Matter can exist in one
of three states
of matter: a gas, a liquid, or a solid. A gas
is highly compressible and will assume both the shape and the volume of its
container. A liquid
is not compressible and will assume the shape but not the volume of its container.
also is not compressible, and it has a fixed volume and shape of its own.
Mixtures can be separated into pure substances, and pure substances can be either compounds or elements.
A familiar example of a
mixture is salt water. A sample of salt water has the same composition throughout.
It can be separated into pure substanceswater and ordinary table saltby
a physical process, such as distillation.
Pure water is collected in the flask on the right. When all of the water has been distilled from the mixture, pure saltNaClwill remain in the flask on the left. Both water and salt are pure substances. They cannot be further separated into simpler substances by any physical process. Each, however, can be decomposed into other substances by a chemical process, namely electrolysis. The following movie shows water being decomposed into oxygen and hydrogen.
In order to classify a
sample of matter as a mixture or a pure substance, we must answer a series of questions.
Each of the following can be classified as a heterogeneous mixture, homogeneous mixture, compound, or element. How would you classify each?