What makes water sooooooo special?

http://www.schooltube.com/video/b36a222fcdfef2db9af8/Properties-Of-Water

Properties of Water• Polar molecule

• Cohesion, adhesion, capillary action

• High specific heat

• Density – greatest at 4oC

• Universal solvent of life

What does a water molecule look like?

Why is a water molecule polar?

The oxygen atom tends to pull our

electrons towards itself!!

Again…why is a water molecule considered to be polar?

• BECAUSE it has opposite partial charges at the ends of it.

Still can’t remember that a water molecule

has charged ends? THEN BE AMAZED WITH THIS DEMO!!

Because water molecules are polar it allows them to…..

ANIMATION

Each water molecule

can form hydrogen bonds with up to four neighbors!!

• Water has a variety of unusual properties because of attractions between these polar molecules.– The slightly negative regions of one molecule are

attracted to the slightly positive regions of nearby molecules, forming a hydrogen bond.

– Each water molecule can form hydrogen bonds with up to four neighbors.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 3.1

HYDROGEN BONDS

Extraordinary Properties that are a result of hydrogen bonds:

1. Adhesion

2. Cohesion

3. Capillary action

4. Surface tension

5. Holds heat to regulate temperature (High heat capacity)

6. Less dense as a solid than a liquid

7. Versatile solvent

TERMS

cohesion = water attracted to other water molecules because of polar properties

adhesion = water attracted to other materials

surface tension = water is pulled together creating the smallest surface area possible

Cohesion, Adhesion and Surface Tension

Organisms Depend on Capillary Action

Because water has both adhesive and cohesive properties, capillary action is present.ANIMATION

Capillary Action = water’s adhesive property is the cause of capillary action. Water is attracted to some other material and then through cohesion, other water molecules move too as a result of the original adhesion.

Ex: Think water in a straw

Ex: Water moves through trees this way

Surface tension (Surface tension (related to cohesion)related to cohesion)– Water has a greater surface tension than most

other liquids because hydrogen bonds among surface water molecules resist stretching or breaking the surface.

– Water behaves as if covered by an invisible film.

– Some animals can stand, walk, or run on water without breaking the surface.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Can we break surface tension?DEMO!!

What is being broken if we can break it?

Hydrogen BondsHydrogen Bonds

ANIMATIONANIMATION

High Specific Heat of WATER

• ANIMATION

What trends did you notice?

What does this short animation tell us about water’s HSH?

Three-fourths of the earth is covered by water. The water serves as a large heat sink responsible for:

• Prevention of temperature fluctuations that are outside the range suitable for life.

• Coastal areas having a mild climate

• A stable marine environment

It takes much more energy to raise the temperature of water compared to other solvents because hydrogen bonds hold the water molecules together!

High Specific Heat is the amount of heat that must be absorbed or lost to change its

temperature by 1oC.

Evaporative Cooling• The cooling of a

surface occurs when the liquid evaporates

• This is responsible for:– Moderating earth’s

climate

– Stabilizes temperature in aquatic ecosystems

– Preventing organisms from overheating

Density of Water

The density of water:

1. Prevents water from freezing from the bottom up.

2. Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation.

3. Makes transition between season less abrupt.

Water is the solvent of Life!

Solute – substance dissolved in a solvent to form a solution

Solvent – fluid that dissolves solutes

Example: Ice Tea – water is the solvent and tea and sugar the solutes

Universal Solvent