User:Martin Njoroge

=Water =

Changing Tetrahedrality
Each water molecule makes an instantaneous bond with four other water molecules, forming a tetrahedron shape. These shapes are imperfect, and their degree of imperfection changes with temperature and pressure conditions. One result is that water is resistant to heating and cooling, an important characteristic for sustaining life. Because water responds to temperature changes relatively slowly, it effectively regulates organism body temperatures. Large bodies of water also change temperature gradually. According to "Biosphere 2000: Protecting Our Global Environment," different heating and cooling rates for land and water cause air circulation and wind, and are partially responsible for Earth's weather patterns.

A Versatile Solvent
More materials, including life-essential vitamins and minerals, can dissolve in water than in any other solvent. Water can travel through cell membranes and deliver the nutrients an organism needs to function.

Attraction Between Molecules
Water molecules are highly attracted to each other. This means water transports easily through soil, root systems, into leaves and back into the atmosphere as a gas without breaking apart and attaching itself to other substances. Without this property, the chemical processes behind plant life would not be possible.

Freezing Density
Unlike other substances, water expands as it freezes and decreases in density. The fluid reaches its maximum density at 46 degrees Fahrenheit, then gets progressively lighter as it moves closer to its freezing point. Ice floats on top of the water in winter time instead of sinking, protecting the aquatic life below.

Ability to Hold Nutrients and Oxygen
Earth's organisms need both nutrients and oxygen to survive. Water can hold both. Cold water can support more oxygen, while warm water typically has more nutrients, according to "Biosphere 2000: Protecting Our Global Environment." Populations of aquatic species are the largest where nutrient-laden warm water and oxygen-rich cold water mix together. State Changes Supporting Energy Transfer The fact that water changes from liquid to gas at a relatively low temperature supports transfer of the sun's energy around the Earth. The Sun initially supplies heat to turn fluid water into gas. When vapor condenses into a liquid to create rain, the process creates energy. This helps distribute solar energy more evenly around the planet. Heat Capacity Relative to other compounds, water requires a great deal of energy to heat. Scientists describe this property as a compound's heat capacity. Water's exceptional heat capacity buffers living organisms and their environments from temperature extremes. Aquatic life depends on water's high heat capacity to protect them from thermal shock; land animals carry their own supply of this thermal buffer within them in the form of blood, lymph and other bodily fluid. Polarity The yellow and black spheres represent a polar water molecule's oxygen atom bonded to a positive ion. Because of their asymmetry and the nature of their electron configurations, water molecules have an innate polarity despite having no net charge. The two hydrogen atoms carry a positive charge, while the oxygen atom holds a negative charge. Water's polarity allows it to dissolve other polar molecules, such as sugars and salts, in solution via hydrogen bonding. Hydrogen bonds form between one pole of a water molecule and an ion of the appropriate charge. Sodium chloride, or common table salt, dissolves in water because its sodium atoms are weakly attracted to water molecules' negative poles. Chloride ions form hydrogen bonds with the positive hydrogen atoms in water molecules. These hydrogen bonds form and break easily. Water makes these ions and other polar molecules available for life's essential chemical processes. Surface Tension and Adhesion Water striders exploit surface tension to skate across liquid water's surface. Hydrogen bonding of water molecules to other water molecules makes it adhere to itself, creating surface tension. Plants rely on surface tension to move water throughout their systems via capillary action. Capillary action in plants' vascular systems overcomes gravity and allows water to rise through these narrow channels thanks to a combination of its surface tension and its adhesion to molecules lining the capillary. Although adhesive water may seem like an oxymoron, at a molecular level water clings to itself and other surfaces well because of those weak, but constantly shifting, hydrogen bonds.