Chemistry: Paradigm In Chemistry

Paradigm in chemistry

Figure 1

Every chemist or even someone who does not about chemistry instantly knows the picture in Figure 1 as water. Actually it is not water. It is just a geometric figure consisting of a letter ‘O’ and two letter ‘H’ that is linked together by two lines, prepared by writing white paper with black ink. When we look at the figure, however, we perceive as a water by the eye. That is, in our mental image we see a colorless liquid, and we remember a several of physical properties and chemical reactivity that is related with water that we drink when we get thirsty. The picture in Figure 1 is therefore only a macroscopic representation of an assumed submicroscopic entity. Even more, the picture symbolizes the concept

“Phlogiston” used to be a theory of combustion, burning that postulated fire-like element called “phlogiston” is released during the burning . It was appeared to be true for some cases like many compounds releases gas and mass reduces. However some experiments showed that some substances actually gained weight when they burned, rather than losing weight as might have been expected if a real substance had been lost by burning. Rather than abandoning the phlogiston theory, however, some of its advocates rationalized the results by proposing that phlogiston had negative weight. So as we can see that once we have become accustomed to thinking about a problem in a certain way, it becomes quite difficult to think about it differently. Recognizing that contemporary chemistry is based on widely accepted paradigms does not mean that we should resist using them. So by going from this point of view let us start to question the basic concepts or fundamental concepts that has already been accepted as correct hundred percent and how they are dictating our chemical understanding. Chemists think of atoms and molecules as basic units of everything. We work with mental pictures of atoms and molecules, and we rotate, twist, disconnect, and reassemble physical models in our hands . Where do these mental images and physical models come from? It is useful to begin thinking about the

Instead, we observe it only indirectly, such as through the change in illuminated pixels on a computer display. With such instruments, it is essential that we recognize the difficulty in freeing the observations from constraints imposed by our expectations. To a layperson, a UV–vis spectrum may not seem all that different from an upside-down infrared spectrum, and a capillary gas chromatogram of a complex mixture may appear to resemble a mass spectrum. But the chemist sees these traces not as lines on paper but as vibrating or rotating molecules, as electrons moving from one place to another, as substances separated from a mixture, or as fragments from molecular cleavage. Thus, implicit assumptions about the origins of experimental data both make the observations interpretable and influence the interpretation of the data. With that caveat, what do we know about molecules and how do we know it? We begin with the idea that organic compounds and all other substances are composed of atoms—indivisible particles which are the smallest units of that particular kind of matter that still retain all its properties. It is an idea whose origin can be traced to ancient Greek philosophers. Moreover, it is convenient to correlate our observation that substances combine only in certain ratios with the notion that these submicroscopic entities called atoms combine with each other only in certain ways. Much of our fundamental information about molecules has been