Practicing chemists use models, diagrams, symbols, and figures to represent phenomena which cannot be detected by the human senses. Although research suggests that these external representations (ERs) can also be used to address the challenges that students have in learning chemistry, it is not clear how instructors' use of ERs aligns with their perceptions of student learning difficulties. In other words, do instructors use ERs to address what they perceive as students' major challenges in learning chemistry, or are they using ERs for other reasons? The answer to this question could have implications for the professional development of chemistry instructors, including both classroom instructors and laboratory facilitators. As a pilot study to guide the development of a larger project focused on the use and interpretation of ERs, we interviewed eleven general chemistry teaching assistants at a major university in the U.S. Southwest about their use of ERs when facilitating acid–base titration laboratory activities. Our data suggest that there is a lack of alignment between teaching assistants’ primary reported use of ERs and the primary challenge that they perceive their students have when learning about acid–base titrations. We discuss potential reasons for this misalignment, as well as implications for teaching assistant training related to the use of ERs in the laboratory learning environment.

中文翻译：

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在入门化学实验室课程中进行酸碱滴定教学时，助教对学生学习挑战的看法与使用外部表征之间的关系†

执业的化学家使用模型，图表，符号和图形来表示人类的感知无法检测到的现象。尽管研究表明这些外部表征（ER）也可用于解决学生在化学学习中所面临的挑战，但尚不清楚教师对ER的使用如何与他们对学生学习困难的看法相吻合。换句话说，教师是使用ER来解决他们认为是学生在学习化学过程中面临的主要挑战吗？还是因为其他原因而使用ER？这个问题的答案可能会对化学老师的专业发展产生影响，包括课堂老师和实验室辅导员。作为一项引导大型项目开发的试点研究，该项目着重于ER的使用和解释，我们采访了美国西南部一所主要大学的11名一般化学助教，介绍了他们在促进酸碱滴定实验室活动中使用ER的情况。我们的数据表明，助教的主要报告的ER使用与他们在学习酸碱滴定法时认为学生所面临的主要挑战之间缺乏一致性。我们讨论了这种错位的潜在原因，以及与在实验室学习环境中使用ER相关的助教培训的含义。我们的数据表明，助教的主要报告的ER使用与他们在学习酸碱滴定法时认为学生所面临的主要挑战之间缺乏一致性。我们讨论了这种错位的潜在原因，以及与在实验室学习环境中使用ER相关的助教培训的含义。我们的数据表明，助教的主要报告的ER使用与他们在学习酸碱滴定法时认为学生所面临的主要挑战之间缺乏一致性。我们讨论了这种错位的潜在原因，以及与在实验室学习环境中使用ER相关的助教培训的含义。