Properties of Water

Water is a polar molecule Its overall charge is unequally distributed The oxygen region has a partial negative charge Each hydrogen has a partial positive charge

The polarity of the water results in weak electrical attractions between neighboring molecules Called hydrogen bonds

This polarity gives rise to water’s unique properties including: 1. Water’s cohesive nature 2. water’s ability to moderate temperature 3. floating ice 4. versatility of water as a solvent

Cohesive nature Cohesion: the attraction of water molecules to each other Due to hydrogen bonding

cohesion Creates surface tension A measure of how difficult it is to stretch or break the surface of a liquid

cohesion Vital for water transport in plants

adhesion Adhesion: The attraction of water molecules to other polar substances Due to hydrogen bonding

adhesion Ex. Glass has polar molecules Glass can hydrogen bond Attracts the water molecules Some of the pull is up This makes the meniscus

3. Moderation of Temperature by water Water has a high specific heat Specific heat: the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1*c

so…

4. Floating of ice on liquid When temperature falls from 4*c to 0*c, water freezes because molecules move too slowly to break the hydrogen bonds Form a crystalline lattice Fewer molecules in ice than an equal volume of liquid water

In general, how is this important to life?

5. water: the solvent of life