Water is one of the most important substances on Earth. Without water, life as we know it could not exist. But what exactly makes water so special and important? Let’s take a closer look at some of the unique properties of water that make it essential for life.
Water Is a Liquid at Normal Temperatures
Most substances are gases, solids, or liquids only at specific temperatures. For example, iron is usually a solid but melts into a liquid at high temperatures. Water is unique because it is a liquid at the temperatures typically found on Earth’s surface.
If water froze at 50°F instead of 32°F, most Earth’s water would be frozen solid! The fact that water is liquid at normal temperatures allows it to flow, evaporate, and be used by living organisms.
Water Is Polar
Water molecules have a slightly positive charge on one end and a slightly negative charge on the other end. The presence of polarity in water molecules makes them uniquely special. The positive and negative ends attract each other like weak magnets.
This polarity allows water molecules to stick together. It also lets water dissolve many ionic compounds and other polar substances. This is incredibly important for life – it allows water to transport nutrients in and out of cells.
Water Has Strong Surface Tension
Surface tension happens when water molecules on the surface stick together tightly, forming a “skin” on top of the water. This surface tension enables objects like water striders to walk on water without sinking.
It also allows tubes and veins in plants and animals to draw water upwards against gravity. Capillary action from surface tension pulls water through soil to reach plant roots.
Water Has High Heat Capacity
Water can absorb a lot of heat before it begins to get hot. It takes about five times as much heat to raise the temperature of water compared to the same volume of air.
This high heat capacity helps regulate Earth’s temperature. It also helps regulate body temperature in humans and other animals.
Water Expands When It Freezes
Most substances get smaller when they freeze and become solids. But frozen water (ice) is actually less dense and takes up more space than liquid water.
This is because water molecules form a crystal structure when frozen that pushes molecules slightly farther apart. If ice sank, bodies of water would freeze from the bottom up, which would be disastrous for life.
Water Is a Universal Solvent
Water is sometimes called the “universal solvent” because it can dissolve more substances than any other liquid. This allows water to easily transport nutrients, minerals, and other important compounds through itself and through living organisms.
Water Has High Heat of Vaporization
It takes a lot of heat to turn liquid water into water vapor or steam. This is because hydrogen bonds between water molecules must be broken in order for water to evaporate.
This high heat of vaporization allows water to absorb large amounts of heat from the environment without large temperature changes. Sweating takes advantage of this property to cool human bodies.
Water Exhibits Cohesion
The hydrogen bonds between water molecules create cohesion, or a tendency for water molecules to stick together. This cohesion allows trees and plants to transport water from roots to leaves.
Cohesion combined with surface tension allows water to flow upward from roots into small capillaries in plants. This passive water transport method is called capillary action.
Conclusion
As you can see, water has many special properties that make it essential for life on Earth. Water can dissolve substances, regulate temperatures due to its high heat capacity, prevent bodies of water from freezing completely, and facilitate transportation through plants and animals because it can stick to itself.
Earth is sometimes called the Blue Planet because over 70% of its surface is covered in water. Our lives depend on this unique molecule. Next time you drink water, remember to value its remarkable properties that make it precious.
References
Eisenberg, D., & Kauzmann, W. (2005). The structure and properties of water. Oxford University Press. https://global.oup.com/academic/product/the-structure-and-properties-of-water-9780195143011?cc=us&lang=en&
Ball, P. (2008). Water as an active constituent in cell biology. Chemical Reviews, 108(1), 74-108. https://pubs.acs.org/doi/10.1021/cr068037a
Franks, F. (Ed.). (2013). Water: A comprehensive treatise (Vol. 1). Springer Science & Business Media. https://www.springer.com/gp/book/9780306477878