We all know what water is… or do we?
Sure, it sounds rather dramatic to suggest that I stare at water every time I encounter it, absolutely baffled by water as if it is an alien substance, but to some degree, I do. Whether or not I outwardly show it, I do often observe substances — such as water — when presented with them while questions fly through my mind: what is it made of; how does it interact with other matter; what causes it to have the physical properties that it has?
Some may say these questions can easily be answered: water is H2O, which means it is made of two hydrogen atoms and one oxygen atom, and its properties come from the fact that it is a liquid; done!
But you could take it a step further:
Why is water a liquid?
Consider NH3 (ammonia), which is one of the compounds that is most similar to water. Like water, ammonia is a simple, polar molecule that consists of a single non-metal atom bonded to hydrogen. One of the most obvious physical differences between the two compounds is that water is liquid under normal conditions while ammonia is a gas (unless ammonia gas is dissolved in water, which is the case in most forms of cleaning ammonia).
Water is a small molecule with very little mass, and like other molecules with low molecular mass, water should technically be a gas. Then what causes water to be a liquid?
Water molecules aren’t heavy enough to be a liquid on their own, but because water possesses a unique property called hydrogen bonding, the water molecules are pulled together just enough to land in the liquid phase and not the gaseous phase. Hydrogen bonding isn’t technically a bond, but it’s a phenomenon where the oxygen atoms in water pull the elections slightly closer to themselves, giving themselves a slight negative charge, while the hydrogen atoms, having their electrons pulled away from them, gain a slight positive charge. Because opposite charges attract, the hydrogen atoms of one molecule are slightly attracted to the oxygen atom of another water molecule, causing water molecules to cling to each other more strongly than they otherwise would have.
Why does water expand when freezing?
Another strange fact about water is that, unlike most substances, water expands upon freezing. This is strange because substances almost always condense and occupy less volume as they cool down, but the hydrogen bonds cause water molecules to spread apart and arrange themselves into a less dense crystal structure as water freezes.
Because the water molecules occupy more space, the water’s overall density is now lower and therefore these water crystals (more commonly known as ice) float on liquid water.
Is water an acid, or is it a base?
Water is both an acid and a base, but it is neither an acid nor a base.
Well, how do you figure that? Technically, water is neither, but it could be considered both because of what makes up acids and bases.
Simply put, an acid is a compound that contains positively charged hydrogen ions (H+), and when placed in water, an acid increases the number of hydrogen ions in the water, but when a base is dissolved in water, it increases the number of negatively charged hydroxide ions (OH–). Interestingly, when a base and acid react, the hydrogen and hydroxide ions combine, leaving behind water (H+ and OH– equals H2O).
Therefore pure water is completely neutral, only consisting of water molecules; acidic water contains more hydrogen ions; and basic water contains more hydroxide ions.
Water’s ability to act as either a base or an acid has led some people to give water the unofficial name hydroxylic acid, which suggests the presence of a hydroxide ion, indicating that it is a base, though simultaneously labeling it as an acid.
What do you think about water?
Onward American 