As the molecules of water are polar, not only do they tend to stick together but they also have a slight attraction to the walls of the vessels within which they are contained. This causes them to stick to the walls, a force known as adhesion. An example of this is capillary action, which is defined as the elevation of depression of the surface of a liquid when it is in contact with the sides of a solid. Capillary action depends on the forces created by surface tension and the forces of adhesion of the water molecules to the solid.If the forces of adhesion of the liquid to the solid are greater than the forces of cohesion within the liquid (surface tension), the surface of the liquid will dome upwards, and the liquid will rise up the tube.
This action is present by water in clean glass tubes. If the forces of cohesion are greater than the forces of adhesion, the surface of the liquid will dome inwards, and the liquid will begin to fall (if there is a way for it to escape). This action is present by water in greasy glass tubes (in which the force of adhesion is small).Lubrication:Water is used very commonly, both biologically and artificially as a lubricant.
A lubricant is a substance which may be fluid to semi-fluid, and is used to reduce the friction and abrasion between moving parts. This friction, especially in biological terms, may lead to serious damage of the parts involved. All tissue within the human body is fragile, and therefore, to a certain extent, must be protected against the everyday ‘wear-and-tear’ to which they are subjected.A common biological lubricant is mucus. It is composed of carbohydrate fibres with water trapped within them- this explains why mucus becomes hard and flaky once it has dried out and all of the water has escaped.
Due to its lubrication property, mucus is found lining passages, which experience the friction of moving materials. For example, the oesophagus is lined with mucus in order to reduce the abrasion as the bolus of food swallowed travels down the food pipe, preventing damage to any epithelium tissue. Water is also found as a constituent of synovial fluid, secreted by membranous sacs, known as bursae, found between the bones. The thick synovial fluid reduces the friction as the bones move over each other at the joints, decreasing the amount of damage through use.Transparency:Water’s transparency is a huge benefit to many organisms.
Transparency is the ability of a substance to allow light to pass through it. This is what allows the depths of the ocean to be colonised by large numbers of aquatic plants, which form the basis of every aquatic food chain. As the light is able to penetrate through the water, it enables the plants to photosynthesise. This not only keeps them and the millions of other organisms dependent on them for food alive, but it also allows oxygen to be produced and eventually released into the atmosphere from the water. Another example of how water’s transparency benefits living organisms is the ability for mammals to see, as the aqueous and vitreous humour found in mammalian eyes (which helps keep the pressure within the eyes high) largely consists of water.
No doubt, reading through these properties of water conjures up images of the shear essentialness of water within the mind. Put simply, without this modest compound, earth would be a barren place, devoid of all live. It is our very essence and yet it is still a slave to us, such is the parasitic nature of man.
We use it care free for cooking and cleaning, for bathing and carrying away wastes.Our factories use more water than any other material and our demand for it is ever increasing, as the population of this fourth rock from the sun soars, almost exponentially. However, mockingly, it is also our master. Great civilisations have risen where water was plentiful- they have fallen where supplies failed.
Men have killed one another over muddy holes and have been forced to worship rain Gods. Often droughts have been partnered by famine, disease and war. As demand for water grows, man will need to make better use of his supplies.
The more he learns about this fourth element of the earth, the better he will be able to face his challenge.