A diagnostic instrument was developed to evaluate the basic chemistry concepts held by freshmen students of the three Chemistry undergraduate courses offered by the University of São Paulo. The instrument minimizes the use of algorithms or memorization by students and values high-order cognitive skills. Analysis of the students' performances reveals systematic use of "displacement reaction" as an algorithm and a mechanical use of Le Chatelier's Principle. Failure in comprehending the chemical equation and chemical language drives students to alternative models for chemical reactions in aqueous solution. For instance, reaction would occur between "ionic pairs" and/or between species situated in separate compartments.

São apresentadas algumas tendências modernas do ensino de química, em termos de ensino no contexto, treinamento de habilidades profissionais e construção da cidadania. São discutidos alguns problemas nos conteúdos de química, principalmente dos livros de ciências de 8a série, mostrando-se que alguns assuntos são impróprios para alunos dessa faixa etária e outros envolvem apenas a memorização, contribuindo para o afastamento dos alunos do estudo de ciências. Finalmente, são apontados diversos equívocos conceituais, comuns em livros didáticos, que dificultam a aprendizagem.

In this article we present some of the modern trends in the teaching of chemistry, involving teaching in context, training of professional skills and development of citizenship. We also discuss some problems with the content of chemistry, mainly as found in science textbooks for 8th-level students. There are parts of the content that deal with issues inappropriate for the age of the students, while others require merely memorization, thus turning students away from science. Finally, we point out several conceptual mistakes, commonly found in textbooks and which make learning even more difficult.