In my first blog I will be discussing the properties of water and what makes it so special. This will help answer how water is essential for life on Earth and how it has enabled even the largest organism to flourish. In this blog we will also explore how the chemistry of water was discovered through time, and the secrets we are still attempting to unravel.
Water possesses many unique properties which we often don't consider to be important that are unlike many other molecules: The fact that water is a liquid at room temperature is the most important quality it holds. Because of its polar covalent bonding, (with hydrogen at delta positive and oxygen at two delta negative) strong hydrogen bonds form between molecules which makes the intermolecular force harder to break, increases its boiling point. This gives water a high specific heat capacity (heat needed to raise BP by 1 degrees centigrade) allowing stable conditions for habitats such as aquatic life to flourish in lakes and oceans. Water being in a liquid form also makes transportation within organisms far easier than a highly viscous or solid solution. It can also act as a medium for reactions to take place because it is in a liquid. The fact water is colourless is also a very important feature as it is responsible for the evolution of life beyond prokaryotes. Although we cant be certain, it is widely accepted that life on earth began approximately 3.6 billion years ago in our oceans. Life started as simple, single celled organisms known as prokaryotes A prokaryote is a single-celled organism that lacks a nucleus, mitochondria, or any other membrane-bound organelle. For life to evolve into the complex eukaryotes which are the cells that make up most modern day organisms it had to cross over through the vital stage of cyanobacteria which is a slightly more complex form of single celled organism that relies on photosynthesis. Therefore without colourless water the cyanobacteria would not be able to photosynthesise underwater thus halting life at prokaryotes. Another property that water has allowing life on Earth to flourish is its cohesion. Hydrogen atoms have single electrons which spend most of their time toward the oxygen atom, leaving their outsides positively charged. The oxygen atom has eight electrons, and often a majority of them are around on the side away from the hydrogen atoms, making this face of the atom negatively charged. Since opposite charges attract, the hydrogen atoms of one water molecule like to point toward the oxygen atoms of other molecules. This creates what's known as "hydrogen bonds" between molecules make water extraordinarily sticky. This is vital for life in plants as it allows plants to draw up water in long chains through the xylem. This allows plants to effectively siphon water against gravity and draw up water through the stalk for photosynthesis. Because of these "hydrogen bonds" water also holds a unique property when freezing. Usually when a liquid freezes, liquid particles move closer together and form strong bonds with one another. This allows more particles in the same area, the solid is denser than the liquid. However when water freezes the negative charges on the oxygen push the particles apart. This means that at 4 °C it becomes less dense as the water molecules begin forming hexagonal crystals of ice as the freezing point is reached. This is important for life as if ice did sink, it could cause entire lakes and other collections of water to freeze solidly, killing all life. Instead floating ice that's less dense forms an insulating layer over the lake preventing it from freezing. This allows life in lake to continue and not freeze. However if there was very little water none of these properties would be essential. Water is special because of is its abundance; water is the 2nd most common particle after hydrogen and makes up 70% of our planets surface area (300 million cubic miles). This allows ideal conditions for using water in photosynthesis and drinking, as well as ideal living conditions for aquatic life. The discovery of the chemistry of water started in 1766. An Englishman Henry Cavendish isolated a gas that he called "flammable air" because it burned readily. Priestley noted that when flammable air and common air were ignited with a spark in a closed vessel, a small amount of "dew" formed on the glass walls. When Cavendish repeated the experiment, he found that the dew was actually water. This is know as the oxyhydrogen effect Cavendish assumed that water was present in each of the two airs before ignition. In June 1783, Lavoisier reacted oxygen with inflammable air, obtaining "water in a very pure state." He correctly concluded that water was not an element but a compound of oxygen and flammable air, or hydrogen as it is now known. Despite the amount of research put into water scientists still do not know everything. Ice still holds many questions; the hexagonal lattice shapes in ice can be altered if pressure and the temperature of this ice is changed. Ice can rearrange itself into 15 known different ways showing how the properties can be changed without affecting the formula. However scientists are still unsure how this works and are also convinced there are still more formations of ice to be discovered. It is also not fully understood why ions act differently around water. When an ion comes into contact with water the structure of water is changed causing it to immerse itself around the ion.
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