Chemistry Notes I
(C) - Copyright, 1996, F.W. Boyle, Jr.

Chemistry is the study of matter, the things that make up this world and the universe. All matter falls into two categories, pure and impure. Most of the matter in the world can be classified into three groups based on physical characteristics. These groups are solids, liquids, and gases. These are common names that have meanings in life that are the same as the meanings in chemistry.

The basic building blocks of matter are known are atoms. Atoms are the smallest part recognizable as a particular type of matter.

The Elements, as listed in the Periodic Table, are shown in their form as atoms. Most can exist as a single atom in the pure state. Some of the gases compounds exist as two atoms (diatomic) in their most basic form. These are:

H2 O2 N2 F2 Cl2 Br2 I2
In the Periodic Table, these materials are shown only as single atoms.

Another name for matter is substance. All Elements are pure substances. Other types of matter or substances called compounds can also be pure as long as all only that compound is in the sample. For example, sodium chloride (NaCl) is a pure substance. Table salt however often contains sodium iodide (NaI) for health purposes and thus would not be a pure substance. When moving from the elemental level to the compound level, one must change the basic idea of composition. The elements in a compound are intimately bound together having undergone a chemical reaction to form this new matter.

The most common matter in the world is the mixture. A mixture exists when more than one element or compound is mixed with others. If the material were to be studied, various methods of physical separation could be found to get the elements and/or compounds back to their pure state. Some of the methods of purification are distillation, filtering, electrolysis, etc.

Mixtures come in two types, the homogeneous mixture where, to the eye, the sample of matter (substance) appears to be only a single substance (matter) and the heterogeneous mixture where, to the eye, the sample of matter (substance) looks like a mixture, for example, ground black pepper and salt.

When two or more substances are mixed the most common reaction in nothing. However, in many cases, the substances put in (called reactants) undergo a chemical reaction and are transformed into a new substance(s). One of these easiest ways to decide if a chemical reaction occurred is if the matter involved has a different appearance after the suspected reaction. When sodium metal is placed in a flask with chlorine gas, a violent reaction occurs and sodium chloride (table salt) is formed. The sodium was a silvery metal and the chlorine gas is a yellow-green gas. Of course, we all know that sodium chloride is a white crystalline substance. If pure sodium metal is reacted with pure chlorine gas, the product of the reaction will be pure sodium chloride.

An important thing to note is that a particular compound ALWAYS has the same type and number of elements in the it. This is why no matter where in the universe you go, water is alway 2 hydrogen atoms attached (bonded) to one oxygen atom and the chemical formula is:


There are millions of compounds in the universe. If you look at the Periodic Table you will see that there are around 103 elements. In order to grasp the immenseness of the number of compounds, you should realize that those elements can combine together in millions of combinations and that any time the number of atoms of the elements in the compound change, a new compound is formed. For instance, hydrogen and oxygen normally for water, H2O. Hydrogen and oxygen under specific laboratory conditions can go together to form another compound, H2O2, commonly known as hydrogen peroxide. So you can see, any time the number and type of elements in a compound change, you have changed the compound you are dealing with.

Compounds can be simple like NaCl or complex like DNA, whose chemical structure is too large to show here. Sucrose, the common household sugar, is a combination of 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms. Octane is a compound found in gasoline. It contains 8 carbons and 18 hydrogens. These substances that contain carbon and hydrogen are commonly called hydrocarbons, hydro- coming from hydrogen.

Most are familiar with the term, carbohydrate. Looking carefully at the name, you should be able to determine that these compounds contain carbon and water. Think about hydrate and dehydrate as these terms relate to water in substances. Many chemical compounds contain water in a form that can be driven off. Heating sucrose drives off water as steam and leaves behind the carbon. When a chemical compound contains carbon and water, it is placed in the carbohydrate category.

These categories have been established by chemists so that chemists from different parts of the world, who probably speak different languages, can communicate.