Beautiful Chemistry

Okay, I need a moment to rant a little and reiterate what the purpose of my blog is. Chemistry is a beautiful science. Molecules, atoms, bonding-it is filled with all the lovely simplicities and complexities that give rise to our universe. I have just written about water and how crucial it is to life. Look at the immense diversity of life on this planet and realise that it is a simple molecule of two hydrogens and one oxygen that makes it possible. Even more amazing is my personal favourite molecule DNA. This simple, and I mean ridiculously simple especially when compared to the proteins that actually make up the human body, molecule is what encodes the amazing diversity that we see everyday. And yet this amazing and beautiful science is marred with fear-mongering and hate. 

I really can't stand this "chemical-free" culture that has arisen because it is a complete lie! Everything is a chemical. Life is chemical, water is chemical, the earth is chemical. Chemicals are diverse. Some are good, some are bad. Just like human beings. Some are nice, some are mean, some are okay on their own but terrible when they get together. Chemicals are not evil. Because chemicals are what makes up matter, you can't ever have anything that is chemical-free. It is blatant false advertising (can we get litigious about this?) and creates a culture of hate. The most damning chemicals in the world are nature-made poisons, a little strychnine anyone? Did you know that while asprin (acetyl salicylic acid) is man-made it is actually better for you than its natural counterpart, salicylic acid isolated from willow bark. This is because the acetyl group that chemists put on the the salicylic acid mitigates many of the harsh side effects that salicylic acid has. 

So what is the solution to help rail against those that would denigrate chemistry and chemicals? Well that is what I see the purpose of my blog as. Ask me your chemistry questions and I will answer them as non-technical as possible. I wish to spread the knowledge that I have gained in the 10 years that I have been studying chemistry and share it with the world to show the world there is nothing to be scared of and the chemistry is a big part of their lives, whether they know it or not. I encourage other scientists to do the same. We can't sit back and shake our heads, laughing or getting angry at the numerous people falling victim to this smear campaign. We need to take arms (metaphorically) and share our knowledge, making chemistry fun and interesting. Giving people the knowledge they need to combat the misinformation they are given on a daily basis. It is part of being an ethical scientist that we share what we learn, not just with other scientists, but with non-scientists as well.

Combat the fear-mongering with knowledge and education. chemical free nonsense 

Water Water Everywhere

If there was one molecule that I could spend weeks writing about, it would be water. It isn't a complicated structure, like strychnine. It isn't a huge money making pharmaceutical like Lipitor. This is the molecule that is required for life, and yet there isn't a single atom of carbon-the element that forms the backbone of life-in it. The presence of water is the single most important indicator for the possibility of life on other planets. You can live weeks without food, you can only live days without water. What is so important about this simple molecule that some of us are able to take for granted? Let's talk about its chemistry.

Water, aqua, eau, dihydrogen monoxide, whatever your word for it is, is made up of two hydrogen atoms bonded covalently to a single oxygen atom. A covalent bond is one where the two atoms share electrons between them. This is different from an ionic bond, where electrons are transferred from one atom to another to create ions, one positive ion and one negative ion, and these ions are then attracted to each other via that whole "opposites attract" thing, known in the science world as electrostatic forces. Table salt, or sodium chloride, is an example of a compound held together by an ionic bond rather than a covalent bond. That was a lot of jargon, so to simplify things, you can think of an ionic bond like two atoms dating, or living together. Each atom is currently content with the arrangement, but if things should go awry they can easily separate themselves and go on their merry way. Conversely, covalent bonds are atom marriages. Much bigger commitment, everything is shared between the two, and breaking up is much more difficult. So back to water. Water has a polygamous marriage happening, with the two hydrogen atoms. Also, not all atom marriages involve a 50-50 sharing of assets (electrons). Some atoms tend to be a little needier (or greedier) and will hoard more of the assets (electrons). Oxygen is one such atom. Oxygen is what we call an electronegative atom. To be specific, it is the second most electronegative atom on the periodic table (fluorine is the most electronegative). This makes oxygen a big electron hog. This results in the two electrons that make up the oxygen-hydrogen bond spending most of their time on the oxygen end of the bond. The result is that the hydrogen end of the molecule has a partial positive charge (a full positive charge would mean that we now have an ionic species-we don't.) and the oxygen end has a partial negative charge. This polarity of the bonds is crucial! When you have many water molecules together, they each have this polar bond (partial positive on one end and partial negative on the other). The molecules will then order themselves such that the positive end of one molecule lines up with the negative end of another molecule, in a fashion similar to ionic bonds. Now these bonds are much weaker than covalent or ionic bonds, but are still extremely important in dictating the properties of water. These bonds are called hydrogen bonds. 

Hydrogen bonds are what makes water highly cohesive and gives it a high surface tension. The surface tension is what allows insects like water striders to walk on its surface, and also what it hurts so much to do a bellyflop into a pool. This is also why water has such a high boiling point (100 C) where as similar molecules, like H2S, are gases at 25 C. Hydrogen bonds are also what makes ice float. In liquid water, there remains a lot of disorder, with these hydrogen bonds continually breaking and reforming. As the water changes state from liquid to gas, the amount of order increases. The molecules are frozen in such a way to maximise the bonds. This makes the solid state much less dense than the liquid state, and thus the ice floats on top of the river, pond, sea. Imagine trying to go ice-fishing if this wasn't the case.

The polarity of the water molecule is also key to life. Humans are over 60% water by mass. All living cells have a significant water content. Cells are made up of, and defined by, a phospholipid bylayer called the cell membrane. Phospholipids are made up of a head group that likes water (hydrophilic) and a tail group that doesn't (hydrophobic). When these phospholipids are mixed with water they arrange themselves in a two-layered sheet with the the tails on the inside of the sheet away from the water and the heads remain on the outside edge mixing with the water, forming a spherical species called a vesicle, that has water on the inside and the outside, but not within the wall.  As these vesicles evolved into more complex structures we got life that eventually evolved into the multicellular beings that we are. Crazy to think that it was the properties of water that dictated that evolution, eh?

References:

Pratt, C. W.; Cornely, K. Essential Biochemistry 2004, John Wiley & Sons, Inc. Hoboken, NJ.