The Structure of Matter

In this investigation you used electricity to decompose water into two gases. You knew that the gases were different because they reacted differently to the burning and glowing splints. Since water is referred to as H₂O, a first guess would be that hydrogen (H) and oxygen (O) were created in the experiment. The test for hydrogen is a small explosion when exposed to a burning splint. The test for oxygen is igniting a glowing splint. If you look back on the results of the experiment, you find that the hydrogen gas filled one test tube while the oxygen filled half of the other test tube. There was twice as much hydrogen as oxygen. That’s where the 2 comes from in the chemical formula H₂O.

Hydrogen and oxygen are elements. An element is any material that cannot be broken down into simpler materials by chemical means. You are probably familiar with many elements like hydrogen, oxygen, zinc, gold, or helium. Other elements like strontium and beryllium are more exotic and less likely to be familiar to you. Every kind of matter you observe in your everyday life is made up of the chemical elements. There are only about a hundred different kinds of chemical elements. This is an amazing discovery of chemistry — everything you observe in the world is made of different combinations of a hundred elements. Chemistry is the study of how these elements combine and the characteristics of these combinations.