Properties Of Water
- Science Holic
- 8 hours ago
- 3 min read
Author: Shuhan Yu
Editors: Serena Tsao, Miriam Heikal
Artist: Becky Li
Water is often not given a lot of thought, but it's ubiquitous and keeps things going. We drink it, we cook with it, our bodies are mostly made up of it, and the planet is mostly covered in it. What makes water remarkable, however, isn’t just how much of it exists- it’s the unusual properties it possesses. Features like cohesion, adhesion, heat capacity, being able to dissolve so many substances, and even why ice floats all add to water being special. Without these properties, life on our planet would not exist.
To understand why water acts so anomalously, it is helpful to look at its structure. A water molecule consists of two hydrogen atoms and an oxygen atom. Because of how the electrons are shared between the three atoms, the oxygen end is slightly negatively charged, and the hydrogen end is slightly positively charged. As a result, water is a polar molecule - one side carries a negative charge and the other a positive one. This polarity allows water molecules to form hydrogen bonds, which happen when the hydrogen of one water molecule is attracted to the oxygen of another. A hydrogen bond is basically a weak pull between the slightly positive hydrogen atom in one molecule and the slightly negative oxygen atom in another. Even though each hydrogen bond is weak on its own, there are so many of them that together they give water its unique and important properties.
One example is cohesion, the tendency of water molecules to stick to one another. You can see this property in converging water droplets or when you overfill a glass by just a small amount, and the water bulges up above the edge without spilling. This cohesion also produces surface tension, which allows small insects such as water striders to literally walk on water. Water also demonstrates adhesion when it sticks to other objects. For example, water moves up the thin tubes in plants by sticking or adhering to the walls of the tubes, as cohesion pulls the other water molecules along. This coordination of adhesion and cohesion, also known as capillary action, is the way that plants can pull water all the way from the roots to the leaves of the plant.
Another important property is the high specific heat of water: it takes a great deal of energy to heat water by a single degree. That is why large bodies of water, such as lakes or seas, take so long to warm up in the summer and to cool down in winter. Consequently, water controls the climate of Earth and regulates temperatures from getting too far out of balance. It also helps living things maintain constant body temperatures. Essentially, water acts as an insulator against sudden heat fluctuations, which is essential to the planet and to living things as well.
Water is also called the "universal solvent" because it can dissolve more substances than any other liquid. Its polarity allows water molecules to surround and separate other molecules or ions. That's why salt disappears when you put it in water—the positive and negative poles of water pull the positive sodium and negative chloride ions apart. In the human body, this property is required because it allows blood (which is mostly water) to carry nutrients, gases, and waste products throughout. Without this characteristic, cells would be incapable of acquiring the materials that they need to survive.
Lastly, water possesses a very bizarre feature when solid: it becomes significantly less dense as a solid compared to other substances, which makes ice float. Without this property, lakes and oceans would freeze from the bottom up, entombing and killing any aquatic organisms. Instead, it forms a layer of ice on the surface and prevents the water underneath from freezing, allowing fish and other life to survive the winter. It's one of those little things about nature that has a profound effect.
Water is so much more than something we swim in and drink. Its four major properties—cohesion, adhesion, high specific heat, universal solvent, and ice’s floatability—are all necessary for life. All these unusual features derive from its polarity and hydrogen bonds. Despite its prevalence, water isn't ordinary: it's why life is even feasible on this planet.
Citations:
Khan Academy. (n.d.). Water and life review. In Chemistry of life. Khan Academy. Retrieved from
https://www.khanacademy.org/science/ap-biology/chemistry-of-life/structure-of-water-and-
Kontogeorgis, G. M., et al. (2022). Water structure, properties and some applications – A review.
Comments