BIOL 331

Lecture 2

Properties of Water

                                                                

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

Chemical bonds

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

 

Structures of ice and water

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

 

Related notes on water:

Temperature effects on water

Other Properties of Water

Salinity

Viscosity

Density

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