Hello followers. I apologise for the long delay since my last entry; as many chemists will understand, I had an exam to prepare for. An exam which is the most important of the Ph.D. path. So I can now get back to entertaining your chemistry questions (please keep them coming). During my hiatus, I also took in a chemistry conference in Hawaii. It was there that the inspiration for today's blog comes from. Here is a picture of a packet of sunscreen. If you notice, it says that it is "chemical free". So what is in this sunscreen? Let's take a look at the back of it: Active ingredients are zinc oxide and titanium dioxide. Those sound like chemicals to me.Chemistry is the study of matter; therefore, anything that has matter is a chemical. Matter is comprised of atoms. Anything with atoms is a chemical. I am sure you can now see where I am going with this. This sunscreen is a chemical. This makes this packet blatant false advertising. If it isn't matter, then what is it? Energy?
This to me highlights one of the many negative public images that chemistry has and that chemists like me try to fight against. Just because something is a chemical, doesn't make it evil or dangerous! This actually goes hand-in-hand with the idea that just because a chemical is natural it is better. This one always makes me scratch my head as the most toxic things on this earth are nature made not man made. We have yet to even come close. Some chemicals are dangerous. Some cause cancer. Others can cause burns. Some will kill you. But you use chemicals everyday, and some are great. Some fight cancer. Can you imagine life without medicines? Those are chemicals. Imagine life without PLASTIC. Hell, imagine life without matter. Without chemicals there wouldn't be life.
Also, be careful when using things that say "natural, chemical-free". Often what these products are made of are botanicals (chemcials from plants). These are still chemicals and it is very easy to develop allergies to these chemicals, especially if you already have a sensitive skin. (This comes from a personal anecdote and the advice of a doctor.)
Let's talk about matter for a bit. As I said, matter is comprised of atoms (side note: the concept of the atom was proposed by Democritus of Abera around 300 B.C. long before John Dalton in 1803 A.D.) When we talk about elements, we are talking about a substance that is comprised of only a single type of atom. Copernicium is the newest element: symbol Cn, number 112. When we take about molecules (I, for example, am a small molecule synthetic chemist) we are taking about compounds comprised of more than one atom type. Example: Hydrogen is an element; it is comprised of only one type of atom. Water is a molecule; it is made of hydrogen atoms and oxygen atoms. Chemical changes or reactions refer to the conversion of one (or more) type of matter into another type of matter. For example: converting water into hydrogen gas and oxygen gas. Remember: matter cannot be created or destroyed, but merely change form.
I mentioned that I am a small molecule synthetic chemist. What this means is that my research is concerned with making small molecules. But what is meant by "small molecule" especially considering we are talking about atoms here. To measure molecules we talk about their atom/molecular weight and this is in the units grams per mole (g/mol). (The concept of the mole is a whole other entry so I will skip over that for now.) To get the molecular weight you simply add the atomic weights of all atoms in the molecule. Hydrogen is 1g/mol; oxygen is 16 g/mol; water, which has two hydrogen atoms and one oxygen atoms, is 18 g/mol. A "small molecule" is generally considered to be one under 700 g/mol. There is another type of molecule called "macromolecules". These are molecules whose molecular weight is well over 1000 g/mol. These are generally polymers. So things like DNA, proteins, and plastics are all macromolecules. You are one big, walking, talking collection of macromolecules!
Hopefully I have dispelled some previously negative views you had about what exactly chemicals are. Keep those chemistry questions coming friends!
References:
Petrucci, R. H.; Harwood, W. S.; Herring, F. G. General Chemistry 8th ed. 2002; Prentice Hall Inc. Upper Saddle River, N. J.
Gray, T. The Elements 2009, Black Dog & Leventhal Publishers, Inc. New York, N. Y.
