Chemical composition

Chemical composition refers to the arrangement, type, and ratio of atoms in molecules of chemical substances. Chemical composition varies when chemicals are added or subtracted from a substance, when the ratio of substances changes, or when other chemical changes occur in chemicals.

Overview

Chemical substances are made up of one type of atom or molecule. The chemical composition of a pure substance corresponds to the relative amounts of the elements that constitute the substance itself. It can be expressed with our understanding of the molecular structure, which quantifies the number of atoms or molecules in a particular sample of matter.

Determining Chemical Composition

The chemical composition of a compound can be determined by chemical analysis. Various methods have been developed to identify the elements and compounds in a substance. These methods fall into several categories including spectroscopic, chromatographic, and gravimetric.

Spectroscopic Methods

Spectroscopy is a technique that uses the interaction of energy with a sample to perform an analysis. This can be further divided into atomic and molecular spectroscopy.

Chromatographic Methods

Chromatography separates the components of a mixture based on the speed at which they move through a system.

Gravimetric Methods

Gravimetry involves determining the amount of material present by weighing the sample.

Chemical Composition of Matter

The chemical composition of matter pertains to the elements within a substance and their proportions. For example, water, with a chemical formula of H2O, consists of two hydrogen atoms and one oxygen atom.

See Also

• Chemical substance
• Chemical formula
• Chemical compound
• Chemical reaction
• Chemical element

References

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