從科學史中理論模型的發展暨認知學心智模式探討化學概念的理解－層析理論的模型化案例

Abstract

模型是一種想法、一個物件、事件、歷程或一個系統的表徵。模型化﹙modeling﹚試圖將「不明確」或「沒有看過」的事物與想法呈現，因此模型蘊含「本源」（source）與「標的」（target）兩個領域。模型化是一種轉換的歷程；在嘗試轉換的程序中，注意力被切換、轉移至特定的意義領域而呈現躍進（leaping）的狀態，因而容易產生創造性的想法，因此模型化（modeling）是一種創造性有意義學習過程。 層析法（chromatography）是物質科學中最常用的分離技術之一，因此是儀器分析課程中十分重要的一部分。層析法的分離作用源自被分離物質和分離系統間的集體現象，涉及分子間作用力、分子的動態分布等概念；相關研究顯示層析技術作用原理的概念理解對大部分學生是複雜和有困難的。 本研究分成三個階段。第一階段，從科學史的角度輔以文獻探討的方式，確認出層析理論發展的五個理論模型－過濾模型、吸附模型、板理論模型、速率模型以及效化熱力學模型。 第二階段，以孔恩的科學革命、拉卡托斯的研究綱領和勞丹的研究傳統等三種科學哲學觀分析層析理論模型的發展，瞭解模型是如何取代。研究結果顯示層析理論的發展是從因果解釋模型如過濾、吸附等分離作用模型發展為兩相間分配板理論模型，隨機分配的速率模型及合併動力學、熱力學形成的最適化模型。理論發展過程中，遭遇必須解決如：成分完全分離、動相的限制、靜相的限制等概念性問題時新理論模型才會出現。新理論模型並促進新的層析儀器的類型的設計和應用，使得分離的一些經驗問題得以解決。因此層析理論模型的發展並非完全累積的，而是聯合、分化和改變的演化歷程，本研究認為層析理論的發展較符合勞丹的科學發展理論。 本研究的第三階段主要探討學習者對於模型的認識表徵(「模型表徵類別」)與層析單元教學以前之相關化學先備能力對於層析單元學習成效與層析模型建構之影響。受試學生是台北某私立技術學院專科部化工科，選修『儀器分析』課程的64位四年級學生（年齡19-21歲），該課程在實驗期間，由研究者利用透過科學史分析所發展出來的模型化導向教學模式（modeling approach teaching）進行層析單元的教學。研究者首先利用根據Grosslight等人(1991)對於模型認識之相關研究結果所自行發展的「學生模型表徵問卷」將受試學生分為「構念－理論」、「構念－空間」、「實體－理論」以及「實體－空間」等四種模型表徵類別後，分別在層析單元教學前與教學後，探討受試者「模型表徵類別」與「化學先備能力」對於層析模型之建構與層析單元成就之影響。 第三階段的主要研究發現為(1)受試學生對於模型之表徵類別與化學先備能力均顯著影響其層析單元之學習成就；(2) 受試學生對於模型之表徵類別與化學先備能力對層析單元之學習成就影響無顯著交互作用；(3)受試學生在層析單元教學前，選擇吸附理論模型為適當層析模型者顯著多於另外三種層析模型；(4) 受試學生在層析單元教學後，選擇隨機的兩相分配速率理論模型為適當層析模型者顯著多於另外三種層析模型；(5)受試者「模型表徵類別」與「先備能力」對於教學前、後之層析模型建構均無顯著影響。由以上(3)、(4)發現，可以推論學生的層析模型建構大致符合科學史發展，也符合教學之進度。然而在單元教學後實際要求受試者解釋層析特例時，發現雖然大部分學生在認知上選擇隨機的兩相分配速率模型為最適當的層析模型，然而在解釋層析特例時，卻大都採過濾模型。

A model is a surrogate object or a conceptual representation of an object, an event, a process or a system. Modeling is the process of using a model to gain an insight of the ambiguous thought or to make invisible event visualable. Hence, a model is always embedded both ‘source’ and ‘target’. Modeling is a conversion process. In the conversion process, attention is shuttled between source and target. When attention is shifted to focus on a specific discipline, then it is in a leaping state and therefore makes thinking more creative. Modeling should be a meaningful learning process.

Chromatography is one of the most commonly used separation method in the material science. And it is a very important subject in the content of instrumental analysis course. Separation effect of chromatography is resulted from interaction of collective properties of the substances to be separated and the separation system itself. The mechanism of the separation process involved intermolecular forces and molecular dynamic distribution. Related science educational researches show that the concept of chromatography is complicate and difficult to learn for most students.

Three parts are included in this study. Literature is reviewed and history of science is discussed in the first step. Five theoretical models are recognized from the history and development of theory in chromatography. There are filtration model, adsorption model, plate theory model, rate theory model, and optimized thermodynamic model.

The study is then followed by discussion of philosophy of science in order to appraise the development of theoretical models of chromatography. Three philosophic perspectives on science evolution, which includes Kuhn’s “Paradigm Shift”, Lakatos’s “Scientific Research Programme”, and Laudan’s “Research Tradition”, were used to illustrate the relation of relevant models and the way a model is replaced. The results revealed that the development of the theory of chromatography is an evolving process from cause-effect model (i.e., filtration, adsorption model), plate theory model, rate theory model, to the optimal model with combination of dynamics and thermodynamic. In the developing process, the new model is built only when the conceptual problem is faced, such as: total separation of composition, limitation of mobile and stationary phase. The merge of a substituted theoretical model always accelerates new design of the instrument or broaden the application of chromatography. It then results in new solution for the encountered problem of separation of varied materials. Hence, the development of theoretical models of chromatography is not totally in according with accumulative perspective. Instead, it is a process of integration, differentiation, and progressive evolution. This study recommends that the development of the theory of chromatography is more consistent with scientific progress theory of Research Tradition of Laudan.

The third part of the study investigated the relationships between the learners’ epistemological representations of models and the prior knowledge in chemistry with their learning achievement and concept change in chromatography. Sixty-four subjects (age 19-21 years) are from the Chemical Engineering Department of a 5-Years Program of Technical College in Taipei area. All the subjects took the ‘Instrumental Analysis’ course during the experiment. The researcher to teach chromatography applies modeling approach instruction, which developed from analysis of the history of science and philosophy. A developed questionnaire is utilized for categorizing the intrinsic representations of model of the students. Four groups of students: construct- theory, construct -spatiotemporal, concrete-theory, and concrete-spatiotemporal were identified. The results demonstrate that: (1) the intrinsic representations of models and the prior knowledge of the students significantly affect their learning achievement (2) there is no interaction between the intrinsic representations of models and prior knowledge of the students in the effect of the learning achievement of students (3) the adsorption model is chose by the students significantly more than the other three models before the instruction. (4) the rate theory model is chose by the students significantly more than the other three models after the instruction. (5) influence of the intrinsic representations of models and the prior knowledge of the students on their model construction is not found before and after the instruction.

From results of (3) and (4), it suggested that students’ model construction is complied with development of science history and teaching plan. After the instruction, it is however found that the students incline to use the filtration model to explain gel permeation chromatography even though they adopted the rate theory model.