Question

a student performs a reaction twice. in the second trial he increases the temperature of the reaction and notes that the reaction happens more quickly.the concludes that this means the reations was endothermic. what is wrong with the students reasoning

Answer 1

Increasing the temperature of the reaction would result in an increase in the average kinetic energy of the atoms/molecules of the individual components in the reaction mixture, increasing the frequency of successful collisions between these molecules, and thus increasing the rate of reaction. This does NOT imply that the reaction is endothermic, although an endothermic reaction would have its rate enhanced through the kinetic particle theory (as in this instance), while an exothermic reaction would experience an antagonistic effect caused by the increased frequency of successful collisions between the reactant particles (atoms, molecules, etc) versus the thermodynamics of the reaction per se (an exothermic reaction would have its rate enhanced through the removal of heat energy).
On a different note, increasing the temperature of the reaction does NOT imply an increase in the overall amount of heat energy of the reaction mixture as this would also depend on the number of particles in the reaction mixture (temperature is a measure of kinetic energy, and NOT of heat energy).

Answer 2

Yes. Heating increases reaction rates, endothermic or exothermic.

Heating favors greater degree of completion for endothermic reactions vs. exothermic, shifting equilibria somewhat.