CHEM

• is a common substance on Earth that we often overlook its unique characteristics.

  Water
• The attraction between the positive end of one water molecule and the negative end of another is called hydrogen bonding, which gives water some unusual properties.
• Hydrogen bonds form when a partially positively charged hydrogen atom from one water molecule attracts an electron pair from a partially negatively charged oxygen atom in another water molecule.
• Water molecules are also attracted to other polar molecules and to ions.

  A charged or polar substance that interacts with and dissolves in water is

  said to be hydrophilic: hydro means

  "water," and philic means "loving."


  Water as a solvent
• In contrast, nonpolar molecules like oils and fats do not interact well with water.

  They separate from it rather than dissolve in it and are called hydrophobic: phobic means "fearing."
• refers to the attraction of molecules for other molecules of the same kind, and water molecules have strong cohesive forces thanks to their ability to form hydrogen bonds with one another.

  Cohesion
• refers to the attraction of molecules for other molecules of a different kind.


  Adhesion
• The mass per unit volume of a substance.

  Density of a Liquid water 1 g/cm3

  Density of Ice 0.9168 g/cmg

  Water's lower density in its solid form is due to the way hydrogen bonds are oriented as it freezes.

  Density
• Specifically, in ice, the water molecules are pushed farther apart than they are in liquid water.

  Because it is less dense,

  ice floats on the surface of liquid water

  Density
• is the amount of heat needed to raise the temperature of one gram of a substance by one degree Celsius. water has a high specific heat capacity

  -the specific heat capacity of water is about five times greater than that of sand.

  Metal heats faster than the water because it requires less energy to heat it up.

  The land cools faster than the sea once the sun goes down, and the slow-cooling water can release heat to nearby land during the night.

  Specific Heat Capacity
• are the forces that hold atoms together within a molecule.

  Intramolecular forces
• are forces that exist between molecules.

  Intermolecular forces
• is formed by the complete transfer of valence electron(s) between atoms.

  lonic bond
• This bond is formed between atoms that have similar electronegativities—the affinity or desire for electrons.

  Covalent bond
• is formed between same atoms or atoms with very similar electronegativities

  nonpolar covalent bond
• is formed when atoms of slightly different electronegativities share electrons.

  polar covalent bond
• are attractive forces between the positive end of one polar molecule and the negative end of another polar molecule

  Dipole-dipole forces
• an attractive force that results from the electrostatic attraction between an lon and a neutral molecule that has a dipole.

  lon - Dipole Interactions
• This is a special kind of dipole-dipole interaction that occurs specifically between a hydrogen atom bonded to either an oxygen, nitrogen, or fluorine atom.

  Hydrogen Bonding
• tho weakest of the intermolecular forces and exist between all types of molecules, whether lonic or covalent-polar or nonpolar. The more electrons a molecule has, the stronger the London dispersion forces are.


  London Dispersion forces
• Ionic Bond


  A type of chemical bond where one atom donates an electron to another atom, resulting in the formation of ions. Occurs when atoms have significantly different electronegativities. Represented by a plus and minus sign between ions.
• Covalent Bond


  A type of chemical bond where two atoms share electrons to achieve a stable electron configuration. Occurs when atoms have similar electronegativities. Represented by a single or double line between atoms.