认知冲突策略在概念转变教学中的应用

研究表明,引发学生的认知冲突作为一种教学策略,能够有效地实现迷思概念的转变。介绍了认知冲突和概念转变的相关含义和理论,例举了国外认知冲突策略在概念转变教学中成功应用的一些研究案例,包括化学平衡、电化学计算和电解质等。     

整合多重表征 促进概念深度理解——以“原电池”为例

有效整合多重表征,是促进学生科学概念深度理解的一种有效策略。本研究整合了科学教育领域中的3个多重表征框架的内容,对高中必修模块的“原电池”进行了教学设计。首先引导学生依次学习原电池的宏观装置、微观原理和电极符号,初步建构原电池概念,之后基于氢氧燃料电池关联表征,让学生建构原电池的装置原理二维模型图,理解原电池概念,最后依托生活中的纽扣电池应用二维模型图实现表征转换,解决实际问题,实现对原电池概念的深度理解。     

认知冲突策略在概念转变中的应用研究

引发学生的认知冲突作为一种促进概念转变的教学策略在国外已得到深入研究和认可。也有学者提出了异议,认为认知冲突策略有时并不能实现预期的概念转变,甚至对学习者产生消极影响。认知冲突策略的实施还受制于一些其他因素的影响,如学习者的前知识水平、动机、兴趣等。本文从概念转变过程的动态理论模型分析认知冲突策略对概念转变的作用机制,以期为认知冲突策略在概念转变教学中的成功应用提供理论基础。     

概念同化教学中探究实验设计研究——以“可逆反应”概念教学为例

通过对"可逆反应"概念教学中探究实验的设计,提出一种具有普遍意义的概念同化教学中探究实验的设计思路与结构。具体包括"以新概念为基础设计实验,学生以原有概念去解释实验,利用认知冲突探究实验,利用探究结果同化概念"。旨在解决如何充分利用探究实验完成概念同化教学。     

高中生“化学平衡”概念结构的研究

根据认知心理学关于概念结构的理论,对高中生“化学平衡”概念的自由分类进行多维标度和聚类分析,得出高中生的“化学平衡”概念由2个维度组成,学生的分类属于关联聚类,揭示了影响学生概念结构的因素,并对概念教学提出了建议。     

促进概念转变的科学课堂教学研究——以“化学式”概念教学为例

促进概念转变是课堂教学的关键。通过对概念转变原理和概念表征的嬗变分析,以"化学式"概念教学为例,提出了一种具有普遍意义的概念教学结构,具体包括"激活前概念、修正完善概念、建立概念模型、厘清迷思概念、活化科学概念"5个教学过程。在实际课堂中,这一概念转变链必须与认知逻辑链、组织形式链有机对应,才能有效促进概念的转变。     

国际科学教育视角下1-9年级学生“物质”核心概念进阶维度研究

概念转变理论、认知架构理论、概念形成理论都验证了核心概念建构的重要性。基于核心概念建构的进阶路径,介绍了学生理解“物质”概念进阶表征框架、“物质”和学生能力水平进阶表征框架、“物质”结构的学习进阶表征框架、“物质”核心概念区块理论表征框架和“物质”概念描述理论表征框架,并以“水的认识”为例分析了其构造图和结果空间。基于美国、英国、澳大利亚、爱尔兰、新加坡、加拿大阿尔伯塔省、加拿大安大略省、中国台湾、中国大陆9个国家或地区1至9年级科学课程文件,梳理了学生“物质”核心概念,并从“成分与辨识”“性质与应用”“变化与转化”3个视角划分了学生“物质”核心概念进阶维度,介绍了“物质”核心概念进阶测量方法,以期对我国科学教育有所启示。     

创建模型探讨化学概念本质的教学实践——以“饱和溶液”为例

中学化学“饱和溶液”概念的教学中,容易忽视学生已有的前概念,忽视概念建构的过程以及对概念背后本质原理的挖掘,常依托实验来建构概念,导致学生不能充分认识到概念的本质原理。尝试创建模型,采取将模型与实验相结合,用模型解释或预测实验的方式,帮助学生更好地建构并理解“饱和溶液”概念及其本质。     

核心素养视角下“分子和原子”的教学实践与反思

通过对“分子和原子”教学实践的观察和分析,探讨了核心素养视角下化学概念教学的方法和策略。讨论认为,化学概念的诠释与演绎要基于学生的认知能力,要遵循“抽象→具象→抽象”的建构历程,而多维、深刻的参与性则有助于概念的高质量建构。     

关注大概念的教学设计与实践——以“气体摩尔体积”为例

以高中化学中的“气体摩尔体积”概念教学为例,分析了基于大概念教学的必要性,建构了“解读基本概念教学价值,编写基本理解和基本问题,创设有层递性的学习活动”的大概念教学的模式,有利于更好地凸显学科概念本身的价值和意义,形成具有持久价值和迁移价值的关键性的方法、思维和能力。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.