It can also act as an ionic substance because of this property. Other ionic substances such as salt, sugars and amino acids or any polar molecules will readily dissolve in it because the ions are attracted to either the hydrogen or the oxygen atoms. Non polar substances are insoluble in water.
Water has a very high specific heat capacity (SHC). This means that it is good at maintaining its own temperature at a steady level, irrespective of the temperature fluctuations in the surrounding environment. The high SHC is ideal for keeping the temperature of humans (and other organisms) at a steady level as well. This is especially important when we consider that most organisms cannot survive temperature fluctuations of even 1°C. The human body must be kept at 37°C and change of up to 2°C may be tolerated but any more would cause havoc within the organism and it may even die.
The latent heat of vaporisation (LHV) is another useful property of water and is similar to the SHC. LHV is the amount of energy required to turn one gram of a liquid (water in this case) into a vapour. Water has a high LHV but if it did not, then ponds would dry up quickly and the air humidity would vary a lot more than it does at present. Similarly, if it had a higher LHV, then we would not dehydrate as quickly and we would produce more urine which would also be less concentrated. Because it can absorb quite a lot of heat before its temperature rises, the blood is used to transport heat from inside the body to the skin surface, where it is lost to the environment. If the human body needs to cool, water is itself lost as sweat. When the water in the sweat evaporates, it cools the skin.
Water molecules are attracted to other water molecules. This is because the oxygen end of water has a negative charge and the hydrogen end has a positive charge. The hydrogen atoms of one water molecule are attracted to the oxygen from other water molecules. This attractive force (also known as hydrogen bonding) is what gives water its cohesive properties. These cohesive properties also give water the ability to travel through vessels and to the top of tree trunks. If these forces were weaker, then trees would not grow to be as tall as they are. Because of the cohesion, water also has the highest surface tension of any liquid except mercury. Sometimes insects walk on water - it is because of surface tension. Hydrogen bonds are holding the molecules of water together, forming a surface "skin" that an insect can walk on (if it spreads its weight out over the surface).
Surface tension is responsible for water sticking together in small drops. As a water droplet falls, it stays together until it hits the surface. This is because the hydrogen bonding is keeping water together until it becomes a certain size at which point gravity overcomes the attractive forces between the molecules and the droplet ‘splits’ apart.
Surface tension is related to the cohesive properties of water. Capillary action however, is related to the adhesive properties of water. If a straw is submerged into a glass of water, then some of the water will rise to e higher than the water level outside the straw. This is possible because the slightly charged water molecules are attracted to the straw molecules and can slowly ‘climb’ up the inside of the straw. However, capillary action is limited by gravity and the size of the straw. This is why only a small amount of water can climb along the straw and this is why a meniscus if formed in a glass of water. The solubility of water is also excellent. Most reactions with occur in the body as well as cellular reactions) occur in water
Features and Processes involving Water
Water is the crucial component in the formation of nucleotides (DNA and RNA). Nucleic acids are not simply made when the 3 components needed (phosphoric acid, deoxyribose/oxyribose and an organic base such as adenine, cytosine, guanine, thymine and uracil) are mixed together. There needs to be a reaction which causes these 3 components to bond and be ‘strung’ together. This involves condensation.
A - The hydroxyl in the deoxyribose (sugar) bonds with the hydrogen in the organic base and the hydroxyl in the alcohol bonds with the other hydrogen in the pentose base to form water (condensation).
B – A single nucleotide of deoxyribose nucleic acid (DNA) has been formed
C – Condensation happens between single nucleotides as well (between the phosphate and sugars) to form the whole strand of DNA
In the human body, water is needed inside cells, but it is also needed for transport substances around the body. The blood carries many chemicals like glucose in solution. The balance between the water in cells and in the blood has to be kept. The kidneys help to maintain the balance with ultrafiltration, where any excess of substances, including water, are removed from the body. In the nephrons, inside the kidney, a high pressure is built up which squeezes water, urea, ions and sugars out of the blood and into the bowman’s capsule. As the substances flow along the nephrons, useful quantities are reabsorbed back into the blood. At this point, most of the water will be reabsorbed but there will be a little excess left over which will come out of the nephron, into the ureter and down to the bladder as urine. During this process, the water will also act as a transporting agent for the urea and the other waste products.
Another important reaction which involves water is respiration. The aim of respiration is to provide energy for the body to use. In this instance, the glucose is oxidised to produce energy, as well as carbon dioxide and water. Because of the aim of this process, water can be labelled a by-product or a useless product but it is actually very important that water can be produced. If water was not available, then it is possible that oxygen gas would be produced which would instantly kill humans (because the body would think that the person has cut themselves, which is why there will be oxygen gas, and the body would form a scab along all blood vessels, stopping all the processes of life).
Bibliography
Advanced Biology – By Roberts, Reiss and Monger. Published by Nelson
Information - http://ga.water.usgs.gov/edu/waterproperties.html mmmmmmlllhttp://daphne.palomar.edu/jthorngren/water.htm mmmmmmlllhttp://www.uni.edu/~iowawet/H2OProperties.html mmmmmmlllhttp://ga.water.usgs.gov/edu/waterproperties.html mmmmmmlllhttp://encyclopedia.farlex.com/Properties+of+water
