Water has also a specific heat capacity. This means that a lot of heat energy is needed to change the state of water from liquid to gas (100°C to change from liquid to gas). This means that water does not change its temperature very easily. This is ideal in human and animal bodies as it allows the temperature of the body to stay maintained. Also, because human cells are made up of mostly water, the specific heat capacity allows the cells to not get denatured. If the temperature does rise in plants or animals then water can act as a cooling system because of the high latent heat of evaporation. As water is evaporated in plants (transpiration) and animals (sweating), it extracts heat from around it therefore results in cooling the organism.
When water is frozen and its state changes from liquid to solid, the solid state (ice) is less dense than the liquid state so therefore ice floats on water. The ice on top of the water acts as an insulating layer, which allows aquatic life to continue even in freezing conditions.
Water molecules are also highly cohesive. Cohesion occurs when water molecules stick together due to their hydrogen bonds. The cohesive property of water is significant in living organisms. For example the cohesion of water allows plants to pull up water through xylem vessels from the roots to the leaves, this is called the transpiration stream. Also, when water molecules are held together tightly, it forms an elastic film known as surface tension. This allows creatures such as water skaters to move across the water.
Because of water's strong hydrostatic forces water is incompressible. This provides support for soft-bodied creatures such as worms, slugs and jellyfish, which means they do not require a supporting skeletal system. Water allows cells filled with water to become turgid, and due to its incompressibility plants can support themselves.
Water is also used to split up molecules by adding water. This is called hydrolysis and is essential to animals and plants because it allows them to utilise stored foods, which are in long chains by breaking them into smaller molecules.
Another property of water is that it is transparent, which means that water allows light to pass through it. This is important in plants because it allows light to enter the chloroplasts in plant cells, which allows photosynthesis to occur. It is also important for the eye so that light can reach the retina in order to see.
Water is the medium for many reactions, especially those that occur in cells. Water is key in condensation reactions where water is removed from molecules to bond them together, this occurs with many sugars and carbohydrates.
Because of all the properties of water, it makes water the most important substance in our planet. There are no other substances that have properties that are similar to water or share such varied characteristics.
