We all know that water is essential for life. In fact, all organisms are made mostly of water and live in an environment dominated by water. What makes water so important? What are some unique properties of water? Read this article to find out!
Polarity and Hydrogen Bonds
The chemical formula of water is H2O, meaning that two hydrogen molecules and one oxygen molecule make up water. However, when the atoms share their electrons, oxygen tend to pull the electrons to itself more, causing an unequal sharing of electrons and the formation of polar covalent bonds. This also results in the partial negative charge for oxygen and partial positive charge for hydrogen. The polar property of water and the partial positive and negative charges enables hydrogen bonding between each water molecule. Hydrogen bonds constantly form, break, and reform, which gives water its unique properties.
Cohesion and Adhesion
Cohesion refers to water molecules’ ability to attract each other, and adhesion refers to their ability to attract other substances. Cohesion and adhesion could not be made possible if hydrogen bonds are not present. Hydrogen bonds hold water molecules together, which make water structured.
Plants getting water from the roots is an example of the cohesion and adhesion properties of water. When the water from the leaves starts to evaporate, hydrogen bonds allow the water molecules to be interconnected, thus pulling water up from the root. Meanwhile, adhesion allows water to move upwards against gravity.
High Surface Tension
Have you ever wondered why some insects can walk across a lake? Surface tension refers to the measure of how hard it is to stretch or break the surface of a liquid, and the collective strength of hydrogen bonds allows water to have high surface tension.
High Specific Heat and High Heat of Vaporization
Water has the ability to absorb heat from the air that is warmer and release the stored heat to the air that is cooler. Due to the strength of collective hydrogen bonds, it takes a lot of energy, or heat, to warm up water. This also allows water to have high heat of vaporization - the quantity of heat a liquid must absorb for one gram of it to be converted to gas.
Expansion Upon Freezing
When ice and water are placed together, it is the ice that always floats, meaning that the solid state of water is less dense than the liquid state of water. This is a rare condition as most liquids’ solid states are denser. Hydrogen bonds are spread out far apart when water is in the solid states, causing it to be less dense. This is an important property as it allows the existence of aquatic life - the fishes wouldn’t freeze with the ice when it is cold!
Water as a Solvent
Due to its polar nature, water is able to dissolve ions and polar substances such as sodium chloride (NaCl). Hydrophilic refers to a property of any substance that has an affinity for water, while hydrophobic refers to a property of any substance that is nonionic and nonpolar and seems to repel water. Cell membranes are made up of two layers of phospholipids, with hydrophilic heads and hydrophobic tails. When being in water, the hydrophilic heads automatically face outward and interact with water, while the hydrophobic tails face inwards. This structure is called phospholipid-bilayer, and it is selectively permeable, allowing vital functions of the cells to be carried out.
Hope this article helped you learn more about the properties of water! Thank you so much for reading!
Written by: Benetta Wang
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