Physical and Chemical Properties of Sea Water

Hydroden Bonding (+ with - charges)

Water is the only substance that occurs naturally in all three phases: solid, liquid, and gas.  In liquid water, HYDROGEN BONDS hold most of the molecules together. A hydrogen bond is a weak attraction of a hydrogen atom (H+) with an electronegative atom such as nitrogen (N-3), oxygen (O-2), or flourine (F-).  As water cools, the movement of the molecules slows and they pack together more tightly.  This is why cold liquid water is DENSER than warm water.  Density is a measure of how much of some entity is within a fixed amount of space.  Density=Mass(g)/Volume(L).  Water freezes when the molecules move so slowly that the hydrogen bonds 'take-over'; locking the molecules into a 3-dimensional pattern.  The same mass of water now occupies more volume as ice than as liquid water, so ice is les dense than liquid water and floats.  This is extremely unusual and very important for aquatic organisms living on, in, or beneath the ice.  In ice, the water molecules are held together by the hydrogen bonds in the ice crystal.  When ice melts, energy (in the form of heat) is required to break the hydrogen bonds, and to increase the speed of the molecules.  Because of the hydrogen bonds, more heat is required to melt ice or to convert liquid water into water vapor; giving water a high HEAT CAPACITY.

The next lecture I will discuss heat capacity.