M. Clara Magalhães, M. Gabriela T. C. Ribeiro, Solubility educational project, 11th International Symposium on Solubility Phenomena, Including Related Equilibrium Processes, Aveiro, Julho, 2004, Proceedings, 52.
2004-07-25

Autores:
M. Clara Magalhães *
M. Gabriela T. C. Ribeiro

Instituições:
*Universidade de Aveiro
REQUIMTE, Departamento de Química e Bioquímica da Faculdade de Ciências da Universidade do Porto

Resumo:

Solubility and solutions resulting from dissolution of solutes are omnipresent in the history of the earth - they participate in the lithosphere, hydrosphere, and atmosphere composition and processes occurring therein; life itself (macroscopic and microscopic) couldn’t exist without them; they are present in all levels of human daily life (the morning coffee, the soft drinks with or without gas, our preferred perfumes and paintings, the dry and wet cleaning, …) and in agricultural, medical, pharmaceutical and many other industrial activities. The called environmental problems are often a result of excess of solubility, and can sometimes be resolved by its decrease. This ubiquitous nature of the phenomenon turns solubility invisible both in scientific and educational terms.

An educational project centred in experimental methodologies (from primary school to university) has being developed in order to:
- show the importance of solubility in some of the daily aspects and the life itself;
- promote the interest by the study of phenomena related with solutions in general and saturation in particular; and
- be used at an introductory level to introduce and develop themes like the formation of solutions, solutes and solvents, types of solutions, saturation, crystallization, factors affecting saturation, and at an advanced level physical-chemistry parameters related with some properties of the solutions where concepts like solubility product, and supersaturation will appear.

This project wants to bring into focus the usual forgotten subjects at pre-university levels as gas-liquid and liquid- liquid solubilities, supersaturation, nonaqueous solvents, organic solutes, and polymers. It will be focused on experiments that can be use under low resources situations with daily life materials.

Experimental activities addressed to primary school pupils were already organized and tested. They can be consulted by the teachers at http://educa.fc.up.pt/experiencias.php?id=4. At this level the experiments try to answer questions like: What is a solution? Can be dissolved more than one solute in a solvent? Is stirring necessary to dissolution? The solutes are always solids? The solvent is always water? In a given volume of solvent can be dissolved whichever amount of solute? Sea salt, limestone, powdered refreshments, sugar, olive oil, ethanol, and other substances dissolve equally in the same volume of water? How temperature affects solubility? The experiments were designed to place children facing common situations related with dissolution and solubility and to reflect about them.

To higher levels (pupils aged from 10 to 15) experiments where designed to introduce less common subjects as difference between dissolution and melting, gas - liquid solubility, liquid - liquid solubility, nonaqueous solvents and organic solutes. At the preuniversity level some of the previous experiments were explored in order to introduce more advanced concepts as solubility product, enthalpy of reaction and the relation between enthalpy and the solubility.