When we look at a molecule of water, we know that the hydrogen molecules carry a small positive charge and the single oxygen carries a negative charge, because the molecules are charged, it makes water a polar molecule. The fact that water is a polar molecule is very important to many of its properties.
When water molecules join together, the two different charges have an effect. Two opposite charges attract, so the negative charges of the oxygen’s, are attracted to the positive charges of the hydrogen’s, this causes a strong bond, known as a hydrogen bond.
Hydrogen bonds stick to each other, i.e. they are Cohesive, and this cohesion holds the molecules together when they move, meaning that water and dissolved substances can be moved in a cell with ease, these dissolved substances and water are moved around organisms via these transport systems.
Not only is water an important solvent, but it is also an essential medium for living organisms. It is important in two ways-
- It is essential for survival
- It provides an environment for many species.
In terms of survival, water does 2 important things. It acts as a supporter, and a heat holder. As water stays as a liquid at the temperature and pressure that organisms live at, increasing the pressure will not reduce the volume of water; this means that it will allow transport systems to pump (transfer) fluid under pressure.
Water can also absorb a large amount of heat, before a temperature change takes place; this is known as a high specific heat capacity. This means that because all living organisms are composed of a high percentage of water, their cells can remain at an almost constant temperature.
Also because of waters high specific heat capacity, it has two other important properties.
Water has a high latent of heat of vaporization; this means that to turn water in to a vapor, a lot of heat is needed. In order to lose this heat mammals produce sweat, when the water in the sweat evaporates, heat is taken away from the body in large amounts.
Water also has a high latent heat of fusion; this simply means that water will lose a large amount of heat, before it turns into ice.
This is important as the specific heat capacity of water is very important in order to maintain the temperature of living organisms, including their environment.
Water also provides a vast environment for many species, as it covers the majority of the Worlds surface, an estimated 1.4 billion cubic kilometers. The majority of the species that live in water also use it as a source of oxygen, for example most fish use gills to get dissolved oxygen from the surrounding water.
