实验室制备乙烯的探究式学习

乙烯的实验室制法是中学化学中的一个重要实验,从探究式学习的角度,用对照实验分析并解决了乙醇和浓硫酸的最佳体积配比为1:3,反应温度控制在160˜180℃为宜等问题.并以此为例阐述了探究式学习过程中的基本思路与实施方法.     

对二氧化碳的化学性质演示实验的改进

人民教育出版社九年义务教育三年制初中化学教材演示实验[5-7]：向盛有紫色石蕊试液的试管里通入二氧化碳,观察石蕊试液颜色的变化,待石蕊试液颜色变化后停止通人二氧化碳,取少量溶液放在酒精灯火焰上加热,再观察石蕊颜色的变化（图1）。     

过氧化钠与二氧化碳反应的演示实验设计

高中化学新教材第一册第三章中有“过氧化钠与水的反应的演示实验” ,学生观察实验后情绪高涨 ,但有些疑惑 ,他们一直认为水是用来灭火的 ,为什么水还能“生火”呢 ?并且好多学生问 :二氧化碳是否也可以用来“生火” ?书中只有过氧化钠与二氧化碳反应 ( 2Na2 O2 +2CO2 =2Na2 CO3 +O2 )的知识点 ,而没有相关的实验 ,为了给学生以感性认识 ,激发他们的探究意识 ,打破思维定式 ,经过多次探索和实践 ,特设计如下实验。方法一1　实验用品药匙、石棉网、长玻璃管、三角架、棉花、Na2 O2粉末2　实验装置 (三角架略 )图 13　实验步骤与现象( 1)…     

将实验创新纳入探究式教学中

在新教材使用中以备课组为科研小组,尝试开展探究式教学。实验是探究式教学必不可少的重要环节,实验创新又是科研过程的必由之路。总结了备课组近几年来对实验在探究学习的作用、关系和创新价值的认识和做法。     

蒙古文版探究式“氢气实验室制法”CAI课件实验效果研究

以新的教学理念为指导,设计研制了蒙古文版探究式"氢气实验室制法" CAI课件,对呼和浩特市蒙古族学校和通辽市腰林毛都中学初三学生进行了蒙古文版探究式"氢气实验室制法"CAI课件实验效果研究,并对其实验结果进行了统计分析,发现蒙古文版探究式CAI课件对培养学生能力和提高课堂学习效率方面有重要作用.提出了怎样设置探究式问题情景、探究式CAI课件对初中化学蒙授教学有何益处、在初中化学教学中蒙授教师如何应用CAI课件进行探究式教学等启发与建议.     

化学探究式教学评价指标及其试测的研究

依据具有探究式教学特征要素的化学教学基本过程及其建构性教学功能,设计化学探究式教学过程的专家评价表和学生调查问卷,对几个化学课例进行评价,对所得相关数据进行统计分析。表明所建构的教学环节和评价指标基本恰当,对推进以探究式为主的多样化教学方式具有重要的启示。     

2例有机实验的改进

中学化学教学中一直沿用教材中设计的乙烯和乙炔的实验室制法的装置图来制取这2种气体,并直接用来验证它们的性质。毋庸讳言,这种做法是不合理的,也缺乏科学性。有必要加以改进。     

碳酸钠与硫酸反应制取二氧化碳的实验研究

实验室制取CO2一般用盐酸和大理石,但存在以下3个问题:(1)为提高反应速率需要用浓度比较大的盐酸,盐酸属于挥发性强酸,对皮肤和黏膜有很强的刺激及腐蚀作用;(2)产物中混有HCl和H2O,需要净化处理;(3)反应不彻底,浪费试剂。用块状Na2CO3晶体与稀H2SO4溶液反应制取CO2气体,可以克服上述问题。     

注重实验探究活动及学习体验的教学*——实验室制取二氧化碳

以化学实验为主的探究活动及学习体验,是化学学习的重要途径。以“实验室制取二氧化碳”为例,设计了“反应原理”“发生装置”“收集方法”“验满方法”等4个教学环节,对实验室制取气体的一般思路和方法进行建模。课上创设了3个学生活动,让学生尽情地动手动口动脑去体验,还创设了3个实验探究以解决3个认知冲突。学生在这样的课堂中生发感知、思维、情感、意志、价值观等多维的真实的内在体验,逐步形成化学学科观念、科学思维、质疑精神和创新意识,从而转变学习方式。     

品味"物质的量"教学

《化学教育》2003年第6期刊登了朱文祥、裴毅两位老师“让我们给‘物质的量’命个名”一文。文章指出“物质的量”作为一个物理量名称的不严谨为学生及化学工作者带来诸多不便。介绍了英、美等国化学教材、专著中“mole”概念的引入、使用。作者认为十分必要给“物质的量”取个特定的名称,     

探究“二氧化硫的性质”教学设计

为了优化二氧化硫性质的教学设计,提高教学效益,从生活情境切入,利用微型仪器和生活替代品开展实验探究活动,引导学生认识二氧化硫酸性氧化物的通性、特性及既有氧化性又有还原性的两面性,构建较为完整的二氧化硫知识体系;激发学习兴趣,培养环境意识和辩证唯物主义的世界观。     

Application of Supercritical Carbon Dioxide for the Preparation of Drug-Cyclodextrin Inclusion Compounds

Inclusion complexes of drugs into cyclodextrins (CDs) can be obtained at the solid state by means of supercritical dioxide (SCCO₂). A successful inclusion with a yield >98.5% has been achieved with piroxicam and -CD. The temperature and the time of exposure to SCCO₂ have a significant effect on the inclusion yield while the pressure has a negative effect. However, there is a strong interaction between temperature and pressure and this interaction has a positive influence. The molar ratio piroxicam--CD and the addition of ternary alkaline agents were also found to be significant factors. The dissolution rate of the complexes formed using SCCO₂ was found to be significantly higher than that of the physical mixture. Inclusion complexes have also been obtained with miconazole treating mixtures of miconazole, CDs and citric acid by SCCO₂. This new technique of inclusion of poorly soluble drugs into CDs allows the preparation of solid complexes without using organic solvents and thus without residues.     

Carbon Dioxide Fixation Method for Electrosynthesis of Benzoic Acid from Chlorobenzene

Carbon dioxide fixation technique was developed as an alternative dechlorination method of chlorobenzenes.Electrolysis of chlorobenzene was carried out in a one-compartment cell fitted with an alu- minium anode and a platinum cathode.Electrolysis in N,N-dimethylformamide(DMF)solution contain- ing 0.1 M of tetrapropylammonium bromide(TPAB)at 0℃,100 ml/min of CO_2 flow rate and 120 mA/cm~2 of current density was found to be the optimum conditions of this electrocarboxylation,which gave 72% yield of benzoic acid from chlorobenzene.These conditions were then applied to 1,2-dichlorobenzene and 1,3-dichlorobenzene in order to convert them to their corresponding benzoic acids.     

在超临界CO2聚合反应中应用的表面活性剂的研究

概括了表面活性剂在以超临界CO2 为介质的分散反应和乳化反应中的应用研究进展。重点介绍了几种重要的表面活性剂的结构、机理及应用 ,并指出在应用超临界CO2 技术进行的聚合反应中 ,表面活性剂具有重要的作用及广阔的应用前景。     

Low-temperature Data for Carbon Dioxide

We investigated empirical data for the vapor pressure (154≤T≤196 K) and the heat capacity (12.52≤T≤189.78 K) of solid carbon dioxide. A computer algebra system (CAS) was used for all calculations. From the numerical point of view, we have adopted a cubic piecewise polynomial representation for the heat capacity and reached an excellent agreement between the available empirical data and the calculated ones. Furthermore, we have obtained values for the vapor pressure and heat of sublimation at temperatures below 195 right down to 0 K. The theoretical key prerequisites are: 1) Determination of the heat of sublimation of 26250 J · mol⁻¹ at vanishing temperature and 2) Elaboration of a ‘linearized’ vapor pressure equation that includes all the relevant properties of the gaseous and solid phases. It is shown that: 1) The empirical vapor pressure equation derived by Giauque & Egan remains valid below the assumed lower limit of 154 K (a similar argument holds for Antoine’s equation), 2) The heat of sublimation reaches its maximum value of 27211 J · mol⁻¹ at 58.829 K and 3) The vapor behaves as a (polyatomic) ideal gas even for temperatures below 150 K.     

Low-temperature Data for Carbon Dioxide

Summary. We investigated empirical data for the vapor pressure (154≤T≤196 K) and the heat capacity (12.52≤T≤189.78 K) of solid carbon dioxide. A computer algebra system (CAS) was used for all calculations. From the numerical point of view, we have adopted a cubic piecewise polynomial representation for the heat capacity and reached an excellent agreement between the available empirical data and the calculated ones. Furthermore, we have obtained values for the vapor pressure and heat of sublimation at temperatures below 195 right down to 0 K. The theoretical key prerequisites are: 1) Determination of the heat of sublimation of 26250 J · mol⁻¹ at vanishing temperature and 2) Elaboration of a ‘linearized’ vapor pressure equation that includes all the relevant properties of the gaseous and solid phases. It is shown that: 1) The empirical vapor pressure equation derived by Giauque & Egan remains valid below the assumed lower limit of 154 K (a similar argument holds for Antoine’s equation), 2) The heat of sublimation reaches its maximum value of 27211 J · mol⁻¹ at 58.829 K and 3) The vapor behaves as a (polyatomic) ideal gas even for temperatures below 150 K.     

CH_4、CO_2与O_2制合成气用Ni-Ce/γ-Al_2O_3催化剂的制备与催化活性的关系

利用 DTA-TGA、TPR、XRD和 XPS等表征手段 ,对用不同方法制备的催化剂进行表征 ,并结合催化剂的活性评价结果 ,研究 Ni-Ce/γ-Al2 O3催化剂的制备方法与催化活性的关系 .结果表明 ,无论浸渍法或共沉淀法制备的催化剂 ,都具有较高的 CH4转化活性 .这说明在反应过程中甲烷的活化仅与催化剂表面存在Ni物种相关 ,而与催化剂上 Ni Al2 O4的还原程度关系不大 .但对于 CO2 的活化 ,共沉淀法制备的催化剂 ,在高温还原预处理和反应过程中 ,晶型不完整的 Ni Al2 O4所还原生成的新鲜态的、低价 Ni物种 ,具有较强的活化能力 .因此共沉淀法制备的催化剂较浸渍法制备的催化剂具有更高的 CO2 的转化率和 CO的收率     

液相法制备纳米氧化锡防团聚方法综述

针对液相法制备纳米氧化锡颗粒团聚的问题,以溶胶-凝胶法为例,介绍了防团聚的几种措施:加入表面活性剂,有机溶剂洗涤,共沸蒸馏及冷冻干燥等.这几种方法虽可以制备出粒径较小,均匀,分散性好的粒子,但也各有优缺点:反应时加入表面活性剂,容易引入杂质;有机溶剂洗涤廉价而便利,但是存在洗涤凝胶滤饼时溶剂漏滤的问题;而共沸蒸馏需要特殊的减压装置,比较看来,利用有机溶剂洗涤是一种相对方便的办法.     

CO2加氢合成二甲醚的催化剂的制备

先采用均匀沉淀法制备出CuO—ZnO催化剂,然后以CuO—ZnO催化剂作为晶核采用水热合成法制备出CuO—ZnO／HZSM-5（氢型ZSM-5分子筛）复合催化剂．利用X射线衍射和氨程序升温脱附手段对复合催化剂进行表征,并应用于CO2催化加氢合成二甲醚的反应．研究结果表明,在相同的反应条件下,这种CuO—ZnO／HZSM-5复合催化剂与采用物理混合法制备出的复合催化剂相比具有更好的催化效果,不但提高了CO2的转化率、二甲醚的选择性以及二甲醚和甲醇的总选择性,同时还改善了催化剂的稳定性．     

Utilization of Supercritical Carbon Dioxide for the Preparation of 3-Hydroxyflavone and β-Cyclodextrin Complex

The solubility of 3-hydroxyflavone in water can be enhanced by forming complex with β-cyclodextrin (β-CD). In this study we introduced supercritical carbon dioxide as a substitute solvent to prepare 3-hydroxyflavone-β-cyclodextrin complex. The maximum drug loading determined by UV spectroscopy in complex was 14.7 wt.%, which was comparable to that of 1:1 complex (17.34 wt.% of 3-hydroxyflavone). The solubility of the drug loaded in the complex was better than that of pure drug in water. The enhanced solubility was attributed to the formation of the complex and the solubility of the β-cyclodextrin in water.