|MadSci Network: Biochemistry|
In general, vinegar is a solution of about 5% acetic acid (CH3COOH) dissolved in water (H2O). However, there are many different kinds of vinegars (for example, rice vinegar, distilled vinegar, balsamic vinegar, etc.), and vinegar can be made at home by letting wine oxidize (in fact the word vinegar comes from a Latin term meaning 'sour wine'). Most of these vinegars contain other things besides acetic acid and water, and some of them may have higher or lower concentrations of acetic acid. So really, vinegar is just the name for a large group of acetic acid solutions.
Okay, so in order to answer your question, I looked up the chemical definiton of the word compound. The American Heritage dictionary says that a chemical compound is, "a pure, macroscopically homogeneous substance consisting of atoms or ions of two or more different elements in definite proportions that cannot be separated by physical means," and that, "a compound usually has properties unlike those of its constituent elements."
Webster's dictionary says that a chemical compound is, "a union of two or more ingredients in definite proportions by weight, so combined as to form a distinct substance; as, water is a compound of oxygen and hydrogen," and goes further to note that, "every definite chemical compound always contains the same elements, united in the same proportions by weight, and with the same internal arrangement."
So, is vinegar a compound? I'm afraid not. As you can see from the definitions above, a chemical compound is composed of distinct elements that cannot be separated by physical means. The properties of vinegar are not distinct from the properties of water and acetic acid, water and acetic acid do not have to be combined in exact proportions to make vinegar, and the water and acetic acid in vinegar can be separated by boiling (distilling) vinegar.
However, you may have noticed that both acetic acid and water meet the requirements of the definitions above and ARE chemcial compounds. So vinegar is a solution of at least two chemical compounds.
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