山东省中学化学实验现状的调查分析与改革措施

本文在对山东省部分重点中学和普通中学的教师和学生进行问卷调查的基础上,从教师、学生对化学实验的认识及态度、实验条件、实验内容、实验教学方法及手段、实验考核等几个方面进行了统计分析,分析出目前中学化学实验教学的有利之处及存在的不足,并提出了改革的措施。     

探究可燃物燃烧条件的实验改进

阐述了验证白磷燃烧条件演示实验的改进方法,从实验的设计意图、实验装置的准备、实验的具体操作与实验现象、实验过程中应注意的事项等方面作了完整的介绍。     

钾燃烧条件及产物组成的实验探究

从加热方法与钾块大小2个角度对钾燃烧条件与产物组成进行实验探究,认为开放体系中进行钾燃烧实验成功的关键是固体能迅速升温至钾的着火点,减少钾表面氧化膜的厚度,保留较多的金属钾。因此至少预热瓷坩埚2 min,再加入豌豆或更大的金属钾块才可观察到钾燃烧的现象。燃烧的黑色物质冷却后变为橙红色,以超氧化钾为主,燃烧产生的白烟中含有少量的碳酸钾。     

铁丝在氧气中燃烧的实验改进

“铁丝在氧气中燃烧”是初中化学教材中证明氧气化学性质的一个演示实验,该实验证明了氧气比较活泼,在一定条件下可以和金属发生剧烈反应。但是与木炭在氧气中燃烧、硫在氧气中燃烧、蜡烛在氧气中燃烧的演示实验相比,铁丝在氧气中燃烧的实验存在着一些不足的地方,针对这些不足,对铁丝在氧气中燃烧的实验进行了改进。1实验存在的问题按照教材要求,铁丝在氧气中燃烧的实验,须将铁丝绕成螺旋状,并在铁丝的末端绑上一根火柴杆,实验时先将火柴杆点燃,待火柴杆将燃尽时,迅速伸入盛满氧气的集气瓶中。这样的操作存在2个问题:第一,火柴燃烧的程度不…     

对白磷燃烧实验的改进

由于白磷的燃点低,在自然条件下能够与氧气发生剧烈的氧化反应,使得通过白磷的燃烧来研究物质燃烧的条件操作困难,任何不慎操作都会使实验失败甚至威胁到实验人员的安全。因此设计了将白磷放置于可控制氧气流速的实验装置中,人工控制氧气的流速并能确定反应温度,较好地解决了上述操作难题,该方法直观、简便、危险性小,并能使学生容易推导出物质燃烧的条件。     

对燃烧条件探究实验的绿色化改进

通过对现行初中化学教材中燃烧条件探究实验的理性分析,以学生已有的生活经验和化学知识为基础,选择学生所熟知的可燃物--纸条和木炭作实验物品,对燃烧条件探究实验进行了绿色化改进。从根本上解决了教材实验的污染问题,将氧气、二氧化碳的实验室制法与性质实验及一氧化碳的可燃性等前后几部分教学内容紧紧地联系在一起,降低了学生的学习难度,培养了学生的创新意识,降低了实验成本,提高了教学的有效性。     

倾倒二氧化碳熄灭阶梯蜡烛实验的改进

“阶梯蜡烛实验”是初中化学重要实验之一。通过实验主要反映出二氧化碳不燃烧,也不支持燃烧,密度比空气大的性质。为了提高本实验的成功率以及使学生能够清晰地观察实验现象,对该实验进行改进,从实验改进目的、实验装置介绍、实验操作步骤以及实验说明4大部分对实验进行解释。     

DIS数字实验探究蜡烛燃烧现象

新课标将科学探究置于各内容主题之首,同时渗透在各主题内容之中,沪教版九年级《化学》教材,为加深学生对灭火原理的认识和提高学生科学素养,演示有关蜡烛的2个实验,然而由于受到实验条件的限制,实验现象的解释学生存在问题,借助数字实验对实验进行设计很好地解决了问题。     

“木炭还原氧化铜”实验改进的对比与设计

遵循实验改进的科学原则,立足中学化学教学实际,对文献中"木炭还原氧化铜"的实验改进从反应物的选取、热源和反应装置3个方面分类比对、分析。结合教学实际对该实验进行了显性化设计,提出具体改进建议。     

乙醇与钠反应的实验探究与改进*

针对钠与乙醇反应的实验进行探究与改进。探索出反应试剂的最佳用量,可在较长时间内观察到氢气燃烧时的淡蓝色火焰;通过实验条件模拟、利用酒精检测仪检测,探究乙醇蒸气燃烧的条件,得出采用最佳试剂用量进行实验时乙醇蒸气对氢气的燃烧并未产生影响。实验改进后,在普通可见光下,也可明显地观察到氢气燃烧时的淡蓝色火焰。     

"Alpha"-, "beta"- and "delta"-anhydrodigitoxigenin

The syntheses of 3β-hydroxy-5β-carda-14, 20:22-dienolide (= «β»-anhydro-), 3β-hydroxy-5β-carda-8:14, 20:22-dienolide (= «α»-anhydro-) and «δ»-anhydro-digitoxigenin (= probably 3β-hydroxy-5β, 14β-carda-8, 20:22-dienolide) by the best ways known to date, have been described. «δ»-Anhydro-digitoxigenin represents the thermodynamically most stable isomer. In this isomer the double bond in position 8 is unaffected by hydrogenation with Pt in acetic acid; with perbenzoic acid an epoxide results from which, on hydrogenation, the double bond can be regenerated in its original position. Analogous reactions are known to occur in the 8:14-epoxides.     

化“材”为“筑”

Chemistry is a central, practical and creative discipline. The development of chemistry plays an important role in the progress of science and society, as well as the improvement of the quality of human life. This paper introduces the chemical knowledge of stone, concrete, glass and other inorganic nonmetallic building materials by the anthropomorphically story. Taking nanomaterials as an example, the prospect of building materials development in the future is put forward.     

Making "wheels" and "cubes" from triangles

[Mn(IV)Mn(II)3] triangular units directed by the presence of tripodal alcohols self-assemble in the presence of azide and acetate ligands to form either a [Mn24] "wheel" or a [Mn32] "cube".     

"Turn-on" fluorescent sensing with "reactive" probes

Chemical probes are valuable tools for the investigation of biochemical processes, diagnosis of disease markers, detection of hazardous compounds, and other purposes. Therefore, the development of chemical probes continues to grow through various approaches with different disciplines and design strategies. Fluorescent probes have received much attention because they are sensitive and easy-to-operate, in general. To realize desired selectivity toward a given analyte, the recognition site of a fluorescent probe is designed in such a way to maximize the binding interactions, usually through weak molecular forces such as hydrogen bonding, toward the analyte over other competing ones. In addition to such a supramolecular approach, the development of fluorescent probes that sense analytes through chemical reactions has witnessed its usefulness for achieving high selectivity, in many cases, superior to that obtainable by the supramolecular approach. Creative incorporations of the reactive groups to latent fluorophores have provided novel chemical probes for various analytes. In this feature article, we overview the recent progress in the development of turn-on fluorescent probes that are operating through chemical reactions triggered by target analytes. Various chemical reactions have been implemented in the development of many reactive probes with very high selectivity and sensitivity toward target analytes. A major emphasis has been focused on the type of chemical reactions utilized, with the hope that further explorations can be made with new chemical reactions to develop reactive probes useful for various applications.     

"Clickable" polymersomes

Polymersomes, composed of amphiphilic polystyrene-block-poly(acrylic acid) (PS-b-PAA), with the periphery being covered with azide groups, were used for further functionalization using "click" chemistry.