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对温室效应模拟实验的商榷 总被引:1,自引:0,他引:1
以"阳光照射下二氧化碳和空气的温度变化不同"的思路来模拟温室效应的实验设计是不科学的,因为不同气体在阳光下温度变化不同是由于不同气体的比热容不同造成的.通过做实验以及对实验数据的分析发现,模拟实验中发生的是热传递现象而不是温室效应. 相似文献
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在学生利用"数字化手持技术"测定在太阳光下不同气体温度随时间变化和在红外灯照射下不同浓度CO2温度随时间变化,得出CO2是影响大气"温室效应"的主要气体之一以及CO2浓度越高"温室效应"越大的实验结果的基础上,对152名高三选修化学的学生进行调查,从宏观和微观2个角度探查学生对"温室效应"的认知.结果显示学生对有关常见的知识认知水平比较高,但总体认知不够全面和深入. 相似文献
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以“探秘温室气体的温室效应”为项目主题,在初中化学“气体的制取”复习课中开展项目式教学。在建构温室效应模型的基础上,学生遵循控制变量法设计实验,并综合应用气体性质和制备的相关知识,选择合适的化学反应,自主设计发生装置、除杂装置、收集装置,以满足项目实际需求。项目还采用了基于热成像检验温室气体的创新实验设计,缩短了实验时长,提高了科学性。项目的实施提高了学生迁移应用知识的能力,发展了实验探究与实践素养,培养了建模能力,增强了社会责任感。 相似文献
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探究了基于色度传感器的酒精检测实验, 尝试将实验从定性层面上升到定量层面, 发展成为酒精检测的探究性和创新性实验, 以期为传感技术应用于高中化学实验教学提供一些借鉴和思考。色度传感器在本实验中提供了即时、直观的数据支持, 拓展了实验原理在生活中的应用;开阔了学生的视野, 培养了学生的创新意识。 相似文献
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在九年级<化学>下册第七章溶液[1]的教学过程中发现,学生对于气体溶解度的影响因素存在理解困难.教材中对这部分内容没有设计实验探究环节,只是给出理论上的结论[1].初三学生还处于直觉经验性思维向逻辑思维的过渡阶段,对概念的理解、判断、推理在很大程度上仍然离不开直观形象的支撑[2].基于此,在教学过程中进行了积极地探索,利用廉价易得的一次性注射器和雪碧饮料设计了一组实验,形象地展示了气体溶解度受温度和压强的影响情况.通过创设具体的实验情境,学生可以直观地观察到气体溶解度受温度和压强影响,体验科学探究的乐趣,增强了教学效果. 相似文献
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人教版义务教育课程标准实验教科书九年级《化学》上册第117页关于"二氧化碳对生活和环境的影响"中谈到:近几十年来,由于人类消耗的能源急剧增加,森林遭到破坏,大气中的二氧化碳的含量不断上升.大气中的二氧化碳气体能像温室的玻璃或塑料薄膜那样,使地面吸收的太阳光的热量不易散失,从而使全球变暖,这种现象叫温室效应.教学时,由于此概念比较抽象,学生不好理解,为了增强学生的感性认识,让学生亲眼目睹"温室效应"会导致气温升高,从而树立环保理念,笔者设计了温室效应模拟实验演示器,经使用取得了较好的实验效果,现介绍如下. 相似文献
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现行人民教育出版社初、高中化学课本关于CO2、SO2气体的溶解性叙述为:通常1体积的水约能溶解1体积的CO2气体,增加压强还会溶解更多;SO2气体易溶于水。但对于CO2气体与.SO2气体的水溶性教课书中没有设计实验,且气体的溶解性没有固体的溶解性那么直观易懂。为了促进学生对气体水溶性的直观认识,加深理解,笔者设计了CO2气体与SO2气体的水溶性实验,现象明显易操作。 相似文献
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针对微型化学实验中实验产物量少的特点,将手持技术的氧气传感器作为检测器应用于"二氧化锰催化过氧化氢分解制取氧气"的微型化学实验之中,是进一步减少微型化学实验中化学试剂用量的新途径和新方法。通过计算机对数字化实验结果的曲线展示,将实验现象转化成直观的数字与图像,使实验结果更加精准,学生能在实验中同步观察实验进程,使学生对实验现象的主观感知和定量理解更加深入,探究也更加准确。 相似文献
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Linear oligomeric supramolecular assemblies of defined length have been generated using the Vernier principle. Two molecules, containing a different number (n and m) of mutually complementary binding sites, separated by the same distance, interact with each other to form an assembly of length (n x m). The assembly grows in the same way as simple supramolecular polymers, but at a molecular stop signal, when the binding sites come into register, the assembly terminates giving an oligomer of defined length. This strategy has been realized using tin and zinc porphyrin oligomers as the molecular building blocks. In the presence of isonicotinic acid, a zinc porphyrin trimer and a tin porphyrin dimer form a 3:4 triple stranded Vernier assembly six porphyrins long. The triple strand Vernier architecture introduced here adds an additional level of cooperativity, yielding a stability and selectivity that cannot be achieved via a simple Vernier approach. The assembly properties of the system were characterized using fluorescence titrations and size-exclusion chromatography (SEC). Assembly of the Vernier complex is efficient at micromolar concentrations in nonpolar solvents, and under more competitive conditions, a variety of fragmentation assemblies can be detected, allowing determination of the stability constants for this system and detailed speciation profiles to be constructed. 相似文献
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Vernier‐Templated Synthesis,Crystal Structure,and Supramolecular Chemistry of a 12‐Porphyrin Nanoring
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Dr. Dmitry V. Kondratuk Dr. Johannes K. Sprafke Dr. Melanie C. O'Sullivan Dr. Luis M. A. Perdigao Dr. Alex Saywell Dr. Marc Malfois Prof. James N. O'Shea Prof. Peter H. Beton Dr. Amber L. Thompson Prof. Harry L. Anderson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12826-12834
Vernier templating exploits a mismatch between the number of binding sites in a template and a reactant to direct the formation of a product that is large enough to bind several template units. Here, we present a detailed study of the Vernier‐templated synthesis of a 12‐porphyrin nanoring. NMR and small‐angle X‐ray scattering (SAXS) analyses show that Vernier complexes are formed as intermediates in the cyclo‐oligomerization reaction. UV/Vis/NIR titrations show that the three‐component assembly of the 12‐porphyrin nanoring figure‐of‐eight template complex displays high allosteric cooperativity and chelate cooperativity. This nanoring–template 1:2 complex is among the largest synthetic molecules to have been characterized by single‐crystal analysis. It crystallizes as a racemate, with an angle of 27° between the planes of the two template units. The crystal structure reveals many unexpected intramolecular C?H???N contacts involving the tert‐butyl side chains. Scanning tunneling microscopy (STM) experiments show that molecules of the 12‐porphyrin template complex can remain intact on the gold surface, although the majority of the material unfolds into the free nanoring during electrospray deposition. 相似文献
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Yasuo Yoshihashi Masaki Sato Yuto Kawano Etsuo Yonemochi Katsuhide Terada 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1281-1285
Magnesium Stearate (MgSt) is a widely used lubricant for preventing tablet compression trouble. It is known that the powder characteristic of MgSt is different among MgSts manufactured by different methods and conditions. These differences affect blending efficiency with pharmaceutical additives. The purpose of this study is to evaluate the physicochemical properties of MgSt by thermal effusivity sensor for in-process monitoring of powder blending. MgSts having different physicochemical properties and granulated sugar spheres were used for model excipients. V-blender was used for powder blending. Thermal effusivity values of each of the ingredients in the blend were measured using one of the sensors prior to placing the ingredient in the blender. The effect of magnesium stearate addition to uniform ingredients can be clearly identified using the sensors. Compared to effusivity data and powder density, effusivity data correlated with the powder characteristics of magnesium stearate. These results suggested that effusivity can be used for end point detection of blending process for various magnesium stearates with sugar sphere. When various magnesium stearates were added to the granule, required time for achieving homogeneous powder blend was different. Blending behavior would be affected by the physicochemical characters. Blend uniformity and blended states of granules containing magnesium stearate can be detected nondestructively without intricate sampling process. Thermal effusivity sensors are an efficient tool to monitor the real time blending behavior of pharmaceutical ingredients. 相似文献
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The toxic gases,such as CO and NO,are highly dangerous to human health and even cause the death of person and animals in a tiny amount.Therefore,it is very necessary to develop the toxic gas sensors that can instantly monitor these gases.In this work,we have used the first-principles calculations to investigate adsorption of gases on defective graphene nanosheets to seek a suitable material for CO sensing.Result indicates that the vancancy graphene can not selectivly sense CO from air,because O2 in air would disturb the sensing signals of graphene for CO,while the nitrogen-doped graphene is an excellent candidate for selectivly sensing CO from air,because only CO can be chemisorbed on the pyridinic-like N-doped graphene accompanying with a large charge transfer,which can serve as a useful electronic signal for CO sensing.Even in the environment with NO,the N-doped graphene can also detect CO selectively.Therefore,the N-doped graphene is an excellent material for selectively sensing CO,which provides useful information for the design and fabrication of the CO sensors. 相似文献
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Highly sensitive absorption measurements on various samples may be carried out by Fiber-optic Evanescent Wave Spectroscopy (FEWS) in the mid-IR. Such measurements have already been done on solids, liquids and gases, using chalcogenide glass fibers or crystalline fibers. Segments of crystalline AgClBr fibers may be used as sensors of much higher sensitivity if their middle sections are pressed to form flat waveguides. We carried out measurements on micrograms of insoluble or slightly soluble particles in water, when they sedimented on the flattened parts of such sensors. Measurements were also carried out on few micrograms of dry particles that had been pressed onto the flattened parts. Flattened fiber sensors may therefore be used for measurements on micrograms of particles and they can be used for identifying the chemical nature of particles of organic, inorganic or biological materials and for studying their properties. The FEWS method, based on flattened mid-IR fiber sensors, is simple, inexpensive and does not require sample processing. It would be useful for measurements on very small quantities of particles for biomedical applications, for environmental protection, for drug enforcement agencies and for homeland security. 相似文献
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《Electroanalysis》2004,16(22):1843-1851
Miniaturized solid‐state ion sensors based on field‐effect transistors on silicon can take advantage of the capabilities of microelectronics and microsystems technology for the integration of combined functionalities. Optimized solid‐state chemical sensors usually require specific materials and fabrication processes. However, if standard fabrication processes can be used, integrated chemical sensor systems can be developed in a shorter time and in a cost effective way. We show that, for applications in which a long operating time is not required, such as in disposable biomedical sensors, good integrated sensor systems can be fabricated with standard materials and processes. Specific examples are presented, such as multisensor systems, sensors with integrated signal‐processing circuits and sensors with particle manipulation electrodes. 相似文献
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Shiwei Chen Jinliang Zhang Huilong Liu Tongyue Qiu Haoxiang Tang Zunmin Zhang 《Molecules (Basel, Switzerland)》2022,27(21)
Rational design of thermotropic liquid crystal (LC)-based sensors utilizing different mesophases holds great promise to open up novel detection modalities for various chemical and biological applications. In this context, we present a dissipative particle dynamics study to explore the unique anchoring behavior of nematic and smectic LCs at amphiphile-laden aqueous-LC interface. By increasing the surface coverage of amphiphiles, two distinct anchoring sequences, a continuous planar-tilted-homeotropic transition and a discontinuous planar-to-homeotropic transition, can be observed for the nematic and smectic LCs, respectively. More importantly, the latter occurs at a much lower surface coverage of amphiphiles, demonstrating an outstanding sensitivity for the smectic-based sensors. The dynamics of reorientation further reveals that the formation of homeotropic smectic anchoring is mainly governed by the synchronous growth of smectic layers through the LCs, which is significantly different from the mechanism of interface-to-bulk ordering propagation in nematic anchoring. Furthermore, the smectic LCs have also been proven to possess a potential selectivity in response to a subtle change in the chain rigidity of amphiphiles. These simulation findings are promising and would be valuable for the development of novel smectic-based sensors. 相似文献