发挥小学化学实验教学功能的策略初探

在小学科学教学实践中,化学实验具有特殊的教学功能。小学科学实验设计的合理与否,以及小学科学教师对实验教学功能的认识和落实程度,会最终影响小学科学实验的教学效果。本文主要从小学科学实验的设计和小学科学教师2个方面出发,在对各版本小学科学教材化学实验和现有教学情况分析的基础上,对实验设计提出整体的改进建议;同时,要求小学科学教师应该结合教学资源和学生基础,重视实验情境化和科学实验方法化,充分发挥小学化学实验的教学功能。     

五年制专科小学教育专业的教学大纲和教材与小学科学课程标准和教材的对比

对小学科学课程标准与五年制专科小学教育专业“科学·化学”教学大纲中对化学知识内容的要求,以及小学《科学》和高等专科学校《科学·化学》教材中涉及的化学知识内容进行了对比。同时就五年制专科层次小学教育专业化学课程存在的问题进行了讨论,并提出了选择合适的课程教学内容、加强化学实验和化学教材建设、建立理论课程和实验教学新体系模块等建议。     

小学科学化学实验教学中的注意分散研究

小学科学中的化学实验是学生获取科学认识的重要方式。经观察研究发现,小学化学实验教学中存在明显的注意分散现象。实验教学过程中的注意分散问题会影响学生科学探究能力的培养,阻碍学生科学知识的获取和科学概念的形成。通过观察小学科学的课堂以及分析小学科学2012-2018年的优质课视频,根据课堂中注意分散的不同现象,划分了注意分散的类型;结合教育目标分类学、认知负荷理论及注意资源限制理论,剖析了小学化学实验教学中注意分散的原因,提出解决小学化学实验教学中注意分散问题的对策。     

小学科学中化学实验的课堂完成情况及问题分析

小学科学课堂中化学知识的讲授主要以实验为主,课堂上化学实验能否完成是实验能否发挥三维教学功能的首要条件,也影响小学生对化学知识或常识能否有效获取。主要分析了小学科学课堂教学中化学实验的完成情况,并对存在的问题进行了分析,为今后小学化学实验的课堂实施及改进提出了建议。     

化学实验教学:冷与热的思考

对比初中化学评优课和常态课中实验教学的状况,分析化学实验在评优课中受热捧而日常教学遭冷遇的原因。依据2011年版义务教育化学课程标准中有关实验教学的规定和要求,提出从化学实验教学功能全面发挥的视角,提高对化学实验及其教学的认识,加强对化学实验教学的研究。建议从强化化学实验的功能意识、加强实验内容和功能的联系、注重实验教学行为的转变、重视学生良好实验习惯的养成等4个方面,提高化学实验教学质量。     

化学实验教学情景及其创设策略研究

创设生动活泼的教学情景是化学新课程对化学实验教学提出的新要求。本文对化学实验教学情景的含义、种类和功能及其创设策略进行了探讨。     

小学教育专业“化学实验”教学的几点思考

通过分析和讨论目前高等院校小学教育专业大学化学实验教学的现状,提出了小学教育专业化学实验教学在教学内容、教学课时和考核方式等方面的具体措施,以满足现代教学需要。     

以实验为中心组织教学发展学生智力的几点尝试

化学是以实验为基础的科学。化学实验在化学教学中起着特殊的重要作用。因此,许多化学教师都在研究加强和改进实验教学,积极探索科学的实验教学方法。传统的实验教学,一般都是按以下几个步骤来进行的：提出问题——教师演示——得出结论。     

化学实验是研究性学习的重要途径

化学研究性学习应以课堂教学为主阵地,在中学化学教学中,充分利用化学学科"以实验为基础"的基本特征,挖掘和开发化学实验在研究性学习中的功能,对于改变学生的学习方法,形成终身学习的能力,培养科学探究能力具有重要的意义。对化学课堂中如何利用实验教学开展研究性学习从几个方面进行了探讨。     

小学科学教材中化学实验设计可行性研究

小学科学课融合化学等多学科知识于一体, 化学知识的讲授主要以实验为主, 化学实验设计的可行性是实验能否顺利实施及小学生对化学知识能否有效获取的一个重要环节, 因此小学科学教材呈现出的化学实验设计直接影响小学科学教师的教育教学实践活动。主要分析了现有小学科学教材中的化学实验设计的可行性, 为今后的小学科学教学及教材修订提出了建议。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.