You are about to become acquainted with the fascinating world of PHYSICS. You will learn about the various natural and physical laws and phenomena. Physics is concerned with those aspects of nature which can be understood in a fundamental way in terms of elementary principles and laws. The forces of physics and the laws of nature are at work in every piece of machinery and equipment. It is by these forces and laws that the machinery and equipment produce work.

In the following paragraphs you will learn about matter, magnetism, electricity, motion, properties of mass, temperature, pressure, various laws and principles of physics dealing with motion, gases, hydraulics and pneumatics, and basic information on metals. After studying this chapter, you will have the fundamental, basic knowledge to understand what electrical and mechanical devices are all about and how they work.

MATTER

If western science has roots, they probably lie in the rubble that was once ancient Greece. Except for the Greeks, ancient people had little interest in the structure of materials. They accepted a solid as being just that-a continuous, uninterrupted substance. One Greek school of thought believed that if a piece of matter, such as copper, were subdivided, it could be subdivided indefinitely and still only that material would be found. Others reasoned that a limit exists to the number of subdivisions that could be made and have the material still retain its original characteristics. They held fast to the idea that all substances are built upon a basic particle. Experiments have revealed that, indeed, several basic particles, or building blocks, are within all substances.

Matter cannot be created nor destroyed. This law holds within the experimental error of the

most precise chemical reactions. This theory of the conservation of energy will be discussed later in this chapter. Matter is defined as anything that occupies space and has weight; that is, the weight and dimensions of matter that can be measured. Examples of matter are air, water, clothing, and even our own bodies. So, we can say matter is found in any one of three states: GASEOUS, LIQUID, and SOLID.

In the following paragraphs we will describe how substances are classified as elements and compounds and how they are made up of molecules and atoms. We will then learn about protons, electrons, and the physics of electricity.

ELEMENTS AND COMPOUNDS

An element is a substance that cannot be reduced to a simpler substance by chemical means. Examples of elements with which you are in every day contact are iron, gold, silver, copper, and oxygen. Over 100 known elements are in existence. All the different substances we know about are composed of one or more of these elements.

When two or more elements are chemically combined, the resulting substance is called a COMPOUND. A compound is a chemical combination of elements that can be separated by chemical means. Examples of common compounds are water, which consists of hydrogen and oxygen, and table salt, which consists of sodium and chlorine. A MIXTURE, on the other hand, is a combination of elements and compounds, not chemically combined, that can be separated by physical means. Examples of mixtures are air, which is made up of nitrogen, oxygen, carbon dioxide, and small amounts of rare gases, and sea water, which consists chiefly of salt and water.

MOLECULES

A MOLECULE is a chemical combination of two or more atoms, (atoms are described in the next paragraph). In a compound the molecule is the smallest part that has all the characteristics of the compound. Consider water, for example. Depending on the temperature, it may exist as a liquid (water), a solid (ice), or a gas (steam). Regardless of the temperature, it will still have the same composition. If we start with a quantity of water, divide this and pour out one half, and continue this process enough times, we will end up with a quantity of water that cannot be further divided without ceasing to be water. This quantity is called a molecule of water. If this molecule of water is divided, instead of two parts of water, we will have one part of oxygen and two parts of hydrogen (H₂O).