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