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The Structure and Different Stages of Matter

Compressed Air Wiki Physics of Air Compressors Basic Theory

To understand the workings of compressed air, a basic introduction to physics can come a long way. We start by explaining the structure of matter. In the second part you will learn more about the four different states of matter and its molecules.

What is matter made of?

All matter, be it in gaseous, liquid or solid form, is composed of atoms. Atoms are therefore the basic building blocks of matter, though they nearly always appear as part of a molecule. A molecule is a number of atoms grouped together with other atoms of the same or a different kind. Atoms consist of a dense nucleus that is composed of protons and neutrons surrounded by a number of small, lightweight and rapidly-spinning electrons. Other building blocks exist; however, they are not stable. All of these particles are characterized by four properties:
- their electrical charge
- their rest mass
- their mechanical momentum
- their magnetic momentum

The number of protons in the nucleus is equal to the atom's atomic number. The total number of protons and the number of neutrons are approximately equal to the atom's total mass, since electrons add nearly no mass. This information can be found on the periodic chart. The electron shell contains the same number of electrons as there are protons in the nucleus. This means that an atom is generally electrically neutral.

The Danish physicist, Niels Bohr, introduced a build-up model of an atom in 1913. He demonstrated that atoms can only occur in a so called stationary state and with a determined energy. If the atom transforms from one energy state into another, a radiation quantum is emitted. This is known as a photon. These different transitions are manifested in the form of light with different wavelengths. In a spectrograph, they appear as lines in the atom's spectrum of lines.

What are the four stages of matter?

Atoms held together by chemical bonding are called molecules. These are so small that 1 mm3 of air at atmospheric pressure contains approx. 2.55 x 1016 molecules.In principle, all matter can exist in four different states:

- the solid state

- the liquid state

- the gaseous state

- the plasma state

In the solid state, the molecules are tightly packed in a lattice structure with strong bonding. At temperatures above absolute zero, some degree of molecular movement occurs. In this state, there is as vibration around a balanced position, which becomes faster as the temperature rises. When a substance in a solid state is heated so much that the movement of the molecules cannot be prevented by the rigid lattice pattern, they break loose, the substance melts and it is transformed into a liquid. If the liquid is heated further, the bonding of the molecules is entirely broken, and the liquid substance is transformed into a gaseous state, which expands in all directions and mixes with the other gases in the room. When gas molecules are cooled, they lose velocity and bond to each other again to produce condensation. However, if the gas molecules are heated further, they are broken down into individual sub-particles and form a plasma of electrons and atomic nuclei.