Chemical and Physical Properties of Water
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Water is the most common liquid found on earth. It is abundantly found almost everywhere in the universe and on earth. The body weight of a living thing is made in such a way that it is mainly composed of water. The percentage of water in a human being is about 50 – 70% while in other living organisms is about 95%. Water has a number of physical and chemical properties, but this assignment will only discuss the unique properties of water that make it vital to all living organisms to survive.
Water has several properties and only those essential to living organisms will be discussed and these are as follows.
WATER IS A UNIVERSAL SOLVENT
A solvent is a solution in which a solute dissolves. The reason as to why water is known as a ‘universal solvent’ is that many different things can be dissolved in it than in any other liquid. Some of the substances cannot be used in the body unless it is in a solution form. Maitland (1978) agrees with this by saying that “most gases dissolve readily in water most notably those that are essential for life.” According to Maitland (1978), it is true to say that for some gases like oxygen can only be used by an organism if it is dissolved in water, for example fishes use dissolved oxygen for respiration.
WATER HAS HIGH COHESION
Cohesion means ‘the sticking together of particles of the same substances.’ Water has the attraction force to molecules of similar substances; this is due to the hydrogen bond which is found in a molecule of water. This force of attraction allows water to move upwards hence carrying with it minerals and nutrients that are needed for the plant to survive. In other words it means that water is the only known medium by which the nutrients and mineral salts can be transported. Water transports dissolved substances in the roots of plants and also transports dissolved food substances through the simple blood vessels in a human body.
The high cohesive nature of water is used in the process of transpiration in plants. This happens in such a way that during the day when the plant is transpiring the pull exerted by transpiration makes water to move from the roots to the leaves of the plant and vice versa when it is dark.
WATER HAS HIGH SURFACE TENSION
According to Agarwa (1974), surface tension has been defined as, ‘a measure of how difficult it is to stretch or break a liquid surface.’ Water is able to form a tough film on its surface due to its high tension character or property. This surface of water supports aquatic life, for many large animals float on the surface due to up thrust. Maitland, (1978), prostitulates that ‘the pelogical habitat proper occurs only in larger bodies of standing water where there is sufficient area and depth for the water to be relatively uninfluenced by the substrate.’ From this statement it can be said that water is a habitat where whales live.
It is not easy to compress water due to its high surface tension as a result of this, water acts as a skeleton called hydrostatic skeleton. This type of skeleton is found in soft bodied animals such as an earth worm. In this skeleton the fluid is secreted from the body and pressed against the body muscles and the muscles contracts against the fluid. In this way, the shape and form of this group of animals is maintained.
LATENT HEAT OF VAPORISATION
The word vaporation can also be termed as evaporation. Evaporation is defined as the change of state from liquid to gas or vapour. Evaporation is essential in keeping the human body cool and not only is it essential to human beings but is also vital to plants in that when excess water is lost during transpiration there is excess heat being lost which brings about the cooling effect. When water evaporates, for example from the surface of the skin or a leaf, it carries with it excess heat. The production of sweat helps in lowering the body temperature when it is too high. This is so vital because the body may overheat easily if certain measures are not taken to cool the body down. Kent (2000:23) says that, ‘heat is lost from the surface when water evaporates from it.’ Therefore, water acts as a cooling mechanism. Water really plays an important role in the cooling mechanism of plants and animals.
PENETRATION OF LIGHT
One of the properties of water is that of being colourless and transparent. This property allows light rays to penetrate water, therefore, enabling organisms that make their own food to survive in water. Light plays an important role in photosynthesis as it is converted to chemical energy which in turn drives the synthesis of glucose from carbon dioxide and water which are the inorganic substances from which plants make their own food. When light energy strikes the chloroplasts containing chlorophyll, water in the stoma is split into hydrogen and oxygen by the process known as photolysis. Hydrolysis the opposite of photolysis takes place in animals in the process of digestion by breaking food molecules.
The green plants are the only agents that provide carbohydrate foods which acts as the basis from which more complex food such as proteins are made by the addition of various elements from the soil. This explanation means that without light being penetrating water, aquatic plants could not survive in water bodies and hence imbalance of nature.
WATER HAS SPECIFIC HEAT CAPACITY
Specific heat capacity has been explained that ‘the temperature will drop more slowly as heat is removed because of so much heat inputs or heat loss is required to raise or lower the temperature of water.’ (Eckert et al 2000). This statement means that water makes air to have a stable temperature as it absorbs heat from the air which is warm and release heat to the air which is cold. This phenomenon is observed in land and sea breeze.
To sum up on the above account, water remains as an important substance as it helps in many different ways in the life of an organism. In other words, it is true to say that no organism can survive without water because water is used in most important reactions and processes in living organisms, hence the statement, ‘water is life.’
- Agarwa (1974), Cell Biology, Genetics, Molecular Biology, Evolution and Ecology, Chad and company Ltd, New Delhi.
- Kent (2000) Advanced Biology, Oxford University Press, China.
- Maitland (1978), Biology of Fresh Water, Blackie and Sons Ltd, London.
- Eckert et al (2000), Animal Physiology, U.S.A., London.
- Peter et al, (1992), Biology Of Plants, Worth Publishers Inc, U.S.A., London.
- Purves et al (2000), Life, the Science Of Biology, Sinaver Associate Inc, London.
- Smith et al (2006), Elements of Ecology, Benjamin Cumming, U.S.A. London.
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