The Extraordinary The Extraordinary Properties of WaterProperties of Water

WaterWater

•A water molecule (H2O), is made up of three atoms: one oxygen and two hydrogen.

H

HO

The Water MoleculeThe Water Molecule

• PolarityPolarity–A water molecule is polar

because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.

(+)(-)

•Polar water molecules Polar water molecules act like magnetsact like magnetsand attract each otherand attract each other

Hydrogen BondsHydrogen Bonds

-form between the negative end form between the negative end of one water molecule and the of one water molecule and the positive end of another.positive end of another.

-a hydrogen bond is weaker than -a hydrogen bond is weaker than an ionic or covalent bondan ionic or covalent bond

BP and FP of WaterBP and FP of Water

•At sea level, pure water boils at At sea level, pure water boils at 100 °C and freezes at 0°C.100 °C and freezes at 0°C.

•212212°°F and 32F and 32°°FF

Properties of WaterProperties of Water

•CohesionCohesion

Properties of WaterProperties of Water

•CohesionCohesion•AdhesionAdhesion

Properties of WaterProperties of Water

•CohesionCohesion•AdhesionAdhesion•High Specific HeatHigh Specific Heat

Properties of WaterProperties of Water

•CohesionCohesion•AdhesionAdhesion•High Specific HeatHigh Specific Heat•High Heat of High Heat of VaporizationVaporization

1. Cohesion1. Cohesion

•Attraction between particles Attraction between particles of the same substanceof the same substance

- Explains why water is Explains why water is attracted to itselfattracted to itself

Results in:Results in:Surface tensionSurface tension (a (a

measure of the measure of the strength of water’s strength of water’s

surface) surface)

allows insects to allows insects to walk on the walk on the

surface of water surface of water

Jesus Lizard

• The Basilisk lizard makes use of the high surface tension of water to accomplish the incredible feat of walking on water's surface.  The Basilisk can't actually walk on water; rather, it runs on water, moving its feet before they break through the surface.  Take a look:

• The 'Jesus' Lizard (473k movie)• http://www.visionlearning.com/library/

module_viewer.php?mid=57

2. Adhesion2. Adhesion•Attraction between two different Attraction between two different substances. substances.

- water forms hydrogen bonds - water forms hydrogen bonds with other surfaces such as glass, with other surfaces such as glass, soil, plant tissues, and cotton. soil, plant tissues, and cotton.

.

• ExplainsExplains capillary capillary actionaction--water molecules will pull water molecules will pull each other along when in a each other along when in a thin glass tube. thin glass tube.

• i.e. moves water up the i.e. moves water up the tubes of plants from roots tubes of plants from roots to leavesto leaves

3. High Specific Heat3. High Specific Heat

Amount of heat needed to raise Amount of heat needed to raise or lower 1g of a substance 1° C.or lower 1g of a substance 1° C.

•Water can absorb or release a Water can absorb or release a lot of heat energy with little lot of heat energy with little change in temperature.change in temperature.

As a result, water warms slowly and cools slowly.

So, the oceans store heat.

And, the body (mostly water) does not lose heat easily.

4. High Heat of 4. High Heat of VaporizationVaporization

For water to evaporate, For water to evaporate, hydrogen bonds must be hydrogen bonds must be broken. As water evaporates, broken. As water evaporates, it removes a lot of heat with it.it removes a lot of heat with it.

The “extra” energy needed to break hydrogen bonds means that evaporating water cools surfaces.

Explains why sweating is a great way to stay cool.

5. Water is Less Dense 5. Water is Less Dense as a Solidas a Solid

•Ice is less dense than liquid water (ice floats).

•In winter, ice floats on lakes.

Explains why fish can live in a lake in the winter; the lake freezes from the top down.

Water as a Solvent

• The partial charges on water molecules help make it an excellent solvent.

• Water dissolves many substances by surrounding charged particles and "pulling" them into solution.

For example, common table salt, sodium chloride, is an ionic substance that contains alternating sodium and chlorine ions.

When table salt is added to water, the partial charges on the water molecule are attracted to the Na+ and Cl- ions.  The water molecules surround the ions, separate them, and slowly dissolve the salt. 

Negative oxygen ends of water molecules will surround the positive sodium ions.

Positive hydrogen ends will surround the negative chlorine ions.