Hydrogen Bonding

• Hydrogen Bonding is a type of chemical intermolecular bond that occurs when a hydrogen atom bonds with a highly electronegative atom
• The properties of water arise from the attractions between oppositely charged atoms
• Polar Covalent Bonds: electrons are shared unequally as one element is more electronegative
• Water is a polar molecule, the overall charge is unevenly distributed
• Polarity allows water molecules to form hydrogen bonds with eachother
• In a water molecule, oxygen is more electronegative, granting it a partial negative charge
• Cohesion: When two of the same molecules form a hydrogen bond (water molecules)
• Adhesion: When two different molecules form a hydrogen bond
• Hydrophobic: Repelled by water
• Hydrophilic: Attracted to water
• One result of cohesion through hydrogen bonding is surface tension
• Surface tension is a measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension due to the strong cohesive forces between its molecules.
• Water's high specific heat allows it to stabilize it's temperature. This helps moderate temperature in organisms and ecosystems
• Water's high specific heat can be traced back to hydrogen bonding

  • Heat absorbed: Hydrogen Bonds break
  • Heat released: Hydrogen Bonds form
• Evaporative Cooling: Evaporation (or Vaporization) is the transformation of a substance from liquid to gas
• Water is less dense as a solid than as a liquid, so it floats on the surface of the liquid.
• Solution: A liquid that is a homogenous mixture of substances
• Solvent: The substance that dissolves a solute
• Solute: The substance that is being dissolved
• Aqueous Solution: Dissolved in water

  • Water is a versatile solvent due to its polarity which allows it to form hydrogen bonds easily
• When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called a hydration shell
• An Acid is a substance that increases H+(hydrogen ion) concentration in a solution
• Base reduces H+ (Hydrogen ion) concentration in a solution