Our journey continues! Last time, we learnt a bit about the strange properties of water, a molecule that shouldn’t exist as a liquid at normal conditions. A liquid that expands when frozen and it’s all thanks to special chemical bond – hydrogen bond.
That’s not all where the hydrogen bond plays a role! Have you ever wondered why, for example a water strider, can move on the surface of a lake or pond. Water striders don’t fall under water because of the water’s surface tension. You may notice it when you pour water in the glass, you can put a little bit more than is the volume of the glass with water level over the glass’ rim without spilling. Almost no other liquid allows you to do that. And again, we can thank hydrogen bond to allow that!
Water molecules display an incredible ability to stick to each other. In the liquid form, the hydrogen atoms of one water molecule are attracted to the oxygen atom of another water molecule. Each water molecule can form up to four of these hydrogen bonds. At the surface, though, the most outer layer of molecules, has fewer molecules to cling to, therefore compensates by establishing stronger bonds with its neighbours, this leading to the formation of the surface tension – upper layer acts more flexible to keep low energy state (remember, everything in the universe is lazy and wants to have the least possible amount of energy). This cohesiveness of water molecules is totally unique among liquids. Water molecules simply stick together, which is something humans should also do!
The importance of the hydrogen bonds in water doesn’t end there. The way water molecules stick together helps life on Earth tremendously. Water molecules in your body are able to pull each other even through the tiniest blood vessels carrying oxygen and nutrients to parts that would otherwise be hard to reach. The bond is so strong, it allows water to move naturally against the force of gravity! Thanks to that, plants can suck water up from deep below the surface to nourish the leaves and branches that grow in the sunshine.
We take this ability for granted but our everyday life is dependent on it. Because of it, we can pump water around the radiators in our homes and water the plants in our gardens. This stickiness of water molecules to each other also makes very difficult to compress it, the water molecules are already very close. And the magical thing is that when something is hard to compress, the easier it is to move it around if you apply a pressure to one side of it.
Of course, all liquids are considered as in-compressible but water does it on a totally different level. Even at the deepest point in the ocean, the water gets its volume squashed just by few percent!
Fun fact: In movie Gravity (2013), Sandra Bullock cries at weightless state and her tears float around to make cool 3D effect. The reality is still cool but probably less cinematic. All tears would accumulate on your face and would stick to it. Their strong surface tension would not allow them just simply float around. Check videos of astronaut Chris Hadfield on YouTube, he shows how differently things act at the state of weightlessness.
Moreover, water doesn’t just stick to itself. It sticks to anything! There is no more universal solvent than water. Many scientists tried to find some but this is probably one of those cases where you cannot do better than nature. Sodium chloride (also known as a common salt) easily dissolves in water. The hydrogen bonds pull the sodium and chlorine atoms away from the crystal, leaving them to float freely. Water loves to do that with a lot of things, which is the reason why it practically doesn’t exist in a pure state. Almost every known chemical compound will dissolve in water at least little bit! By little bit, I mean to a detectable extent. This all also causes that water is one of the most reactive and corrosive chemicals we know.
This ability is a key to life’s existence. Water can dissolve various kinds of nutrients and move them through our bodies wherever they’re required. None of the fundamental molecules of life – DNA, proteins, molecules that make up cell membranes, etc – wouldn’t work (or maybe even form) without water. These complicated, sophisticated molecules have been shaped throughout billions of years of evolution of trial and error. They can have certain sections easily soluble in water, using hydrogen bonds, and other sections that repel water, like oil refusing to mix. The billions and billions of molecules with varying shapes and sizes inside your body only fold into the right structures to do their jobs because their interaction with water helps them to form the correct three-dimensional formats.
There is still more! Like Mpemba effect when hot water freezes faster than cold water! Why is that? We don’t know! There are theories but none explains it completely. To describe all peculiar things about water, I would need a whole book, there is some for sure.
Water is so common to us. It’s absolutely everywhere, yet we still don’t know everything about it. We drink it, we wash things with it, we clean ourselves with water, swim in it, we boil it or freeze it…our bodies are from 70% just water!
I am now a blob of water writing about water and hoping that some other blob of water will like it enough to return next week for another dose of knowledge about water!
Next time, we’ll move from the scientific area to more practical area in relation to drinking water. See you next week!