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以“海带中碘的提取”为例,提供文献让学生课前阅读,完成“海带中碘的提取”流程设计,并进行成果交流。在此基础上,进行方案实施,并进行总结评价。研究结果认为,将知识与实践结合,能够激发学生探究热情;将自主文献研究、方案设计、实验验证结合,可以培养学生的科学探究和创新能力;应该注重教-学-评一致性;需要进一步提高教师的实验实际操作能力和知识引导能力。 相似文献
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以探寻二氧化碳的工业捕集方案为项目主题,开展初中化学二氧化碳的性质及其转化的教学。学生通过“建立价类二维模型并设计二氧化碳的理想转化路径”“实验探究二氧化碳的实际转化”“解决二氧化碳的工业转化”等3个项目子任务理解了物质“组成、性质、变化”之间的关系,运用手持技术数字化实验探究了二氧化碳在不同碱溶液中的吸收效率,发展了实验探究能力,构建了物质转化在化工生产领域的认知模型,提高了思维迁移的能力。从“碳捕集”到“碳利用”的进阶解决问题模式,有利于学生化学学科核心素养的内化。 相似文献
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高三元素化合物专题复习要关注学生探究意识的提升和解决情境探究问题思维框架的搭建。在元素化合物探究活动设计中,将有关碘及其化合物的物质转化过程和探究反应中"异常现象"的原因进行有机整合,围绕如何设计实验方案开展实证活动,搜集证据证实或证伪猜想来展开教学。阐述了探究活动设计的思路与开展方式,形成了解决问题的一般思维模型,并进行了教学反思。 相似文献
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以“盐水洗鼻”中洗鼻液的配制为抓手和主要任务,通过学生将任务拆解成子任务并转化为化学问题,在合作探究、实际操作中,掌握溶质、溶剂及溶质质量分数之间的关系,配制出符合标准的洗鼻液。 相似文献
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以“探究食品脱氧剂中的化学问题”为项目学习主题,以探究食品脱氧剂的主要成分、脱氧原理、能量转化形式为项目学习活动,呈现了基于项目学习的高中化学教学设计思路、教学流程,进行了项目教学实施,并结合前后测、学生自评互评和教师评价量表从知识、能力、素养等方面分析了实施项目教学后的效果。 相似文献
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1教学目标设计[设计说明]“硫的转化”一节用3课时,第1课时学习含硫物质在自然界中的转化,第2课时学习含硫物质在实验室中的转化,第3节学习含硫物质在生产生活中的转化。本节课是学生在了解了含硫物质在自然界中的转化的基础上,引导学生探究在实验室如何实现不同价态硫元素之间的转化。运用氧化还原反应的理论来了解二氧化硫等含硫元素的物质的性质。本节课过程设计的思路是:首先是使学生进一步明确在实验室中开展探究活动的一般方法和步骤;其次是开展具体的探究活动。教师需要充分预计到探究活动中出现的各种情况以及解决的办法,为学生提供必须的试剂、药品,提供完全开放的探究环境,由学生自主完成探究任务。在学生进行探究活动前,一定要要求他们遵循“观察预测实验(设计合理的实验方案、选择合理的试剂和药品、注意观察实验现象和出现的问题)分析、归纳、整理得出结论”的实验程序。通过活动探究,重点认识二氧化硫的性质即氧化性、还原性、酸性和漂白性。[知识与技能目标](1)学生掌握使0价、 4价、 6价元素之间的转化,了解二氧化硫的性质。(2)通过在实验室探究不同价态硫元素之间的转化,使学生掌握运用氧化还原反应寻找合适的氧化剂和还原剂来实现不同价态含硫物质... 相似文献
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从学生实验能力培养出发,以"液-液萃取"实验内容为例,对较为常见的教学内容"乙醚萃取醋酸水溶液中醋酸"和"四氯化碳萃取碘水中碘"进行比较,提出选用"四氯化碳萃取碘水中碘"作为"液-液萃取"教学内容。并在此基础上,增加"四氯化碳回收"和"碘水中碘的含量测定"为拓展教学内容。教学实践表明:重组的"液-液萃取"项目,不仅丰富了教学内容,增强了实验项目的趣味性和综合性,更重要的是增加了学生课堂动手训练机会,同时对于培养学生化学实验素养、提高对环境保护的意识和自主探究学习精神起到了积极推进作用。 相似文献
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正探究型教学是课堂教学的重要形式,也是提升学生学科核心素养的有效方式,在落实时,教师需要处理好"放手"与"引导"之间的关系。1探究型教学的现状在新课改的引领下,教师的探究型教学走向了两个极端:有些形似探究的课堂活动,其实是在教师"严密布局"中展开的,造成了教师"放手"而学生实则被动探究的假象,这是换一种表现形式的"灌输式"教学;有些教师将课堂全部交予学生,没有任何方法与情境设定,从而导致课堂教学效率低下,部分能力相对较差的学生,整节课都处于无序的状态下,形成了教师"放手"而学生实则无效探究的状态。 相似文献
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Eduardo Q. Luz Diego Seckler Janylson Souza Araújo Leonardo Angst David B. Lima Elise Ane Maluf Rios Ronny R. Ribeiro Daniel S. Rampon 《Tetrahedron》2019,75(9):1258-1266
A mild and efficient iron (III)-catalyzed C3 chalcogenylation of indoles has been developed and the role of the iodide ions in this transformation was investigated. EPR experiments revealed the reduction of Fe(III) to Fe(II) under the reaction conditions, supporting the formation of molecular iodine in the system, which in effect catalyze the reaction. The scope of the chalcogenylation was broad and the synthesis of more functionalized 3-selenylindoles was explored. 相似文献
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S. M. Steinberg G. T. Schmett G. Kimble D. W. Emerson M. F. Turner M. Rudin 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(1):175-183
Iodine-129 is a fission product and highly mobile in the environment. Along with other stable isotopes of iodine, 129I is released during reprocessing of nuclear fuel and must be trapped to prevent the release of radioactivity to the environment.
Past studies have provided evidence that iodine can become associated with natural organic matter (NOM). This research explores
the use of NOM (sphagnum peat and humic acid) to sequester iodine from the vapor and aqueous phases. NOM-associated iodine
may be stable for geological storage. NOM-sequestered iodine can be recovered by pyrolysis to prepare target materials for
transmutation. The nature of the NOM-iodine association has been explored. 相似文献
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The kinetics and mechanism of the formation, growth and dissolution of iodine films on platinum during the electrooxidation of iodide have been investigated using rotating-disk and ring-disk techniques. The dissolution-precipitation mechanism of film formation and a linear growth law for film growth has been confirmed. The iodine film on platinum is believed to be made up of an ionically insulating barrier layer covered by a porous overlayer. The oxidation behavior of iodide and ferrous species shows that the iodine film is predominantly an iodide-ion conductor. Also, a film transformation, responsible for the transient features observed during iodide oxidation has been confirmed. This transformation changes the mechanism of iodide transport through the film from a partly “pore”-type to a Grotthus-type mechanism. The ring current maximum, which occurs at the same instant as the disk current minimum, reveals the mechanism of dissolution of iodine film during the transient period as involving complexation with iodide. Evidence for the mass-transport-controlled component of the potentiostatic transient response has been obtained from the sinusoidal hydrodynamic modulation response. 相似文献
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A direct transformation from methyl ketones to secondary or tertiary amides has been developed through a novel electrochemical approach and a wide scope of formamides could be utilized as the amide sources. This transformation was promoted by in situ generated iodine through electrolysis of sodium iodide under mild, metal-free conditions. This electrochemical procedure could avoid the use of stoichiometric iodine and afforded the target products in good to excellent yields. 相似文献
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无烟煤中碘燃烧释放和转化行为研究 《燃料化学学报》2017,45(3):265-271
采用逐级化学提取法研究无烟煤及其不同温度燃烧产物中碘的各种赋存状态;以小型管式炉模拟煤燃烧装置,考察了加热温度、加热时间、O_2流量以及通入水蒸气对无烟煤中不同形态碘燃烧释放影响及其机理。结果表明,无烟煤中碘主要以有机结合态、铁锰氧化物结合态和水溶态形式存在。加热温度对碘释放和转化有明显影响,碘释放率随温度升高而增加,500-900℃是碘释放的主要阶段。其中,700℃以前,水溶态、离子交换态和有机结合态碘大部分释放,小部分转化为碳酸盐结合态、铁锰氧化物结合态和残留态碘;铁锰氧化物结合态碘主要在700-900℃释放,部分残留态碘在1 100℃前也可释放。无烟煤中碘释放率随燃烧时间延长和O_2流量增大而增大,水蒸气的参与能明显促进碘的释放。在1 100℃、通入水蒸气、O_2流量120 m L/min、燃烧20 min时,93.8%-95.9%碘主要以HI和I_2释放。 相似文献
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YC He J Yang GC Yang WQ Kan JF Ma 《Chemical communications (Cambridge, England)》2012,48(63):7859-7861
We describe an exceedingly rare example of solid-state single-crystal-to-single-crystal transformation from a 2D layer to a known 3D framework via lattice iodine release, which involves the formation of a new Cu-O ligand bond and a change in the metal coordination geometry. 相似文献
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Both 2E- and 2Z-3-iodoacrolein O-methyl oximes are prepared in two steps from ethyl propiolate. Lithium–iodine exchange is effected and the resulting organolithium reagents added to several electrophiles, including styryl isocyanate which gives a conjugated O-methyl oxime enamide of the type found in the side chains of the oximidine, lobatamide and CJ-12950 natural products. The Pd(0) catalysed cross-coupling of these iodoalkenes is also explored. 相似文献
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P. Yi 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1689-1692
Iodine is a bio-intermediate and redox-sensitive element in the oceans and understanding the relationship between transformation of iodine species promotes them as indicators of biochemical cycling in the ecosystems. To gain an insight into the transformation of iodine species, correlations between the iodine species (127IO3 ?, 127I?, 129I?, 129IO3 ?) and marine parameters (temperature, salinity, oxygen, total phosphorus, nitrate and ammonium) are assessed here for the Baltic Sea during different seasons. The datasets used cover the periods of August 2006, April 2007 and November 2009. The results indicate that the correlations between radioactive 129I, stable 127I species and marine parameters mainly response to their respective sources as well as oceanographic environments. Also, insignificant correlations of iodine species and nutrients data (total phosphorus, nitrate and ammonium) are observed, suggesting that transformation activity of iodine species in the Baltic Sea is not directly linked to biological production. 相似文献