合作探究教学提高化学实验教学实效性

伴随着中学教学改革的不断深入,探究式教学已经成为热点和难点问题;本文探讨了合作探究教学的概念,分析了理论来源,设计了教学方法,并结合化学教学实践提出了若干重要环节。     

化学概念教学中学生归纳与演绎思维的培养*——基于对“电解质”概念教学的分析

归纳与演绎思维在化学概念的形成、巩固和应用过程中发挥着重要作用,化学概念教学中归纳与演绎思维的培养要遵循生为主体师为主导、概念教学与思维培养相统一、思维培养和概念教学循序渐进、归纳演绎与分析综合相结合的原则。以“电解质”概念的教学为例,分别从化学概念教学中归纳思维的培养和演绎思维的培养等2个维度对具体培养路径进行了阐释。     

基于学科理解的“物质成分”大概念教学*

以“物质成分”大概念教学为例,基于学科理解,以探究物质成分的相关化学史为线索设计教学,引导学生在追溯“物质成分”相关概念、理论的发展过程中,逐渐建构物质成分的宏观、微观、宏微结合视角。并在解决探究物质成分的真实问题的过程中,培养学生基于证据进行推理的科学论证能力,通过认识视角的发展,体会科学理论是在不断发展和进阶的,初步建立科学发展观。     

“电离与离子反应”的单元教学设计与实施*——食盐精制:从微观角度看粗盐中可溶性杂质的去除

在“食盐精制:从微观角度看粗盐中可溶性杂质的去除”的单元教学中,通过初识粗盐中的杂质、微观角度看氯化钠、微观角度看粗盐溶液、微观角度认识除杂方法、设计除杂方案并实施等活动,促进学生理解与应用电离、离子反应等核心概念,引领学生解决真实问题,形成解决除杂实验问题的基本思路,实现能力素养的发展。经过多轮次教学改进,结合教学实践及其教学效果抽提出“聚焦核心概念和学生必做实验,实现认识能力的进阶与实际问题解决过程高度融合”“通过学科实践及实验探究,建立宏观、微观、符号关联,突出证据推理,构建思维模型”“通过持续性评价活动,外显学生的前概念,促进概念转变,形成化学学科思维方式”等教学策略。     

“素养为本”的化学课堂教学*——以“原子晶体”为例

基于“素养为本”视角,以“原子晶体”的教学为例,对教学主题内容、教学现状及学情进行分析;以发展学生化学学科核心素养为主旨确定教学目标;以“微粒-微粒间的相互作用-物质的聚集状态-物质性质”的认识思路为主线,以“模型认知,建构概念-证据推理,归纳性质-微观探析,探究结构-科学史实,揭示价值”的任务型教学流程,达到落实并发展学生化学学科核心素养的目的。     

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。     

发展学生化学学科核心素养的课例研究——以“离子反应”为例

以高中化学“离子反应”概念教学为例,阐述了发展学生化学学科核心素养的课例研究思路和教学活动设计。围绕离子反应概念、离子方程式书写、离子反应发生条件等知识内容,挖掘教学内容与学科核心素养内涵的联系,创设真实且富有价值的问题情境,开设高水平的实验探究活动,注重微观分析过程,将离子反应概念的学习与从微观离子角度分析水溶液中反应的认识思路进行整合,力求发展学生的化学学科核心素养,帮助学生形成对“离子反应”概念的整体认识。     

溯源辨析“活化分子”概念在化学教材中的角色定位*

“活化分子”作为国内化学教育领域广为人知的科学概念,在各类相关化学教材中都有介绍。然而在国外多种经典化学教材中却完全没有“活化分子”的概念,反映出国内外化学教育领域对化学反应速率理论相关知识点的处理上存在明显的差异与分歧。通过溯源关键历史文献,回顾了“活化分子”概念的形成及其在化学反应速率理论发展过程中的角色演变,指出“活化分子”概念已经退出反应速率理论的舞台,在教材中应更多地呈现其在科学史方面的价值,而不是科学价值。     

皖西地区探究式化学教学开展情况的调查与思考

探究式教学是素质教育具体化和深化,是教学改革的重要趋向。本文通过对皖西地区部分完全高中的师生调查,揭示了现阶段的探究式化学教学存在着的不少问题,建议教师要在理论上提高认识,加强学习,树立以学生发展为本的观念;在教学策略上要多管齐下,因材施教,不断提高学生的探究意识和探究水平;在教学过程中要精选探究内容,进行选择性的科学探究。     

化学课堂探究教学“制订计划”的评价

为了解化学课堂探究教学“制订计划”的有效性,在课堂观察与分析的基础上,提出化学课堂探究教学“制订计划”系统分析量表,并结合具体化学课堂探究教学,从计划制订的主体、计划制订的过程、计划内容本身等3个方面解析了“制订计划”环节。结果启示：化学课堂探究教学“制订计划”系统分析量表能科学有效地指导化学课堂探究教学,特别是其“制订计划”的设计、实施与评价。     

Chemical durability of MoO<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> and K<Subscript>2</Subscript>O-MoO<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Thermal and chemical durability studies of the phosphate glasses belonging to the binary MoO₃-P₂O₅ and the ternary K₂O-MoO₃-P₂O₅ systems are reported. The chemical resistant attack tests carried out on the free alkaline MoO₃-P₂O₅ glasses show that the glass associated with the P/Mo ratio 2 has the high chemical durability. It shows also a high glass transition temperature value. The above findings are interpreted in terms of the cross-link density of the glasses and the strength of the M-O bonds (M=P, Mo). The influence of K₂O addition on the properties (density, T _g, durability) of this binary high water resistant glass is studied. It is found that the chemical durability along with the other physical properties are reduced by the incroporation of K₂O in the glass matrix. The results were explained by assuming the formation of non-bridging oxygens and weak bonds. The mechanism of the dissolution of these glasses is proposed.     

Imidazole‐Aided Native Chemical Ligation: Imidazole as a One‐Pot Desulfurization‐Amenable Non‐Thiol‐Type Alternative to 4‐Mercaptophenylacetic Acid

Various bioactive proteins have been synthesized by native chemical ligation (NCL) and its combination with subsequent desulfurization (e.g., conversion from Cys to Ala). In NCL, excess 4‐mercaptophenylacetic acid (MPAA) is generally added to facilitate the reaction. However, co‐elution of MPAA with the ligation product during preparative high‐performance liquid chromatography sometimes reduces its usefulness. In addition, contamination of MPAA disturbs subsequent desulfurization. Here, we report for the first time that imidazole can be adopted as an alternative to MPAA in NCL using a peptide‐alkylthioester. The efficiency of the imidazole‐aided NCL (Im‐NCL) is similar to that of traditional MPAA‐aided NCL. As model cases, we successfully synthesized adiponectin(19‐107) and [Ser(PO₃H₂)⁶⁵]‐ubiquitin using Im‐NCL with a one‐pot desulfurization.     

Interaction of solid electrolyte La<Subscript>0.88</Subscript>Sr<Subscript>0.12</Subscript>Ga<Subscript>0.82</Subscript>Mg<Subscript>0.18</Subscript>O<Subscript>2.85</Subscript> with hydrogen,water vapor,and carbon dioxide

The air,Au/La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85/Au,air cells are studied by an impedancemetry method before and after a week-long exposure at 700°C to atmospheres of hydrogen, humid air, and carbon dioxide. Blank specimens of the same electrolyte are examined by methods of x-ray diffraction, Raman scattering (RS), and x-ray photoelectron spectroscopy. The fact that the shape of the RS spectra and the shape of the electrode impedance dispersion alter unequivocally suggests that, at the very least, the electrode surface interacts with all the gases. The interaction in question is reversible in the case of hydrogen and carbon dioxide. In the case of water vapor, the interaction is irreversible.Translated from Elektrokhimiya, Vol. 41, No. 2, 2005, pp. 198–205.Original Russian Text Copyright © 2005 by Shkerin, Kovyazina, Beresnev, Kalashnikova, Martemyanova.This revised version was published online in April 2005 with corrections to the article note and article title and cover date.     

Synthesis of Disulfide Surrogate Peptides Incorporating Large‐Span Surrogate Bridges Through a Native‐Chemical‐Ligation‐Assisted Diaminodiacid Strategy

The use of synthetic bridges as surrogates for disulfide bonds has emerged as a practical strategy to obviate the poor stability of some disulfide‐containing peptides. However, peptides incorporating large‐span synthetic bridges are still beyond the reach of existing methods. Herein, we report a native chemical ligation (NCL)‐assisted diaminodiacid (DADA) strategy that enables the robust generation of disulfide surrogate peptides incorporating surrogate bridges up to 50 amino acids in length. This strategy provides access to some highly desirable but otherwise impossible‐to‐obtain disulfide surrogates of bioactive peptide. The bioactivities and structures of the synthetic disulfide surrogates were verified by voltage clamp assays, NMR, and X‐ray crystallography; and stability studies established that the disulfide replacements effectively overcame the problems of disulfide reduction and scrambling that often plague these pharmacologically important peptides.     

<Superscript>63</Superscript>Cu and <Superscript>139</Superscript>La NMR and chemical bonding in anion-deficient perovskite LACu<Subscript>0.81</Subscript>Ni<Subscript>0.19</Subscript>O<Subscript>2.5+δ</Subscript>

The ⁶³Cu and ¹³⁹La NMR spectra of the low-(δ = 0.25) and high-temperature (δ = 0) phases of lanthanum cuprate LACu_0.81Ni_0.19O_2.5+δ have been obtained. Quantum chemical calculations of the electronic structure of the high-temperature phase have been performed. It is found that the observed metal-semiconductor phase transition is attended by changes in the degree of atomic ordering and in the character of electronic conductivity over certain types of “copper” centers.     

Addition reactions of nitrones on the reconstructed C(1 0 0)-2 × 1 surfaces

In this paper, the reactions of nitrone, N-methyl nitrone, N-phenyl nitrone and their hydroxylamine tautomers (vinyl-hydroxylamine, N-methyl-vinyl-hydroxylamine and N-phenyl-vinyl-hydroxylamine) on the reconstructed C(1 0 0)-2 × 1 surface have been investigated using hybrid density functional theory (B3LYP), Møller–Plesset second-order perturbation (MP2) and multi-configuration complete-active-space self-consistent-field (CASSCF) methods. The calculations showed that all the nitrones can react with the surface “dimer” via facile 1,3-dipolar cycloaddition with small activation barriers (less than 12.0 kJ/mol at B3LYP/6-31g(d) level). The [2+2] cycloaddition of hydroxylamine tautomers on the C(1 0 0) surface follows a diradical mechanism. Hydroxylamine tautomers first form diradical intermediates with the reconstructed C(1 0 0)-2 × 1 surface by overcoming a large activation barrier of 50–60 kJ/mol (B3LYP), then generate [2+2] cycloaddition products via diradical transition states with negligible activation barriers. The surface reactions result in hydroxyl or amino-terminated diamond surfaces, which offers new opportunity for further modifications.     

MoS<Subscript>2</Subscript> single slab as a model for active component of hydrodesulfuration catalyst: a quantum chemical study 1. Molecular and electronic structure of Mo<Subscript>12</Subscript>S<Subscript>24</Subscript> macromolecule and its adsorption complex with H<Subscript>2</Subscript>S

The molecular and electronic structure of Mo₁₂S₂₄ macromolecule as the MoS₂ single slab structure was calculated by the density functional theory (DFT) method with the B3P86 hybrid exchange-correlation functional. The results of calculations point to slight relaxation of coordinatively unsaturated Mo and S atoms, which is consistent with the published data. The calculated width of the forbidden band (0.85–0.98 eV) is comparable with the experimental value (1.30 eV) and similar to that obtained from DFT calculations with periodic boundary conditions (0.89 eV). The surface Mo centers in the Mo₁₂S₂₄ macromolecule are more reduced than the internal (Mo^IV) atoms. In order to characterize the adsorption capacity of coordinatively unsaturated Mo centers, a Mo₁₂S₂₄·6H₂S adsorption complex was calculated. The structure and energy characteristics of the adsorption complex point to a weak donor-acceptor interaction of the π-lone pair of H₂S molecule with the surface (reduced) Mo centers. The active center of thiophene hydrodesulfuration catalysts is formed as a result of the oxidative addition of hydrogen followed by occlusion of hydrogen into the MoS₂ matrix. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2189–2193, October, 2005.     

Synthesis of Epigoitrin from (R)‐(+)‐4‐Hydroxy‐γ‐butyrolactone

Epigoitrin is one of the major components of several natural species, including Isatis indigotica Fort, turnip, and cabbage. It presents antithyroid and antivirus activities. Here, we report an efficient and practical method for the chemical synthesis of epigoitrin from commercially available (R)‐(+)‐4‐hydroxy‐γ‐butyrolactone.     

Total Chemical Synthesis and Biological Activities of Glycosylated and Non‐Glycosylated Forms of the Chemokines CCL1 and Ser‐CCL1

CCL1 is a naturally glycosylated chemokine protein that is secreted by activated T‐cells and acts as a chemoattractant for monocytes. 1 Originally, CCL1 was identified as a 73 amino acid protein having one N‐glycosylation site, 1 and a variant 74 residue non‐glycosylated form, Ser‐CCL1, has also been described. 2 There are no systematic studies of the effect of glycosylation on the biological activities of either CCL1 or Ser‐CCL1. Here we report the total chemical syntheses of both N‐glycosylated and non‐glycosylated forms of (Ser‐)CCL1, by convergent native chemical ligation. We used an N‐glycan isolated from hen egg yolk together with the Nbz linker for Fmoc chemistry solid phase synthesis of the glycopeptide‐^αthioester building block. 3 Chemotaxis assays of these glycoproteins and the corresponding non‐glycosylated proteins were carried out. The results were correlated with the chemical structures of the (glyco)protein molecules. To the best of our knowledge, these are the first investigations of the effect of glycosylation on the chemotactic activity of the chemokine (Ser‐)CCL1 using homogeneous N‐glycosylated protein molecules of defined covalent structure.     

Interatomic interactions and electronic structure of NbSe<Subscript>2</Subscript> and Nb<Subscript>1.25</Subscript>Se<Subscript>2</Subscript> nanotubes

Atomic models of achiral NbSe₂ nanotubes are suggested. Band structure calculations have been performed to investigate the electronic structure and determine the parameters of interatomic interactions. The distribution of the density of states and pair bond occupancies of NbSe₂ nanotubes are analyzed in relation to the type of the atomic configuration and the tube diameter; the results are compared with the band structure of the 2H-NbSe₂ crystal. Calculations have been carried out on hypothetical superstoichiometric nanotubes with a formal composition Nb_1.25Se₂ as possible quasi-one-dimensional nanoforms of autointercalated niobium diselenide.Original Russian Text Copyright © 2004 by A. N. Enyashin, V. V. Ivanovskaya, I. R. Shein, Yu. N. Makurin, N. I. Medvedeva, A. A. Sofronov, and A. L. IvanovskiiTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 579–588, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.