CHAPTER I 

 SOME PROPERTIES OF SEA WATER 



Section 1. The Concept of Water Structure 



Water has certain special features which distinguish it from other liquids . 



First, water is distinguished by its exceptional mobility: mechanical mobility, i.e., move- 

 ment and oscillation, and thermal, i.e. , conversion from one phase to another, in which case the 

 transition vapor-water-ice (or, even bypassing the intermediate phase, vapor-ice) and the reverse 

 are realized at ordinary earth temperatures and are accompanied by the generation or absorption of 

 an enormous quantity of heat. 



According to the kinetic theory of thermal motion, molecules move from place to place con- 

 stantly and chaotically (gas molecules), or they are in constant vibrational motion (the molecules of 

 a solid). At low temperatures, the properties of the molecules of a liquid approach those of a 

 solid, while at high temperatures, they approach those of gas molecules. The intensity of the 

 molecular motion determines the thermal state of the body. 



When the temperature is increased, the distance between the molecules increases, therefore, 

 the density of the substance should decrease with a rise in temperature, while the thermal capacity 

 should increase. Water is one of the few exceptions in this respect. Pure water is densest at a 

 temperature of approximately 4°; when temperature decreases, density decreases slowly and when 

 freezing occurs, density decreases sharply. Actually the density of pure ice at 0° is approximately 

 9 percent less than that of pure water at the same temperature. 



The thermal capacity of water is higher than that of any other substance on earth except hy- 

 drogen and liquid ammonia. The thermal capacity of water gradually decreases beginning at 0° and 

 continues till approximately 30° and only then begins to increase. 



The latent heat of fusion of pure water is greater than that of any other substance on earth ex- 

 cept ammonia. 



The heat of vaporization of water is considerably higher than that of any other substance on 

 earth. 



Several theories have been propounded to explain all these and other anomalies of water. In 

 these theories it has been assumed that water is a mixture of vapor, water and ice molecules, 

 which differ in structure and density. The higher the temperature of the water, the greater will be 

 the vapor-molecule content; the lower the temperature, the greater the ice-molecule content. Ice 

 molecules are not as dense as water molecules. 



If we examine water as an aggregate of molecules that differ in structure and density, we will 

 find that two processes operate simultaneously when water cools: the first is a normal decrease in 

 volume, the second an increase in volume due to the formation of the large, less dense ice 



