Chemical Properties of Water

Water is an amphoteric substance (acts as acid or base) depending on the substance that the water reacts with. Water molecules may dissociate as shown below  

---

This chapter will briefly survey some basic physical and chemical properties of water as well as the possible relevance of these properties to aqueous organic chemistry in terms of reactivity, selectivity (chemo-, regio-, and stereo-), and phase-separations. 

The chemical properties of water determine what compounds will leach out of soil and vegetation, and hence what chemicals other plants and animals will be exposed to. For instance, acidic water will extract alkaloids from plant materials. 

A. The special chemical properties of water make it ideal as the main physiologic solvent for polar substances in the body. 

This chapter begins with descriptions of the physical and chemical properties of water, to which ail aspects of cell structure and function are adapted. The attractive forces between water molecules and the slight tendency of water to ionize are of crucial importance to the structure and function of biomolecules. We review the topic of ionization in terms of equilibrium constants, pH,... 

It is important to recognize acid-base as a behavior. We say, for example, that hydrogen chloride behaves as an acid when mixed with water, which behaves as a base. Similarly, ammonia behaves as a base when mixed with water, which under this circumstance behaves as an acid. Because acid-base is seen as a behavior, there is really no contradiction when a chemical like water behaves as a base in one instance but as an acid in another instance. By analogy, consider yourself. You are who you are, but your behavior changes depending on whom you are with. Likewise, it is a chemical property of water to behave as a base (accept H+) when mixed with hydrogen chloride and as an acid (donate H+) when mixed with ammonia. 

Park, H., and Robinson, J. R. Physico-chemical properties of water insoluble polymers important to mucin/epithelial adhesion. J. Con. Rel. 2 47—57, 1985. 

Give one physical property of water and one chemical property of water. 

Even for the most important solvent - water - the investigation of its inner fine structure is still the subject of current research [8-15, 15a] f Numerous different models, e.g. the dickering cluster model of Franck and Wen [16], were developed to describe the structure of water. However, all these models prove themselves untenable for a complete description of the physico-chemical properties of water and an interpretation of its anomalies [304]. Fig. 2-1 should make clear the complexity of the inner structure of water. 

Chemical properties are the characteristic ways a substance can react to produce other substances. Physical properties are the ways a substance can be identified without changing its characteristic composition. For example, water can react with very active metals to produce hydrogen and another compound. That reactivity is a chemical property of water. Water can also freeze to ice at 0°C (eqnal to 32°F) or it can evaporate to water vapor, neither of which changes it from H2O. These are physical properties of water. 

In fact, man himself is fabricated of H bonding substances. We feed, clothe, and house ourselves in H bonded materials. What is the key to the catholic importance of this chemical interaction in our environment It is, no doubt, to be found in the H bonding properties of water since all of the physical and chemical properties of water are determined or influenced by H bonding. And this interaction pervades our chemistry simply because all living things evolved from and exist in an aqueous environment. It is hardly an exaggeration to say that in the chemistry of living systems the H bond is as important as the carbon-carbon bond. 

Table 2.3.3 Methods and technologies commercially available for the monitoring of physico-chemical properties of water bodies...

Since it is reasonable to assume the scrubbing medium to be water or a solvent that effectively has the physical and chemical properties of water, Hqq can be assigned values usually encountered for water systems. These are given in the following table ... 

Figure 1-4 Some physical and chemical properties of water. Physical (a) It melts at 0°C (b) it boils at 100°C (at normal atmospheric pressure) (c) it dissolves a wide range of substances, including copper(II) sulfate, a blue solid. Chemical (d) It reacts with sodium to form hydrogen gas and a solution of sodium hydroxide. The solution contains a little phenolphthalein, which is pink in the presence of sodium hydroxide.

The principles of solution chemistry known from elementary handbooks apply in a concentration range of about 10 — M. The procedures and methods that work very well at concentrations greater than 10 M must not be extrapolated to lower concentrations. This is because distilled water used in the laboratory is not pure water, but contains dissolved components of air, materials leached from the container (e.g., silica), and other components. The contribution of the solutes to the physical and chemical properties of water is negligible when their concentrations are low enough, and the presence of impurities in distilled water can be... 

Despite such wide divergences, the basic point of commonality is that both bacteria and whales live in environments where the physical controls imposed by the physico-chemical properties of water - be they viscosity or acoustic transmission -predetermine what is biologically possible. To this simple example could be added many other physical and chemical constraints. In the case of water - echoing Lawrence Henderson s (1913) prescient remarks on the way in which the physicochemical glove matches the hand of life - one could list such factors as its power as a solvent, dielectric properties, transparency, latent heat of evaporation, and decrease of density when frozen. These properties are all central in various ways to life... 

Noncovalent interactions are usually electrostatic that is, they occur between the positive nucleus of one atom and the negative electron clouds of another nearby atom. Unlike the stronger covalent bonds, individual noncovalent interactions are relatively weak and are therefore easily disrupted (Table 3.1). Nevertheless, they play a vital role in determining the physical and chemical properties of water and the structure and function of biomolecules because the cumulative... 

Noncovalent bonds (i.e., hydrogen bonds, ionic interactions, van der Waals forces, and hydrophobic interactions) play important roles in determining the physical and chemical properties of water. They also have a significant effect on the structure and function of biomolecules. 

The peculiar enhancement of the catalytic activity in biphasic medium for the hydroformylation of the water-soluble acrylates seems to be due to the physical and chemical properties of water [21]. Indeed, it is assumed that water stabilizes... 

Physico-Chemical Properties of Water at High Temperature and Pressure 423... 

---