water’s life supporting properties
TRANSCRIPT
Water’s Life-Supporting Properties
The structure of Water
The end with the two hydrogen atoms is slightly positive.
Oxygen end of the molecule has a slight negative charge
POLAR MOLECULE!!
The 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).
Hydrogen bond
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.
Hydrogen
bonds
Life-Supporting Properties of WATER
WATER
H2O
Cohesion &
AdhesionRelated 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 the effects of hydrogen bonding explain most of water´s unique properties
Life-Supporting Properties of WATER Cohesion & AdhesionRelated to
high surface tension
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
Surface tension:Molecules are pulled equally in all directions by neighboring molecules
Capillary Action:When a liquid flows through a narrow space
Life-Supporting Properties of WATER
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
Life-Supporting Properties of WATER Temperature Moderation(High heat capacity)
TEMPERATURE measure of the average energy of random motion of the particles in a substance.
When two substances differ in temperature, thermal energy in the form of heat is transferred from the warmer substance to the cooler one
water heats up much more slowly than metal→ because of hydrogen bonding, water has a better ability to resist temperature change than most other substancesTHERMAL ENERGY total amount of energy associated with the random movement of atoms and molecules in a sample of matter
Life-Supporting Properties of WATER
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 WATERDissolve
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 WATERLow density
of ice(changes in
density) 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
Ice floats because its molecules are less densely packed than those in liquid water.
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
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