Chemistry has been an important part of society since ancient times. The producing of metals for ornaments and weapons and the use of embalming fluids dates back to before 1000 B.C. Theories were then put forward by many people and by about 400 B.C. the Greeks proposed that matter was made up of the four fundamental substances called fire, earth, water, and air. The Greeks also considered that perhaps matter is actually made up of an infinite number of infinitesimally small subunits which they called atomos which later became atoms. The next 2000 years (until the sixteenth century) of chemistry history we call the alchemy period. There were some important advances during this period as several elements were discovered and as people learned to make mineral acids. However much of this period was dominated by fakes taking advantage of the ignorance of the time.

The sixteenth century saw some foundations of modern chemistry being laid as people learned how to extract metals from ore and how to use some minerals for medicinal applications. We should probably call Robert Boyle the first true chemist as he learned how to perform quantitative experiments and discovered the relationship between pressure and volume of air. Boyle also began to develop better concepts about the elements. He viewed a substance to be an element if it could not be broken down into two or more simpler substances. This led to the death of the original list of four elements.

It was not until the eighteenth century that combustion was finally understood based upon the experiments of Lavoisier who discovered that oxygen was involved in combustion and also that life was supported by a process which involved oxygen. It observations led to his discovery of the Law of Conservation of Mass: Mass can be neither created nor destroyed..

In the early 1800's, the chemist Proust discovered what is now known as theLaw of Definite Proportion: A given compound always contains the exactly the same proportion of elements by mass.. This discovery led Dalton to consider that atoms might be the individual particles that make up the elements. Dalton noted that carbon and oxygen formed two different compounds with different properties and different masses -- one of them contains exactly twice as much oxygen as the other. This principle was found to apply to other elements as well and led to the Law of Multiple Proportions: When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always to reduced to small whole numbers..

Now take a practice quiz to help you understand if you understand the basic concepts.
You must use your real name when it asks for a name.
The test will only submit when you have answers all of the questions correctly.
If you are not taking this course for credit please do not answer all the questions correctly for I don't want to be flooded with email answers to the tests.

Web Author: Dr. Leon L. Combs
Copyright 2000 by Dr. Leon L. Combs - ALL RIGHTS RESERVED