Water Properties Lab

Water is Polar Covalent

Hydrogen Bonds

• Weak bonds between like molecules

Cohesion

• Attraction of water to water

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

Water Drop Shapes

• Water cohesion to itself and forms a nice, round drop.

• 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

• More Cohesive More Adhesive

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.

Climbing Property of Water• Colors are

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

• Black is composed of all the colors.

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.

Adhesion to paperCohesion of water to water

Oil is hydrophobic

• Oil and water do not mix.

Oil is on top

Water is on bottom

Food coloring dissolves in water.

• Water is polar.• Food coloring is polar.• Oil is nonpolar (no charge).• Oil has no hydrogen bonding.

• Polar molecules dissolve

polar molecules.

Stirring oil and water

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

Oil sheen on water (oil on top of water in a thin layer)

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

• dead sea life

• human life

• cost of clean-

• up

Amphipathic

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

Like detergent.