“凝固点降低法测定萘的摩尔质量”实验的改进研究

文章对＂凝固点降低法测定萘的摩尔质量＂实验的改进进行了研究：使用环己烷作溶剂和沸石以控制过冷度;使用新装置以控制寒剂与被测液间的温差;使用微机辅助实验记录结果.改进后实验表明：测定结果准确性高、重复性好.实验几乎不受实验室温度及湿度影响,操作简便、安全,省时.     

凝固点降低法测定摩尔质量实验的教学体会

本文分析了SWC-LG凝固点实验装置测定摩尔质量实验中存在的三方面问题:实验体系环境不友好、寒剂温度控制困难、人工数据采集处理.提出以下改进方法:采用水做溶剂的测定体系、低温恒温槽控制温度以及数据采集处理自动化.通过改进可以使该实验成为绿色环保、实验测量准确的本科教学实验.     

凝固点降低法测定摩尔质量实验装置的改进

对凝固点降低法测定摩尔质量的实验装置进行了改进.实验结果表明,改进后的装置操作方便,所得结果准确、重现性好.以环己烷作溶剂、萘为溶质测得萘摩尔质量的相对误差均在1%以内.     

凝固点降低法测定溶质摩尔质量实验的改进

通过改变凝固点降低法测定溶质摩尔质量实验中的搅拌装置,对一个经典的基础实验装置进行了改进,这种改进克服了实验过程中平衡温度不易观察的缺陷,实验效果明显提高.     

凝固点下降法测分子量实验改造与计算机采样

对凝固点下降法测分子量的实验作了改造，采用电子贝克曼温度计和计算机采集数据，提高了实验自动化水平，避免了水银可能的污染。     

凝固点降低法测萘摩尔质量实验条件的探讨

针对"凝固点降低法测萘摩尔质量"实验中萘-苯溶液过冷温度很难找准的问题,进行了反复实验,结果表明:纯苯的凝固点温度为5.4℃,与教材一致.25 mL苯中分别加1.0、1.1、1.2、1.3、1.4、1.5 g萘溶液进行过冷,则最低温度为4.91～4.69℃,呈依次下降势态;回升最高温度在5.30～4.93℃之间,过冷温差为0.37～0.24℃.通过控制加冰量和速度的方法控制过冷温度,以每分钟降低0.2℃比较合适,所测萘的摩尔质量为117.62 g·mol-1,与标准值相比误差为-8.23%.该实验条件为在有限的时间内达到良好的实验效果提供了参考.     

用现代演绎经典——基础物理化学教学实验的改进与实践

以"凝固点降低法测定摩尔质量"和"溶液表面张力的测定"实验为例,通过对经典物理化学实验的实验方法和装置的改进,实现了经典实验与现代科技完美结合,进而达到了改变学生的学习和思考方式,即由过去的被动学习变为现在的主动学习,由完全的验证性实验变为在原有实验基础上能自己独立思考、设计的实验。教学实践证明,这种改进的实验教学方法和手段受到了学生的一致好评,收到了较好的教学效果,提高了实验教学水平。     

低温固液相图的制作

针对传统实验“二元合金相图”在实验中存在的操作困难,精准度差和环境污染等问题,改用熔点较低的物质制作同液相图,用凝固点降低测定装置系统制作步冷曲线,采用燃烧热实验贝克曼温度测定装置实现了样品冷却过程温度数据的在线采集及步冷曲线的同步显示,改进后实验温度精度由0．2℃精准到0．001℃,实验相对误差由原来约3％降到约1．5％,操作更简便易行,且用药量减少,实验时间短,安全,基本无污染物存在与排放,可以替代原金属相图实验．     

Excel和Origin在物理化学实验数据处理中的应用

结合物理化学中的经典实验——凝固点降低法测定萘的摩尔质量的实例,介绍利用Excel和O rigin软件对全自动凝固点下降法测量仪所测的TXT格式数据进行处理的方法.此种方法除用在物理化学实验中外,科学研究中其他大型仪器所测的实验数据分析处理也可采用此法作图.     

首届中国中学生数理化学科能力竞赛化学实验全国总决赛试题（高一）补铁剂中铁元素含量的测定（目视比色法）

1 实验目的 用目视比色法测定补铁剂中铁元素的含量． 2 实验原理 通过眼睛观察比较待测溶液与标准比色液颜色深浅来确定物质含量的方法,叫作目视比色法．在一系列试管中装有不同浓度的标准比色液（因浓度不同形成颜色深浅差异的色阶）,将待测溶液与标准比色液进行比较,若待测溶液与色阶中某溶液的颜色深浅相同,则说明2份溶液的浓度相等;若待测溶液颜色深浅介于相邻2个标准比色液之间,则待测溶液的浓度计为2个标准比色液浓度的算术平均值．     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.     

汉字倒说

汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。     

团图为数的图中的闭团贯数

Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F.     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

Social and Cultural Influence on Word Meaning

Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language.     

钱生钱!

我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了     

Inequalities for inscribed simplexes

The problem on the geometrc inequalities involving an n-dimensional simplex and its inscribed simplex is studied. Aninequality is established, which reveals that the difference between the squared circumradius of the n-dimensional simplex andthe squared distance between its circumcenter and barycenter times the squared circumradius of its inscribed simplex is not lessthan the 2(n-1)th power of n times its squared inradius, and is equal to when the simplex is regular and its inscribed siplex is atangent point one. Deduction from this inequality reaches a generalization of n-dimensional Euler inequality indicating that thecircumradius of the simplex is not less than the n-fold inradius. Another inequality is derived to present the relationship betweenthe circumradius of the n-dimensional simplex and the circumradius and inradius of its pedal simplex.