共查询到20条相似文献,搜索用时 78 毫秒
1.
通过调查发现学生在学习化学平衡之后,仍然对化学平衡中的5大中心概念问题:(1)动态平衡的判断;(2)浓度、温度、压强(体积)等对化学平衡的影响;(3)浓度、温度、压强(体积)等对化学平衡反应速率的影响;(4)盐类对溶解平衡的影响;(5)惰性气体对化学平衡的影响等存在大量的迷思概念。在此基础上论文汇总了学生在化学平衡学习过程中存在的重要迷思概念以及对重要迷思概念产生原因进行了分析,最后得出结论,传统的教学很难转变学生的迷思概念。 相似文献
2.
通过谈话、问卷调查等研究方法设计化合物与混合物迷思概念的二段式检测工具,分析辽西地区九年级学生化合物与混合物迷思概念的主要类型,归纳为生活经验型、名词产生型、概念混淆型和宏微错位型等4个方面,并且从性别、所在地区等方面探讨影响迷思概念的外在因素.对获得的数据结果进行spss13.0统计分析. 相似文献
3.
了解学生化学概念学习中存在的错误或模糊认识有利于提高概念教学的成效。选取了一些与环境化学相关的概念进行调查,从中找出学生存在的模糊认识,客观分析了学生环境化学迷思概念的成因,并提出了教学建议。 相似文献
4.
5.
利用二段式测验准确诊断高三化学复习中学生的迷思概念对于教师顺利实施概念转变教学、选择适当的复习教学策略、提高高三复习效益有着重要的意义。详述了二段式测验题的类型、编制、施测和分析方法,并结合具体教学实例(化学平衡)讨论如何利用二段式测验诊断高三化学复习中学生的迷思概念。 相似文献
6.
7.
设计了一个面向高年级本科生或低年级研究生的计算化学探索实验,即利用密度泛函理论(DFT)计算烯丙基正离子的旋转异构反应。该实验设计了反应物结构优化、过渡态寻找、内禀反应坐标建立等过程,可以较为全面地帮助学生了解计算化学的基本概念与操作,加深对分子微观结构的感知以及对过渡态理论中“旧键即将断裂,新键即将形成”概念的理解。本实验通过旋转异构反应的势能面的构建,也可以帮助学生认识反应热力学和动力学的差别。通过进一步的电荷布居分析以及前线轨道分析,可以帮助学生直观地学习并理解分子的电子结构以及反应活性位点概念。 相似文献
8.
物理化学中的热力学公式在不同条件下有不同的衍变形式,极易诱导学生产生错误理解。通过实例分析,对热力学能和焓变化计算公式、赫姆霍兹自由能和吉布斯自由能判据、热力学基本方程等的使用和理解中存在的一些问题予以讨论。 相似文献
9.
10.
11.
The stability constants of the Sm(NO3)2+ complex were determined at three temperatures, using the solvent extraction method. It was found that:K
1
0
=63.6 at 17°C, 30.3 at 35°C, 20.1 at 50°C. This corresponds with the formation of a Sm(H2O)(NO3)2+ complex at 17°C and a Sm(H2O)2(NO3)2+ complex at 50°C.
Der Einfluß der Temperatur auf die Bildung von Samarium Nitrato Komplexen
Zusammenfassung Die Stabilitätskonstanten von Sm(NO3)2+ Komplexen wurden mittels der Lösungsmittelextraktionsmethode bei drei Temperaturen bestimmt. Dabei ergab sichK 1 0 =63.6 bei 17°C, 30.3 bei 35°C und 20.1 bei 50°C. Das entspricht der Bildung eines Sm(H2O)(NO3)2+ Komplexes bei 17°C und eines Sm(H2O)2(NO3)2+ Komplexes bei 50°C.相似文献
12.
F. Millich J. D. Eick G. P. Chen T. J. Byerley E. W. Hellmuth 《Journal of Polymer Science.Polymer Physics》1993,31(6):729-733
Materials that polymerize without substantial volume contraction have numerous valuable applications in dentistry and other fields. Two new symmetrical aliphatic spiro-orthocar-bonates, formulated from cis- and trans-2-hydroxymethyl-cyclohexanol to give 2,3,8,9-di(tetramethylene)-1,5,7,11-tetraoxaspiro [5,5] undecanes, showed, by density determinations in dilute solution, that expansion occurs with polymerization. The cis / cis-spiroorthocarbonate racemic mixture showed a 3.9% expansion upon polymerization, and the trans/trans racemic mixture showed a 3.5% expansion. The densities were determined by pycnometry, with a precision reliable to at least four figures. This method is thus recommended for cases of soluble monomer/polymer pairs for which the density difference will be small and where the partial specific volumes are independent of concentration, thereby avoiding the complexities of variable physical states of monomer and/or polymer. © 1993 John Wiley & Sons, Inc. 相似文献
13.
以丙酮和N,N-二甲基甲酰胺(DMF)为混合溶剂,实验室自制固-固相变材料为相变工作物质,醋酸纤维素(CDA)为高分子载体,利用静电纺丝技术制备了相变调温纤维,研究了溶剂配比、纺丝液浓度、纺丝电压等对纤维形貌的影响。结果表明:以N,N-二甲基甲酰胺(DMF)和丙酮为溶剂(体积比为1/4),在纺丝液质量分数为22%、纺丝... 相似文献
14.
15.
LI Hui-qing ZHENG Xiao-yan ZHAO Ya-qin YANG Bin-sheng Institute of Molecular Science Key Laboratory of Chemical Biology Molecular Engineering of Ministry of Education Shanxi University Taiyuan P. R. China 《高等学校化学研究》2009,25(3)
It is known that urea and guanidine hydrochloride(GuHCl) induce conformational change of proteins in a certain range of molar ratios. In our research,α-naphthylamine(NA) above 10-4 mol/L at pH 7.0 was discovered to perturb the conformation of CopC,a copper resistant protein with a Greek β-barrel motif; this was reflected by the greater fluorescence quenching and red-shifted emission peak of CopC. The conformation change of CopC was also verified in acrylamide collision experiment by comparing quenching leve... 相似文献
16.
Dong Kyun You Ji Hye Lee Hyonseok Hwang Hyoshik Kwon Myung Hwan Park Kang Mun Lee 《Tetrahedron letters》2017,58(33):3246-3250
1,3,5-Tris-(o-carboranyl-methyl)benzene (closo-1) and its nido-form (nido-1) were synthesized and fully characterized. The solid-state molecular structure of closo-1 was determined by single-crystal X-ray diffraction analysis. Compound closo-1 exhibited an intense single emission in various organic solvents that was red-shifted with increasing solvent polarity. The positive solvatochromic effect and theoretical calculation results at the first excited (S1) optimized structure of closo-1 strongly suggest that this emissive band can be assigned to an intramolecular charge transfer. Meanwhile, nido-1 showed a pronounced red-shift of the emissive band compared to that of closo-1 and aroused low-energy emission. The specific emissive features of nido-1 were attributed to the elevation of its HOMO level, estimated by cyclic voltammetry. The photophysical changes by conversion from closo-1 to nido-1 allowed the emissive color-tunable sensing of fluoride. Thus, the tris-o-carboranyl compound showed great potential as a chemodosimeter for fluoride anion sensing, detectable by the naked-eye. 相似文献
17.
J. L. Oscarson S. E. Gillespie J. J. Christensen R. M. Izatt P. R. Brown 《Journal of solution chemistry》1988,17(9):865-885
The aqueous reactions, {ie865-1}were studied as a function of ionic strength at 275, 300, and 320°C using a flow calorimetric technique. Log K, H and S values were determined from the fits of the calculated and experimental heats while Cp values were calculated from the variation of H values with temperature. The log K and H values for the first two reactions agree well with literature values at these temperatures. No previous results have been reported for the third reaction. The use of equations containing identical numbers of positive and identical numbers of negative charges on both sides of the equal sign (isocoulombic reaction principle) was applied to the log K values determined in this study. The resulting plots of log K for the isocoulombic reactions vs. I/T were approximately linear, which demonstrates that the Cp values for these reactions are approximately zero.Deceased 5 September 1987 相似文献
18.
We have reformulated the phase change approach to the theory of conical intersections suggested by Zilberg and Haas [S. Zilberg, Y. Haas, Adv. Chem. Phys. 124 (2002) 433]. We use the fact that the phase change loop variable in polar co-ordinates in the space of nuclear co-ordinates is related to the transformation of the diabatic VB states defined at the apex of the cone in a conical intersection. Thus one can use the basis transformation generated by θ to yield a sequence of orthogonal pairs of VB structures (anchors) at any value of in the loop in nuclear configuration space. In this way the branching plane concept becomes related to VB wavefunctions based on the correspondence between the two angles. The theory is developed in detail using a simple three orbital three electron example. Examples are presented for four and six orbitals. In the later case, our results differ from those of Zilberg and Haas. 相似文献
19.
高分子控温相变免疫分析法测定苯妥因 总被引:11,自引:4,他引:7
利用水溶性高分子聚合物N-异丙基丙烯酰胺和抗体的偶联,用异硫氰酸荧光素标记苯妥因作为竞争物建立了免疫测定苯妥因的新方法,与均相方法相比灵敏度有很大提高,其灵敏度达到25μg/L,测定可在30min内完成。这一新方法可望应用于苯妥因的临床检测。 相似文献
20.
J. L. Zeng Z. Cao D. W. Yang F. Xu L. X. Sun X. F. Zhang L. Zhang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):507-512
The effects of multi-walled carbon nanotubes (MWNTs) on the phase change enthalpy (ΔH) and the thermal conductivity (κ) of a solid-liquid phase change materials (PCM), palmitic acid (PA), have been investigated.
The results showed that both the ΔH and the κ of the composite were lower than that of PA when the loading of MWNTs was small. As the concentration of MWNTs
in the composites increased, the ΔH of the composites was slightly improved and then decreased linearly. However, the κ of the composites was monotonously increased
from the minimum value. When the loading of MWNTs increased to 5% and no surfactant was added, the κ of the composite was
enhanced to be 26% higher than that of PA. The κ of the composite could be enhanced by CTAB instead of SDBS when the loading
of MWNTs was small, as SDBS showed no obvious effect on the κ of the composites. Furthermore, the effects of surface modification
of MWNTs on the ΔH and the κ of the composites have also been investigated. 相似文献