Why is it so special?
Water. It covers two thirds of the earth and is the essential to all life and the world as we know is would not be the same without it. Water is among one of the most abundant substances on earth and it is key to survival. It is vital for transporting substances around the body making it an excellent transport medium. This is because it dissolves more substances than any other liquid. Water is also a part of photosynthesis which is what plants rely on and water in itself acts as a habitat for a large variety of life. In this way water is so important. Despite its simple structure, water is extraordinary in its properties. It is made up of hydrogen and oxygen atoms and there is an attraction between the slightly negative oxygen of one water molecule and the slightly positive hydrogen of other molecules. This creates an electrostatic attraction and results in the water being sticky. Each molecule will attract others to form a liquid that has the ability to transport substances. This characteristic is particularly important in the way that water moves through a plant as it demonstrates how it has the right amount of fluidity. Water is the base which chemical reactions work upon. Within cells reactions occur in water due to its ability to dissolve many substances. This comes from the nature of its polarity. Water molecules are polar as they demonstrate a separation of charge which allows covalent substances to dissolve in it unlike some solvents e.g. ethanol. Another intriguing property of water would be that as it cools it contracts, however at 4°C the molecules do the opposite and the structure begins to expand. This means the spaces between the molecules become wider and the density therefore decreases. The result of this is that the solid form, known as ice, floats on its liquid form. This makes water very unique as no other substance displays this capability. In its solid form, water is very interesting. There is proof that ice can come in 15 different forms which explains the complexity of its structure when the water is frozen. A hexagonal structure is formed which then leaves gaps in between the molecules. Linking to the fact that water molecules are adhesive, other molecules such as nitrogen and methane can become trapped within the hydrogen bonds. These substances can only escape when the ice melts and structure collapses and the molecules become close together again. On a body of water there is evidence of a high surface tension due to the greater attraction in the water molecules below the surface due to the hydrogen bonds in comparison to the water molecules on the surface in contact with the air. Tension is created due to the water molecules contracting and maintaining its structure. This, again makes water key for transport within plants. The chemistry of water – when was it discovered? Before the chemical revolution around the 1780’s, water was believed to be an element and no one truly understood its structure. The real chemistry of water was discovered by a man known as Antoine Lavoisier who determined the fact that water was in fact made up of two different elements, oxygen and hydrogen. This was further researched and in 1800 a scientist called William Nicholson passed electricity through slightly acidic water and discovered that the volume of hydrogen and oxygen that was given off was in the ratio 2 parts to 1 part (2:1). It wasn’t until the middle of the 19th century that water was classed as the parent of a whole class of molecules. What are scientists still trying to find out about water? To this day, scientists are still working at unravelling the remaining mysteries of water. For example; they are still unable to explain why ice is slippery and scientists are trying to understand what happens at the surface of ice to try and explain this. Research is also currently looking into the way in which the hydrogen bonds reform and change themselves whether it is due to the bonds flickering on and off or the water molecules rotating slowly or even due to assistance from surrounding molecules. At the moment scientists are doing in depth studies into this key area involving the complexity of the bonds that make up water. Research into ions and the relation to water is also a key area as scientists want to know more about how the water surrounds the ions and the significant difference that the ions make to the structure of the water. Through practical observation and theory, there is continued developments in what makes water so special and, to this day, scientists are still overwhelmed by the uniqueness of this compound.
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Ciara Branagan
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October 2016
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