oxygen shares its two unpaired electrons with two hydrogen atoms water’s molecular structure:
TRANSCRIPT
CovalentBond
CovalentBond
Oxygen shares its two unpaired electrons with two hydrogen atoms
Water’s Molecular Structure:
Polar Covalent Bonds:A covalent molecule that has a slight positiveand negative charge on opposite ends.Example:
Water
*in a polar covalent bond, one atom is moreelectronegative than the other.
Electronegativitythe tendency for an atom to attract electrons
Solubility•Polar charges attract it to other polar molecules
•sugars, ionic compounds (like salt), and some proteins
•Not attracted to nonpolar substances like lipids (fats)
http://www.questacon.edu.au/html/squad_activities/assets/images/oil-and-water.jpg
Hydrogen Bonds:•Weak, polar covalent bonds.•Form rapidly and break rapidly
Example:Between water molecules
H-Bonding explains unique properties: cohesion, adhesion, high heat capacity, evaporative cooling, the low density of ice, the ability of water to dissolve many substances
http://www.realeyz.com/photo/macro/photos/leaf_drops.jpg
CohesionMolecules of the same substance are attracted to each other
•Leads to surface tension and water droplets
AdhesionAttraction between molecules of different substances
Ex: glass and water
http://staff.um.edu.mt/rlib1/sm/wpe32.jpg
CapillarityAttraction that causes the surface of the liquid to rise when in contact with a solid.
Cohesion-Adhesion Theory
-As water evaporates from leaves, it tugs on the water molecules below-Cohesion and adhesion pull water up and replace missing water molecules-Water enters the roots by osmosis
www.emc.maricopa.edu/.../BioBookPLANTHORM.html
Did you ever wonder: How does water move from roots to leaves when a tree doesn’t have a heart to pump the water?
Denisty of Ice•Most solids are more dense than their liquids
•This makes solids sink
•Ice is less dense than liquid water
•Due to H-Bonds•Important to life because bodies of water freeze top down•Allows life to survive below
http://shiftingbaselines.org/blog/images/Iceberg.jpg
pH ScaleMeasurement of the concentration of hydrogen ions
Acid:High concentration of [H+](or hydronium ion);low conc. of [OH-]
Base:High [OH-](a.k.a. hydroxide ion);low [H+]
pH = -log [H+]
Stomach Acid = pH 2