共查询到19条相似文献,搜索用时 96 毫秒
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“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。 相似文献
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微观表征插图是重要的化学教学素材,是学生对三重表征在头脑中加工内化的重要认识媒介。为了能在“化学反应原理”模块教学中更好地发挥微观表征插图的价值,通过内容分析法,对中国人教版高中化学教科书和美国高中化学教科书Chemistry: Concepts and Applications在此模块的微观表征插图设计进行了比较分析。结果显示,2种版本教科书中的微观表征插图在该模块插图总数中的占比较少,呈现最多的主题内容均为过程微观表征;缺少“化学反应的方向、限度和速率”主题的微观表征插图;2者表征的形式水平较高,但美版教材更好地融合了“宏、微、符”3类表征。最后,基于分析结果对教科书“化学反应原理”模块中微观表征插图的设计与使用提出了相关建议。 相似文献
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我国大陆和台湾的化学(科学)教材在化学启蒙方面的内容编写有着各自的特点和优势,因此以我国大陆人教版初中《化学》与我国台湾康轩文教版《自然与生活科技》为例,通过问卷调查法与对比分析法,研究化学启蒙阶段的学生对待化学的态度以及海峡两岸教材中“实验”“插图”“科普知识”等3部分内容的设置差异。结果表明:(1)化学实验是启蒙阶段学生对化学感兴趣的起始点,也是初接触时的难点,其中以我国台湾《自然与生活科技》教材中化学实验的探究性及层次性更深;(2)化学启蒙阶段教材中插图的科学性、清晰度以及精美程度对学生学习化学的兴趣和态度有较大影响;(3)化学教材中的模型图实物化有助于学生拨云见日,了解化学的真实模样。 相似文献
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“金属的化学性质”是初高中化学学习的重要内容,该部分内容涉及到重要的化学观念和化学学科核心素养,如元素观、转化观、微粒观、STS观,以及宏观辨识与微观探析、证据推理与模型认知素养。但是初三学生认知水平受限,在教学中不能深入电子转移的微观角度,不能充分认知模型、应用模型。为弥补这一问题,本研究基于化学学科核心素养,进行“金属的化学性质”的初高中衔接教学研究。 相似文献
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3‐Aminopropyltriethoxylsilane (APS), N‐[3‐(Trimethoxylsilyl)propyl]‐ethylenediamine, N‐[3‐(Trimethoxylsilyl)propyl]diethyenetriamine were assembled onto silicon surfaces. Using a mixture of acetone and water as solvent, factors which would affect the formation of amino‐terminated self‐assembled monolayers (SAMs), such as water content in solvent and reaction time, were investigated. The structural information of SAMs was collected from contact angle measurements, ellipsometric thickness measurements and X‐ray photoelectronic spectroscopy. Reaction time and water content in solvent produced dominant effects on the formation of amino terminated SAMs. The method introduced in this paper also presents a simple and controllable way to prepare amino‐terminated SAMS. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Suellen Cadorin Fernandes Deise Maria Pereira de Oliveira Santos Iolanda Cruz Vieira 《Electroanalysis》2013,25(2):557-566
In this study a biosensor with laccase immobilized in a chitosan matrix was developed. Prior to the laccase immobilization the chitosan was cross‐linked with genipin, a naturally‐occurring cross‐linking agent, and incorporated into a carbon‐paste electrode. Analytical parameters for caffeic acid, such as repeatability (2.7 %), reproducibility (3.0 %), linearity (0.27 and 33 µM; r2≥0.9983), limit of detection (LOD=0.18 µM) and recovery (96–103 %), were determined. The method was applied in the determination of the total phenolic content of mate herb samples. The good performance of the method can be attributed to the effective immobilization of laccase in the cross‐linked support. 相似文献
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Synthesis and characterization of high refractive index polyimides derived from 2,5‐Bis(4‐Aminophenylenesulfanyl)‐3,4‐Ethylenedithiothiophene and aromatic dianhydrides 下载免费PDF全文
Hyeonuk Yeo Jiye Lee Munju Goh Bon‐Cheol Ku Honglae Sohn Mitsuru Ueda Nam‐Ho You 《Journal of polymer science. Part A, Polymer chemistry》2015,53(7):944-950
The authors describe the synthesis and characterization of the polyimide (PI) series containing a 2,5‐bis(4‐aminophenylenesulfanyl)‐3,4‐ethylenedithiothiophene (APSEDTT) moiety in their main chain. The APSEDTT monomer with high sulfur content was prepared and polymerized with several aromatic dianhydrides such as 4,4′‐[p‐thio bis(phenylenesulfanyl)]diphthalic anhydride (3SDEA), 4,4′‐biphthalic anhydride (BPDA), and 4,4′‐oxydiphthalic anhydride (ODPA) by the traditional two‐step polycondensation procedure. All PIs exhibited high transparency, higher than 75% at 550 nm for a thickness of about 20 μm and good thermal properties such as thermal decomposition temperatures (T10%) in the range of 409–521 °C. In addition, the PIs have extraordinarily excellent optical properties in refractive index and birefringence as originally designed. In particular, the PI derived from APSEDTT and 3SDEA showed a high refractive index (1.7586), and a low birefringence (0.0087) because of their very high sulfur content (27.7%). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 944–950 相似文献
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The hierarchical porous nitrogen‐doped carbon materials (HNCs) were prepared by using nitrogen containing gelatin as the carbon source and nano‐silica obtained by a simple flame synthesis approach as the template. All of the as‐obtained HNCs show much higher Li storage capacity as compared with commercial graphite. Specifically, HNC‐700 with biggest micropore volume and highest nitrogen content exhibited optimal reversible capacities of 1084 mAh·g??1 at the current density of 37.2 mA·g?1 (0.1 C) and 309 mAh·g?1 even at 3.72 A·g?1 (10 C). This result suggests that HNCs should be a promising candidate for anode materials in high‐rate lithium ion batteries (LIBs). 相似文献
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阐释了学科教学认识和促进学生认识发展教学的基本内涵,在此基础上结合化学学科和“原电池”的内容特点,从有关“原电池”的学科知识、课程知识、学生理解的知识、教学策略及表征的知识等4个方面,论述了“原电池”主题的学科教学认识的构建。 相似文献
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An O3‐type Oxide with Low Sodium Content as the Phase‐Transition‐Free Anode for Sodium‐Ion Batteries 下载免费PDF全文
Chenglong Zhao Dr. Maxim Avdeev Prof. Liquan Chen Prof. Yong‐Sheng Hu 《Angewandte Chemie (International ed. in English)》2018,57(24):7056-7060
Layered transition metal oxides NaxMO2 (M=transition metal) with P2 or O3 structure have attracted attention in sodium‐ion batteries (NIBs). A universal law is found to distinguish structural competition between P2 and O3 types based on the ratio of interlayer distances of the alkali metal layer d(O‐Na‐O) and transition‐metal layer d(O‐M‐O). The ratio of about 1.62 can be used as an indicator. O3‐type Na0.66Mg0.34Ti0.66O2 oxide is prepared as a stable anode for NIBs, in which the low Na‐content (ca. 0.66) usually undergoes a P2‐type structure with respect to NaxMO2. This material delivers an available capacity of about 98 mAh g?1 within a voltage range of 0.4–2.0 V and exhibits a better cycling stability (ca. 94.2 % of capacity retention after 128 cycles). In situ X‐ray diffraction reveals a single‐phase reaction in the discharge–charge process, which is different from the common phase transitions reported in O3‐type electrodes, ensuring long‐term cycling stability. 相似文献
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以高效氯氰菊酯为芯材, 乙基纤维素为壁材, 采用溶剂蒸发法制备了微胶囊, 并对其理化性能进行表征, 通过单因素实验研究了工艺参数对微胶囊外观形貌、 粒径大小及分布、 包封率、 载药量和缓释性能的影响. 结果表明, 乳化剂种类和剪切时间可以显著影响微胶囊的外观形貌; 随着乳化剂用量增大, 微胶囊粒径减小, 分布变窄, 当Tween-80用量从4%增加至8%时, 微胶囊平均粒径从59.9 μm减少到29.8 μm, 跨距也从1.21减少到0.72. 随着芯壁比(质量比)减小, 微胶囊粒径和包封率均逐渐增大, 载药量逐渐减小, 当芯壁比为1:1.75时, 包封率可以达到70%以上. 微胶囊释放动力学模型符合Ritger-Peppas模型(lgQ=lgk+nlgt); 平均粒径相近而载药量不同时, 初期载药量最小的样品释放速率慢, 累积释放率低; 载药量相近而平均粒径不同时, 粒径大的样品释放速率低, 累积释放率也低. 相似文献
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采用流程图结构分析方法对新人教版、新鲁科版、旧人教版3版高中化学教材中“离子反应”内容难度进行测评和比较。研究发现,新教材在核心概念的引入、衔接、组织方式上发生了重要变化。新人教版呈现了层次更加丰富、组织更加合理、意义更加饱满的“离子反应”知识结构体系,新人教版更加注重情境推理与解释表征策略的运用,创设合理情境,在情境中蕴含问题,在问题的解决过程中形成概念;新鲁科版注重宏微符的三重表征,凸显对比和比较的表征策略,为学生展现把握概念内涵与应用的多种路径和多个维度。 相似文献