Transcript Water - Honors

Water
Necessary for Life
Structure of Water
• H20
• Covalent Bonds
– Electrons are shared
H
+
H
• Oxygen is more
electronegative than other
molecules
– Means it pulls on the “shared”
electrons more
• Since electrons are negative, then
there is a slight negative charge on
Oxygen side of molecule
• Leaves a slight positive charge on
Hydrogen side of molecule
-
O
+
Polarity
• Polar molecules have a slightly positive
side and a slightly negative side
– they act like magnets
– Water is a polar molecule
• So are proteins and carbs
– Earth also has “poles”, due to magnetic
charges
Polarity (cont)
• Polar molecules are
hydrophillic
– ‘water – loving’
– Attracted to other
water molecules and
other polar
molecules
– Opposite – hydrophobic
– Nonpolar molecules are
‘water-fearing’, like oil
Hydrogen Bonds
• The attraction between
the negative side of one
polar molecule and the
positive side of another
polar molecule
– Allows polar molecules
to be attracted like
magnets
– weak bond – easily
broken
Water Drop on Leaf
Notice how the drop forms as the molecules all stick together
Adhesion and Cohesion
Notice how the water drop is attracted to the branch
The branch is made of polar molecules
adhesion – sticking to other polar molecules
cohesion – sticking to other water molecules
Surface Tension
• Creates a thin “film”
or surface on top of
the water
• Caused by Adhesion
and Cohesion
– Allows for water strider
to sit on top of water
despite the fact that it
is heavier and more
dense than water
Universal Solvent
Positive and negative poles are attracted to
charges in salts and other polar molecules,
causing them to dissolve easily
Density
Water is more dense than ice so ice floats – allows lakes
to freeze from top down, which is good for the fish.
Capillary Action
• Water will “climb” up very thin tubes
– Allows for water to travel up the stems of plants
Life exists because of water
remember, we are over 70% water,
the Earth is over 70% water