Chemistry 1027A/B Chapter 1: Chapter 1.doc
Document Summary
Matter is made up of very tiny units called atoms, of which we know about 114 types. Each type of atom is the building block of a different chemical element, thus there are 114 elements. 90% of all elements are natural and the remaining percentage of elements is those synthesized in the laboratories. When two or more elements are joined, they form a compound. A molecule is the smallest entity having the same proportions of the constituent atoms as does the compound as a whole. An element and compounds are referred to as substances. When two or more substances mix, they form a mixture. When a mixture is uniform in composition and properties throughout, it is known as a homogeneous mixture or solution (e. g. ordinary air, seawater, and gasoline). When the composition and physical properties vary from one part of the mixture to another, it is known as a heterogeneous mixture (e. g. sand and water).