Water abundant and stable page 153 top, 7 th Ed., 2010
Color of water From underwater, looking up In any pool having a white bottom, if more than 3 or 4 feet deep, the water will appear noticeably blue, not colorless.
Water structure and its polarity Due to its two lone pairs (unshared electron pairs) and its two bonding pairs, the water molecule has a bent shape derived from a tetrahedron. That bent shape causes water to be polar, so it attracts other polar molecules.
An electrostatically- charged rod deflects water <ul><li>A positively-charged rod attracts the stream of polar molecules. </li></ul><ul><li>Surprisingly, a negatively charged rod also attracts a stream (because the water molecules rotate). </li></ul>
Desert has little water and thus drastic temperature changes
Water’s Temperature Range as a Liquid <ul><li>The temperature range that water remains a liquid is rather large compared to related molecules. </li></ul>
Water relatives (Hydrides of congeners, i.e., related elements) Hydrides of chalcogens [stinkogens] Group VIA
Melting points & Boiling Points of compounds related to water (hydrides of similar groups). Note the hydrides of F, O, and N are dramatically out of line due to their Hydrogen “bonding”.
Ice has a regular arrangement using four Hydrogen “bonds” to each water molecule. This open network leaves large empty spaces, so ice is less dense than liquid water.
Solid benzene sinks in liquid benzene (the usual), but ice floats in liquid water (at left).
Heat involved (per gram) in the Phase Changes of Water
Surface tension is used by some insects to float on water.
Surface tension & meniscus combine to make “capillary action” Meniscus (Greek means little crescent) is due to the liquid’s adhesion to the glass being greater than the liquid’s cohesion to itself. So, the liquid creeps up at the surface near the glass. The surface tension tries to keep the minimum surface area so the meniscus rises.
Surface tension explanation Molecules in interior of the liquid are surrounded by attractive forces, but molecules in the surface layer have only attractions to below. So, it is as if there is a skin having a strong tendency to make a minimum surface area.
Reduce surface tension by adding surfactant (soap or detergent). Acute angle Obtuse angle surface surface
Hydrologic cycle (Convection on a grand scale) The energy is provided by the sun, but the cycle is also driven by the rising of the light water vapor molecule. Since more evaporation occurs near the equator and condensation occurs more near the poles, this causes wind, weather, storms, and runoff.
Cloud (and precipitation) formation at fronts and at mountains.
Glacier National Park “ Rain shadow” on the East side of the continental divide
Freeze-thaw volume change <ul><li>Water leaks through cracks in pavement. </li></ul><ul><li>Freezing causes expansion and more breaking of pavement. </li></ul><ul><li>Thaw and drainage of liquid water causes an unsupported hole which is further crumbled by traffic. </li></ul>
Barnard Glacier, Mt. Mc Kinley, Alaska before 1969
Ice regelation, Wire cuts but refreezes behind cut