ANALYTICAL CHEMISTRY AND PROBLEMS IN SOCIETY

Analytical Chemistry: The Impact Factor for 2019 Analytical chemistry is a subfield of chemistry that focuses on the study of chemical composition and characterization of various substances. It plays a crucial role in a wide range of industries, including pharmaceuticals, forensics, environmental sciences, and materials chemistry. One important metric used to evaluate the credibility and impact of research in this field is the impact factor. In this article, we will explore the concept of impact factor and its significance for analytical chemistry in the year 2019.What is Impact Factor?Impact factor is a measure of the average number of citations received by articles published in a specific scientific journal. It is calculated by dividing the total number of citations received in a particular year by the total number of articles published in the previous two years. The impact factor provides an indication of the influence and visibility of a journal within the scientific community.Importance of Impact FactorThe impact factor serves several important purposes in the field of analytical chemistry. Firstly, it helps researchers identify high-quality journals to publish their work. Journals with higher impact factors are generally considered more prestigious, and publishing in these journals can enhance the visibility and impact of the research.Secondly, impact factor is often used by funding agencies and institutions to assess the quality and significance of research produced by scientists. Researchers with a strong publication record in high-impact journals are more likely to receive grants and obtain academic positions.Moreover, the impact factor can provide insights into emerging trends and advancements in analytical chemistry. Journals with rising impact factors may indicate a growing interest and recognition of specific research areas, while declining impact factors may suggest a shift in scientific focus or the emergence of new rival journals.Impact Factor for Analytical Chemistry Journals in 2019In 2019, several analytical chemistry journals exhibited notable impact factors, indicating their influence within the field. Here are a few examples:1.Analytical Chemistry - This journal is one of the most renowned in thefield, consistently publishing high-quality research. In 2019, its impact factor was 6.785, reflecting its importance and relevance.2.Journal of Analytical Chemistry - With an impact factor of 2.801, thisjournal continues to contribute significantly to the advancement of analytical chemistry.3.Analytical and Bioanalytical Chemistry - This journal focuses on theinterface between analytical chemistry and the life sciences. In 2019, itachieved an impact factor of 3.286, highlighting its interdisciplinary approach.4.Talanta - This international journal encompasses all branches ofanalytical sciences. In 2019, it attained an impressive impact factor of 5.339, solidifying its position as a leading platform for analytical chemistry research.It’s important to note that impact factors vary across different databases and disciplines. Therefore, it is advisable to refer to multiple sources to obtain a comprehensive understanding of the impact factors for analytical chemistry journals.ConclusionThe impact factor serves as a critical metric for evaluating the influence and quality of research in the field of analytical chemistry. It assists researchers in choosing suitable journals for publication, aids funding agencies in decision-making, and provides insights into emerging trends. By recognizing the impact factors for analytical chemistry journals in 2019, scientists can stay informed about the latest developments and contribute to the growth of the field.。

《药学英语》课程教学大纲一、课程教学目的与任务开设药学英语旨在从培养高级应用型人才的目标出发，结合药学及相关专业学生毕业后的工作实际，力求为他们提供其未来工作岗位所需要的专业英语知识和技能。

通过教学，提高学生借助辞典和其他工具书籍，阅读国外文献的能力，并为将来我国执业药师与国际接轨做准备。

二、理论教学的基本要求学完该课程后，在知识、技能和能力上分别应达到的以下程度：了解英文药学文献的写作特点和格式，学习如何分析和理解英语长句。

英国药典和美国药典的背景知识和使用方法，了解FDA的职责和功能；理解各章节PartA部分课文意思及PartB部分药品说明书中的常见例句；掌握掌握药品说明书必须书写的10个项目及其常用词汇，能够归纳出一些常见的化学基团的英文词缀；能用所学知识书写简单的英语药品说明书。

三、实践教学的基本要求本课程实践学时全部以课堂对话形式进行，无单独实验项目。

四、教学学时分配五、教学内容Unit 1教学目的和要求：通过本章节学习，理解课文意思；掌握药品说明书的作用、项目；能够归纳出一些常见的化学基团的英文词缀。

教学重点：常用专业单词，如Pharmaceutical等的用法。

教学难点：文章翻译；常见的化学基团的英文词缀。

主要内容：PartA Foreign Investment in Chinese Pharmaceutical Sector；PartB 第1节药品名称；PartC China—from self-sufficiency to World Leadership。

Unit 2教学目的和要求：通过本章节学习,使学生理解课文意思；掌握常用专业单词，如supervision等的用法；掌握描述药物性状的常见句型；掌握药物性状的常用表达方式。

教学重点：常见的药物性状。

教学难点：常见描述药物性状的单词或短语。

主要内容：PartA FDA: Policeman or Teacher；PartB 第2节药物性状；PartC Data Required for Drug Approval。

最低有效浓度的英文缩写LOD (Limit of Detection) is the abbreviation for the Lowest Observable Concentration. It is a crucial parameter in analytical chemistry and is widely used in various fields such as environmental monitoring, pharmaceutical analysis, and forensic science. LOD represents the lowest concentration of a substance that can be reliably detected and distinguished from background noise.Accurate determination of LOD is essential in analytical methods as it provides information about the sensitivity and reliability of the measurement. It helps to establish the lower limit of quantification, ensuring that the results obtained are within the linear range of the instrument. LOD is typically determined by analyzing a series of samples with known concentrations and measuring the signal-to-noise ratio.There are several methods commonly used to determine LOD, including the signal-to-noise ratio method, the standard deviation method, and the blank method. The signal-to-noise ratio method involves measuring the signal response of a sample with a known low concentration and comparing it to the background noise level. The LOD is then calculated as a certain multiple of the standard deviation of the noise.The standard deviation method determines LOD by analyzing a series of blank samples and calculating the standard deviation of their responses. The LOD is then defined as a certain multiple of the standard deviation. This method is particularly useful when the background noise is relatively constant.The blank method involves analyzing a series of blank samples and calculating the average response. The LOD is then defined as a certain multiple of the average response. This method is suitable when the background noise is not constant and varies significantly.It is important to note that LOD is influenced by various factors, including the instrument's sensitivity, the sample matrix, and the analytical method used. Different methods may yield different LOD values for the same analyte. Therefore, it is crucial to carefully select the appropriate method and consider the specific requirements of the analysis.In conclusion, LOD (Limit of Detection) is a critical parameter in analytical chemistry. It represents the lowest concentration of a substance that can be reliably detected and distinguished from background noise. Accurate determination of LOD is essential for establishing the lower limit of quantification and ensuring the reliability of analytical measurements. Various methods, such as the signal-to-noise ratio method, the standard deviation method, and the blank method, can be used to determine LOD. Careful consideration of the specific requirements of the analysis is necessary to select the appropriate method and obtain reliable results.。

学化学的好处英语作文Title: The Benefits of Studying Chemistry。

Studying chemistry brings numerous advantages that extend far beyond the confines of the laboratory. From understanding the world around us to unlocking career opportunities, delving into the realm of chemistry opens doors to a myriad of possibilities. Here are several compelling reasons why learning chemistry is invaluable:1. Understanding the World: Chemistry is the science of matter, its properties, composition, and interactions. By studying chemistry, we gain insights into the fundamental building blocks of the universe. From the structure of atoms to the complex reactions that drive biological processes, chemistry provides a lens through which we can comprehend the natural world.2. Critical Thinking Skills: Chemistry encourages analytical thinking and problem-solving. When faced with achemical reaction or a complex formula, students learn to break down problems into smaller components, identify patterns, and devise solutions. These critical thinking skills are transferable to various other fields and are highly valued in academia and the workforce.3. Practical Applications: The applications of chemistry are vast and diverse. From developing new pharmaceuticals to designing sustainable materials, chemistry plays a crucial role in addressing global challenges. By studying chemistry, students equip themselves with the knowledge and skills to contribute to advancements in medicine, technology, and environmental protection.4. Career Opportunities: A background in chemistry opens doors to a wide range of career opportunities. Graduates can pursue careers in research, academia, healthcare, environmental science, and industry. Whether working in a laboratory, a manufacturing plant, or a classroom, chemists play pivotal roles in shaping the world around us.5. Innovation and Discovery: Chemistry is a dynamic field that thrives on innovation and discovery. From groundbreaking experiments to revolutionary theories, chemistry constantly pushes the boundaries of what is possible. By studying chemistry, students become part of this exciting journey of exploration and discovery.6. Global Impact: Many of the world's most pressing issues, such as climate change, pollution, and disease, have chemical components. By studying chemistry, students are empowered to tackle these challenges head-on. Whether developing alternative energy sources, designing eco-friendly materials, or combating infectious diseases, chemists have the potential to make a significant impact on a global scale.7. Personal Enrichment: Beyond its practical applications, studying chemistry can enrich our lives in profound ways. It fosters a sense of wonder and curiosity about the world, encouraging lifelong learning and exploration. Whether conducting experiments in the lab ormarveling at the beauty of molecular structures, chemistry has the power to inspire and captivate.In conclusion, the benefits of studying chemistry are manifold and far-reaching. From gaining a deeper understanding of the natural world to unlocking career opportunities and driving innovation, chemistry plays a vital role in shaping our past, present, and future. By embracing the study of chemistry, we not only expand our knowledge but also contribute to the collective pursuit of knowledge and progress.。

critical reviews in analytical chemistry缩写
《CriticalReviewsinAnalyticalChemistry》缩写为CRAC，是一本由化学、分析化学和化学物理学界知名学者组成的编辑委员会主持的国际性综述类学术期刊。

该期刊的主要目的是向读者提供高质量的综述文章，包括最新的实验和计算结果，以及在化学和分析化学领域的前沿研究进展。

CRAC期刊的主题范围囊括了所有的化学和分析化学领域，包括分析方法、仪器和技术的开发、环境分析、生物分析、食品分析等。

每篇文章都是由专家学者撰写，基于对当前领域的深入研究和实践经验，提供有针对性的综述和评论。

在CRAC期刊上发表文章的作者需要具备很高的学术水平和研究能力，以确保文章内容的质量和可信度。

同时，该期刊也对文章的撰写和结构提出了很高的要求，以确保文章的可读性和逻辑性。

因此，CRAC期刊发表的文章往往被广大读者和同行学者所认可和引用。

作为分析化学领域的重要学术期刊，CRAC期刊对于推动分析化学领域的研究和发展具有重要意义。

在该期刊上发表的文章，不仅可以促进研究者之间的交流和合作，也可以为学术界和工业界提供有价值的参考和指导。

总之，CRAC期刊作为一个高质量的综述类学术期刊，在推动化学和分析化学领域的发展和创新方面发挥着重要作用。

相信在未来的发展中，CRAC期刊将会继续发挥其重要的作用，为学术界和工业界提供更好的服务。

我喜欢化学和原因英语作文Chemistry is a fascinating field of study that has captivated my interest and curiosity for years. As a student, I have always been drawn to the intricate workings of the natural world and the ability to understand and manipulate the fundamental building blocks of matter. Chemistry, with its rich history, diverse applications, and endless possibilities, has become a passion of mine, and I am eager to explore and expand my knowledge in this dynamic discipline.One of the primary reasons I am enamored with chemistry is its ability to unravel the mysteries of the universe. From the smallest subatomic particles to the complex structures of living organisms, chemistry provides the tools and principles to comprehend the intricate relationships that govern the physical and chemical properties of matter. The idea of being able to delve into the fundamental nature of substances, to understand how they interact and transform, ignites a sense of wonder and excitement within me.Moreover, the practical applications of chemistry are truly astounding. This field of study has revolutionized numerousindustries, from medicine and pharmaceuticals to materials science and energy production. The development of life-saving drugs, the creation of innovative materials, and the search for sustainable energy solutions are just a few examples of the tangible impact chemistry has on our daily lives. Knowing that the knowledge I acquire in chemistry can be directly applied to improve the world around me is a profound motivator.Another aspect of chemistry that captivates me is its interdisciplinary nature. Chemistry seamlessly integrates with other scientific fields, such as biology, physics, and environmental science, allowing for a holistic understanding of the natural world. The ability to connect different branches of science and to see the interconnectedness of various phenomena is both intellectually stimulating and practically valuable. This interdisciplinary approach encourages me to think critically, to make connections, and to approach problems from multiple perspectives.Furthermore, the experimental nature of chemistry appeals to my analytical and problem-solving skills. The process of designing and conducting experiments, collecting and analyzing data, and drawing conclusions is both challenging and rewarding. I find immense satisfaction in the process of scientific inquiry, where hypotheses are tested, theories are refined, and new discoveries are made. The hands-on experience of working in a laboratory setting,manipulating equipment, and observing the tangible results of my efforts is exhilarating.Beyond the academic and scientific aspects, I am also drawn to the rich history and the ongoing advancements in the field of chemistry. The contributions of pioneering chemists, such as Marie Curie, Dmitri Mendeleev, and Linus Pauling, have shaped our understanding of the world and paved the way for continued progress. Studying the evolution of chemical theories, the development of new techniques and instruments, and the current frontiers of research inspires me to become part of this dynamic and ever-evolving discipline.Additionally, the problem-solving skills and critical thinking abilities I have developed through the study of chemistry have been invaluable in my overall academic and personal growth. The ability to analyze complex problems, break them down into manageable components, and devise creative solutions has not only benefited me in my chemistry coursework but has also proven useful in other areas of study and in everyday life. The logical and systematic approach inherent in chemistry has equipped me with a valuable set of skills that I can apply across a wide range of endeavors.As I continue my educational journey, I am excited to delve deeper into the world of chemistry. The opportunity to conduct research, collaborate with peers and mentors, and contribute to theadvancement of scientific knowledge is a thrilling prospect. I am particularly interested in exploring the fields of organic chemistry, biochemistry, and materials science, where I believe I can leverage my passion and skills to make meaningful contributions.In conclusion, my fascination with chemistry stems from its ability to unravel the mysteries of the natural world, its practical applications in improving our lives, its interdisciplinary nature, its experimental and problem-solving aspects, and its rich history and ongoing advancements. As I continue my academic and personal journey, I am committed to pursuing a career in chemistry, where I can apply my knowledge, skills, and passion to make a positive impact on the world around me. The vast potential of this field, coupled with my unwavering enthusiasm, drives me to excel and to contribute to the ever-expanding frontiers of chemical knowledge.。

trends in analytical chemistry约稿模板Title: Trends in Analytical Chemistry: A Comprehensive OverviewIntroduction:Analytical chemistry plays a crucial role in various fields, including pharmaceuticals, environmental sciences, food safety, and forensic science. As technology advances, the field of analytical chemistry continues to evolve and embrace new methodologies and techniques. This article aims to provide a comprehensive overview of the emerging trends in analytical chemistry, highlighting their significance and potential implications.1. Miniaturization:One of the prominent trends in analytical chemistry is the miniaturization of analytical devices and systems. Miniaturization offers several advantages, including lower sample and reagent consumption, reduced analysis time, and portability. Techniques such as microfluidics, lab-on-a-chip, and nanosensors have gained attention due to their ability to perform rapid and sensitive analysis in small volumes. Miniaturization has opened up new possibilities for point-of-care diagnostics, on-site monitoring, and personalized medicine.2. Advanced Mass Spectrometry:Mass spectrometry (MS) has been a key analytical tool for decades, but recent advancements have significantly enhanced its capabilities. High-resolution MS, tandem MS, and ion mobility MS have improved the detection and identification of complexanalytes, including metabolites, proteins, and peptides. Furthermore, the development of ambient ionization techniques has enabled direct analysis of samples in their native environment, eliminating the need for sample preparation. These advancements have revolutionized the fields of metabolomics, proteomics, and omics sciences.3. Big Data and Data Analytics:The advent of big data has had a profound impact on various scientific disciplines, including analytical chemistry. Analytical chemists are now faced with large and complex datasets generated from various analytical techniques. Thus, the need for effective data management, data processing, and data analytics has become increasingly important. Data integration, machine learning algorithms, and chemometrics are being employed to extract meaningful information, identify patterns, and make predictions, leading to better decision-making and optimization of analytical processes.4. Sustainable and Green Analytical Chemistry:With increasing environmental concerns, there is a growing emphasis on sustainable and green analytical chemistry practices. This includes developing eco-friendly sample preparation techniques, reducing waste generation, and utilizing renewable resources. Techniques such as microwave-assisted extraction, supercritical fluid extraction, and solid-phase microextraction are gaining popularity due to their reduced solvent consumption and energy requirements. Additionally, green analytical chemistry involves using environmentally friendly reagents and developing recyclable or biodegradable analytical tools.5. Multi- and Cross-Disciplinary Approaches:Analytical chemistry has always been an interdisciplinary field, but recent trends indicate a shift towards multi- and cross-disciplinary approaches. Collaborations with experts from fields such as materials science, nanotechnology, biology, and computer science have led to significant advancements. Integration of analytical chemistry with these disciplines has resulted in the development of innovative techniques such as plasmonics-based sensing, bioanalytical nanomaterials, and data-driven analytical models, expanding the scope and applicability of analytical chemistry. Conclusion:The field of analytical chemistry is constantly evolving, driven by emerging trends and technological advancements. This article has provided a comprehensive overview of some of the prominent trends, including miniaturization, advanced mass spectrometry, big data analytics, sustainable practices, and cross-disciplinary approaches. It is evident that these trends will continue to shape the future of analytical chemistry and pave the way for novel analytical methods, instruments, and applications.。

分析化学学科介绍英语作文Analytical chemistry is a branch of chemistry that focuses on the identification and quantification of chemical compounds. It involves the use of various techniques and instruments to analyze samples and determine their chemical composition.One of the key goals of analytical chemistry is to ensure the quality and safety of products. This can involve testing for impurities, contaminants, or other substances that may affect the properties of a product.Analytical chemistry is also important in environmental monitoring and protection. By analyzing samples from air, water, and soil, analytical chemists can identifypollutants and assess their impact on the environment.In the field of forensics, analytical chemistry plays a crucial role in the analysis of evidence. By using techniques such as chromatography and spectroscopy,forensic chemists can identify substances found at crime scenes and provide valuable information for criminal investigations.Another important application of analytical chemistryis in the pharmaceutical industry. Analytical chemists are responsible for testing the purity and potency of drugs, ensuring that they meet regulatory standards and are safefor human consumption.Overall, analytical chemistry is a diverse and dynamic field that plays a vital role in various industries and scientific research. It requires a combination oftheoretical knowledge, practical skills, and critical thinking to effectively analyze and interpret chemical data.。

Lesson 3 Analytical ChemistryAnalytical chemistry is the science of making quantitative measurements. In practice, quantifying analytes in a complex sample becomes an exercise in problem solving. To be effective and efficient, analyzing samples requires expertise in:1the chemistry that can occur in a sample2analysis and sample handling methods for a wide variety of problems (the tools-of-the-trade)3proper data analysis and record keepingTo meet these needs, Analytical Chemistry courses usually emphasize equilibrium, spectroscopic and electrochemical analysis, separations, and statistics.Analytical chemistry requires a broad background knowledge of chemical and physical concepts. With a fundamental understanding of analytical methods, a scientist fac ed with a difficult analytical problem can apply the most appropriate technique(s). A fundamental understanding also makes it easier to identify when a particular problem cannot be solved by traditional methods, and gives an analyst the knowledge that is needed to develop creative approaches or new analytical methods.1 GravimetryGravimetry is the quantitative measurement of an analyte by weighing a pure, solid form ofthe analyte. Obtaining pure solids from solutions containing an unknown amount of a metal ion is done by precipitation.Since gravimetric analysis is an absolute measurement, it is a principal method for analyzing and preparing primary standards. A typical experimental procedure to determine an unknown concentration of an analyte in solution is as follows:quantitatively precipitate the analyte from solutioncollect the precipitate by filtering and wash it to remove impuritiesdry the solid in an oven to remove solventweigh the solid on an analytical balancecalculate the analyte concentration in the original solution based on the weight of theprecipitateGravimetric Determination of Iron:Determine constant weight of the cruciblesOxidation of iron samplePrecipitation of iron hydroxideIgnition of iron hydroxide to iron oxideDetermine constant weight of the crucibles plus iron oxideCalculation of iron in the sample2 TitrationTitration is the quantitative measurement of an analyte in solution by completely reacting itwith a reagent solution. The reagent is called the titrant and must either be prepared from a primary standard or be standardized versus a primary standard to know its exact concentration.The point at which all of the analyte is consumed is the equivalence point. The number of moles of analyte is calculated from the volume of reagent that is required to react with all of the analyte, the titrant concentration, and the reaction stoichiometry.The equivalence point is often determined by visual indicators are available for titrations based on acid-base neutralization, complexation, and redox reactions, and is determined by some type of indicator that is also present in the solution. For acid-base titrations, indicators are available that change color when the pH changes. When all of the analyte is neutralized, further addition of the titrant causes the pH of the solution to change causing the color of the indicator to change.If the pH of an acid solution is plotted against the amount of base added during a titration, the shape of the graph is called a titration curve. All acid titration curves follow the same basic shapes.Strong Acid Titration CurveAt the beginning, the solution has a low pH and climbs as the strong baseis added. As the solution nears the point where all of the H+ are neutralized,the pH rises sharply and then levels out again as the solution becomes morebasic as more OH- ions are added.Manual titration is done with a buret, which is a long graduated tube toaccurately deliver amounts of titrant. The amount of titrant used in the titrationis found by reading the volume of titrant in the buret before beginning thetitration and after reaching the endpoint. The difference in these readings is thevolume of titrant to reach the endpoint. The most important factor for making accurate titrations isto read the buret volumes reproducibly. The figure shows how to do so by using the bottom of the meniscus to read the reagent volume in the buret.The end point can be determined by an indicator as described above or by an instrumental method. The most common instrumental detection method is potentiometric detection. The equivalence point of an acid-base titration can be detected with a pH electrode. Titrations, such as complexation or precipitation, involving other ions can use an ion-selective electrode (ISE). UV-vis absorption spectroscopy is also common, especially for complexometric titrations where a subtle color change occurs.For repetitive titrations, autotitrators with microprocessors are available that deliver the titrant, stop at the endpoint, and calculate the concentration of the analyte. The endpoint is usually detected by some type of electrochemical measurement. Some examples of titrations for which autotitrators are available include:Acid or base determination by pH measurement with potentiometric detection.Determination of water by Karl Fischer reagent (I2and SO2in methyl alcohol and pyridine) with coulometric detection.Determination of Cl in aqueous solution with phenylarsene oxide using amperometric detection.3 ExtractionExtractions use two immiscible phases to separate a solute from one phase into the other. The distribution of a solute between two phases is an equilibrium condition described by partition theory. Boiling tea leaves in water extracts the tannins, theobromine, and caffeine (the good stuff) out of the leaves and into the water. More typical lab extractions are of organic compounds out ofan aqueous phase and into an organic phase.Analytical Extractions4 Precipitation (Insoluble Salts)Many metal ions form compounds that are insoluble in water. We call them insoluble salts or precipitates. Common precipitates are carbonates, hydroxides, sulfates, and sulfides. Ions that we consider spectator ions when discussing acid-base equilibria will form insoluble salts.An insoluble salt in contact with water maintains an equilibrium with the ions. In simple cases where there are no common ions or competing equilibria, the ion concentrations depend only on the equilibrium constant for the particular precipitate. When we talk about solubility equilibria we always write the equilibrium with the solid on the left. For example:Ba(IO3)2 (s)Ba2+(aq) + 2 IO3-(aq)The equilibrium constant expression for an insoluble salt is written following the same rulesas for any other equilibrium. The equilibrium constant is called the solubility product, K sp. The K sp expression for the above equilibrium is:K sp = [Ba2+][IO3-]2K sp Values for Some PrecipitatesFormula Name K spAgCl silver chloride 1.8×10-10Al(OH)3aluminum hydroxide 2×10-32BaCO3barium carbonate 5×10-9Words & Phrasesamperometric [] adj. 测量电流的analyte [] n. （被）分析物buret [] n. 滴定管；量筒carbonate [] n. 碳酸盐complexometric [] n. 络合滴定（法）coulometric [] n. 库仑滴定crucible [] n. 坩埚endpoint [] n. 端点equilibrium [] n. 平衡（复数形式：equilibria）filtering [] n. 过滤gravimetry [] n. 重量测定法hydroxide [] n. 氢氧化物impurity [] n. 不纯，杂质insoluble [] adj. 不能溶解的，不能解决的neutralization [] n. 中和（作用）reagent [] n. 反应物, 试剂solute [] n. 溶解物，溶质solvent [] n. 溶剂spectroscopic [] adj. 分光镜的，借助分光镜的sulfate [] n. 硫酸盐sulfide [] n. 硫化物tannin [] n. 单宁酸theobromin [] n. 可可碱titrant [] n. 滴定剂（滴定标准液）analytical balance n. 分析天平aqueous phase n. 水相equivalence point n. 等量点graduated tube n. 刻度管immiscible phase n. 不混溶相ion-selective electrode n. 选择性离子电极organic phase n. 有机相partition theory n. 分配理论potentiometric adj. 电势测定的precipitation n. 沉淀(作用) quantitative measurement n. 定量测量solubility solution product n. 溶度积stoichiometry n. 化学计量法，化学计量学第3课分析化学分析化学是定量测量的科学。

对化学专业的看法的英语作文英文回答：Chemistry is the study of matter and its properties as well as how matter changes. It is a broad field that encompasses many different subdisciplines, including analytical chemistry, biochemistry, inorganic chemistry, organic chemistry, and physical chemistry. Chemists usetheir knowledge of chemistry to develop new materials, drugs, and technologies, and to solve problems in areassuch as energy, the environment, and health care.Chemistry is a challenging but rewarding field of study. It requires a strong foundation in mathematics and physics, as well as a good understanding of the scientific method. However, the rewards of a career in chemistry can be great. Chemists are in high demand in a variety of industries, and they can earn a good salary. Additionally, chemistry is a fascinating and intellectually stimulating field that can provide a lifelong source of learning and enjoyment.Here are some of the reasons why I am interested in studying chemistry:I am fascinated by the natural world and how it works. Chemistry is the study of the fundamental building blocksof matter, and it allows me to understand the world around me on a deeper level.I am interested in solving problems. Chemistry is a problem-solving discipline, and I enjoy using my knowledgeof chemistry to find solutions to real-world problems.I am creative and innovative. Chemistry is a creative field that allows me to express my creativity and develop new ideas.I am passionate about making a difference in the world. Chemistry is a powerful tool that can be used to solve important problems and improve people's lives.I believe that a career in chemistry would be a perfectfit for me. I am passionate about chemistry, and I am confident that I have the skills and abilities to succeed in this field. I am excited to learn more about chemistry and to use my knowledge to make a difference in the world.中文回答：我对化学专业的看法。

(完整版)化学专业英语一、基础词汇篇1. 原子与分子Atom（原子）：物质的基本单位，由质子、中子和电子组成。

2. 化学反应Reactant（反应物）：参与化学反应的物质。

Product（物）：化学反应后的物质。

Catalyst（催化剂）：能改变化学反应速率而本身不发生永久变化的物质。

3. 物质状态Solid（固体）：具有一定形状和体积的物质。

Liquid（液体）：具有一定体积，无固定形状的物质。

Gas（气体）：无固定形状和体积的物质。

4. 酸碱盐Acid（酸）：在水溶液中能电离出氢离子的物质。

Base（碱）：在水溶液中能电离出氢氧根离子的物质。

Salt（盐）：由酸的阴离子和碱的阳离子组成的化合物。

5. 溶液与浓度Solution（溶液）：由溶剂和溶质组成的均匀混合物。

Solvent（溶剂）：能溶解其他物质的物质。

Solute（溶质）：被溶解的物质。

Concentration（浓度）：溶液中溶质含量的度量。

二、专业术语篇1. 有机化学Organic Chemistry（有机化学）：研究碳化合物及其衍生物的化学分支。

Functional Group（官能团）：决定有机化合物化学性质的原子或原子团。

Polymer（聚合物）：由许多重复单元组成的大分子化合物。

2. 无机化学Inorganic Chemistry（无机化学）：研究不含碳的化合物及其性质的化学分支。

Crystal（晶体）：具有规则排列的原子、离子或分子的固体。

OxidationReduction Reaction（氧化还原反应）：涉及电子转移的化学反应。

3. 物理化学Physical Chemistry（物理化学）：研究化学现象与物理现象之间关系的化学分支。

Chemical Bond（化学键）：原子间相互作用力，使原子结合成分子。

Thermodynamics（热力学）：研究能量转换和物质性质的科学。

4. 分析化学Analytical Chemistry（分析化学）：研究物质的组成、结构和性质的科学。

高三自我评价的学术志趣与偏好英文回答：Academic Interests and Preferences.As a high school senior, I have developed a strong academic interest in the field of science, particularly biology and chemistry. I am fascinated by the intricacies of living organisms and the chemical processes that occur within them. This interest has been nurtured through my involvement in various science-related activities, such as participating in science fairs, conducting experiments, and reading scientific journals.One of the reasons I am drawn to biology is the opportunity it provides to explore the wonders of life. From studying the complex structures of cells to understanding the mechanisms of genetics, biology offers a glimpse into the amazing world of living organisms. I find it incredibly rewarding to learn about theinterconnectedness of different organisms and how they adapt to their environments.Chemistry, on the other hand, appeals to my analytical and problem-solving skills. I enjoy the logical thinking required to understand chemical reactions and the ability to apply this knowledge to real-world situations. Whether it's balancing equations or predicting the outcome of a reaction, chemistry challenges me to think critically and creatively.In terms of preferences, I am someone who thrives in a hands-on learning environment. I enjoy conducting experiments and engaging in practical applications of the concepts I learn in the classroom. For example, in my chemistry class, I particularly enjoyed performing titrations and observing color changes that indicated the completion of a reaction. These hands-on experiences not only deepen my understanding of the subject but also make the learning process more enjoyable.Furthermore, I appreciate the value of collaborativelearning. Working in groups allows me to exchange ideas, learn from my peers, and develop important teamwork skills. In my biology class, for instance, we often engage in group discussions and conduct group projects that require us to work together to solve problems or analyze data. This interactive approach not only enhances my understanding of the subject but also fosters a sense of camaraderie among classmates.In conclusion, my academic interests lie in the fields of biology and chemistry. The study of biology allows me to explore the wonders of life, while chemistry challenges me to think analytically and apply my knowledge to real-world situations. I thrive in a hands-on learning environment and appreciate the value of collaborative learning. These interests and preferences have shaped my academic journey and will continue to guide my future pursuits.中文回答：学术志趣与偏好。

去化学实验室老师和学生的情景对话英语作文Here is a 700-word English essay on a dialogue between a chemistry lab teacher and students:It was a typical day in the chemistry lab at Oakwood High School. The air was filled with the familiar scent of various chemicals and the sound of bubbling solutions. As the students gathered around their workstations, their chemistry teacher, Ms. Johnson, stepped to the front of the class, ready to guide them through the day's experiment."Good morning, class," she began, her voice calm and authoritative. "Today, we'll be exploring the fascinating world of acid-base titrations. This is an essential technique in analytical chemistry, and it will help us understand the delicate balance of pH in our everyday lives."The students listened intently, their eyes fixed on their teacher, eager to learn."Now, before we begin, I want to remind you all of the importance of safety in the lab," Ms. Johnson continued, her gaze sweeping across the room. "Remember, we're working with potentially hazardous substances, so I expect you to follow the safety protocols to the letter. Goggles on, gloves on, and no horseplay, understood?"The students nodded in unison, the seriousness of the task at hand evident on their faces."Excellent," Ms. Johnson said, a small smile tugging at the corners of her mouth. "Let's get started, then. I'll walk you through the process step-by-step, and I want you all to take careful notes. This is crucial information that you'll need to know for the upcoming exam."As the class began the experiment, Ms. Johnson moved from one workstation to the next, offering guidance and answering questions. She was patient and thorough, ensuring that each student understood the concepts and techniques.One student, Sarah, raised her hand tentatively. "Ms. Johnson, I'm a bit confused about the endpoint of the titration. Can you explain that part again?""Of course, Sarah," Ms. Johnson replied, making her way to Sarah's station. "The endpoint is the point at which the titration reaction is complete, and it's indicated by a distinct color change in the solution. Let me show you how to identify it."She proceeded to walk Sarah through the process, using clear and concise language to explain the nuances of the technique. Sarah's face lit up with understanding, and she eagerly began to follow the steps, her confidence growing with each passing minute.Across the room, another student, Michael, was struggling with the titration setup. Ms. Johnson noticed his frustration and approached him, placing a gentle hand on his shoulder."Michael, I can see you're having a bit of trouble there. Let's take a step back and go through it together, okay?"Michael nodded gratefully, and the two of them worked through the setup, with Ms. Johnson providing encouragement and guidance. Soon, Michael was on his way, his experiment running smoothly.As the class progressed, the students became more and more engaged, asking thoughtful questions and sharing their observations. Ms. Johnson beamed with pride, watching as her students grappled with the concepts and applied them in a hands-on setting.When the allotted time for the experiment had elapsed, Ms. Johnson called the class to attention. "Alright, everyone, let's wrap things up. I want you all to record your findings and clean up your workstations. Remember, safety first!"The students quickly tidied their areas, their excitement palpable as they discussed their results and compared notes. Ms. Johnson moved from one group to the next, offering feedback and insights, ensuring that each student had a solid understanding of the day's lesson.As the bell rang, signaling the end of the class, the students filed out of the lab, their faces alight with the thrill of scientific discovery. Ms. Johnson watched them go, a sense of satisfaction washing over her. She knew that moments like these were what made teaching so rewarding – the opportunity to ignite a passion for science in the hearts and minds of her students.With a contented sigh, Ms. Johnson began to tidy the lab, already looking forward to the next class and the chance to continue guiding her students on their journey of scientific exploration.。

UNIT 1 CHOOSING AN IDEAL UNIVERSITY1.在选择学校时，为什么会把费用放在第一位呢？因为费用是留学的客观条件之一。

大部分家庭都会把费用问题作为首要筛选条件，从中选择符合自身条件的国家，适合的城市，乃至学校。

Why is the admission considered as the first priority in the selection of the school? Because the tuition is one of the essential conditions when studying abroad. Most of the families would put financial issue as the primary consideration, which helps them to choose the right country, city or even school.2.托福、雅思的考试分数也是择校的重要条件之一。

很多学生先准备成绩，后申请大学。

对于大部分学生而言，获得良好的分数也是必要条件之一。

The grade of TOEFL or IELTS is also one of the important premises. Before applying schools, many student have already got the English grade. Therefore a better grade on English is one of the essential conditions for most students.3.在美国，比较热门的专业有以下几个：统计，金融，市场营销，土木工程，航天科技，生物科学等。

如果考虑到职业规划的问题，这些专业是很不错的选择。

In US, the popular majors are statistics, finance, marketing, architecture, astronautics and bio-technology. If you are thinking about your career plan, those specialties are recommended.UNIT 2 APPLYING TO THE TARGETED UNIVERSITY 1.研究生阶段的学习通常是为了获得一个硕士或博士学位，而一些大学也提供研究生文凭课程。

analytical chemistry的参考文献格式"Analytical Chemistry"（分析化学）的参考文献格式通常会遵循国际通用的引文风格，例如APA（American Psychological Association）、ACS（American Chemical Society）等。

以下是一个使用ACS风格的参考文献格式的示例：对于期刊文章：作者姓氏,作者名字的首字母.文章标题.期刊名字,年份,卷号（期号）,页码范围.例如：Smith,J.A.Determination of Trace Elements in Environmental Samples. Analytical Chemistry,2020,92(5),345-356.对于书籍：作者姓氏,作者名字的首字母.书名.出版地:出版社,出版年份.例如：Johnson,R.S.Analytical Chemistry:Principles and Techniques.New York: Wiley,2018.对于会议论文：作者姓氏,作者名字的首字母.论文标题.会议名字,会议地点,会议日期,页码范围.例如：Brown,M.L.Advances in Mass Spectrometry for Environmental Analysis. Proceedings of the International Symposium on Analytical Chemistry,Paris,France, June15-18,2019,112-120.请注意，具体的参考文献格式可能会根据不同的学术期刊或出版物有所不同，因此最好查阅目标期刊或出版物的官方指南以获取准确的引文要求。

1.(a) chemical process 化学过程(b) natural science自然科学(c) thetechnique of distillation 蒸馏技术2.It is the atoms that make up iron, water, oxygen and the like/and so on/andso forth/and otherwise.（正是原子构成了铁、水、氧等）3.Chemistry has a very long history, in fact, human activity in chemistry goesback to prerecorded times/predating recorded times.（化学具有悠久的历史，事实上，人类的化学活动可追溯到无记录时代以前）4.According to the evaporation of water, people know that liquids can changeinto gases under certain environment.（根据水的蒸发现象,...）5.You must know the properties of the material before you use it.(在你使用这种材料之前,...)IV. Translation(Chemistry is one of there fundamental natural sciences,...)化学是三种基础自然科学之一，另外两种是物理和生物。

自从宇宙大爆炸以来，化学过程持续进行，甚至地球上生命的出现可能也是化学过程的结果。

人们也许认为生命是三步进化的最终结果,第一步非常快,其余两步相当慢。

这三步是：（I）物理进化（化学元素的产生），（II）化学进化（分子和生物分子的形成）；和（III）生物进化（有机物的形成和发展）。

Chapter 1 Matter and MeasurementChemistry is the science of matter and the changes it undergoes. Chemists study the composition, structure, and properties of matter. They observe the changes that matter undergoes and measure the energy that is produced or consumed during these changes. Chemistry provides an understanding of many natural events and has led to the synthesis of new forms of matter that have greatly affected the way we live.Disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, organic chemistry, physical chemistry, analytical chemistry, polymer chemistry, biochemistry, and many more specialized disciplines, e.g. radiochemistry, theoretical chemistry.Chemistry is often called "the central science" because it connects the other natural sciences such as astronomy, physics, material science, biology and geology.1.1. Classification of MatterMatter is usually defined as anything that has mass and occupies space. Mass is the amount of matter in an object. The mass of an object does not change. The volume of an object is how much space the object takes up.All the different forms of matter in our world fall into two principal categories: (1) pure substances and (2) mixtures. A pure substance can also be defined as a form of matter that has both definite composition and distinct properties. Pure substances are subdivided into two groups: elements and compounds. An element is the simplest kind of material with unique physical and chemical properties; it can not be broken down into anything simpler by either physical or chemical means. A compound is a pure substance that consists of two or more elements linked together in characteristic and definite proportions; it can be decomposed by a chemical change into simpler substances with a fixedmass ratio. Mixtures contain two or more chemical substances in variable proportions in which the pure substances retain their chemical identities. In principle, they can be separated into the component substances by physical means, involving physical changes. A sample is homogeneous if it always has the same composition, no matter what part of the sample is examined. Pure elements and pure chemical compounds are homogeneous. Mixtures can be homogeneous, too; in a homogeneous mixture the constituents are distributed uniformly and the composition and appearance of the mixture are uniform throughout. A solutions is a special type of homogeneous mixture. A heterogeneous mixture has physically distinct parts with different properties. The classification of matter is summarized in the diagram below:Matter can also be categorized into four distinct phases: solid, liquid, gas, and plasma. The solid phase of matter has the atoms packed closely together. An object that is solid has a definite shape and volume that cannot be changed easily. The liquid phase of matter has the atoms packed closely together, but they flow freely around each other. Matter that is liquid has a definite volume but changes shape quite easily. Solids and liquids are termed condensed phases because of their well-defined volumes. The gas phase of matter has the atoms loosely arranged so they can travel in and out easily. A gas has neither specific shape nor constant volume. The plasma phase of matter has the atoms existing in an excited state.1.2. Properties of MatterAll substances have properties, the characteristics that give each substance its unique identity. We learn about matter by observing its properties. To identify a substance, chemists observe two distinct types of properties, physical and chemical, which are closely related to two types of change that matter undergoes.Physical properties are those that a substance shows by itself, without changing into or interacting with another substance. Some physical properties are color, smell, temperature, boiling point, electrical conductivity, and density. A physical change is a change that does not alter the chemical identity of the matter. A physical change results in different physical properties. For example, when ice melts, several physical properties have changed, such as hardness, density, and ability to flow. But the sample has not changed its composition: it is still water.Chemical properties are those that do change the chemical nature of matter. A chemical change, also called a chemical reaction, is a change that does alter the chemical identity of the substance. It occurs when a substance (or substances) is converted into a different substance (or substances). For example, when hydrogen burns in air, it undergoes a chemical change because it combines with oxygen to form water.Separation of MixturesThe separation of mixtures into its constituents in a pure state is an important process in chemistry. The constituents of any mixture can be separated on the basis of their differences in their physical and chemical properties, e.g., particle size, solubility, effect of heat, acidity or basicity etc.Some of the methods for separation of mixtures are:(1)Sedimentation or decantation. To separatethe mixture of coarse particles of a solidfrom a liquid e.g., muddy river water.(2)Filtration. To separate the insoluble solidcomponent of a mixture from the liquidcompletely i.e. separating the precipitate(solid phase) from any solution.(3)Evaporation. To separate a non-volatilesoluble salt from a liquid or recover thesoluble solid solute from the solution.(4)Crystallization. To separate a solidcompound in pure and geometrical form.(5)Sublimation. To separate volatile solids,from a non-volatile solid.(6)Distillation. To separate the constituents of aliquid mixture, which differ in their boilingpoints.(7)Solvent extraction method. Organiccompounds, which are easily soluble inorganic solvents but insoluble or immisciblewith water forming two separate layers canbe easily separated.1.3 Atoms, Molecules and CompoundsThe fundamental unit of a chemical substance is called an atom. The word is derived from the Greek atomos, meaning “undivisible”or “uncuttable”.An atom is the smallest possible particle of a substance.Molecule is the smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms;a group of like or different atoms held together by chemical forces. A molecule may consist of atoms of a single chemical element, as with oxygen (O2), or of different elements, as with water (H2O).A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons. Until March 2010, 118 elements have been observed. 94 elements occur naturally on earth, either as the pure element or more commonly as a component in compounds. 80 elements have stable isotopes, namely all elements with atomic numbers 1 to 82, except elements 43 and 61 (technetium and promethium). Elements with atomic numbers 83 or higher (bismuth and above) are inherently unstable, and undergo radioactive decay. The elements from atomic number 83 to 94 have no stable nuclei, but are nevertheless found in nature, either surviving as remnants of the primordial stellar nucleosynthesisthat produced the elements in the solar system, or else produced as short-lived daughter-isotopes through the natural decay of uranium and thorium. The remaining 24 elements so are artificial, or synthetic, elements, which are products of man-induced processes. These synthetic elements are all characteristically unstable. Although they have not been found in nature, it is conceivable that in the early history of the earth, these and possibly other unknown elements may have been present. Their unstable nature could have resulted in their disappearance from the natural components of the earth, however.The naturally occurring elements were not all discovered at the same time. Some, such as gold, silver, iron, lead, and copper, have been known since the days of earliest civilizations. Others, such as helium, radium, aluminium, and bromine, were discovered in the nineteenth century. The most abundant elements found in the earth’s crust, in order of decreasing percentage, are oxygen, silicon, aluminium, and iron. Others present in amounts of 1% or more are calcium, sodium, potassium, and magnesium. Together, these represent about 98.5% of the earth’s crust.The nomenclature and their origins of all known elements will be described in Chapter 2.A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together in a defined spatial arrangement by chemical bonds. Compounds that exist as molecules are called molecular compounds. An ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. Usually, the positively charged portion consists of metal cations and the negatively charged portion is an anion or polyatomic ion.The relative amounts of the elements in a particular compound do not change: Every molecule of a particular chemical substance contains acharacteristic number of atoms of its constituent elements. For example, every water molecule contains two hydrogen atoms and one oxygen atom. To describe this atomic composition, chemists write the chemical formula for water as H2O.The chemical formula for water shows how formulas are constructed. The formula lists the symbols of all elements found in the compound, in this case H (hydrogen) and O (oxygen). A subscript number after an element's symbol denotes how many atoms of that element are present in the molecule. The subscript 2 in the formula for water indicates that each molecule contains two hydrogen atoms. No subscript is used when only one atom is present, as is the case for the oxygen atom in a water molecule. Atoms are indivisible, so molecules always contain whole numbers of atoms. Consequently, the subscripts in chemical formulas of molecular substances are always integers. We explore chemical formulas in greater detail in Chapter 2.The simple formula that gives the simplest whole number ratio between the atoms of the various elements present in the compound is called its empirical formula. The simplest formula that gives the actual number of atoms of the various elements present in a molecule of any compound is called its molecular formula. Elemental analysis is an experiment that determines the amount (typically a weight percent) of an element in a compound. The elemental analysis permits determination of the empirical formula, and the molecular weight and elemental analysis permit determination of the molecular formula.1.4. Numbers in Physical Quantities1.4.1. Measurement1.Physical QuantitiesPhysical properties such as height, volume, and temperature that can be measured are called physical quantity. A number and a unit of defined size are required to describe physical quantity, for example, 10 meters, 9 kilograms.2.Exact NumbersExact Numbers are numbers known withcertainty. They have unlimited number of significant figures. They arise by directly counting numbers, for example, the number of sides on a square, or by definition:1 m = 100 cm, 1 kg = 1000 g1 L = 1000 mL, 1 minute = 60seconds3.Uncertainty in MeasurementNumbers that result from measurements are never exact. Every experimental measurement, no matter how precise, has a degree of uncertainty to it because there is a limit to the number of digits that can be determined. There is always some degree of uncertainty due to experimental errors: limitations of the measuring instrument, variations in how each individual makes measurements, or other conditions of the experiment.Precision and AccuracyIn the fields of engineering, industry and statistics, the accuracy of a measurement system is the degree of closeness of measurements results to its actual (true) value. The precision of a measurement system, also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results. Although the two words can be synonymous in colloquial use, they are deliberately contrasted in the context of the scientific method.A measurement system can be accurate but not precise, precise but not accurate, neither, or both. A measurement system is called valid if it is both accurate and precise. Related terms are bias (non-random or directed effects caused by a factor or factors unrelated by the independent variable) and error(random variability), respectively. Random errors result from uncontrolled variables in an experiment and affect precision; systematic errors can be assigned to definite causes and affect accuracy. For example, if an experiment contains a systematic error, then increasing the sample size generally increases precision but does not improve accuracy. Eliminating the systematic error improves accuracy but does not change precision.1.4.2 Significant FiguresThe number of digits reported in a measurement reflects the accuracy of the measurement and the precision of the measuring device. Significant figures in a number include all of the digits that are known with certainty, plus the first digit to the right that has an uncertain value. For example, the uncertainty in the mass of a powder sample, i.e., 3.1267g as read from an “analytical balance” is 0.0001g.In any calculation, the results are reported to the fewest significant figures (for multiplication and division) or fewest decimal places (addition and subtraction).1.Rules for deciding the number of significantfigures in a measured quantity:The number of significant figures is found by counting from left to right, beginning with the first nonzero digit and ending with the digit that has the uncertain value, e.g.,459 (3) 0.206 (3) 2.17(3) 0.00693 (3) 25.6 (3) 7390 (3) 7390. (4)(1)All nonzero digits are significant, e.g., 1.234g has 4 significant figures, 1.2 g has 2significant figures.(2)Zeroes between nonzero digits aresignificant: e.g., 1002 kg has 4 significantfigures, 3.07 mL has 3 significant figures.(3)Leading zeros to the left of the first nonzerodigits are not significant; such zeroes merelyindicate the position of the decimal point:e.g., 0.001 m has only 1 significant figure,0.012 g has 2 significant figures.(4)Trailing zeroes that are also to the right of adecimal point in a number are significant:e.g., 0.0230 mL has 3 significant figures,0.20 g has 2 significant figures.(5)When a number ends in zeroes that are notto the right of a decimal point, the zeroes arenot necessarily significant: e.g., 190 milesmay be 2 or 3 significant figures, 50,600calories may be 3, 4, or 5 significant figures.The potential ambiguity in the last rule can be avoided by the use of standard exponential, or "scientific" notation. For example, depending onwhether the number of significant figures is 3, 4, or 5, we would write 50,600 calories as:5.06 × 104 calories (3 significant figures)5.060 ×104calories (4 significant figures), or5.0600 × 104 calories (5 significant figures).2.Rules for rounding off numbers(1)If the digit to be dropped is greater than 5,the last retained digit is increased by one.For example, 12.6 is rounded to 13.(2)If the digit to be dropped is less than 5, thelast remaining digit is left as it is. Forexample, 12.4 is rounded to 12.(3)If the digit to be dropped is 5, and if anydigit following it is not zero, the lastremaining digit is increased by one. Forexample, 12.51 is rounded to 13.(4)If the digit to be dropped is 5 and isfollowed only by zeroes, the last remainingdigit is increased by one if it is odd, but leftas it is if even. For example, 11.5 is roundedto 12, 12.5 is rounded to 12.This rule means that if the digit to be dropped is 5 followed only by zeroes, the result is always rounded to the even digit. The rationale is to avoid bias in rounding: half of the time we round up, half the time we round down.3.Arithmetic using significant figuresIn carrying out calculations, the general rule is that the accuracy of a calculated result is limited by the least accurate measurement involved in the calculation.(1) In addition and subtraction, the result is rounded off to the last common digit occurring furthest to the right in all components. Another way to state this rules, is that, in addition and subtraction, the result is rounded off so that it has the same number of decimal places as the measurement having the fewest decimal places. For example,100 (assume 3 significant figures) + 23.643 (5 significant figures) = 123.643,which should be rounded to 124 (3 significant figures).(2) In multiplication and division, the resultshould be rounded off so as to have the same number of significant figures as in the component with the least number of significant figures. For example,3.0 (2 significant figures ) ×12.60 (4 significant figures) = 37.8000which should be rounded off to 38 (2 significant figures).1.4.3 Scientific NotationScientific notation, also known as standard form or as exponential notation, is a way of writing numbers that accommodates values too large or small to be conveniently written in standard decimal notation.In scientific notation all numbers are written like this:a × 10b("a times ten to the power of b"), where the exponent b is an integer, and the coefficient a is any real number, called the significant or mantissa (though the term "mantissa" may cause confusion as it can also refer to the fractional part of the common logarithm). If the number is negative then a minus sign precedes a (as in ordinary decimal notation).In standard scientific notation the significant figures of a number are retained in a factor between 1 and 10 and the location of the decimal point is indicated by a power of 10. For example:An electron's mass is about 0.00000000000000000000000000000091093822 kg. In scientific notation, this is written 9.1093822×10−31 kg.The Earth's mass is about 5973600000000000000000000 kg. In scientific notation, this is written 5.9736×1024 kg.1.5 Units of Measurement1.5.1 Systems of Measurement1.United States Customary System (USCS)The United States customary system (also called American system) is the most commonly used system of measurement in the United States. It is similar but not identical to the British Imperial units. The U.S. is the only industrialized nation that does not mainly use the metric system in its commercial and standards activities. Base units are defined butseem arbitrary (e.g. there are 12 inches in 1 foot)2.MetricThe metric system is an international decimalized system of measurement, first adopted by France in 1791, that is the common system of measuring units used by most of the world. It exists in several variations, with different choices of fundamental units, though the choice of base units does not affect its day-to-day use. Over the last two centuries, different variants have been considered the metric system. Metric units are universally used in scientific work, and widely used around the world for personal and commercial purposes. A standard set of prefixes in powers of ten may be used to derive larger and smaller units from the base units.3.SISI system (for Système International) was adopted by the International Bureau of Weights and Measures in 1960, it is a revision and extension of the metric system. Scientists and engineers throughout the world in all disciplines are now being urged to use only the SI system of units.1.5.2 SI base unitsThe SI is founded on seven SI base units for seven base quantities assumed to be mutually independent, as given in Table 1.1.Table 1.1 SI Base Physical Quantities and UnitsU n i tN a m e UnitSymbolBaseQuantityQuantitySymbolDimensionSymbolm m l l Le t e r e n g t hk i lo g r a m kgmassm Ms ec o nd stimet Ta mp e r e AelectriccurrentI Ik el v i n KthermodynTΘm i ct e m p e r a t u r em o l e molamountofsubstancen Nc an d e l a cdluminousIvJntensity1.5.3 SI derived unitsOther quantities, called derived quantities, aredefined in terms of the seven base quantities via asystem of quantity equations. The SI derived unitsfor these derived quantities are obtained from theseequations and the seven SI base units. Examples ofsuch SI derived units are given in Table 1.2, where itshould be noted that the symbol 1 for quantities ofdimension 1 such as mass fraction is generallyomitted.Table 1.2 SI Derived Physical Quantities and(symbol) Unit(symbol)UArea (A) squaremeterm V olume (V) cubicmeterm Density (ρ) kilogramper cubicmeterkVelocity (u) meterpersecondmPressure (p) pascal(Pa)kEnergy (E) joule (J) (k Frequency (ν) hertz(Hz)1Quantity of electricity (Q) coulomb(C)AElectromotive force (E) volt (V) (kmsForce (F) newton(N)kFor ease of understanding and convenience, 22SI derived units have been given special names andsymbols, as shown in Table 1.3.Table 1.3 SI Derived Units with special names andsymbolsD e r i v e dq u a n t i t y SpecialnameSpecialSymbolExpressionintermsofotherSIunitsSIbaseunitsp r r ml a n ea n g l e adianad·m-1=1s o l i da n g l e steradiansrm2·m-2=1f r e q u e n c y hertzHzs-1f o r c e newtonN m·kg·s-2p p P N mr e s s u r e ,s t r e s s ascala/m21·kg·s-2e n e r g y ,w o r k ,q u a n t i t yo fh e a jouleJ N·mm2·kg·s-2p o w e r ,r a d i a n tf l u x wattW J/sm2·kg·s-3e l e c t r i cc h a r g e q u a n t i t y coulombC s·Afe l e c t r i c i t ye l e c t r i cp o t e n t i a l ,p o t e n t i a l voltV W/Am2·kg·s-3·A-1i f f e r e n c e ,e l e c t r o m o t i v ef o r c ec a p a c i t a n c e faradF C/Vm-2·kg-1·s 4·A 2e l e c t r i cr e s i s t a n c e ohmΩV/Am2·kg·s-3·A-2e l e c t r i cc o nd u c t a n c siemensS A/Vm-2·kg-1·s2·Aem a g n e t i cf l u x weberWbV·sm2·kg·s-2·A-1m a g n e t i cf l u xd e n s i t y teslaT Wb/m2kg·s-2·A-1i n d henH Wb/m2u c t a n c e ryA ·kg·s-2·A-2C e l s i u st e m p e r a t u r e degreeCelsius°CKl u m i n o u s lumenlmcd·srcd·srl u xi l l u m i n a n c e luxlxlm/m2m-2·cd·sra c t i v i t y( o far a d i o n u c l i d e becquerelBqs-1a b s o r b e dd o se ,s p e c i f i ce n e r g y( i m p a r t e d ) ,grayGyJ/kgm2·s-2e r m ad o s ee q u i v a l e n t ,e ta l .sievertSvJ/kgm2·s-2c a t a l y t i ca c t i v i katalkats-1·molyCertain units that are not part of the SI are essential and used so widely that they are accepted by the CIPM (Commission Internationale des Poids Et Mesures) for use with the SI. Some commonly used units are given in Table 1.4.Table 1.4 Non-SI units accepted for use with theSIN a m e SymbolQuantityEquivalentSIunitmi n u t e mintime1min=6sho u r htime1h6min=36s da y dtime1d=24h=144min=864sdegreeo fa r c °planeangle1°=(π/18)radm i n u t eo fa r c ′planeangle1′=(1/6)°=(π/18radsecondo fa r c ″planeangle1″=(1/6)′=(1/36)°=(π/648)rdhect a r e haarea1ha=1a=1m²l i t r e lorLvolume1l=1dm3=.1m3ton n e tmass1t=13kg=1MgThe 20 SI prefixes used to form decimal multiples and submultiples of SI units are given in Table 1.5.Table 1.5 SI PrefixesF a c t o r NameSymbolFactorNameSymbol1 0 24yottaY 1-1decid1 0 21zettZ 1-2centc。

化学专业英语Chemistry is a scientific field that involves the studyof the composition, structure and properties of matter. It deals with the study of substances such as atoms and molecules, their structure and reactivity. Various branchesof chemistry such as organic chemistry, biochemistry,physical chemistry, analytical chemistry and inorganic chemistry, form the basis of modern chemistry.Organic chemistry is the study of carbon-containing compounds. It deals with the synthesis and study of structure, reactivity, and use of such compounds and their derivatives. Biochemistry involves the study of chemical processes inliving things. Physical chemistry is a branch of chemistrythat deals with the study of physical properties of matter. Analytical chemistry deals with the identification andisolation of compounds and the determination of theirstructure and properties. Inorganic chemistry deals with the study of inorganic compounds, which are those not containing carbon.Other aspects of chemistry include nuclear chemistrywhich deals with the structure and reactivity of atomicnuclei. Environmental chemistry studies the reaction of chemicals and their effects on the environment. Forensic chemistry is the application of analytical chemistry in the investigation of criminal cases. Photochemistry is a branchof chemistry which studies the interaction between radiant energy and matter. Molecular biology combines the principlesof biochemistry and genetics to study the structure andfunction of living organisms at a molecular level. Theinterface between biology and chemistry is studied in the field of bioinformatics.Chemistry is an important field as it provides us with the knowledge to develop new materials, medicines and technologies. The knowledge gained from its study helps us understand the world around us. A degree in chemistry is essential for students who are interested in pursuing a career in this field.。