From seeing to knowing

Yasmin Jayathirtha

Through the articles I have been writing for some time, I have documented experiments (mainly in chemistry) that can be done simply in a classroom or in an ‘unspecialized’ laboratory. On re-reading the articles, I realized that they appear to be demonstrations and not experiments – in the sense of finding out something new or looking at cause and effect. But, chemistry is a descriptive science and one that concerns itself with changes that occur in matter. To learn about these changes, we have to first observe them and then fit them into a pattern. The observations that we make, both qualitative and quantitative, allow us to figure out what is happening at the microscopic level, at the level of the particles. In fact, it is the body of observations that has allowed much of the theory of chemistry to be formulated and converted an encyclopedia of facts into a coherent predictable picture. In fact, Mendeleev who ordered the elements into the periodic table, was able to predict the properties of the new elements he postulated should exist, by comparing the properties of the known ones. So, there is no learning chemistry except through observation. Changes seen by us suggest that something is happening between atoms, molecules, and ions. Among the difficulties that students face in learning chemistry include remembering the reactions and converting an observation into a balanced equation – the fundamental unit of chemistry.

The first observation is to determine whether a chemical change has happened or not. In chemistry textbooks, it will be the part of a chapter entitled – physical and chemical changes. In this article, we will look at combinations of chemicals to observe macroscopic changes. These experiments can be done in test tubes or on small scale reaction surfaces (Fig). Many of these chemicals are also in the products we use regularly and an extension of the experiment can be to test household products to see if we can make the same observations with them.

The author works with Centre for Learning, Bengaluru. She can be reached at [email protected].

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