Water Chapter 3

Water

70-95% water

Water

- a polar molecule- polarity allows water molecules to form hydrogen bonds with each other

- the unequal sharing of electrons and water's V-like shape- means that its overall charge is unevenly distributed- the oxygen region of the molecule has a partial negative charge and each hydrogen a partial positive charge

Oxygen is more electronegative than hydrogen, so the electrons of the covalent bonds spend more time closer to oxygen than to hydrogen

- the slightly positive hydrogen of one molecule is attracted and held together to the slightly negative oxygen of a nearby molecule- weak bonds

- cohesive behavior- ability to moderate temperature- expansion upon freezing- versatility as a solvent

- hydrogen bonds hold water molecules together- helps transport water against gravity in plants

- attraction between different substances, as in between water and plant cell walls- adhesion of water to cell walls by hydrogen bonds helps counter the downward pull of gravity

Cohesion and adhesion in plants

- a measure of how hard it is to break the surface of a liquid- related to cohesion- water has a greater surface tension than most other liquids- at the interface between water and air is an ordered arrangement of water molecules, hydrogen bonded to one another and to the water below. This makes water behave as though coated with an invisible film.

- water absorbs heat from warmer air and releases stored heat as cooler air

Because it can absorb or release relatively large amounts of heat with only a slight change in its own temperature

- a large body of water can absorb and store a huge amount of heat from the sun in the daytime during summer while warming up only a few degrees- the relatively cool ocean reduces coastal air temperature by absorbing heat