WATER

Water Formula

•A water molecule (H2O),

is made up of threethree atoms =

•one oxygen and two hydrogen.

H

H

Water is Polar!

• each water molecule has a slightly negative and a slightly positive end (pole)

• The oxygenoxygen end “acts” negativenegative• The hydrogenhydrogen end “acts” positivepositive• Causes the water to be POLARPOLAR• Overall, Water is neutralneutral (equal

number of e- and p+) --- Zero Net Zero Net ChargeCharge

Hydrogen Bonds Exist Hydrogen Bonds Exist Between Water Between Water

MoleculesMolecules• Formed between a highlyFormed between a highly

Electronegative atom Electronegative atom of a of a polarpolar molecule and amolecule and a HydrogenHydrogen

• ManyMany hydrogen bonds arehydrogen bonds are strongstrong

• Water vs AlcoholWater vs Alcohol

Interaction Between Interaction Between Water MoleculesWater Molecules

What are What are the the

PropertieProperties of s of

Water (in Water (in today’s today’s class)?class)?

Properties of Water (in Properties of Water (in today’s class)today’s class)

•CohesionCohesion

•AdhesionAdhesion

CohesionCohesion• Attraction between particles of the Attraction between particles of the

same substance same substance (( why water is why water is attracted to itself)attracted to itself)

• Results in Results in Surface tensionSurface tension (a measure (a measure of the strength of water’s surface)of the strength of water’s surface)

• Produces aProduces a surface film (almost like surface film (almost like skin on waters’ surface) skin on waters’ surface) on water on water thatthat allows insects to walk on the allows insects to walk on the surfacesurface of water of water

• 3:593:59• https://www.youtube.com/watch?v=RphuMEUY3Oghttps://www.youtube.com/watch?v=RphuMEUY3Og

AdhesionAdhesion• Attraction between two different Attraction between two different

substancessubstances..• Water will makeWater will make hydrogen bonds with other hydrogen bonds with other

surfacessurfaces such as glass, soil, plant tissues, such as glass, soil, plant tissues, and cotton.and cotton.

• CapillaryCapillary actionaction--water molecules will “tow” water molecules will “tow” each other along when in a thin tube.each other along when in a thin tube.

• Example:Example: transpirationtranspiration process which process which plants and trees remove water from the plants and trees remove water from the soil, and paper towels soak up water.soil, and paper towels soak up water.

• https://www.youtube.com/watch?v=At1BJJDcXhk

• :13-1:01

Adhesion Causes Adhesion Causes Capillary ActionCapillary Action

Which gives water the ability to “climb”

structures

3:49-4:31 Thorny Devil example

https://www.youtube.com/watch?v=ZUsARF-

CBcI

Adhesion Also Causes Adhesion Also Causes Water to …Water to …

Form spheres & hold onto

plant leaves

Attach to a silken spider

web

Properties of Water Properties of Water cont.cont.

•Less Dense as a solidLess Dense as a solid

Water is Less Dense as Water is Less Dense as a Solida Solid

• Ice is less denseIce is less dense as a solid than as a liquid (ice floats)

• Liquid water has hydrogen bonds hydrogen bonds that are constantly being broken and constantly being broken and

reformed.reformed.

• Frozen waterFrozen water forms a crystal-like latticecrystal-like lattice whereby molecules are set at fixed distances.

• 47 sec

• https://www.youtube.com/watch?v=NQhjAtCKghE

Water is Less Dense as Water is Less Dense as a Solida Solid

•Which is ice and which is Which is ice and which is

water?water?

Water is Less Dense as a Water is Less Dense as a SolidSolid

WaterWater IceIce