Lec 6 Water Slides - Science Notes PDF

Water and Seawater Learning outcomes: Describe the basic chemistry of the water molecule accurately using terms such as outer electron shells, covalent bonds, partial charges, and H bonding. Discuss the following properties of water: Surface tension, solvency, salinity, thermal, sound and...

Water and Seawater Learning outcomes: Describe the basic chemistry of the water molecule accurately using terms such as outer electron shells, covalent bonds, partial charges, and H bonding. Discuss the following properties of water: Surface tension, solvency, salinity, thermal, sound and light transmission, pressure Describe how the physical properties of seawater vary with water depth 1  The Water in Seawater Henry Cavendish 1760’s discovered composition of water and synthesized it by combusting H2 Henry Cavendish, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7373371 2 Hydrogen Bonds H bonds form between 2 adjacent water molecules 3  Adhesion and Cohesion Hydrogen bonds cause water to be attracted to something – Adhesion- water molecules “stick” to other things – Cohesion- water molecules “stick” to each other https://www.emaze.com/@AIOWZCQT/Bio-Water-Lab:-Sadhana,-Raymond,-David; https://water.usgs.gov/edu/adhesion.html 4  Cohesion: Surface Tension Highest surface tension of any liquid except elemental mercury http://hyperphysics.phy-astr.gsu.edu/hbase/surten.html & http://www.nsf.gov/news/special_reports/water/popup/wg_spider.htm 5  Water as a Solvent Universal solvent Polar & ionic substances dissolve best Nonpolar substances least Left image credit: Mariana Ruiz Villarreal, CK‐12 Foundationhttps://www.usgs.gov/special-topics/water-science-school/science/water-universal-solvent 6  Composition of Seawater 1. Volcanic eruptions → precipitation 2. Weathering of rocks → runoff/rivers 3. Mid-ocean ridge → leaching 7 8  Salinity and Osmoregulation Water flows out Diffusion moves molecules from areas of high concentration to low Diffusion of solvent is called osmosis In this case - water Cell membrane disrupts diffusion of most salts into the cell Water crosses membrane freely 9 Thermal Properties Specific heat capacity: Amount of heat needed to raise the temperature of 1 g of a substance 1°C Water has a high specific heat capacity Air and rocks have relatively low specific heat capacities 10  Heat absorbed or released during a change of phase at Latent Heat: constant temperature and pressure 11 Phase Changes of Water Latent Heat of Vaporization & Evaporation Heat needed to change from liquid to gas. Latent Heat of Latent Heat of Condensation Melting Cooled water vapor turns to Heat needed to liquid and releases heat to the make ice melt environment Latent Heat of Freezing Heat released when water freezes 12  Thought Exercise Which areas on Earth have the largest annual temperature range? Given what we have discussed so far, briefly explain why? 13 Continental regions have a larger annual temperature range than the oceans because the specific heat capacity of water is greater than that of land. Land heats and cools faster than water. Therefore, the northern hemisphere with its larger land mass has warmer summers and colder winters than the southern hemisphere and coastal areas have smaller temperature range than mid-continental regions at the same latitudes. http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/navmenu.php_tab_2_page_6.2.0.htm 14 Density and Thermal Expansion Most materials expand when heated and contract when cooled Pure water violates this rule Seawater follows 15  Pressure Pressure increases with depth in the ocean At 4,000m pressure 400x surface 16 Pressure and Gases in Organisms 17 Light in the Ocean http://en.wikipedia.org/wiki/Electromagnetic_radiation 18  Light is attenuated in seawater Very little sunlight below ~200m Blue light penetrates deepest Red is attenuated at shallow depths https://oceanservice.noaa.gov/facts/light_travel.html 19 nasa.gov 20  Sound in the Ocean Average velocity 1450 m/s 4x faster than in air Speed increases with temperature and pressure Paul Webb Creative Commons https://rwu.pressbooks.pub/webboceanography/chapter/6-4-sound/ 21 Sound Video Video: Inside Nature’s Giants pick up at 55:47 minutes https://www.pbs.org/video/inside-natures-giants-sperm-whale/ https://www.youtube.com/watch?v=lxFQaWSCar0 22 23