We have always been here in one form or another and always will be. This may be a frightening thought to some, but we are in fact everlasting. The matter that we are composed of may change in shape or form, but will always be somewhere in the universe. Even time as we think of it does not necessarily just go forwards, it could go backwards or sideways depending on conditions.
It was a Greek philosopher, Democritus, who, about 400 BC coined the name atom for the smallest piece of matter known at that time. The name means uncuttable, which, until recently was the commonly held belief.
The three states of matter known today are solids, liquids and gases. These states can be changed by the application of heat or pressure. Water at below 0 degrees Centigrade changes to a solid, ice, and at 100 degrees Centigrade to a gas, steam. If the pressure of the atmosphere, commonly known as atmospheric pressure, is reduced water will boil at a lower temperature.
Matter is composed of chemical elements, such as oxygen and sulphur, pure substances that cannot be broken down. Each element has its own particular type of atom which can combine with atoms from other elements to form a different substance called a compound. One atom of oxygen, O, combined with two atoms of hydrogen, H, makes the compound water H2O. A combination of atoms is called a molecule.
Each type of atom has a set number of chemical bonds, called valency bonds, which act as handles to link it to other atoms. Each hydrogen atom has only one bond or handle, whilst each oxygen atom has two bonds, therefore one oxygen atom can link to two hydrogen atoms. In this way a model can be made of even the most intricate compound to show its chemical composition. The most common atom is carbon which has four bonds allowing it to link to numerous other atoms to form complex molecules. Diamonds are composed of a three dimensional lattice of pure carbon atoms, formed under pressure which makes them extremely hard. Another form of carbon is Buckminsterfullerine, called Buckyballs, which are globe shaped clusters of carbon atoms found in soot.
In the early 1900s Ernest Rutherford discovered that each atom has a positively charged nucleus circled by negatively charged particles called electrons, the unit of electric current. Electrons in the outer layer of an atom can leak into the adjoining atom to form a bond, as in electrolysis, where a metal immersed in acid is transferred to the surface of another metal by electricity. Metals share these outer electrons making them good conductors of electricity. These electrons can behave either like particles or waves. Each nucleus is composed of positively charged particles called protons and uncharged particles called neutrons. There are equal numbers of electrons and protons in an atom, creating a balance, but the number of neutrons may vary, thus some elements, called isotopes can be composed of identical atoms, but because of the variation in the number of neutrons they have a different atomic weight. In some elements such as uranium the free neutrons split away and decay, changing into protons and electrons, making the element radioactive.
Since the 1930s many more types of particle have been discovered. An instrument called an accelerator smashes the particles together, splitting them to form new particles such as quarks and neutrinos. Quantum physics investigates the world of subatomic particles. Scientists are trying to compare and bring together the tiniest particle of our world with those in the furthest area of the universe, to show that they are all part of one superforce.
Everything in the universe is controlled by four known forces. Gravity, which always attracts, holds the universe together and prevents us from floating off the earth. Electromagnetism holds the electrons within an atom and can either attract or repel other objects. The weak nuclear force is involved in radioactivity and nuclear fusion, and the strong nuclear force only affects quarks, which appear as pairs or triplets in protons, neutrons and other particles.
The general belief at present is that the universe was formed by the Big Bang millions of years ago. Hot plasma exploded and, on cooling, quarks formed protons and neutrons. Eventually electrons and nuclei formed atoms which continue to evolve. The universe and everything in it is constantly changing, but the amount of matter remains the same. © GMA