Water Properties: Polarity

  1. Sketch the following into your notebook:

Figure 1

  1. Using your table of electonegativty, determine the electornegativty of the following atoms:
  2. O _____
  3. H _____
  4. What is the difference in electronegativity for the two atoms? ______
  5. Draw a Lewis Structure for H2O using your notes from yesterday’s class on Lewis Structures.
  6. Indicate the partial charges on the water molecules with a dipole.
  7. Rewrite: Particularly strong dipole- dipole forces, however, are seen among molecules in which hydrogen is bound to a highly electronegative atom, such as N, O, or F: called a Hydrogen Bond.
  8. Sketch the following schematic of H- bonding:
  1. Rewrite: The H- bonds cause a hexagonal

crystal to form when water becomes ice. This

causes the density of ice to be less than the density

of liquid water because the H- bonds force the mole-

cules to be further apart.

  1. Rewrite: The polarity of the water molecules makes it an outstanding solvent. It’s partial charges can separate net charges that exist in ionic compounds and also pull apart other molecules with partial charges such as sucrose.
  2. Sketch the following schematic of dissolution:
  1. Cohesion- when the same substance is attracted to other molecules that are identical.
  2. Sketch the following schematic of cohesion within a water droplet:
  1. Surface Tension- When cohesive forces take place at the surface of water causing the surface molecules to be attracted to one another and resisting outside forces.
  2. Sketch the following schematic showing stronger cohesion at the surface:
  3. Water molecules are attracted to other water molecules but

not the air above the surface. This causes the cohesive forces

at the surface to be stronger. This allows insects to walk on

water and why drops of water and bubbles are rounded.

  1. Rewrite: Adhesion of water is when water molecules

are attracted to other materials besides water.

  1. Rewrite: Adhesion causes water molecules to stick to the

sides ofglass in a graduated cylinder, which makes a

u- shaped meniscus at the surface.

  1. Sketch the following meniscus:

Figure 6