化学教学内容的学科理解研究——以“醛的结构与性质探究”为例

为在教学中切实落实化学学科核心素养,本研究从“学科”角度切入,针对教学内容探究教师如何进行学科理解。以乙醛课题为载体通过扎根理论分析专家团队基于学科理解的教学内容研讨过程,发现学科理解的对象主要是化学概念,在不同层级的概念理解中融汇化学学科思想方法。以核心概念羰基的理解过程为例,经历以下4个步骤:(1)比较烃类,确定乙醛的特殊性在于羰基;(2)基于乙醛特质挖掘本原性问题:如何基于结构认识羰基的性质;(3)运用比较分类逻辑方法抽提羰基的认识视角:极性多重键;(4)利用原子的杂化方式、电负性认识羰基结构特征,宏微结合发展认识思路。     

化学哲学:化学学科理解维度解构与水平提升路径

经文献分析发现在化学学科理解相关研究中出现一个共性问题,即对化学学科理解的对象认知不一,具有不同程度的差异性。基于此,通过对化学学科理解对象的文献观点分析发现,文献所述化学学科理解对象皆差异性地指向化学知识、化学史及化学哲学三大范畴,但其指向化学哲学的过程是不自觉的、不系统的。因此通过分析化学哲学本体、化学教学的理论基础及其本质、化学教学与化学哲学的“供需”关系,探讨基于化学哲学视角系统梳理化学学科理解对象的可行性、合理性及必要性。最终认为化学哲学是一个系统且具学理性的化学学科理解维度解构路径,同时也是认知主体获得深度且系统的化学学科理解的水平提升路径。     

基于学科理解的“醛的结构与性质探究”教学设计与实施

学科理解是教师教学的坚实基础,教学设计环节首先进行学科理解研究,通过阐释“如何基于极性多重键认识羰基化合物的结构与性质？”本原性问题,对主题学科大概念“有机物构性关系”进行本原性、结构化地理解。从教学目标、教学思路、教学实施过程阐述“醛的结构与性质探究”一课的教学。课后阶段进行学生访谈及分析、专家评价和教师反思总结。系统地呈现基于学科理解的素养为本的课堂教学研究。     

“基于尺度再探原子结构”的教学设计与实施*

教学设计阶段首先进行原子结构学科理解研究,通过阐释如何基于原子核认识原子的构成,如何基于核外电子运动认识原子的结构这2个本原性问题,对主题大概念原子结构模型进行本原性、结构化地理解。继而从教学目标和教学思路设计、教学实施过程、学生收获、教师反思及专家评价等方面,系统地呈现了基于学科理解的“素养为本”“基于尺度再探原子结构”课堂教学的研究过程。     

促进学生认识发展的学科教学认识的构建——以“原电池”为例

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。     

基于化学学科理解的电化学主题认识模型研究*

在核心素养导向的化学教学实践新时代背景下,基于化学学科理解构建相应主题的认识模型,提升教师的化学学科理解水平,进而开展素养为本的课堂教学促进教师专业发展,为化学教育理论和实践研究提供了重要的思路和方向。以电化学主题为例,基于化学学科理解构建其认识模型,以期其研究思路和过程对化学学科其他主题的理论和教学研究具有启示作用。     

“四重四步”教学模式的初中化学教学实践*——以“二氧化碳和一氧化碳”为例

核心素养视域下的初中化学课堂教学需要有一个深入学科本质的教学模式。“四重四步”教学模式通过教师的“四步教学”和学生的基础性认知、本质性认知、结构性认知、价值性认知的“四重认知”实现了由基于知识点的教学到基于化学学科核心素养发展的教、学、评一体化的转变,达成学科育人的要求。     

增进化学学科理解的“反应热”单元整体教学设计

秉承2017年版课标的理念和要求,按照鲁科版新教材的编排体系,系统梳理了对“反应热”的学科理解,包括理解知识本体与其中蕴含的思维方式方法。为增进学生的学科理解,将反应热单元分为3课时:基于体系理解反应热概念,借助内能将反应热与焓变建立联系,焓变的计算。精心设计了每一课时的驱动性问题(任务)以及课中与课后作业评价并进行了教学实践。对比上一轮此内容的单元整体教学,从教学侧重点、教学方法、教学效果等角度进行了反思。     

基于学科理解的“物质成分”大概念教学*

以“物质成分”大概念教学为例,基于学科理解,以探究物质成分的相关化学史为线索设计教学,引导学生在追溯“物质成分”相关概念、理论的发展过程中,逐渐建构物质成分的宏观、微观、宏微结合视角。并在解决探究物质成分的真实问题的过程中,培养学生基于证据进行推理的科学论证能力,通过认识视角的发展,体会科学理论是在不断发展和进阶的,初步建立科学发展观。     

“素养为本”的化学课堂教学*——以“原子晶体”为例

基于“素养为本”视角,以“原子晶体”的教学为例,对教学主题内容、教学现状及学情进行分析;以发展学生化学学科核心素养为主旨确定教学目标;以“微粒-微粒间的相互作用-物质的聚集状态-物质性质”的认识思路为主线,以“模型认知,建构概念-证据推理,归纳性质-微观探析,探究结构-科学史实,揭示价值”的任务型教学流程,达到落实并发展学生化学学科核心素养的目的。     

Di­methyl­phenyl­sulfonium tri­fluoro­methane­sulfonate and methyl­di­phenyl­sulfonium tri­fluoro­methane­sulfonate

The bonding geometry of sulfur in the cations of the title compounds, C₈H₁₁S⁺·CF₃SO₃^? and C₁₃H₁₃S⁺·CF₃SO₃^?, respectively, is similar and is independent of the ratio of the Me/Ph substituents. As expected, in both cations, the S—Ph bonds are somewhat shorter than the S—Me bonds. In both crystal structures, the interaction between cations and anions is similar.     

Methyl­tri­phenyl­stibonium tetra­fluoro­borate

In the title compound, [Sb(CH₃)(C₆H₅)₃]BF₄, there are four independent cations and anions in the asymmetric unit. The geometry around the Sb atom is distorted tetrahedral, with Sb—C distances in the range 2.077 (4)–2.099 (10) Å and angles at the Sb atom in the range 103.3 (3)–119.0 (4)°.     

2,4,6‐Tri­chloro­phenyl­iso­nitrile and 2,4,6‐tri­chloro­benzo­nitrile

The molecular structures of the title compounds, 2,4,6‐tri­chloro­phenyl­iso­nitrile (IUPAC name: 2,4,6‐tri­chloro­phenyl isocyanide), C₇H₂Cl₃N, and 2,4,6‐tri­chloro­benzo­nitrile, C₇H₂Cl₃N, are normal. The two structures are not isomorphous, but do contain similar two‐dimensional layers in which pairs of mol­ecules are held together by pairs of Cl?CN [3.245 (3) Å] or Cl?NC [3.153 (2) Å] interactions. The two‐dimensional isomorphism is lost through different layer‐stacking modes.     

2,4‐Di­nitro­phenyl­hydrazones of 2,4‐di­hydroxy­benz­aldehyde, 2,4‐di­hydroxy­aceto­phenone and 2,4‐di­hydroxy­benzo­phenone

In 2,4‐di­hydroxy­benz­aldehyde 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­amide solvate {or 4‐[(2,4‐di­nitro­phenyl)­hydrazono­methyl]­benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate}, C₁₃H₁₀N₄O₆·C₃H₇NO, (X), 2,4‐di­hydroxy­aceto­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­am­ide solvate (or 4‐{1‐[(2,4‐di­nitro­phenyl)hydrazono]ethyl}benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate), C₁₄H₁₂N₄O₆·C₃H₇NO, (XI), and 2,4‐di­hydroxy­benzo­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­acet­amide solvate (or 4‐­{[(2,4‐di­nitro­phenyl)hydrazono]phenyl­methyl}benzene‐1,3‐diol N,N‐di­methyl­acet­amide solvate), C₁₉H₁₄N₄O₆·C₄H₉NO, (XII), the molecules all lack a center of symmetry, crystallize in centrosymmetric space groups and have been observed to exhibit non‐linear optical activity. In each case, the hydrazone skeleton is fairly planar, facilitated by the presence of two intramolecular hydrogen bonds and some partial N—N double‐bond character. Each molecule is hydrogen bonded to one solvent mol­ecule.     

{[(N‐Methyl‐p‐toluidino)­di­phenyl­phospho­ranyl­idene]­methyl}(N‐methyl‐p‐toluidino)­di­phenyl­phospho­nium iodide

The cationic part of the homodifunctional amino­phospho­ranyl ligand, C₄₁H₄₁N₂P₂⁺·I^?, shows interesting features associated with the N—P—C—P—N skeleton. The P—C(H) bond distances [1.696 (3) and 1.697 (3) Å] possess partial double‐bond characteristics. The nature of the P—C(H) and P—N bonds suggests that the positive charge is only distributed around the P—C—P atoms. The structure has near twofold symmetry through the central methyl­ide‐C atom.     

Bis(μ‐hexa­methyl­enetetr­amine)­bis(aqua­di­bromo­cadmium)­di­aqua­di­bromo­cadmium dihydrate

The title compound, poly­[[di­aqua­di­bromo­cadmium‐μ‐(1,3,5,7‐tetra­aza­tri­cyclo[3.3.1.1^3,7]decane‐N¹:N⁵)‐aqua­cad­mium‐di‐μ‐bromo‐aqua­cadmium‐μ‐(1,3,5,7‐tetra­aza­tri­cyclo[3.3.1.1^3,7]decane‐N¹:N⁵)‐di‐μ‐bromo] dihydrate], [Cd₃­Br₆­(C₆­H₁₂­N₄)₂­(H₂O)₄]·­2H₂O, is made up of two‐dimensional neutral rectangular coordination layers. Each rectangular subunit is enclosed by a pair of Cd₃(μ₂‐Br)₆(H₂O)₃ fragments and a pair of (μ₂‐hmt)Cd(H₂O)₂Br₂(μ₂‐hmt) fragments as sides (hmt is hexa­methyl­enetetr­amine). The unique Cd^II atom in the Cd₂Br₂ ring in the Cd₃(μ₂‐Br)₆(H₂O)₃ fragment is in a slightly distorted octahedral CdNOBr₄ geometry, surrounded by one hmt ligand [2.433 (5) Å], one aqua ligand [2.273 (4) Å] and four Br atoms [2.6409 (11)–3.0270 (14) Å]. The Cd^II atom in the (μ₂‐hmt)Cd(H₂O)₂Br₂(μ₂‐hmt) fragment lies on an inversion center and is in a highly distorted octahedral CdN₂O₂Br₂ geometry, surrounded by two trans‐related N atoms of two hmt ligands [2.479 (5) Å], two trans‐related aqua ligands [2.294 (4) Å] and two trans‐related Br atoms [2.6755 (12) Å]. Adjacent two‐dimensional coordination sheets are connected into a three‐dimensional network by hydrogen bonds involving lattice water mol­ecules, and the aqua, bromo and hmt ligands belonging to different layers.     

Specific heat on Sr<Subscript>2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>7</Subscript> and Sr<Subscript>2</Subscript>Ta<Subscript>2</Subscript>O<Subscript>7</Subscript>

Summary Specific heats on the single crystals of Sr₂Nb₂O₇, Sr₂Ta₂O₇ and (Sr_1-xBa_x)₂Nb₂O₇ were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of T_INC (=495 K) on Sr₂Nb₂O₇ and at the super-lattice phase transition of T_SL (=443 K) on Sr₂Ta₂O₇; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of T_LOW (=95 K) on Sr₂Nb₂O₇. The transition temperature T_LOW decreases with increasing Ba content x and it vanishes for samples of x>2%.     

Chemical durability of MoO<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> and K<Subscript>2</Subscript>O-MoO<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Thermal and chemical durability studies of the phosphate glasses belonging to the binary MoO₃-P₂O₅ and the ternary K₂O-MoO₃-P₂O₅ systems are reported. The chemical resistant attack tests carried out on the free alkaline MoO₃-P₂O₅ glasses show that the glass associated with the P/Mo ratio 2 has the high chemical durability. It shows also a high glass transition temperature value. The above findings are interpreted in terms of the cross-link density of the glasses and the strength of the M-O bonds (M=P, Mo). The influence of K₂O addition on the properties (density, T _g, durability) of this binary high water resistant glass is studied. It is found that the chemical durability along with the other physical properties are reduced by the incroporation of K₂O in the glass matrix. The results were explained by assuming the formation of non-bridging oxygens and weak bonds. The mechanism of the dissolution of these glasses is proposed.     

Three-component systems LiBr-LiVO<Subscript>3</Subscript>-Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript> and LiBr-Li<Subscript>2</Subscript>SO<Subscript>4</Subscript>-Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>

Phase equilibria in the three-component systems LiBr-LiVO₃-Li₂MoO₄ and LiBr-Li₂SO₄-Li₂MoO₄ have been studied using differential thermal analysis (DTA). Eutectic compositions have been determined (mol %): in the system LiBr-LiVO₃-Li₂MoO₄, 56.0 LiBr, 22.0 LiVO₃, and 22.0 Li₂MoO₄ with a melting temperature of 413°C; and in the system LiBr-Li₂SO₄-Li₂MoO₄, 65.0 LiBr, 14.0 Li₂SO₄, and 21.0 Li₂MoO₄ with a melting temperature of 421°C. Phase fields have been demarcated.