An element is a substance that can not be broken down into simpler substances by ordinary means. A few more than 100 elements and the many combinations of these elements-compounds or mixtures-account for all the materials of the world. Exploration of the moon has provided direct evidence that the earth’s satellite is composed of the same elements as those on earth. Indirect evidence, in the form of light received from the sun and stars, confirms the fact that the same elements make up the entire universe. Before it was discovered on the earth, helium (from the Greek helios, meaning “sun”) was discovered in the sun by the characteristic light it emits.
MATTER AND ENERGY
Chemistry focuses on the study of matter, including its composition, its properties, its structure, the changes that it undergoes, and the laws governing those changes. Matter is anything that has mass and occupies space. Any material object, no matter how large or small, is composed of matter. Incontrast, light, heat, and sound Are forms of energy. Energy is the ability to produce change. Whenever a change of any kind occurs, energy is
involved; and whenever any form of energy is changed to another form, it is evidence that a change of some kind is occurring or has occurred.