8-14 is basic
  • 7 is neutral (water)
• Buffer: substances that minimize change in pH
  • Accept H+ from solution when in excess
  • Donate H+ when depleted in solution
  • Ex: Carbonic Acid (H2CO3) in blood plasma