Water’s ESTRUCTURE AND Life-Supporting Properties (HYDROGEN BONDS)
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Water’s ESTRUCTURE AND Life-Supporting
Properties(HYDROGEN BONDS)
The structure of Water
Oxygen end of the molecule has a slight negative charge
POLAR MOLECULE!!
The end with the two hydrogen atoms is slightly positive.
Hydrogen bondThe electromagnetic attractive interaction between polar molecules, in which hydrogen (H) is bound to a highly electronegative atom, such as nitrogen (N), oxygen (O) or fluorine (F).
is NOT A TRUE BOND but a strong dipole-dipole attraction, and should not be confused with a covalent bond
Q:How can water molecules be compared to magnets?
A:Both water molecules and magnets have opposite poles that cause them to be attracted to each other in a specific orientation.
Life-Supporting Properties of WATER
WATER H2O
Cohesion &
Adhesion
Related to high surface
tension
Temperature Moderation
(High heat capacity)
Dissolve Substances
(Universal solvent)
Low density of
ice
(changes in density)
The polar nature of water and theeffects of hydrogenbonding explainmost of water´sunique properties
Life-Supporting Properties of WATERCohesion & Adhesion
Related to high surface
tension
Surface tension:Molecules are pulled equally in all directions by neighboring molecules
Capillary Action:
When a liquid flows through a narrow space
COHESION: property of like
molecules (of the same substance)
to stick to each other due to mutual
attraction with HB.
ADHESION: property of different
molecules or surfaces to cling to
each other thanks to HB
COHESION+
ADHESION
Surface tension: Result of cohesive forces between adjacent molecules Molecules are pulled equally…
Capillary Action: the result of cohesive and adhesive forces…When a liquid flows through a narrow space
Temperature Moderation
(High heat capacity)
water heats up much more slowly than
metal→ because of hydrogen bonding, water
has a better ability to resist temperature
change than most other substances
THERMAL ENERGY total amount of
energy associated with the random movement of atoms and molecules in a sample of matter
Life-Supporting Properties of WATER
When two substances differ in temperature, thermal energy in the form of heat is transferred from the warmer substance to the cooler one
TEMPERATURE measure of the average
energy of random motion of the particles in a substance.
Temperature Moderation
(High heat capacity)
THERMAL ENERGY total amount of
energy associated with the random movement of atoms and molecules in a sample of matter
TEMPERATURE measure of the average
energy of random motion of the particles in a substance.
. HB RELATION:Some thermal energy breaks hydrogen bonds → water absorbs the same amount of thermal energy but undergoes less temperature change than the metal
As water cools, it forms hydrogen bonds → releases thermal energy in the form of heat, so there is less of a drop in temperature than in metal
Life-Supporting Properties of WATER
Dissolve Substances
(Universal solvent)
SOLUTION Uniform mixture of two or more substances
SOLVENT The substance that dissolves the other substance and is present in the greater amount
SOLUTE The substance that is dissolved and is present in a lesser amount
HB RELATION: areas of slight electric
charge attract the polar ends of water molecules. Water molecules cling to these charged regions and separate the sugar molecules from one another
EXAMPLE
Sodium chloride dissolves as Na+ and
Cl-ions become attracted to water
molecules and break away from the
surface of the solid
Life-Supporting Properties of WATER
DENSITY: amount of matter
in a given volume.
In most substances the solid
state is more dense than the
liquid. Water is just the
opposite—its solid form
(ice) is less dense than the
cold liquid form
HB RELATION: Because the molecules in liquid water are moving faster than those in ice, there are fewer and more short-lived hydrogen bonds between molecules. The liquid water molecules can fit more closely together
Ice floats because its
molecules are less densely
packed than those in liquid
water.
Low density of ice
(changes in density)
Life-Supporting Properties of WATER
Video water’s life-supporting properties
• http://www.youtube.com/watch?v=aVmU3CLxvgU 4 MIN
• http://www.youtube.com/watch?v=HVT3Y3_gHGg 11 MIN
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