高中化学项目教学案例——探寻柠檬水中的维生素C

选取“维生素C”这一生活中常见的还原性物质,面向已经学习“氧化还原反应”基础知识的高一年级学生开展项目教学活动。通过提出项目问题、师生共同拆解项目问题设计研究方案和子任务、学生实施子任务研究等项目教学环节,在形成相应子任务成果的同时,进一步帮助学生巩固从氧化性和还原性视角认识化学物质性质的认识角度,建立基于物质性质定量分析目标物质含量的实验思路和思维框架,提升学生对于氧化还原反应功能和价值的认识。     

“乙醛溶液的电解”课堂演示实验研究

针对中学化学实验教学中电解有机物的空白现状,应用Schiff试剂定性检测电解液中乙醛浓度的方法,开发了一个电解乙醛的课堂演示实验。该实验将有机化学中的氧化还原反应与电解过程相结合,以此发展学生对电解池工作原理以及有机化学反应机理的认识。通过实验探究,培育学生“科学探究与创新意识”和“科学态度与社会责任”的学科素养。     

“原电池”的项目式教学*——探究“水动力”盐水灯发光之谜

以“菲律宾能源救星”创设探究情境,以“水动力”盐水灯发光之谜展开项目式学习探究设计之旅,在项目任务推进中对“水动力”盐水灯的原理和影响因素展开深入探究,重建学生对原电池的模型认知;设计并制作“家庭版”水动力灯,最终回归到指导抗震减灾等社会场景中去,加强学科与真实情境的结合与应用,锻炼和提升学生的科学精神与社会责任感,发展学生的化学学科核心素养。     

以“位构性”模型建构和学科能力发展的必修“原子结构 元素周期律”教学设计和实践*

在高中必修阶段“原子结构 元素周期律”主题已有研究的基础上,将“位构性”系统模型与学科能力活动任务相结合,提出了本研究的理论框架,进行了单元整体的教学设计并实施。通过预设学生的表现水平,设计各课时的评价任务,过程性地诊断学生在各个课时中“位构性”模型建构与学科能力的发展水平,描述学生在本章学习过程中的发展变化,促进了学生“证据推理与模型认知”等核心素养的发展。最后,归纳出以“位构性”模型建构和学科能力发展的“原子结构 元素周期律”在教学实践中的有效策略。以期能够对日后开展“原子结构 元素周期律”主题的教学设计与实践能够提供参考和建议。     

高中化学“次氯酸盐的性质”的项目式教学*——84消毒液的使用指南

以“84消毒液的使用指南”为主题,开展高中化学“次氯酸盐的性质”的教学。学生通过完成“一张图说清消毒剂”“探究84消毒液的漂白效果与酸碱性的关系”“探究84消毒液的漂白效果与光照的关系”“探究84消毒液的漂白效果与温度的关系”“84消毒液与酒精混合会有氯气吗”等5个项目任务,理解了次氯酸盐的性质及漂白原理,培养了学生的文献检索能力、实验探究能力以及发展了学生的高阶思维能力。将文献查阅与学生实验相结合,让学生在真实问题的解决中,完成次氯酸盐的性质等相关知识的内化,是顺利完成本项目教学的关键。     

高三复习课“氧化还原反应”的教学实录与反思

基于实证,设计了“氧化还原反应”高三复习课,以“污水处理”为主题,通过创设真实情境,激发生成问题,开展有效活动,引导学生在知识应用中加深对知识的理解,促进知识重构和认识转变,力求实现从虚拟走向真实,从学科走向学生,从经验走向科学,从教学走向教育。     

逆向设计在素养导向的单元教学设计中的应用——以“钠及其化合物”单元为例

逆向教学设计被称为“通过设计促进理解”的教学设计。教学过程中,教师结合课程标准相关要求进行单元逆向教学设计,有助于学生提升学科核心素养,引发深度学习。围绕“钠及其化合物”开展了逆向设计的相关探索。根据逆向设计模板,同时,结合本单元学生需要获取的目标、知识和表现性任务,设计了4个课时的教学任务。单元教学过程整体实现了初始培养学生从微观结构出发,结合实验事实认识钠的性质,进而到学生分析物质性质的相似性和差异性,然后到学生结合相关资料实现鉴别实验方案的设计,最终学生结合相关资料进行纯碱制备工业应用。通过总结学生在“钠及其化合物”单元教学各环节中的表现情况,包括课堂实录、完成表现性任务、以及针对授课学生、同行专家的调研问卷情况,整理了“钠及其化合物”单元教学过程中的相关收获以及反思。相关单元设计的认识可为今后落实“素养为本”的教学提供一定的参考。     

促进学生化学学科核心素养发展的“铁盐和亚铁盐”的单元教学

设计了“铁盐和亚铁盐”的单元教学,以“探究硫酸亚铁的性质”和“线路板腐蚀液的研究”为核心任务,把铁盐与亚铁盐的性质、Fe²⁺和Fe³⁺的相互转化等核心知识贯穿其中,建立从物质类别、元素价态视角研究物质性质及转化的思路方法,促进多维度化学学科核心素养的融合发展。经过多轮次教学改进,结合教学实践过程及其教学效果抽提出“注重应用无机物的认识模型,重点把握研究物质性质的角度和思路”“抓住典型活动,培养学生的关键能力”“设计开放性任务,通过有效的师生对话进行诊断,外显问题解决思路”等教学策略。     

高中化学“铁及其化合物”的项目式教学*——探秘铁肥的合理使用

以“探秘铁肥的合理使用”为主题,开展高中化学“铁及其化合物”的项目式教学。通过完成“确定铁肥的主要成分”“检验铁肥是否变质”“铁肥的合理使用”等3个任务,学生学会不同价态铁元素化合物的转化和检验方法,形成从元素价态和物质类别角度探究物质性质的思路。初步培养了实验探究能力,提升创新意识,发展基于“铁及其化合物价类二维模型建构”的模型认知素养。学生收获了真实新颖、亲身实践、分组合作、交流展示等成就性体验,制作的铁肥保存和合理使用说明书体现了项目式教学的本质特征,实现学习结果的可视性、共享性、交流性。     

大学无机化学中“原电池”的启发探究式教学实践*

介绍了大学无机化学课堂中“原电池”部分的教学实践。通过启发-探究式教学模式,启发学生把常见的氧化还原反应,经过不断的设问和探究,最终设计成原电池,实现了通过原电池装置来证实氧化还原反应发生了电子传递的教学目的。学生在教师的启发下探究、分析、推导、创新和修正,使学生清晰地认识到知识的前后逻辑关系,对氧化还原反应概念、原电池装置有更深刻的理解,培养了学生的科学辩证思维能力。     

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.     

"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.     

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.     

原子量之"变"

原子量是最为基础的科学概念之一,"国际纯粹与应用化学联合会(IUPAC)"之"同位素丰度和原子量委员会(CIAAW)"每两年会修订并发布一次原子量。自2009年起,IUPAC宣布某些元素的原子量不再是常数,这些元素的标准原子量为区间值。为方便使用,对于这些元素,给出一个合理的单一数值,称为常规原子量。何为标准原子量?何为常规原子量?为何某些元素的原子量出现区间值?依据原子量数值的特性,元素可以分为几大类?本文在介绍最新元素周期表中原子量的特点之后,简述原子量测定、标准确定、概念演变的发展历史,讨论原子量的修订与变化等问题。     

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.