Element, compound or mixture?
Matter is commonly found in three chemical forms - elements, compounds
and mixtures. These are not to be confused by the physical forms of matter
- solids, liquids, gases and plasma. All matter is made of atoms, but
it is how these atoms are combined that determines their status as an
element, compound or mixture. Elements Compounds The atoms in a compound are chemically combined in proportions by mass that are always the same for a particular compound. Compounds are easy to identify if you have their formula. Only compounds have formulas with two or more different types of atoms or elements. Carbon dioxide has the formula CO2 therefore it is a compound.
Compounds can be decomposed into their constituent elements. An example is water being chemically decomposed into its two elements, hydrogen and oxygen, by electrolysis: passing electricity though a water solution.
Mixtures do not have formulas and their composition is variable. For example, sea water from the Dead Sea is saltier than water from the Pacific Ocean and air can be clean or polluted. Mixtures can be separated into three categories according
to the size of the individual particles:
All mixtures can be physically separated to obtain their component elements and compounds. (Sometimes this is not an easy process and requires considerable laboratory skills). They do not have formulas, but can have recipes with differing proportions of ingredients!
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