Unique properties of water

Properties of Water

According to the definition provided by Merriam Webster, water is defined as being:

An odorless, tasteless, very slightly compressible liquid oxide of hydrogen H2O which appears bluish in thick layers, freezes as 0oC and boils at 100oC, has a maximum density at 4oC and a high specific heat, is feebly ionized to hydrogen and hydroxyl ions, and is a poor conductor of electricity and a good solvent.

Water has several unique properties that make life possible on earth. First, water is the only natural substance that is found in all three states, liquid, solid and gas, at temperatures normally found on earth (Riley, 1). Second, water has an extremely high heat capacity. Third, water has the highest surface tension of any liquid found on earth with the exception of mercury. Each of these properties affects the functioning of living things.

Water is found in on earth in its liquid, solid and gaseous state. Water reaches a solid state at 0oC. In its solid state, water has a defined shape, taking on the shape of the container in which it was frozen. Water also has a crystalline internal structure and is less dense than its liquid counterpart, which is why ice floats on water (Riley, 2). As a liquid, water has no definite shape but takes on the shape of its container. Water is a liquid between the freezing and boiling point temperatures of 0oC and 100oC. At 100oC, the boiling point, water turns to gas. Like water, gas has no definite shape, but assumes the shape of its container.

This unique property of water molecules makes life on earth possible for several reasons. First, "all known biochemical processes occur in aqueous environments" (Riley 7). For example, photosynthesis requires water and energy from the sun to produce carbohydrates. Photosynthesis creates oxygen, which is necessary for survival. Secondly, the fact that water can exist in three separate states at once is important because heat is transferred through the evaporation and condensation of water. The redistribution of heat energy helps keep the earth cool enough to maintain life (Pidwirny 1). Life on earth is possible because of water's ability to exist in three different states simultaneously.

Water has an extremely high specific heat capacity. Heat capacity is defined as being "the amount of energy required to change the temperature of a substance" (Pidwirny 1). This property allows water to absorb enormous amounts of heat before it begins to grow warm and allows it to release heat gradually when it begins to cool. The high heat capacity of water makes it an ideal cooling and heating substance. For example, the oceans make it possible for life to exist on earth because they create more moderate temperatures by absorbing large amounts of solar heat (Riley 3). Otherwise, it would become too hot for plants and animals to survive. Water also helps organisms to regulate their internal body temperatures (Pidwirny 1).

Water has an extremely high surface tension. Riley defines surface tension as being "the attractive force exerted by the molecules below the surface on those at the liquid-air interface" (6). This means that water is "adhesive and elastic, and tends to aggregate in drops rather than spread out over a surface as a thin film" (Pidwirny 1). The surface tension of water allows for the hydrogen bonding of water molecules, which gives water the ability to wet surfaces by adhering to it. It also lets water stick to structures, even though gravity is pulling it downwards. This is important to life because plants need to be able to transport water and nutrients from their roots. Animals also need to be able to transport nutrients through their bloodstream (Riley 6). The high surface tension of water makes this possible.