Biology, Week 2 – Properties of Water

Describe some of the properties of water that make it so critical.

    Water is essential to life on earth. Without it, there would be no plants, animals, humans, and any other living organisms. Water is made up of one oxygen molecule covalently bonded to two hydrogen molecules. Oxygen, hydrogen, nitrogen, and carbon are considered the “big four” essential elements of life. These four can be combined to form most other important chemicals. Water has many interesting properties, such as heat absorption, solvation, and polarity. Many of water’s properties are something called emergent properties. Emergent properties are properties that neither atom had, but when bonded, those properties appeared. In this essay I will be talking about the properties of water.

    Polarity means that the molecules making up water have partial charges. Oxygen is slightly negative and hydrogen is slightly positive. What this means is that oxygen does not like to share electrons. The oxygen and hydrogen molecules in water are covalently bonded, but oxygen hogs more of the electrons. This unequal sharing of electrons with hydrogen molecules is called hydrogen bonds.

Hydrogen bonds can explain some interesting properties of water. When you jump into a body of water, you are breaking hydrogen bonds. This allows you to break the surface and submerge in the water. This is called surface tension. If you did not break hydrogen bonds, you would simply bounce off the surface of the water. This explains how water striders are able to walk on water. They do not break enough hydrogen bonds to sink below the surface. This also explains how water absorbs heat. When hydrogen bonds are formed, they release heat. Likewise, when they are broken, they absorb heat. So when you jump into water, you break hydrogen bonds, and those hydrogen bonds absorb your body heat, cooling you off. Heat absorption is one of water’s emergent properties.

Ionic bonds, another type of bond, explain why water can dissolve materials such as salt so easily. Whereas hydrogen bonds are formed when molecules unequally share electrons, ionic bonds are formed when a molecule “donates” an electron to another molecule. Let us take table salt for example. Table salt is made up of one sodium molecule ionically bonded to a chlorine molecule. The sodium molecule has one “loose” electron and the chlorine has one extra space in its outermost shell. The sodium donates its loose electron to the chlorine molecule, making salt. When you put a salt molecule in water and mix it, the electronegative chlorine is attracted to the slightly positive hydrogen, and the positive sodium is attracted to the slightly negative oxygen. The sodium tries to bond with the oxygen, and the chlorine tries to bond with the hydrogen. They get wrenched apart, breaking the ionic bond. That is why when you mix salt in water, it dissolves, and you can no longer see it. However, since the sodium and chlorine are still in there, it still tastes salty. Like heat absorption, solvation is also an emergent property of water.

Water is made up of two hydrogen atoms covalently bonded to an oxygen atom. It has hydrogen bonds which explain heat absorption and surface tension. Breaking hydrogen bonds absorbs heat and allows you to break the surface of the water. Water is also polar, which explains one of its emergent properties, solvation. The positive hydrogen attracts the negative chlorine, and the negative oxygen attracts the positive sodium. Together, the hydrogen and oxygen break the sodium chloride’s ionic bond. Water is essential to life as we know it. No living organism can survive without water.

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