基于化学史的微观表征教学策略研究——以“原子的构成”教学为例

以“原子的构成”教学分析和实践为例,通过回溯化学史,讲述电子、原子核、质子、中子等微粒发现的故事,使这些微观知识在学生头脑中形象化和具体化,使之更易被学生理解、接受和表征.通过学生的反馈证明,基于化学史讲故事是一条行之有效的微观表征教学策略.     

进口中间相沥青碳纤维超高温石墨化处理后的特性分析

对P25、P55及XN-90三种进口中间相沥青碳纤维3000℃石墨化处理前后的微观形貌、晶体尺寸、力学性能、导电导热性能及其抗氧化性能进行了表征.结果 表明,三种碳纤维微观结构差异较大,均呈现出较为明显的"指纹"特征.三种碳纤维中XN-90热处理温度最高,晶体尺寸最大,石墨化程度最高,抗氧化性能最好.经过3000℃石墨...     

基于建构化学基本观念的对比教学法——以“质量守恒定律”教学设计为例

在质量守恒定律的教学中,将对比教学法巧妙地运用于史料知识、实验探究、数据分析中,有助于实现学生宏观表征从"质"到"量"的突破,微观表征从"静"到"变"的转化,符号表征从"孤立"到"联系"的完善,从而建立宏观-微观-符号表征之间的联系,学生对定律的认识在从模糊到清晰并臻于科学的过程中,构建物质变化观。     

“化学反应速率”微观模型的创建探究

探讨了构建化学微观模型的价值与原理, 指出利用微观模型帮助学生理解抽象概念的重要意义, 并通过对"化学反应速率"教学现状的分析, 提出构建其微观模型的必要性和可能性。在此基础上, 构建了温度与分子运动、活化分子、活化能的微观模型以及化学反应微观过程与宏观、符号表征相关联的模型。     

高中生化学学习中“映象表征”、“符号表征”及其转换能力的调查分析

为了了解中学生化学学习中"映象表征"的能力以及"映象表征"向"符号表征"的转换能力,采用自编问卷对江苏8所四星级高中的高一学生进行了调查。结果表明,学生"映象表征"能力中的"宏观表征"能力强于"微观表征"能力;"映象表征"向"符号表征"转换能力较弱。提出了化学学习中提高学生表征能力的建议。     

中美高中化学教科书“化学反应原理”模块微观表征插图的设计分析

微观表征插图是重要的化学教学素材,是学生对三重表征在头脑中加工内化的重要认识媒介。为了能在“化学反应原理”模块教学中更好地发挥微观表征插图的价值,通过内容分析法,对中国人教版高中化学教科书和美国高中化学教科书Chemistry: Concepts and Applications在此模块的微观表征插图设计进行了比较分析。结果显示,2种版本教科书中的微观表征插图在该模块插图总数中的占比较少,呈现最多的主题内容均为过程微观表征;缺少“化学反应的方向、限度和速率”主题的微观表征插图;2者表征的形式水平较高,但美版教材更好地融合了“宏、微、符”3类表征。最后,基于分析结果对教科书“化学反应原理”模块中微观表征插图的设计与使用提出了相关建议。     

初三学生化学三重表征转化的眼动实验研究

化学三重表征研究一直深受国内外学者的重视,目前,初级表征的研究已有一定的理论基础,但是,次级表征（即不同表征水平之间的转化）的研究仍是研究的弱点和难点。纸笔检测、口语报告研究方法都存在一定的局限。为了从信息加工过程研究三重表征间转化的基本特点,采用眼动分析法对12名初三学生进行3×3两因素混合实验。结果显示：（1）在初三上册期末,学优生基本可以进行三重表征之间的直接转化;（2）学中生符号表征较强且依赖于符号表征,表现出“双通道协同加工”现象,符号—宏观、微观转化水平较强,宏观—微观、符号和微观—符号、宏观转化水平较弱;（3）学困生普遍缺乏三重表征的思维和意识,三重表征间的转化水平较低,相比较而言,符号-宏观、微观表征转化稍强于宏观-微观、符号表征转化和微观-符号、宏观表征转化。     

微观表征视角下的高中《化学反应原理》教科书插图评价

采用文本分析法对人教版和鲁科版高中《化学反应原理》教科书中微观表征插图的使用情况进行分析。结果显示,2种版本教科书出现的微观表征插图数目均较少,微观表征插图主题内容均偏重“过程”,均只体现到部分重要主题,而且均缺乏“宏观-微观“表征插图。对如何合理认识微观表征插图的意义及系统规划微观表征插图的使用作出讨论。     

基于“宏观-微观-符号”有机融合的离子键教学

离子键是一个比较抽象的概念,无法用直观的观察和实验获得具体的认识。教学中,运用宏观和微观相结合的方法,引导学生从宏观层面感受离子键的真实存在,从微观层面认识离子键的形成和本质,用化学符号表征离子键的形成过程,建立宏观和微观之间的辩证关系,丰富和发展学生对离子键的理性认识。     

多重表征教学:纸牌游戏中的化学平衡观

以多重表征模型为基础的问题解决教学将以跨学科的视域消解理论和实践的张力,防止理科课程与教学变革的内在异化。借助“纸牌游戏”活动开展关于化学平衡专题的教学实践,结果表明,该教学活动能够帮助学生通过微观表征使得符号表征深刻化,实现不同表征之间的转换和错误概念的转变,从而建构深刻的化学平衡的观念。     

化“材”为“筑”

Chemistry is a central, practical and creative discipline. The development of chemistry plays an important role in the progress of science and society, as well as the improvement of the quality of human life. This paper introduces the chemical knowledge of stone, concrete, glass and other inorganic nonmetallic building materials by the anthropomorphically story. Taking nanomaterials as an example, the prospect of building materials development in the future is put forward.     

"Alpha"-, "beta"- and "delta"-anhydrodigitoxigenin

The syntheses of 3β-hydroxy-5β-carda-14, 20:22-dienolide (= «β»-anhydro-), 3β-hydroxy-5β-carda-8:14, 20:22-dienolide (= «α»-anhydro-) and «δ»-anhydro-digitoxigenin (= probably 3β-hydroxy-5β, 14β-carda-8, 20:22-dienolide) by the best ways known to date, have been described. «δ»-Anhydro-digitoxigenin represents the thermodynamically most stable isomer. In this isomer the double bond in position 8 is unaffected by hydrogenation with Pt in acetic acid; with perbenzoic acid an epoxide results from which, on hydrogenation, the double bond can be regenerated in its original position. Analogous reactions are known to occur in the 8:14-epoxides.     

Making "wheels" and "cubes" from triangles

[Mn(IV)Mn(II)3] triangular units directed by the presence of tripodal alcohols self-assemble in the presence of azide and acetate ligands to form either a [Mn24] "wheel" or a [Mn32] "cube".     

"Turn-on" fluorescent sensing with "reactive" probes

Chemical probes are valuable tools for the investigation of biochemical processes, diagnosis of disease markers, detection of hazardous compounds, and other purposes. Therefore, the development of chemical probes continues to grow through various approaches with different disciplines and design strategies. Fluorescent probes have received much attention because they are sensitive and easy-to-operate, in general. To realize desired selectivity toward a given analyte, the recognition site of a fluorescent probe is designed in such a way to maximize the binding interactions, usually through weak molecular forces such as hydrogen bonding, toward the analyte over other competing ones. In addition to such a supramolecular approach, the development of fluorescent probes that sense analytes through chemical reactions has witnessed its usefulness for achieving high selectivity, in many cases, superior to that obtainable by the supramolecular approach. Creative incorporations of the reactive groups to latent fluorophores have provided novel chemical probes for various analytes. In this feature article, we overview the recent progress in the development of turn-on fluorescent probes that are operating through chemical reactions triggered by target analytes. Various chemical reactions have been implemented in the development of many reactive probes with very high selectivity and sensitivity toward target analytes. A major emphasis has been focused on the type of chemical reactions utilized, with the hope that further explorations can be made with new chemical reactions to develop reactive probes useful for various applications.     

"Decoking" of a "coked" zeolite catalyst in a glow discharge

'Decoking' of a 'coked' zeolite catalyst in a glow discharge in oxygen is investigated. The 'decoking' process involves reactions of atomic oxygen (O atoms) with 'coke' and yields gases such as CO, CO₂ as well as other gaseous products that could be easily pumped out.Three different modes of discharge were investigated including a static mode, a flowing-gas mode, and a periodic-purge mode where the oxygen and other gaseous products of the discharge were replaced by fresh O₂ gas after short but regular intervals of time. In some cases, additional heating was also used to provide base temperatures of the order of 100 °C to facilitate penetration of oxygen atoms into the inner layers and cages of the zeolite catalyst.This paper presents some results of spectroscopic analytical techniques used to monitor the atomization of oxygen, oxidation of 'coke', and to confirm the process of 'decoking'. More specifically, radiation emission on the 3 s ⁵S– 3p ⁵P transitions of O around 777.2–777.5 nm were selected for monitoring the atomization of O₂. On the other hand, X-ray photo-electron spectroscopy (XPS) was used to determine the amount of residual carbon and extent of 'decoking'. Furthermore, evolution of CO and CO₂ gases as a function of time was systematically monitored in real time. For CO, the 451.1 nm band head belonging to the B¹ - A¹ bands of the Angstrom system of the CO spectrum was used, while for CO₂, the band head at 353.4 nm belonging to the CO₂⁺ spectrum was used. The rates of evolution of CO and CO₂ were related to the rate of 'decoking' of the catalyst. It is noted that in the periodic-purge mode, about 63% of the total yield of CO from a given sample of the catalyst appears in the first 3-min exposure to discharge whereas it takes up to 15 min to remove nearly 94% of the removable carbon under our experimental conditions.     

营养化学课程翻转课堂的探索与实践

With its tailored learning content, flexible learning environment and directed teacher guidance, the flipped classroom in "nutrition chemistry" has effectively solved the problems of students' specialty, large number and limited time in the course of elective course. The teaching mode based on the cultivation of students' ability and the core of improving scientific literacy was constructed.     

Size evolution study of "molecular" and "atom-in-cluster" polarizabilities of medium-size gold clusters

A study on static polarizabilities for a family of gold clusters (Au(n), n = 6, 12, 20, 34, 54) is presented. For each cluster, a density functional theory perturbation theory calculation was performed to compute the cluster polarizability and the polarizability of each atom in the cluster using Bader's "quantum theory of atoms in molecules" formalism. The cluster polarizability tensor, α(cluster), is expressed as a sum of the atom-in-molecule tensors, α(cluster)=∑(Ω)α(Ω). A strong quadratic correlation (R(2) = 0.98) in the isotropic polarizability of atoms in the cluster and their distance to the cluster center of mass was observed. The cluster polarizabilities are in agreement with previous calculations.