Water
Water Properties: Pure water is virtually colourless and has no taste or smell.
Chemical description: Water's chemical description is H2O, that is, one atom of
oxygen bound to two atoms of hydrogen.
Universal solvent: Water is called the universal solvent because it dissolves more
substances than any other liquid.
pH: Pure water has a neutral pH of 7, which is neither acidic nor basic.
States: solid, liquid and gas
Water is the only natural substance that is found in all three states: liquid, solid (ice),
and gas (steam). It is unusual in that the solid form ice, is less dense than the liquid
form; this is why ice floats.
Freezing and boiling point: Water's freezing and boiling points are the baseline with
which temperature is measured: On the Celsius scale, 0° is water's freezing point, and
100° is water's boiling point. Water freezes at 32° Fahrenheit (F). Water boils at 212° F
at sea level, but at 186.4° at 14,000 feet.
Heat Index: Water has a high specific heat index. This means that water can absorb a
lot of heat before it begins to get hot.
Surface Tension: Water has a very high surface tension. In other words, water is sticky
and elastic, and tends to clump together in drops rather than spread out in a thin film.
Water in the Body: In some organisms, up to 90 percent of their body weight comes
from water. Up to 60 percent of the human body is water, the brain: 70 percent, the
lungs: nearly 90 percent and our blood, about 83 percent.
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The Water Cycle
Earth's water is always in movement, and the water
cycle, also known as the hydrologic cycle, describes
the continuous movement of water on, above and
below the surface of the Earth.
Evaporation: The process by which water is changed from liquid to a gas or vapour.
Sublimation: The changing of snow or ice to water vapour without melting.
Evapotranspiration: The process by which water vapour is discharged to the
atmosphere as a result of evaporation from the soil and transpiration by plants.
Transpiration: The release of water from plant leaves.
Condensation: The process by which water is changed from vapour to liquid.
Precipitation: The discharge of water, in liquid or solid state, out of the atmosphere,
generally upon a land or water surface.
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