Properties of Water for Organism Survival

• NDUI PRISCILLAH

Discuss the assertion that water has several unique properties that make it vital not only for human beings, but for all living organisms to survive.

Introduction

Water is a very important aspect of all living organisms’ plants and animals alike. What makes it so useful and relevant to survival are its unique properties which relate to its functions and hence its relevance to living things as discussed below.

Water is a dipolar molecule

Water is a normal oxide of hydrogen consisting of two hydrogen molecules covalently bonded to one oxygen molecule. The water molecule is not linear and the oxygen atom has higher electro negativity than the hydrogen atoms. The atoms of oxygen carry a slightly negative charge whereas, the hydrogen atoms are slightly positive, this gives the water molecule its dipole movement (en.wikipedia.org). Hence, the water molecule can form up to four bonds with it self and other molecules. This property gives water most of its properties.

Water is a Universal solvent

A solvent is a liquid which dissolves other substances. Because of its ability to form four bond with other molecules (dipole), no other chemically inert solvent is able to dissolve a variety of materials as water nor the amount of them it can hold in solution (Edward J.K 1996). Water is able to dissolve a variety of substances solids, liquids and gases alike. (Edward, 1999) adds on to say “water is the best solvent and provides a medium for the movement of molecules within and outside the cell.” hence water is important in both plants and animals in that it aids movement of materials through diffusion as salts, sugars acids, alkalis and gases such as carbon dioxide (carbonation) and oxygen dissolve in it and can be transported in the organism as a transport medium as in blood, lymphatic and excretory system, the alimentary canal and xylem and phloem (Taylor D.J 1984).

Water is wet

Because of its molecules forming hydrogen bonds with other polar molecules, water makes things wet. This is due to its cohesive and adhesive properties (Dr. Jain VK, 1974). Cohesion is the attraction between like molecules in this case water while adhesion is the attraction of molecules of different substances. This gives water high capillary forces, that is the tendency of water to move up a narrow tube against the concentration gradient. This is a very important property to vascular plants such as trees as it enables water to move along very narrow spaces such as during transpiration which help control the temperature of a plant.

Its cohesion property is also relevant in cells and in translocation of water through xylem in plants. This is also vital in the rising or moving up of sap in plants.

Surface tension

The cohesive property of water brings about surface tension. Besides mercury, water has the greatest tendency to cohere causing its surface to contract to the smallest possible areas as a result of the hydrogen bonds (Edward J.K, 1996), because of this many small organisms are able to settle on water or skate over its surface, thus providing them a habitat, for example the water striders. It also aids reproduction by way of seed dispersal, garmetes and larval stages of aquatic organisms.

Water has a high specific heat capacity

The specific heat capacity of water is the amount of heat required to raise one (1) gram of water from O⁰C to 1⁰C. Compared to other liquids a considerably high amount of energy is required to change the temperature of water (Edward J.K, 1996). This property is also due to the numerous hydrogen bonds between water molecules. This is very vital to both humans and plants as it helps in moderating the earth’s climate by buffering large fluctuations in temperature. It also protects the plants from very harmful temperature fluctuations. High specific heat capacity of water is also vital to marine and fresh bodies of water to help maintain a constant temperature over longer period of time and to be stable over short periods of time.

Latent heat of vaporization

Vaporization or evaporation is the change of state from liquid to gas. The latent heat of vaporization is the energy required to convert a liquid into gas (Vapour) at constant temperature (Dr V.K Jain, 1974). Water has the highest latent heat of vapourisation of all common substances which is about 44 Kj/Mol at 25⁰C. The high latent heat of vaporization of water enables the plants to cool themselves by giving out heat through transpiration. It is also a major factor in the transfer of heat between the ocean and the atmosphere, thereby driving the weather climate. Beside these, animals also use this property in cooling by the sweating and panting in mammals. That is, the opening of the mouth by some reptile’s e.g crocodiles in sunshine and mammals like dogs.

Latent heat of fusion

Latent heat of fusion is the heat required to convert a unit of mass of a solid to liquid at the same temperature. To melt 1gram of ice at 0⁰C, 80cal. (335J) of energy is needed which is very high and caused by the presence of hydrogen bonds. This means water must loose a relatively huge amount of heat energy to freeze. This helps protect the contents of the cells not to be damaged as their environments are less likely to freeze.

Water expansion and density

One of the unique properties of water is that, it reaches its maximum density at 4⁰C and diminishes above and below that temperature. It has a tendency to expand as it freezes and its density is decreased (Dr. Jain V.K, 1974), hence ice has a lower density than water and floats on top of oceans, lakes and rivers. It forms at the surface first and last at the bottom, this provides insulation of the water below it and increase the chances of survival for acquatic organisms especially in cold climates and during cold seasons.

Penetration of light

Water which has no suspended particles is transparent in the visible electro magnetic spectrum. This implies relatively great amounts of infrared and ultra-violet rays can penetrate through it.

This enables acquatic plants to survive as they are able to carry out photosynthesis.

It can therefore be deducted that water indeed has several unique properties related to its importance to all living organism without which most of these might become extinct. Besides these water provides a habitat for millions of living organisms and is also vital in sanitation for human beings helping to prevent the spread of infections such as viruses, protozoa and worms. Hence, water is a very vital aspect without which life might not exist.

BIBLIOGRAPHY

Edward J.K (1996), Concepts of Ecology; fourth edition. Pearson Education. New Jersey.

en. Wikipedia.org/wiki/water

Dr. Jain V.K (1974), fundamentals of Plant Physiology; S. Chand and Company Ltd. New Dhehi

Taylor D.J et al (1984), Biological Science 1 & 2, Cambridge University Press. New York.