Unlike laws made by humans, the laws of nature cannot be broken – not even by Al Gore. We have discovered many natural laws, among them the law of conservation of matter. This law states that matter cannot be created nor destroyed. This is important for many reasons, including the fact that Earth is not growing or shrinking – and barring the occasional stray meteorite, its mass remains constant.
Making up that mass are the elements, which are composed of atoms. For the Earth’s “biosphere” – the crust, oceans, and atmosphere – the most abundant elements are first, oxygen (49.2%); second, silicon (25.7%); third, aluminum (7.5%); followed in order by iron, calcium, sodium, potassium, magnesium, hydrogen and titanium. All of the other one hundred or so known elements make up the last one percent of the mass of the biosphere. This includes some elements that are essential to all life on this planet: carbon, nitrogen, phosphorus, and sulfur.
So other than oxygen and hydrogen, the other “life elements” are present at relatively low levels. It’s a good thing that they cannot be destroyed, as the law of conservation of mass tells us! They can exist in many different forms, however – not just as individual atoms of each element. Most of the time, these elements are part of different compounds – substances that are made up of two or more elements in varying combinations. For example, water is a compound made from two elements, hydrogen and oxygen. Two hydrogen atoms combine with a single oxygen atom to form a water molecule.
Today we are examining carbon in its various forms. Carbon can exist in an elemental form, and we see this in diamonds, graphite, and coal. Yes, each of these is 100% carbon. The different appearances and properties of these substances can be attributed to varying crystalline arrangements of the atoms.
Single carbon atoms are frequently combined with a pair of atoms from the most common element on our planet, oxygen, to form carbon dioxide. This gaseous substance forms about 0.033% of Earth’s atmosphere.
Carbon can exist as the central element in most biomolecules. Fats, proteins, and carbohydrates are all compounds that contain carbon. We call substances that contain carbon “organic” compounds. I commonly refer to Earth as the Water Planet, but as far as life is concerned, we could also consider ourselves the Carbon Planet. Stated quite simply: no carbon, no life.
Carbon is also the central element in many manufactured products. All plastics contain carbon, as do most fertilizers, pesticides, herbicides, and industrial solvents. So carbon compounds can be natural or synthetic.
The world of carbon is incredibly diverse, with a host of substances that are part of the organic chemistry of Earth. Tomorrow, we will look at how these substances react with one another, and how carbon changes from one form to the next – but the total amount of carbon on Earth remains constant, as dictated by the law of conservation of mass.