THE EQUATION OF REACTION: A CLUSTER OF OBSTACLES WHICH ARE DIFFICULT TO OVERCOME

At the beginning of upper secondary school (age 16), when pupils encounter changes in matter, they have to be able to recognise a chemical reaction. They must understand the underlying concepts, must know how to represent the phenomena and have a knowledge of the 'language' used to communicate the nature of what has happened. The Chemical Equation enables them to relate what is happening in the bulk situation with the underlying atomic and molecular changes. To do this requires a large measure of abstraction. We would be deceiving ourselves if we believed that pupils would be able to accomplish, without difficulty, an intellectual process, which took centuries for scientists to construct. In this article, the various stages of the historical development of the concepts implicit in the Chemical Equation will be set out and the consequent pupil difficulties will be analysed.. [Chem. Educ. Res. Pract.: 2004, 5, 327-342]