Defined Words: water, oxygen, hydrogen, polar, Universal Solvent, cohesion, specific heat, cloud
Water is the most essential molecule for life as we know it, and it might be the most versatile molecule on our planet. The structure of water grants it incredible abilities beyond that of other molecules.
Each water molecule is composed three atoms. It has a central atom with 8 protons and 8 electrons called oxygen. The outer electron shell of oxygen only has six of its total eight spots filled. When the shell is filled, the overall energy reduces and the molecule stabilizes. To fill up the last two spots, two hydrogen atoms, the element with 1 proton & 1 electron, pair with each oxygen atom to give it the familiar chemical formula H2O.
Electrons pair to cancel their spin. Two of oxygen’s electrons pair with an electron from hydrogen while the other four group into pairs. These electron pairs sit on one side of the molecule while the hydrogen atoms sit on the other side. The electron pairs cause a local negative charge while the protons of the hydrogen atoms cause a local positive charge. A molecule that has two oppositely charged poles is called polar.
The polarity of water is strong enough to separate ionic compounds that are composed of charged ions. For example, when you introduce salt into water, the positive poles of the water will surround and isolate the negative chloride ions while the negative poles isolate the positive sodium ions. It’s water’s ability to separate compounds with charged parts that gives it the title of Universal Solvent. Of course, water cannot dissolve everything since nonpolar compounds can only be dissolved by other nonpolar compounds, like soap. Water, while soft to the touch, can eventually carve away at mountains and create natural marvels like the Grand Canyon.
Water’s polarity also gives it the ability to stick to itself and other compounds with charge. The hydrogen atoms of some molecules are attracted to the electron pairs of another molecule, keeping a drop of water together. Water’s attraction to itself is called cohesion and it explains another aspect of water’s versatility.
The hydrogen bonds that form between water molecules are much stronger than other compounds. A significant amount of energy must be absorbed to vibrate the molecules enough to break the bonds. This means water will absorb a lot of energy before it changes temperature; we call this the specific heat.
Water’s high specific heat means that it can absorb a great amount of energy from the surroundings. There’s a reason it feels significantly cooler after a rain or why it’s less hot when you’re sitting by the pool. You can see this in action if you pour a cup of cold water into a pot of boiling water: the boiling will stop for a moment as the energy is absorbed by the cold water.
Hydrogen bonding allows water to stick together as a liquid, but it also gives the solid form a lattice structure since each molecule is bonded to four others. The grid-like structure of solid water means that the molecules are farther away from each other in the solid form than the liquid form. This makes water very unique among other compounds, but more importantly it means that ice floats.
Almost every other compound is most dense in the solid form but water is the exception and it allows for something incredible. When our planet lost its carbon dioxide blanket and froze, the oceans were covered with ice. The fact that ice floats means that the water underneath the ice can remain liquid. If ice were denser than water, it would freeze from the bottom-up and kill everything living in the oceans. However, the floating ice insulated the water and allowed life to persist and adapt.
Our planet is far too close to the sun for any water molecules to remain when the planet was forming. It was too hot here and water was too light. The majority of water in our universe is found farther away from stars as ice in space. A rocky body is called a “comet” if it has water in it until it loses its water and the name changes to an “asteroid.” The halo and tail you see around a comet is nothing more than evaporating ice from the sun’s energy. The water on our planet was likely delivered from passing comets.
Water is so essential for life on our planet and the climate is perfectly suited for water’s phase changes. When water molecules absorb enough energy from the sun to break the hydrogen bonds, the less dense gaseous molecule will rise up until it reaches a less dense layer of the atmosphere.
Once it enters the next layer, it will stick to other gaseous water molecules forming a mixture of water and air called a cloud. When the cloud accumulates enough water molecules, it becomes too dense to exist and falls back down in a liquid form. This cyclical process recycles water all over the planet, purifying it as it evaporates.
We would not exist without water and now that we have reached the level of global society, it’s our job to make sure we keep our water safe. The increased use of carbon-based fuels and other chemicals of the industrial world spells trouble for clean water. Many regions plagued by factories experience a mixing of carbon dioxide and water, making the rain acidic which harms the local ecosystem.
Never forget how important water is; never forget how amazing it is either. Find something to love about water and use it as motivation to help protect it and keep it clean. It’s up to us. Water is life.