Water Properties Lab

Water is Polar Covalent

Nonpolar Oxygen (even sharing of e-)

Uneven sharing of e-

Hydrogen Bonds

• Weak bonds between like molecules

p. 3 Cohesion

• Attraction of water to water

• Makes a drop

Polar ends and H-bonds attract

What forms a drop?

• Cohesion causes water to form drops

• surface tension causes them to be nearly spherical

• adhesion keeps the drops in place.

Surface Tension

• Water attracts itself and pulls in to form a “film” on its surface to form a drop.

Adhesion

• Attraction of water to an unlike substance• (like glass)• Note the drop is flatter than on wax paper

p. 4 Water Drop Shapes

• Rounder the drop, the stronger the H-bonds in the drop of water.

• Round drop on wax paper (not strong adhesion to water).

• As adhesion to glass is stronger + pulls the water, it makes a flatter drop.

On wax paper On glass

p. 4 -#6 top Water on wax paper

• Plain wax paper Soapy wax paper

You can break surface tension with soap.

Polar coheres to Polar not Nonpolar

• Water (Polar) has no adhesion to the wax (nonpolar) paper. It would roll right off.

• Water has more adhesion to a glass plate.

p. 6 Climbing Property of Water• CHROMATOGRAPHY:

Colors are separated by densities. Less dense colors go to the top.

• Black is composed of all the colors.

• Capillary action -cohesion (water to water) + adhesion (water to paper)

• Polar water + polar ink (dissolves)

Paper has pores, open spaces

Capillarity – water climbs up small spaces

• The small spaces (pores of the paper) provide adhesion to the water.

• The water makes a column by cohesion to itself. (water to water because they are polar)

Adhesion to paperCohesion of water to water

p. 8 #6 Oil is hydrophobic

• Oil and water do not mix.

• H-bonding is only in polar Oil is on top

Non-polar

Water is on bottom

Polar

polar

polar

nonpolar

#5 Likes dissolve likesPolar dissolves polar, but not

nonpolar• Cell membrane is also amphipathic (polar

+ nonpolar)

Inside the cell membrane

p. 9 # 6Food coloring dissolves in water.

• Water is polar +H-bonds• Food coloring is polar.• Makes a solution (water surrounds the

dye)• Oil is nonpolar (no charge).• And no H- bonds.

Polar molecules dissolve

polar molecules.

Dissolving

• A solute surrounds the molecules of a solvent to make a solution

Stirring oil and water

• The oil will go back to being separate from the water.

D. Oil sheen on water (oil on top of water in a

thin layer)

Interpret #6 Getting rid of oil on water

• Detergent breaks up the oil into very small droplets.

HowStuffWorks "How do you clean up an oil spill?“ (pick a video)

Booms

Burn Off

Hi-pressure water

Slick Sack

• Absorbent

padHand washing

Oil Spills Problems

• a. dead sea life

• b. human life ills

• c. cost of clean-up

p. 9 Interpret 5 Amphipathic(bipolar)

• molecules have (hydrophobic) nonpolar end and to attract oil structure, but also have a region that is polar (hydrophilic) attracts water to wash it away.

Like detergent.

Soap is a surfactant

• That reduces the surface tension

• Breaks the cohesion of water molecules