Chemistry students' difficulties related to the mole concept and mole calculations

Abstract

This research was conducted to investigate what Maltese chemistry students understand by the term 'mole', whether they exhibit any difficulties when working out stoichiometry calculations especially those concerning moles and mass and whether there are any significant differences between the difficulties encountered by male and female students. In order to do so, 285 paper-and-pencil tests were distributed to Form 4 male and female students in both state and church schools. The diagnostic instrument used consisted of two open ended questions, four multiple choice questions and one structured question. When the data were evaluated it was found that many students do not define the term mole as indicated by the IUPAC but instead define it mainly in terms of Avogadro's constant and mass. In addition, most students think that coefficients are needed in a chemical equation just to balance it instead of for mass conservation. They also think that the coefficients show the actual number of moles of substance reacting in the chemical reaction instead of indicating the relative amounts of each substance present. Several difficulties were exposed when students worked out calculations such as distinguishing between moles and molecules, confusing the subscript in a formula with its coefficient in an equation and working the ratios in terms of mass instead of moles. These findings were very similar to those reported by researchers abroad and there were no significant differences between the answers given by male and female pupils.