BIOL 331

Lecture 2

PROPERTY	COMPARISON WITH OTHER SUBSTANCES	IMPORTANCE IN THE OCEAN
Heat capacity & thermal conductivity	Highest of all liquids and solids except liquid ammonia	Prevents extreme temperature ranges encourages heat transfer
Latent heat of fusion	Highest of all except ammonia	Acts as a thermostat at freezing point
Latent heat of vaporization	Highest of all substances	Important in heat and water transfers to the atmosphere
Thermal expansion	maximum density is 4o C. for pure water, lower with increasing salinity	Allows fresher water near freezing to rise to surface, ice floats
Surface tension	Highest of all liquids except mercury	Controls drop formation & behavior, cause of capillary waves
Dissolving power	Dissolves more substances in greater quantities than any other liquid	Makes nutrients of all kinds available to organisms
Transparency	Relatively great	Most transparent in visible range, thus allows underwater photosynthesis
Freezing & boiling point	Much higher than similar substances	Allows most water to exist as a liquid

BOND TYPE	PROPERTIES	ENERGY TO BREAK (Kcal)	EXAMPLES
Nonpolar covalent	Equal sharing of electrons	100s	O₂, H₂
Polar covalent	Polar covalent	~100s	H₂O, NH₃
Ionic	Redistribution of electrons	10s	NaCl, KCl
Hydrogen	Attraction of partial charges	4.5	H₂O with itself and many solutes

WATER	ICE
Molecules more tightly packed	Molecules less tightly packed
Some molecules form clusters, others are free	All molecules structures in a regular lattice
All molecules structures in a regular lattice	Solute molecules are excluded

Most water molecules are free, not locked in clusters.

Clusters are very short lived (less than one-millionth 
of a microsecond).

Water is less structured at higher temperatures.

At pressures over 1000 atmospheres all structure is lost, 
because structured regions are less dense.

Adding heat to water raises its temperature within its
current state.

Adding heat to water existing at a state change boundary
results in no temperature change, only the breaking of hydrogen
bonds.

Defined as the amount of salt in the water.

Expressed as parts per thousand, written .

Vapor pressure decreased by increased salinity.

Increased salinity increases osmotic pressure.

Defined as the resistance of a liquid to flow.

Especially important to very small organisms near the surface.

Viscosity increases with greater salinity and viscosity
  decreases with higher temperature.

Different ions have different effects on viscosity.

Increasing salinity and/or pressure increases density.

Increasing temperature decreases density.