分子模型與立體化學的解題

Molecular Kits and Problem Solving in Stereochemistry

邱美虹(Mei-Hung Chiu) ； 傅化文(Hwa-Wen Fu)

《科學教育學刊》 1卷2期 (1993/12) Pp. 161-188

摘要

本研究的目的是在探討受測者如何使用分子模型（molecular kit）來解決立體化學中（stereochemistry）異構物（isomers）的問題。研究方法乃是利用出聲思維（think-aloud）的技巧來瞭解受測者之心智模式（mental model）在解題過程中所扮演的角色以及策略使用與對分子表徵之理解的情形。根據一般分子表示法，研究者以下列四種型態為主要比較的種類來觀察何種表徵對解題較有利，以及不同表徵與分子模型可能產生的互動關係（interaction）：（1）分子式表示法（2）平面二度空間的表示法（3）三度（或二度半）空間的表示法（4）給予實際以分子模型作好的分子結構。合計共有9個問題。這些題目中有些是相同（或是相似）的分子但表示法不同，以便比較不同表徵對解題的影響。本研究結果顯示，分子表徵方式不同，對學生解題影響頗大。平均而言，學生在解題上的學習成就最高為第四類型。誠如預期，給予實際分子模型學生表現較佳。其他依次為類型一、類型三、類型二。出乎意料的是學生在類型一的表現遠較類型二、類型三為佳（僅與前者達顯著差異，5%）。高成就組的學生對平面的投影之表徵方式能轉換成三度空間來判斷其分子的立體結構，然而低成就組對平面的表示法則往往無法透視（visualize）或想像（imagine）其原子間的相對位置。然而在面對具體的分子模型時，學生在解題上表現較佳，高、低成就組相差最少。故使用分子模型，對低成就組學生幫助頗大。這結果可提供教師教學時的參考。同時高成就組在解題時其所呈現的方式品質（quality）較佳，對問題亦有多樣表徵（multiple representations），有助解題。然而低成就組則往往只視分子為平面結構，造成解題上的錯誤。

關鍵字

心智模式 ； 分子模型 ； 問題表徵 ； 解題

並列摘要

The focus of this present study was on understanding how students solve problems in stereochemistry. In particular, how students solve problems with different representations of moleculars, and the idiosyncratics of their problems-solving strategies. Subjects were individually interviewed by the researcher using the think-aloud method. With this method subjects were given tasks and asked to describe how they were solving the task. The data consist of a transcript of each interview and written work the subject produced. All interviews were tape-recorded and videotaped for later transcription and analysis. The findings suggest that on average, the more successful students outperformed the less successful students in all four types of questions (namely chemical formula, 2D and 3D representations in a paper, and a real molecular model). The biggest difference between the successful students and unsuccessful students was on Type II which required the students to decide what type of isomer a compound is from a planary representation. The biggest difference on their performance indicates that the more successful students were able to transform a 2-D representation to a more useful representation for visualizing spatial relationships among atoms. The smallest difference was on Type IV which provided the students with concrete models for solving problems. This finding suggests that most students were beneficial from receiving 3-D models. One explanation is that it might reduce the students' cognitive load on examining the moleculars from a 2-D perspective.

並列關鍵字

mental models ； molecular kits ； problem representation ； problem solving

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