Bio-Chemistry
The wonders of dihydrogen monoxide
You drink it everyday, but you take for granted the many miracles of H2O. Water is a polar molecule (due to unequal sharing of electrons between the Hyrdogen atoms and the incredibly electronegative oxygen atom) with a bent shape, with 2 lone electron pairs around the central atom, oxygen. H2O's unique properties come from those two electron pairs around the central atom-this allows H2O to bond up to TWO other molcules, through Hydrgoen Bonding (a.ka. H-bonding). This property alone allows water to have some of the most phenomenal properties, like ice being less dense then liquid, aqueous water!!! Even cooler, our beloved dihydrogen monoxide is the only molecule to natuarlly exist on Earth in all three states of matter!!! WOW!
Properities of H2O
1) Cohesion: the ability for H2O to bond to itself; water constantly uses Hydrogen bonds to link itself to other water molecules. We can see an example of this in nature, when water travels up the roots of a tree, by connecting with other water moleucles.
2) Adhesion: the ability for H2O to cling onto other substances; water connects with other substances through Hyrdogen bonds. An example would be when H2O clings onto cell walls.
3) High Surface Tension: surface tension is defined as how hard it is to break the surface of a liquid. H2O usually has a greater surface tension than other liquids, creating H-bonds with vapor, giving it a stronger surface. Because of surface tension, some animals have the ability to walk/travlel upon H2O's surface.
4) High Specific Heat: specific heat is defined as the amount of heat needed to change the temperature for 1°C for 1 gram of a substance, and is usually measured in Joules/gram°C. Water's specific heat is 4.18 J/g°C, which is incredibly high. Much heat is absorbed to break the H-bond, and heat is also absorbed when H-bonds form. It takes a lot of heat to change the temperature of H2O, because much of the heat is being used to break the H-bonds (than to move the particles). And when water temperature drops, many H-bonds form, releasing a lot of heat. Did you know, that in the winter, the cooling water can warm up the air?
5) Heat of Vaporization: heat of vaporization the amount of heat needed for a liquid to turn to a gaseous state. Water has a high heat of vaporization, due to H-bonds (which are broken in order for liquid water to become a gas). This property causes steam burns, when steam condenses into liquid on the skin.
6) Evaporative Cooling: Evaporative cooling is the cooling that takes place after evaporation has occured. The "hottest" molecules leave to a gaseous state-the rest are relatively "cool." This property provides stability in H2O molecules, like sweat prevents overheating of a body.
7) Universal Solvent: H2O is a highly polar molecule, and it dissolves all polar and ionic substances. Solvents with similar intermolecular forces have the ability to dissolve solutes, hence the idea "like dissovles like." Water has the ability to dissolve substances with ionic bonds, such has NaCl (salt)! Likewise, we have the hydrophillic term (a substance that readily absorbs or dissolves in H2O) and hydophobic ( a substance that repels from water; they cannot form H-bonds, due to interactions between nonionic and nonpolar substances).
8) Denisty factor: Water expands as it goes to a solid form-it become less dense (unlike most substances). Again, this is due to H-bonding; when it becomes too "slow" to break the H-bonds, H2O becomes a solid. But H-bonds keep moleucles close enough to be less dense in sold form. We owe life to this!!!
