求解开放性化学题的六种策略

1 准确回忆,逐一列举 这一类是指教材中研究的问题,在教材中可能集中在一起,也可能分散在不同的章节,有的有明确的说明,有的是以后逐步出现的,但通过归纳总结可形成完整的体系.求解时,只要准确回忆、逐一列举即可.     

极端假设法在化学解题中的妙用

假设是科学研究中常用的一种思维方法,也是化学学科解题中常用的技巧和策略之一.华罗庚先生说过:"把一个比较复杂的问题‘退'成最简单最原始的问题,把这最简单最原始问题想通了、想透了.然后再……来一个飞跃上升."这是一个非常精辟的思维方法,这里的"退"是为了"进","退"够了,"退"到"起始点"正是为了看清问题的一般规律,就会有左右逢源,水到渠成的功效.极端假设就是从某个极限状态去考虑问题,并对其进行分析、判断、推理的一种方法,一般是先把思路引向极端状态,使问题简化,从而找出规律,再回过头来认识现实问题.     

The assessment and prevention of answer copying on undergraduate multiple-choice examinations

Multiple-choice examination answer copying was indexed by a comparison of the numbers of items answered incorrectly, and in the same way, as adjacent and distant classmates. In Experiment I, which involved a regular university examination, significant copying did occur, did not differ from front to rear of the lecture hall, and appeared primarily among individuals seated next to one another. Copying was not related to the order in which the examinations were returned. Number correct was related to turn-in order in a U-shaped fashion. No significant copying appeared in a second experiment, where test performance did not contribute to course grade.     

Measuring strategy use in context with multiple-choice items

A number of authors have presented data that challenge the validity of self-report of strategy use or choice of strategy. We created a multiple-choice measure of students’ strategy use based on the work of Kozminsky, E., and Kozminsky, L. (2001), and tested it with three samples as part of a series of studies testing the fit of the DIME model of reading comprehension. One study was conducted at the high school level (N = 175) and two at the undergraduate level (N = 185 and 737). Over the three studies with three different samples, we found good evidence for the internal consistency reliability and concurrent validity of this type of measure. Commonality analysis suggested that strategy use mainly makes a shared contribution to comprehension with other predictors, especially inference, and to some extent vocabulary, background knowledge, and word reading. The measure was relatively easy to construct and easy to administer to large numbers of students, and showed much higher evidence of concurrent validity than self-ratings of frequency of use of strategies.     

Student note-taking in chemistry lectures

Conclusion In this work a method has been developed to evaluate the quantity and quality of students' notes during lectures in any particular context. Because of enormous differences in context from lecture to lecture (including lecturing style and the nature of the subject matter) it does not seem sensible to pursue quantitative estimates which might be claimed to be generalisable to all lectures and all lecturers. However further work along the lines described here may well allow some generalisable conclusions concerning factors that influence the quantity and quality of students' notes, the sense that students can make of their notes in the short and long term, and the potential usefulness of notes for future learning.     

关系推理在化学解题中的应用

关系推理从属演绎推理,其结论是从前提中推出的.物质间的关系是复杂多样的,在组合于特定环境中时,使一些原本孤立的物质有了相关性.根据它们的相互关系,进行逻辑推理,解决问题.关系推理法在化学解题中有广泛的应用.     

Cognitive variables in problem solving in chemistry

Conclusion A problem solver who is successful in securing a solution will need to achieve in relation to the three tasks to which these variables relate: first, the adequate translation of the problem's statements; second, the correct recalling of prior knowledge such as rules and facts and, third, making the relevant linkage between the problem's statements and rules and facts so that a solution sequence emerges. If he or she is familiar with the problem then the tasks of linkage and translation with play the important role in predicting the problem solving performance. For a problem with which he or she is only partially familiar, the three tasks stated will all contribute significantly to the problem solving performance. For an unfamiliar problem, the task of translation will be the best predictor of the problem solver's performance.     

Facilitating problem solving in high school chemistry

The major purpose for conducting this study was to determine whether certain instructional strategies were superior to others in teaching high school chemistry students problem solving. The effectiveness of four instructional strategies for teaching problem solving to students of various proportional reasoning ability, verbal and visual preference, and mathematics anxiety were compared in this aptitude by treatment interaction study. The strategies used were the factor-label method, analogies, diagrams, and proportionality. Six hundred and nine high school students in eight schools were randomly assigned to one of four teaching strategies within each classroom. Students used programmed booklets to study the mole concept, the gas laws, stoichiometry, and molarity. Problem-solving ability was measured by a series of immediate posttests, delayed posttests and the ACS-NSTA Examination in High School Chemistry. Results showed that mathematics anxiety is negatively correlated with science achievement and that problem solving is dependent on students' proportional reasoning ability. The factor-label method was found to be the most desirable method and proportionality the least desirable method for teaching the mole concept. However, the proportionality method was best for teaching the gas laws. Several second-order interactions were found to be significant when mathematics anxiety was one of the aptitudes involved.     

化学解题思维受阻的解脱策略

1　搭桥过渡当题给信息与问题之间存在较大的思维跨度而使思维难以通联时 ,可设定理想而又简单的“思维模型” ,在问题与信息之间建立一座桥梁 ,使思维 (解题 )得以畅通 ,进入“柳暗花明”的解题境界。例 1:(ＭＣＥ 2 0 0 0 .13)在一密闭容器中 ,反应ａＡ(气 )ｂＢ(气 )达到平衡后 ,保持温度不变 ,将容器体积增加一倍 ,当达到新的平衡时 ,Ｂ的浓度是原来的 60 % ,则Ａ .平衡向正反应方向移动了Ｂ .物质Ａ的转化率减少了Ｃ .物质Ｂ的质量分数增加了Ｄ .ａ >ｂ分析 :解题的关键 ,在于如何依据题给信息 ,判定出平衡移动的方向 ,但“容器体积增…     

化学解题中一些规律的应用

规律一:硝酸盐受热分解,除K、Ca、Na的硝酸盐外,如果元素化合价不变.则分解生成的气体中V(NO2):V(O2)=4:1.     

The effect of changes in item sequence on student performance in a multiple-choice chemistry test

It is standard practice to arrange items in objective tests in order of increasing difficulty, on the assumption that such an arrangement increases student motivation and produces more reliable tests. The validity of this assumption was investigated in the context of a multiplechoice chemistry test. Fifty items were arranged in three sequences of difficulty: random (R), easy-to-hard (E-H) and hard-to-easy (H-E). The mean test score was significantly higher for the test sequenced E-H than for the test sequenced H-E. Item difficulty index was raised by placement of the easier items toward the beginning of the test and lowered by placement of these items toward the end of the test. Test reliability was largely independent of item sequence.     

化学教学中结构不良问题的解决策略

结构不良问题主要可以分为三种不同的类型,本文结合结构良好问题与结构不良问题的异同,利用几个具体化学实例来分析化学教学中不同类型结构不良问题的解决策略.     

化学教学中问题解决法初探

问题解决是思维的最一般形式,是人类适应环境、解决生存与发展中各种问题的基本方式。实际的教学中则是通过创设问题情境,在教学内容与学生的求知心理之间建立一种不平衡状态,把学生引入到与问题有关的情境之中。利用此模式的教学是改变以被动接受为主的教学模式,实行探究学习与合作学习的重要途径。     

The effects of different feedback strategies using computer-administered multiple-choice questions as instruction

This study investigated the effects of using different forms of computer-based feedback on high school students' learning of science material. The basic design consisted of two conditions of instructional support (text and questions vs. questions only), two testings (immediate vs. retention), five levels of similarity between lesson and posttest questions, and five feedback conditions: knowledge of correct response (KCR), delayed KCR, answer until correct (AUC), questions only (no feedback), and no questions. Results showed significant benefits for feedback over no feedback, with AUC becoming more advantageous and delayed feedback less so as lesson-posttest question similarity decreased. Also, with decreased question similarity and the availability of supporting text, overall feedback effects tended to decrease. The results are discussed in terms of the information processing effects of the different feedback forms, a factor that CBI designers often fail to exploit in planning feedback conditions.This article is based on a doctoral dissertation submitted to the faculty of Memphis State University by the first author. Reprint requests should be addressed to Steven M. Ross, Department of Foundations of Education, Memphis State University, Memphis, TN 38152.     

极限思想在化学实验题中的应用

1 爆炸实验爆炸实验的成功、失败等原因可用极限思想去分析。例如,氢气与空气混合气体的爆炸实验。在学生观察过教师做的演示实验之后,许多学生也想亲身体验一下。由于这里的爆炸属于“安全”爆破,我也就满足了他们的愿望,但有个条件:必须在参照课本实验后自己设计爆炸实验装置,自带用     

化学问题解决中元认知训练的研究

元认知在化学问题解决中具有重要的作用。在实际教学中，采取自我提问法、相互提问法、讨论法、知识传授法等进行元认知的训练，可有效地提高学生的元认知水平，促进学生问题解决能力的提高。     

终态分析法在化学解题中的应用

从化学反应的本质分析,提出了终态分析法在循环反应、平行反应以及多步反应等方面的应用.     

中考化学开放性试题选材归类例释

化学开放性试题由于解题方法和策略的不确定性,使得不同水平层次的学生都可以从各自角度提出合理的解题方案,从而激发学生学习化学的积极性,有助于提高学生的科学探究能力。化学试题不论什么类型,归纳起来皆由立意、情境和设问三个要素构成。为实现由知识立意向能力立意转变,各省市的中考化学开放性试题在情境设置上呈现出多样性、灵活性和开放性。本文侧重从开放题的立意、情境及设问等选材方面分析这类试题的类型和特点。     

Student affect and conceptual understanding in learning chemistry

This study explores the relationship between affective and cognitive variables in grade 9 chemistry students (n = 73). In particular, it explores how students' situational interest, their attitudes toward chemistry, and their chemistry‐specific self‐concept influence their understanding of chemistry concepts over the course of a school year. All affective variables were assessed at two time points: at the middle of the first semester of grade 9, and at the end of the second semester of grade 9, and then related to students' postinstructional understanding of chemical concepts. Results reveal that none of the affective variables measured at the earliest time point have a significant direct effect on postinstructional conceptual understanding. Looking at the different affective variables as intermediary constructs, however, reveals a pattern in which self‐concept and situational interest measured at the middle of grade 9 contribute to self‐concept measured at the end of grade 9, which in turn, has a positive, significant effect on students' postinstructional conceptual understanding. These results reveal the importance of a strong and positive self‐concept, the feeling of doing well in the chemistry class, for developing a meaningful understanding of scientific concepts. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 44: 908–937, 2007