Water. A complex compound which is crucial in order for us to exist, yet we pay it hardly any attention…what is water? What is this miraculous liquid that provides us with so many things? Well, I’ll tell you: it’s much better than J2O, especially in the long run.
Let’s zoom in- look at water on a molecular level. Water, otherwise known as H2O, consists of the atoms Hydrogen and Oxygen, which are covalently bonded to one another. “What does that mean?” you may wonder. Let me explain. Atoms contain a nucleus which has two types of subatomic particles within- the protons and the neutrons- which give an atom it’s mass. They also have “shells”, aka energy levels; these energy levels contain the third type of subatomic particle: electrons. Whoa! Already so much more interesting than J2O.😊
Now most atoms do not have full outer shells, which are generally required in order for the atom to be stable, so naturally they would be unstable and looking for an atom to complete their outer shell. Kind of like the younger generation nowadays. 😉Thus bonds are formed.
Atoms of different elements have different numbers of electrons in their outer shell (just like how all of us are unique and different), meaning that they can all form a certain number of bonds for however many “spaces” they have. For example, Hydrogen has 1 electron in its outermost shell, and it requires 1 more to complete it; Oxygen has 6 electrons in its outer shell, and requires 2 more. If an Oxygen atom were to bond with Hydrogen atoms then they could be stable, just in a molecular form.
So, one day, an Ollie Oxygen met a Hollie Hydrogen and they got to talking…they both found that they had something in common: they both required a full outer shell! So after much deliberation they came to the conclusion that the best thing to do would be to share their electrons *aww* and stick together- literally. However, they soon realised that being a twosome wasn’t going to work and it (the number of electrons) wasn’t going to be enough, sadly. But then Oxygen came up with a clever idea and said: “Hey Hydrogen, you don’t happen to have a friend who is also suffering from the same problem as you, do you?” And Hydrogen then realised YES! Of course! Hallie Hydrogen! “I do! I can bring her along and we will have enough electrons!!” And that is exactly what happened…so Ollie, Hollie and Hallie lived happily ever after, saving lives and creating life all around the world…kind of like the three musketeers of atoms…
As you can probably guess, after all of that hard work, the three atoms were and still are, incredibly close. This process occurs with many Hydrogens and Oxygens all over the world…and all the molecules come together often, making and breaking Hydrogen bonds- which is rather unusual for liquids. The actual covalent bonds are incredibly strong and hard to overcome, but the intermolecular forces (forces between each individual H2O molecule) are incredibly weak, meaning that water has a low melting and boiling point. Cup of tea, anyone? ☕️
The thing with H2O and its bonding is that it is dipolar! What I mean by this is that when Hydrogen and Oxygen bond, the highly positive Oxygen nucleus pulls the shared electrons in closer, and as a result, making the Oxygen slightly negative. This is what makes a molecule polar but because there are two Hydrogens, the molecule would be called dipolar (not to be confused with bipolar).
Due to the strong dipolar attraction, water is a liquid at room temperature, rather than a gas (like less polar, but similar-sized molecules) as we would know from drinking it. Speaking of, water has very low viscosity, meaning it can flow easily.
The fact that water is a liquid at room temperature can open many things up regarding the uses of H2O; for example: provide habitats for living things in rivers, lakes and seas; form a major component of the tissues in living organisms; provide a reaction medium for chemical reactions and provide an effective transport medium e.g. blood and vascular tissue. You gotta admit- that’s more than J2O will ever do!
Water’s density is quite vital for fish being able to float. But also, so they don’t sink. When most liquids cool, they become more dense, and then become a solid, but with water, things are quite different.
Instead of the top layer freezing, sinking (and taking the fish with it🐠 )and then that whole process repeating until the mass of water is a block of ice, when water temperature drops to 4 degrees Celsius, the molecules align themselves in a structure which is less dense than water! This is the magic of water being polar. Because of this amazing water ability- for ice to be less dense than water– aquatic organisms have a stable environment in which to live through the winter, and ponds and other bodies of water, along with the fish, are insulated against extreme cold (the layer of ice reduces the rate of heat loss from the rest of the pond).
Water is also an incredible solvent; as in, many things can dissolve in water. What actually happens though is when the polar water molecule meets another polar molecule or ionic compound, the positive parts and negative parts are pulled towards one another- you know what they say about opposites attracting– and new bonds are formed (the solute “dissolves” and a solution is formed). Because water is capable of dissolving many things, molecules and ions can move around and react together in it- many of these reactions occur within the cytoplasm of cells (which are over 70% water!). Also, molecules and ions can be transported around living things whilst dissolved in water e.g. glucose, amino acids or vitamins and minerals around our blood- crucial towards our health (more than we can say for J2O…).
Ever seen drops of rain on a flat surface? Notice how the almost-spherical drops don’t spread out? Ever wondered why? Well, I can tell you why. It’s because of the hydrogen bonds between the molecules, pulling them closer- an example of: cohesion. The hydrogen atoms on the surface are bonded to the molecules underneath them as well, meaning they are more attracted to the water molecules underneath than the air molecules above. Because of this, the water contracts and gives water an ability to resist force applied to it- whoa! We call this surface tension.
Surface tension allows columns of water in plant vascular tissue to be pulled up to the xylem tissue together from the roots, and insects, like pond-skaters, can walk on water! Lucky lil bugs.
Let’s move on to the hot topic: water’s high specific heat capacity. What is specific heat capacity? Specific heat capacity is the amount of energy required to raise the temperature of 1kg of a substance by 1 degree Celsius. Water temperature is a measure of the kinetic energy of the water molecules; the hydrogen bonds keep the molecule held tightly together, therefore a high amount of thermal energy is required in order to increase their kinetic energy and temperature. But let’s go to H2O- water requires 4.2kJ of energy to raise 1kg of it by 1 degree Celsius; resulting in water having the property of not heating up or cooling down very quickly.
And, as we know, water is a component of many living things, plus it can often make up the habitat of some of these living things, making it and its high specific heat capacity very important. Living things, including prokaryotes and eukaryotes, need a stable temperature for enzyme-controlled reactions to happen properly. Aquatic organisms also need a stable environment in which to live.
We know water is more than helpful for us and other animals, but did you know water is also helpful towards itself?! Heat energy, now known as the latent heat of vaporisation, helps water molecules to break away from each other to become a gas during evaporation- helpful! Right? The super-strong Hydrogen bonds refuse to be broken easily, so a large amount of energy is required for water molecules to evaporate.
But how is this relevant to us? For homeostasis, my friend. Yes, when we sweat (for example, when we run), the sweat soon evaporates; and this happens so we cool down! (which means we don’t constantly have a headache). Similarly, plants are cooled when water evaporates from mesophyll cells- cool, no?
Now, lets zoom out…as you can tell by now, water is clearly more complex than you previously thought. But lets admit it: water is GREAT – more than we can say for J2O. But that’s another story….
Let’s raise a glass to H2O. Cheers!
More about Mahika: Hi! I’m Mahika. I am 17 years old and currently up to no good studying in Sixth Form. I like to think in a scientific and analytical way, much to the annoyance of my poor mother, whom I treat as if she is an encyclopaedia of facts! However, I love artistic expression and practice it often through art, singing, dance etc… But what’s even better is the satisfaction I get from combining the two; writing in an artistic form whilst talking about science! I hope you also get the same satisfaction from my little essay on water, and learn something new today. 😊
