Water All life, and therefore biology, occurs in a water based (or aqueous) environment. The water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom. The most significant aspect of water is the polarity of its bonds that allow for hydrogen bonding between molecules. This type of intermolecular bonding has several resulting benefits. The first of these is water’s high specific heat. The specific heat is the amount of heat necessary to raise the temperature of 1 gram of that molecule by 1° Celsius. Water has a relatively high specific heat value, due to the extent of hydrogen bonding between water molecules, which allows water to resist shifts in temperature. One powerful benefit is the ability of oceans or large bodies of water to stabilize climates. Hydrogen bonding also results in strong cohesive and adhesive properties. Cohesion is the ability of a molecule to stay bonded or attracted to another molecule of the same substance. A good example is how water tends to run together on a newly waxed car. Adhesion is the ability of water to bond to or attract other molecules or substances. When water is sprayed on a wall, some of it sticks to the wall. That is adhesion. When water freezes, it forms a lattice crystal. This causes the molecules to spread apart, resulting in the phenomenon of ice floating in water. Water is unique in this regard since most solids do not float on the liquid form of their substance because the molecules pack tighter in the solid form. The polarity of water also allows it to act as a versatile solvent. Water can be used to dissolve a number of different substances (Figure 5-1). |
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