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In order to improve the image quality, a molecule of carbon monoxide was placed on the end of the probe.
The image produced by the AFM probe is shown at the very bottom.
But if you need a single-sentence"definition of Chemistry, this one wraps it up pretty well: Chemistry, like all the natural sciences, begins with the direct observation of nature— in this case, of matter.
But when we look at matter in bulk, we see only the "forest", not the "trees"— the atoms and molecules of which matter is composed— whose properties ultimately determine the nature and behavior of the matter we are looking at.
In the 1920's it became possible to measure the sizes and masses of atoms, and in the 1970's techniques were developed that produced images of individual atoms.
For example, the compound mercuric oxide can be broken down by heating into two other substances: 2 Hg O → 2 Hg O one; a certain result (or in this case, a non-result!
Each one moved his hands over a different part of the elephant's body— the trunk, an ear, or a leg— and came up with an entirely different description of the beast.
Chemistry can similarly be approached in different ways, each yielding a different, valid, (and yet hopelessly incomplete) view of the subject.
We will organize the discussion in this lesson along similar lines. (We will get into the details of the definitions elsewhere, but for the moment you probably already have a fair understanding of the distinction; think of a sample of crystalline salt (sodium chloride) as opposed to a solution of salt in water— a of salt and water.) To a chemist, there is a fundamental distinction between a pure substance and a mixture.
But marketers, and through them, the general public, don't hesitate to describe a complex mixture such as peanut butter as "pure". It has been known for at least a thousand years that some substances can be broken down by heating or chemical treatment into "simpler" ones, but there is always a limit; we eventually get substances known as that cannot be reduced to any simpler forms by ordinary chemical or physical means. The most observable (and therefore macroscopic) property is the weight.