共查询到20条相似文献,搜索用时 62 毫秒
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以氯水的教学为案例,运用三重表征方式多元角度认识和理解物质,并用思维导图直观表示三重表征之间的联系。研究结果表明,SOLO分类理论可有效指导教师确定学生的学习最近发展区及有效的教学策略;运用思维导图可直观表示化学知识三重表征之间的逻辑关系,促进学生建构起三重表征的有机整体关系,加速以符号表征为桥梁进行三重表征之间的互译转换,促使学生将多点知识结构发展为关联知识结构、抽象拓展结构水平。因此,在教学中应用思维导图建构化学三重表征的整体关系,有利于提高学生学习结果的质量。 相似文献
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以明矾的净水作用蕴含的化学反应原理为例,着重分析高中“化学1”模块内的7处教学衔接,进而简要论述高中选修模块“化学与生活”“化学反应原理”中的教学衔接。运用思维导图、模型图、概念图、流程图等图示思维教学方式,进行模块内和模块间的知识衔接教学,有利于强化学科理解能力,培养学生的化学核心素养。 相似文献
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介绍了在化学复习课教学中,如何利用思维导图从课前、课中和课后3个阶段引导学生对知识进行系统化的整理,以形成知识体系,并从细节上把握各知识点的应用;同时探讨了思维导图在复习课教学方面的优势。 相似文献
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课堂教学设计是一项十分复杂的教学活动,需要考虑教师、学生、教学内容及教学媒体等诸多要素之间的联系。导图作为一种可视化的教学设计工具,能够使复杂的教学设计直观化、形象化,使教学过程层次化、简洁化,使各种教学要素信息一目了然,是课堂教学活动实施的蓝图。简介3种经典导图,并对原有形式进行拓展与延伸,提出一种新的模型——导教图。从化学新课程改革理念出发,结合“离子反应”的案例探讨了导教图在化学教学设计中的实际应用。 相似文献
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The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted
indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator
model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was
established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing
analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997. 相似文献
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Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared. 相似文献
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Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position. 相似文献
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Stepkowska E. T. Perez-Rodriguez J. L. Jimenez de Haro M. C. Sayagues M. J. 《Journal of Thermal Analysis and Calorimetry》2002,69(1):187-204
Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, Mo, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations
were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples
were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of
hematite Fe2O3. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the
best fitting experimental data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6. 相似文献
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