Looking At Matter

Our universe consists of an enormous amount of space and a sprinkling of more substantial stuff that we can see and has solidity and weight that we call matter. Even though no one really knows what matter is, scientists are quite adept at describing its structure and predicting its behavior. It is obvious to everyone that matter is assembled into many different things from rocks to people to stars to galaxies. It has been the quest of science to discover and understand the underlying commonality of all these things. What is the basic stuff, and how does it interact to form the immense and wonderful variety of the things we know and the changes they undergo.

What science has found is that all objects matter forms are made up of countless, incredibly tiny bits of matter we call atoms. On the submicroscopic level, our world is a virtual sea of atoms, and like a sea the atoms are in constant motion--vibrating, rotating, and whizzing about. When a collection of atoms bind together in a relatively rigid structure, they form things that feel hard, appear solid, and have noticeable weight. We can’t see through solid objects because the atoms are packed too closely together allowing little space for visible light to get through. Even when atoms are locked together in a solid, they haven’t totally given up their movement. They still dance about in position. In fact, when we touch an object and feel its warmth, we are feeling the vibration of its constituent atoms. What we call temperature is simply a measure of atomic motion. The hotter the object, the more its atoms are vibrating. At temperatures above absolute zero (-273 degrees), atoms are always in motion.

When atoms are more loosely bound to each other so that they can collide, slide and move over and around each other, they form squishy stuff we call a liquid--the most ubiquitous example of which is water. Many liquids are transparent because the atoms are far enough apart providing space for light to pass through them. The average atomic motion in a liquid is higher than in a solid so that individual atoms occasionally have enough speed to break away from the mass of the liquid. In an open container, a liquid slowly disappears or evaporates. The higher the temperature of the liquid, the more agitated the atoms become and evaporation increases.

The freest atoms of all are those that form the gases like those in air. The atoms are far enough apart that they feel little attraction for each other. They move about with the speed of bullets, colliding and bouncing off each other. The gases in the air, for example, are ordinarily transparent and feel tenuous and weightless until we feel a breeze or the winds of a storm. Actually, the bombardment of air atoms create a pressure of about 14 pounds on every square inch of our bodies. Substances differ from one another in other ways than their form as solid, liquid, or gas.

There are countless different solids--rocks, metals, plastics, skin, bones, etc. If they are all made up of atoms, why do they differ so in their characteristics? One reason is that all atoms are not alike. There are 92 different naturally occurring atoms of which about half make up most of the things we are familiar with. When a substance is comprised of only one kind of atom such as a piece of iron, we call that substance a chemical element. Since there are 92 different atoms, there must be 92 chemical elements. Some are rare like gold and silver and others like nitrogen, iron, silicon, aluminum, and oxygen are very common. In fact, hydrogen is the most plentiful element making up more than 90 percent of the universe. Elements common to all living things including ourselves are carbon, oxygen, hydrogen, nitrogen, sulfur and phosphorus.

The vast variety of substances around us owe their existence to the fact that atoms not only have a tendency to hook up with each other, but also with different atoms. In so doing, a new substance emerges that often has totally different characteristics. When atoms of the poisonous gaseous element, chlorine, are mixed with the metallic element, sodium (a dangerous material itself because it combine explosively with water), common table salt is formed. A tiny spark causes a mixture of the gases hydrogen and oxygen to combine explosively to form water. The heat of the spark, accelerates a few of the oxygen and hydrogen atoms to collide violently enough to stick together starting a chain like reaction that ends up with all the atoms involved combined in the form of water. It is the interaction of atoms and their ability to associate into complex structures that produce the world that we know. Learning how and why these interactions take place provides the basics upon which to build and understanding of the great bulk of the happenings in our world and the whole universe, but that’s a story for another time.