《中国地质大学(武汉)环境化学Waterintroduction》-公开课件.ppt

Chapter Six Properties of Water Properties of Water Water content of selected organism and foods Distribution of Water on the Earth Hydrologic cycle Composition of natural waters Water as solvent and as ecosystem Water molecule and hydrogen bonding Heat capacity Temperature-density relationship Summary: Important properties of water Water content of selected organism and foods Distribution of Water on the Earth Only a small percentage (3%) of water on Earth is fresh water. Lakes and rivers account for just 0ver 0.1% of the earth’s total water. Hydrologic cycle Evaporation and transpiration Transpiration is a process in which water escapes through the pores on leaf surfaces. Global water use (1900-2000) Composition of natural waters Fresh water: dissolved solids 0.1%. Drinking water standard: dissolved solids 0.05% Major constituents: Ca2+, Mg2+, HCO3-. Sea water: dissolved solids ~3.5% (Dead sea: 25%) Major constituents Cl- 19,000 ppm Na+ 10,600 ppm SO42- 2,600 ppm Mg2+ 1,300 ppm HCO3- 140 ppm Ca2+ 400 ppm Br- 65 ppm K+ 380 ppm Water as solvent and as ecosystem Water is a remarkable solvent, dissolves and transports a wide range of materials. Interacts with soil and particles and gases in the air Water houses ecosystems. A large percentage of the biosphere lives in some form of aqueous environment. Water quality is often defined in terms of the ability of the aqueous environment to support the normal range of biological species. Water molecule and hydrogen bonding H-bonds have a profound effect on the physical properties of water in both its liquid and solid states. Boiling point and melting point Without H-bonds, water would be a gas at the temperature found on earth, and our form of life and environment would not be possible. Heat capacity Heat capacity is the amount of heat required to raise the temperature of a given mass by 1oC. Unit: cal/oC/g Water has the highest heat capacity of any common liquid or solid. H2O: Cp =1 cal/