Properties of Water Unit 2 I. Water Is A Solvent A. Solvent – substance doing the dissolving B. Solute – substance being dissolved C. Major difference in freshwater and sea water is presence of salt (NaCl) II. Structure of Water A. Pure H2O – two hydrogen and one oxygen. B. Salt Water – Six elements and compounds comprise about 99% of sea salts. III. pH of Water A. H2O can separate into H+ and OH- ions. B. The presence of these ions cause water to become acidic or basic. C. pH of pure water – 7 “neutral” IV. Dissolved Oxygen in Water A. Oxygen is found in water even though it does not dissolved easily. B. Dissolved oxygen is measured in parts per million (ppm). C. Ocean water can hold from 1 to 12 ppm depending on the temperature of the water. (oxygen in air is 200 ppm) V. Sea Water A. Ocean water is made up of about 96.5 percent water molecules and 3.5 percent NaCl (table salt). B. Calcium Carbonate is also a common compound found is the seas. VI. Salinity A. Oceanic waters typically have 35g of salt dissolved in 1000g of water (3.5%). B. Salts accumulate in the oceans as rain leach sediments from the land. VII. Temperature A. Ocean water temperatures vary between -2 to 30°C. B. Temperatures below 0ºC are possible because salt water freezes at colder temperatures than pure water. VIII. Pressure A. Organisms on land experience atmospheric pressure. B. Marine organisms experience water pressure and atmospheric pressure. 4 5 6 20m 30m 40m 50m 3 8 9 60m 70m 80m 7 1. Atmospheric pressure: atm 2. With each 10m (33ft) of increased depth, another atmosphere of pressure is added. m 10m 1atm 2 C. Units of Pressure 90m 10atm IX. Buoyancy an upward force exerted by a fluid an object is in. X. Density A. Mass of a substance per unit of volume. B. Formula: D= m/v C. Unit: g/ml or g/cm3 (ml = cm3) D. Density of Pure H2O = 1 g/ml (impurities in water cause the density to increase) E. Principle of Density 1. Objects of greater density than the fluid they are in – will sink in the fluid. 2. Objects of lesser density than the fluid they are in – will float in the fluid.