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

Water on wax paper You can break surface tension with soap. 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 paper Cohesion 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 HowStuffWorks "How do you clean up an oil spill?“ (pick a video) Detergent breaks up the oil into very small droplets. Burn Off Booms Hi-pressure water

Slick Sack Absorbent pad Hand 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.