Students’ understanding of Thermodynamics Bruna I. Grimberg and David E. Meltzer Iowa State University

1. Purpose: To uncover students’ understanding of calorimetry, through the use of the specific heat equation,q=mc(Tf-Ti). Students’ Explanations Distribution, Problem 1 Explanations Distribution, Problem 2 # Students 10% None Methodology: Analysis of 420 quizzes of a freshmen General Chemistry class, college level. The quiz was given immediately after a lecture on Calorimetry. The quiz was required for a grade course. 26% Correct 22% Wrong 42% Incomplete None Correct Wrong Explanations Correct:cause-effect between heat and temperature change. Incomplete: retrieve information given in the problem. Wrong: 13% apparently confuse specific heat with heat. • Problem 1 • The specific heat of water is 4.81 J/g C and the specific heat • of copper is 0.71 J/g C. • Consider equal masses of water and copper each at the same • initial temperature. If we add 100 J of heat to each (water and • copper), which will achieve the highest temperature? Explain. Explanations and Response modes Problem 1 Procedural Analysis, Problem 1 Given Explanation Overall Students 51% Display understanding of temperature change in a thermodynamic system. 16% Confuse heat and temperature. 8% Do not display understanding of heat transfer. Response #Students Students that use equations tend to give incomplete explanations retrieving the data given in the problem. Response Words Symbols Categories of Correct Explanations Explanations: Good Wrong No 42% Water and copper reach the same final temperature 32% Heat lost by copper is equal to the heat gained by water Summary Problem 2 Copper metal of mass m1 and temperature Tc is placed in a calorimeter which contains water of mass m2 at Tw, where Tc is less than Tw. The calorimeter is made of good insulating material and has a lid... Do you think that there is any connection between Twand Tc? Explain your answer. 18% Energy conservation 8% Other • Response using symbols: • 31% offer no explanation • Of the explanations that are given 83% are correct • Response using words: • 96% do offer explanation • Of the explanations that are given 75% are correct • The exclusive use of symbols tends to replace conceptual explanations Categories of Wrong Explanations • The exclusive use of language display a higher level of understanding 48% Water and copper have the same temperature change • The use of symbols and language, display a lower level of understanding, retrieving given data 23% No relation between copper and water heating processes 29% Other • The cause-effect relation between heat and temperature is ignored by 54% of the students Students’ understanding of Thermodynamics Bruna I. Grimberg and David E. Meltzer Iowa State University