共查询到20条相似文献,搜索用时 750 毫秒
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电解质、离子反应、化学键组成一个核心概念群,是学生掌握相关知识的重难点。对北京市普通高中370名高二学生的测查显示:(1)概念掌握的程度为:化学键<离子反应<电解质。(2)“电解质的概念”与“导电原理”“离子反应概念”“离子共存”的掌握程度存在显著相关;电离与离子反应概念的掌握程度显著相关;“导电原理”与“离子反应概念”“离子共存”“离子键与共价键综合辨析”的掌握程度显著相关。表明电解质的概念、导电原理的理解与掌握是概念体系中的重要纽带。(3)优秀、中等、学困3类学生在解决容易和较难2类概念的相关问题上差异最大,而中等难度上的差异相对较小。基于此,提出了相应的核心概念教学对策。 相似文献
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在完成离子反应基础知识教学后,增开1节DIS实验探究离子反应的生长课堂,以问题情境引入课堂,通过利用电导率传感器和温度传感器等手持技术和实验数据曲线图分析,以Qu:Est教学策略开启了学生理解离子反应的钥匙,帮助学生利用DIS实验从“离子反应的本质、进行方向、发生机理……”角度认识离子反应. 相似文献
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以高中化学必修“电离和离子反应”为例,提出了以发展学生宏观辨识与微观探析维度的素养为导向,凸显情境、知识、素养的有效整合,体现“教、学、评”一致性的单元整体教学设计思路和实践操作案例。 相似文献
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常态课的评析,因其贴进教师的真实教学,易于被教师理解和接受;通过高三第二轮小专题复习“离子反应方程式正误判断及与量比有关的离子反应方程式的书写”常态课的评析,揭示了离子反应方程式与量比有关的本质原因:反应体系中基本的离子反应不唯一. 相似文献
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基于中学教学实际,针对师生对复杂离子反应及其离子方程式书写的困惑,通过整理和归纳,把复杂离子反应分为连锁反应、并列反应和竞争反应等3种反应类型,探究了复杂离子反应的规律、分析策略、离子方程式书写的方法及应用。 相似文献
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选取"离子反应"知识作为研究内容,开展了相关化学数字化实验的教学实践,通过二段式测验工具、SOLO分类法的量化分析,来检测化学数字化实验对学生概念改变的影响。结果显示,化学数字化实验能够在一定程度上促进学生的概念改变。 相似文献
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Kerstin Schulze‐Matthi Jürgen Bendig Petra Neubauer Burkhard Ziemer 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):e257-e258
The bonding geometry of sulfur in the cations of the title compounds, C8H11S+·CF3SO3? and C13H13S+·CF3SO3?, respectively, is similar and is independent of the ratio of the Me/Ph substituents. As expected, in both cations, the S—Ph bonds are somewhat shorter than the S—Me bonds. In both crystal structures, the interaction between cations and anions is similar. 相似文献
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Russell G. Baughman Kenneth L. Martin Rajendra K. Singh James O. Stoffer 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(2):o103-o106
In 2,4‐dihydroxybenzaldehyde 2,4‐dinitrophenylhydrazone N,N‐dimethylformamide solvate {or 4‐[(2,4‐dinitrophenyl)hydrazonomethyl]benzene‐1,3‐diol N,N‐dimethylformamide solvate}, C13H10N4O6·C3H7NO, (X), 2,4‐dihydroxyacetophenone 2,4‐dinitrophenylhydrazone N,N‐dimethylformamide solvate (or 4‐{1‐[(2,4‐dinitrophenyl)hydrazono]ethyl}benzene‐1,3‐diol N,N‐dimethylformamide solvate), C14H12N4O6·C3H7NO, (XI), and 2,4‐dihydroxybenzophenone 2,4‐dinitrophenylhydrazone N,N‐dimethylacetamide solvate (or 4‐{[(2,4‐dinitrophenyl)hydrazono]phenylmethyl}benzene‐1,3‐diol N,N‐dimethylacetamide solvate), C19H14N4O6·C4H9NO, (XII), the molecules all lack a center of symmetry, crystallize in centrosymmetric space groups and have been observed to exhibit non‐linear optical activity. In each case, the hydrazone skeleton is fairly planar, facilitated by the presence of two intramolecular hydrogen bonds and some partial N—N double‐bond character. Each molecule is hydrogen bonded to one solvent molecule. 相似文献
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Ming‐Liang Tong Shao‐Liang Zheng Xiao‐Ming Chen 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):960-962
The title compound, poly[[diaquadibromocadmium‐μ‐(1,3,5,7‐tetraazatricyclo[3.3.1.13,7]decane‐N1:N5)‐aquacadmium‐di‐μ‐bromo‐aquacadmium‐μ‐(1,3,5,7‐tetraazatricyclo[3.3.1.13,7]decane‐N1:N5)‐di‐μ‐bromo] dihydrate], [Cd3Br6(C6H12N4)2(H2O)4]·2H2O, is made up of two‐dimensional neutral rectangular coordination layers. Each rectangular subunit is enclosed by a pair of Cd3(μ2‐Br)6(H2O)3 fragments and a pair of (μ2‐hmt)Cd(H2O)2Br2(μ2‐hmt) fragments as sides (hmt is hexamethylenetetramine). The unique CdII atom in the Cd2Br2 ring in the Cd3(μ2‐Br)6(H2O)3 fragment is in a slightly distorted octahedral CdNOBr4 geometry, surrounded by one hmt ligand [2.433 (5) Å], one aqua ligand [2.273 (4) Å] and four Br atoms [2.6409 (11)–3.0270 (14) Å]. The CdII atom in the (μ2‐hmt)Cd(H2O)2Br2(μ2‐hmt) fragment lies on an inversion center and is in a highly distorted octahedral CdN2O2Br2 geometry, surrounded by two trans‐related N atoms of two hmt ligands [2.479 (5) Å], two trans‐related aqua ligands [2.294 (4) Å] and two trans‐related Br atoms [2.6755 (12) Å]. Adjacent two‐dimensional coordination sheets are connected into a three‐dimensional network by hydrogen bonds involving lattice water molecules, and the aqua, bromo and hmt ligands belonging to different layers. 相似文献
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Y. Akishige H. Shigematsu T. Tojo H. Kawaji T. Atake 《Journal of Thermal Analysis and Calorimetry》2005,81(3):537-540
Summary Specific heats on the single crystals of Sr2Nb2O7, Sr2Ta2O7 and (Sr1-xBax)2Nb2O7 were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of TINC (=495 K) on Sr2Nb2O7 and at the super-lattice phase transition of TSL (=443 K) on Sr2Ta2O7; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of TLOW (=95 K) on Sr2Nb2O7. The transition temperature TLOW decreases with increasing Ba content x and it vanishes for samples of x>2%. 相似文献
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A. V. Egorysheva V. D. Volodin T. Milenov P. Rafailov V. M. Skorikov T. D. Dudkina 《Russian Journal of Inorganic Chemistry》2010,55(11):1810-1817
A physicochemical study of glasses based on the MO-Bi2O3-B2O3 and SrO-Bi2O3-B2O3 systems was performed. Glass formation regions were found. The structural and optical properties, as well as the thermal
behavior of the glasses, were studied. 相似文献
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Jem‐Mau Lo Golam Mostafa Ling‐Yin Chang Fen‐Ling Liao Tian‐Huey Lu 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(4):o276-o277
The title compound, C10H18N2S2, acts as an important precursor for the synthesis of the pharmaceutically important diaminedithiol ligand system. The molecule has a local twofold axis and the arrangement of the S2N2 donor atoms in the macrocycle is anticlinal. 相似文献
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S. Shanmuga Sundara Raj Hoong‐Kun Fun Zhong‐Lin Lu Wen Xiao Xiao‐Yang Gong Chang‐Ming Gen 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):1015-1016
The whole molecule of the title compound, C19H14N4O2, is essentially planar, with a highly conjugated π system. In the crystal, the molecules are packed as chains along the [011] direction connected by O—H?N intermolecular hydrogen bonds. 相似文献
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John Nicolson Low George Ferguson James L. Wardell 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):e317-e317
In the title compound, [Sb(CH3)(C6H5)3]BF4, there are four independent cations and anions in the asymmetric unit. The geometry around the Sb atom is distorted tetrahedral, with Sb—C distances in the range 2.077 (4)–2.099 (10) Å and angles at the Sb atom in the range 103.3 (3)–119.0 (4)°. 相似文献
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Hai-Rong Guo Yuan Gao Ai-Dong Li Zhong Yan Di Wu 《Journal of Sol-Gel Science and Technology》2008,45(3):315-318
Pb0.56Sr0.44Zr0.52Ti0.48O3 (PSZT) inverse opal photonic crystals (PCs) have been synthesized by a process of self-assembly in combination with a sol–gel
procedure. PSZT inverse opals show pure perovskite structure with good orders in three dimensions. The evident photonic band
gaps have been observed in the transmittance spectra with a blue-shift phenomenon due to the decrease of opal template periods.
PSZT inverse opals also exhibit the reflection peaks in basic agreement with the calculated results. This three-dimensional
(3D) ordered PSZT inverse opals have shown interesting optical characteristics and potential applications in optoelectronic
and photonic devices. 相似文献