中美高中化学教科书支撑同一知识的实验设计和内容呈现比较——以“影响化学反应速率的因素”为例

以人教版、苏教版、鲁科版高中化学教科书以及美版教科书中支撑影响化学反应速率的因素这一知识内容所涉及的实验内容为研究对象,从实验的设计和内容呈现等方面进行系统地比较,结果表明：国内的教科书中设计的实验探究性更强,对于学生能力的培养更加全面,美国教科书中设计的实验更注重吸引学生的注意力,激发学生的学习兴趣。最后综合分析了不同版本教科书的优缺点,并对实际教学提出一些建议。     

关于能量最低原理的误读——论“凭什么相信计算”之二

不要把能量最低原理与核外电子填充规则混为一谈,后者仅仅是能量最低原理众多应用中的一例。体系"能量越低越稳定"的说法错在忘了它成立的前提:熵固定。Gibbs的说法才是能量最低原理的完整表述,它等价于Clausius的最大熵原理,两者各自有其成立的前提条件。由Gibbs能量最低原理可以导出核外电子的填充规则。宏观和微观世界只有一个能量最低原理。     

化学反应原理的实验探究教学策略初探——以“化学平衡移动原理的应用”复习课为例

在“化学平衡移动原理在氨气制备与检验实验中的应用”课题的教学设计与实践过程中,以平衡移动影响因素为知识线索承载科学探究方法,探讨化学反应原理的实验探究教学策略,将课堂中探究教学的关注点从概念理论的验证和接授延伸至探究思路和方法的形成.     

高二学生“变化观念与平衡思想”素养表现的追踪评价——以化学反应原理模块为例

基于《普通高中化学课程标准(2017年版2020年修订)》和已有研究,明确了化学反应原理模块“变化观念与平衡思想”素养表现水平,基于水平构建了人教版化学反应原理模块各章的评价指标,通过Rasch模型优化形成了质量良好的评价工具。运用评价工具对470名高二学生开展5次追踪评价,获得了2 149个有效样本,分析高二学生在化学反应原理模块“变化观念与平衡思想”素养表现的变化情况和整体现状。     

基于建构主义和反省思维的实验教学——以“丁达尔现象的再认识”为例

以"丁达尔现象的再认识"教学为例,设计一系列"非常规胶体实验"创设教学情境,打破学生思维惯性,基于建构主义和反省思维,探索培养学生学科思维的教学模式。     

Connection between Entropy and Thermal Expansion during the Extreme Compression of a Substance

Russian Journal of Physical Chemistry A - The nature of the dependence of the coefficient of thermal expansion on the degree of compression of a solid is studied in general form. It is shown that...     

Estimation of the Thermophysical Properties of Pentaalkylguanidinium-Based Magnetic Ionic Liquids with Unusual Thermal Expansion Coefficient

The thermal expansion coefficient (α_exp.), the molecular volume (V_m), the entropy of surface formation (S_a), and the Gibbs energy of surface formation (E_a) of four pentaalkylguanidinium-based MILs [C_nTMG][FeCl₃Br] (n=2, 4, 6, 8) were calculated based on the density and surface tension data determined from 278.15 to 323.15 K. In terms of classical semiempirical methods, the standard molar entropy (S⁰), the lattice energy (U_POT), the molar enthalpy of evaporation ( , (298 K)), and the thermal expansion coefficient (α_est.) of the MILs were further estimated. The estimation results indicate that the classical semiempirical methods are suitable for estimating the thermophysical properties of the MILs, except the unusual α_exp., which were extremely larger than those of representative non-magnetic ionic liquids (ILs). We further optimized the estimation methods and discussed the potential reasons for the unusual thermal expansion coefficient of the MILs.     

The Thermal Expansion of GeS and GeTe

The thermal expansion of GeS has been studied above room temperature up to the melting point of 658 ± 5°C by X-ray diffraction techniques using a 190 mm diameter Unicam high temperature camera. The thermal expansion of the crystallographic axes is linear with distinct changes in the rate of expansion at about 250°C, 370°C and 510°C. No first-order structural transformation was observed for this system up to the melting point. The results of additional studies on GeTe are in general agreement with those of others and confirm trends in the thermal expansion behavior of the germanium monochalcogenide series.     

Expansion and Shrinkage of Fibers: Load- and temperature modulated TMA measurements temperature calibration of fiber attachments

The thermal behavior of a drawn PET fiber has been investigated by thermomechanical analysis, TMA, and by differential scanning calorimetry, DSC. Above the glass transition temperature of 79°C, the fiber shrinks to a maximum of 8% of the initial length. Temperature modulated TMA enabled the separation of the thermal expansion from the overlapping shrinkage during the first heating and to calculate the expansivity, _e and the shrinkage coefficient, _s, independent of each other. Young's modulus, E, was measured by TMA with modulation of the tensile stress. Hence, it was possible to record the behavior of _e, _s and E during the structural changes by combining both modulations in a single measurement.A new technique was developed to calibrate the sample temperature. With this, accurate control of the modulated temperature of the specimen was achieved, independent of the changing heating rate.This revised version was published online in November 2005 with corrections to the Cover Date.     

Benzocyclobutadienes: An Unusual Mode of Access Reveals Unusual Modes of Reactivity

The reaction of an aryne with an alkyne to generate a benzocyclobutadiene (BCB) intermediate is rare. We report here examples of this reaction, revealed by Diels–Alder trapping of the BCB by either pendant or external electron‐deficient alkynes. Mechanistic delineation of the reaction course is supported by DFT calculations. A three‐component process joining the benzyne first with an electron‐rich and then with an electron‐poor alkyne was uncovered. Reactions in which the BCB functions in a rarely observed role as a 4π diene component in Diels–Alder reactions are reported. The results also shed new light on aspects of the hexadehydro‐Diels–Alder reaction used to generate the benzynes.     

论“异常实验现象”的教学功能

在调查研究的基础上,从创设教学情境、培养问题意识、发展学科能力和强化心理素质等方面对“异常实验现象”的教学功能进行了探讨,论述了“异常实验现象”的教学价值,并提出了相关教学措施。     

沉淀生成影响氧化还原反应方向的实验设计与异常现象解释

以学生为中心,以问题为导向,讨论了沉淀生成引起氧化还原反应方向改变的实验内容、实验原理、现象解释,引导学生加深对能斯特方程的理解和应用。     

An Unusual Rearrangement and its Dependence on Configuration

In the course of a synthetic study, we encountered an unusual rearrangement that we now report, one that involves a 5‐nitronorbornenyl system having 7‐endo‐ and 7‐exo‐pyridin‐2‐yl groups being treated under Nef‐reaction conditions. The stereoisomers differ in their Nef‐reaction behavior: the isomer with the pyridin‐2‐yl group exo to the NO₂ moiety primarily affords the Nef reaction, however, with formation of a rather unusual rearrangement side‐product. The endo‐pyridyl stereoisomer proceeded exclusively with rearrangement.     

Effect of Thermal Cycles on the Thermal Expansion Behavior of T700 Carbon Fiber Bundles

The relationships between the coefficient of thermal expansion(CTE) of T700 carbon fiber bundles(CFBs) and the thermal cycles were investigated. The microstructure of T700 CFBs was analyzed with Raman spectra and XRD before and after the thermomechanical test. The results indicated that the T700 CFBs exhibited negative expansion in the direction of parallel fibers in the temperature range of -150-150℃. The thermal strain that occurred during the heating and the cooling thermal cycle had an unclosed curve that served as the loop. When the experimental load was the same, the position of strain loop tended to move upward, and the length of the specimen increased continuously with the thermal cycles increasing. The microstructural analysis suggested that the degree of structural order and the degree of orientation along the fiber axis were improved with the increase of thermal cycles. The change of microstructure parameters could be the primary cause of the negative CTE's variation within the T700 CFBs.