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 dropsCohesiondrops surface tension causes them to be nearly sphericalsurface tension 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 paper Cohesion 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 nonpolar

#5 Likes dissolve likes Polar 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?“ HowStuffWorks "How do you clean up an oil spill?“ (pick a video) Booms Burn Off Hi-pressure water

Slick Sack Absorbent pad Hand 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