Transcript Water Properties Lab - Hudson City School District

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
• 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
• Detergent
breaks up the
oil into very
small droplets.
HowStuffWorks "How do you clean
up an oil spill?“ (pick a video)
Burn Off
Booms
Hi-pressure
water
Slick Sack
• Absorbent
pad
Hand washing
Oil Spills
Problems
•
•
•
•
dead sea life
human life
cost of cleanup
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.