Name: recording a reproducible lab experiment
Uploaded: 2020-03-26T07:22:27.000Z
Duration: 3 min 6 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Specialised Topic in Science

112.51.c.1.

112.51.c.1.D.

Proper Lab Notebook Keeping

يتمثل أحد الجوانب الأساسية للعمل في المختبر في الاحتفاظ بسجل دقيق ومحدث للتجربة باستخدام دفتر ملاحظات المختبر. يعد دفتر المختبر ضروريا في كل من الأوساط الأكاديمية والصناعة ، لأنه لا يوفر لك فقط سجلا لما تم إجراؤه بالضبط ، ولكنه يعمل أيضا كمستند قانوني يثبت ملكية وأصالة البحث. 
من الضروري أن تستخدم دفتر ملاحظات بدون كربون مجلدا بحيث يمكن إزالة النسخة وإرسالها إلى المدرس. يجب أن تكتب دائما بالقلم ، وليس بالقلم الرصاص. قبل بدء التجربة، يجب عليك إنشاء تقرير تمهيدي للمختبر في دفتر ملاحظات المختبر. 
للقيام بذلك ، يجب عليك أولا قراءة الإجراء بدقة وتحديد الهدف من التجربة. بعد ذلك ، ستكتب جميع المعلومات الأساسية اللازمة لفهم التجربة والبروتوكول. 
بعد ذلك ، يجب عليك كتابة خطوات الإجراء مع تضمين توضيح الخطوات المعقدة وحسابات القيم التي قد تحتاجها. مجرد نسخ البروتوكول لن يكفي. قد يكون إنشاء مخطط انسيابي ضروريا لمساعدتك. 
ستقوم أيضا بكتابة جميع التفاعلات الكيميائية المتوازنة وتحديد العوائد النظرية مسبقا وتحديد الخصائص الفيزيائية لجميع المواد التي ستستخدمها. ربما تكون الخطوة الأكثر أهمية هي تحديد مخاطر السلامة لجميع المواد المتفاعلة والمنتجات والمذيبات المستخدمة. يجب الحصول على هذه المخاطر من ورقة بيانات سلامة المواد ، أو MSDS ، لكل مادة. 
عندما تكون مستعدا لإجراء التجربة ، ستقوم أولا بتدوين التاريخ والتجربة المعملية التي يتم إجراؤها. بعد ذلك ، قم بتسجيل جميع الخطوات أثناء تنفيذها وقم بتضمين القياسات الدقيقة ، مثل الحجم ودرجة الحرارة والوزن. احتفظ دائما بدفتر ملاحظاتك بالقرب منك وسجل المعلومات على الفور. لا تخدش الملاحظات على المناشف الورقية أو الورق الخردة. 
إذا تم ارتكاب خطأ ، فيجب شطبه باستخدام سطر واحد وكتابة المعلومات الصحيحة على الفور. تأكد دائما من تضمين أي ملاحظات ذات صلة ، مثل تغيير درجة الحرارة أو تغيير اللون أو تغيير الأس الهيدروجيني. قم دائما بتضمين جميع الملاحظات ونقاط البيانات ، حتى القيم المتطرفة والتجارب الفاشلة. لا تقم أبدا بإزالة الصفحات أو نقاط البيانات في محاولة لإخفاء الأخطاء. 
عند الانتهاء من التجربة والانتهاء من حفظ السجلات، قم بشطب الجزء غير المستخدم من الصفحة الأخيرة ثم قم بتوقيع جميع الصفحات وتأريخها. في هذا المختبر ، ستمارس مهارات حفظ الكمبيوتر المحمول عن طريق إجراء نترات بنزوات الميثيل. من الضروري أن تحتفظ بسجل دقيق وشامل لتجربتك من أجل تحليل نتائجك بشكل صحيح عند الانتهاء.

حفظ دفتر المختبر المناسب

<h4>حفظ دفتر المختبر العضوي</h4>
يعد حفظ السجلات مهارة حيوية في مختبرات العلوم والكيمياء العضوية. بدون الملاحظات أو الأوصاف أو الكميات أو الملاحظات المناسبة ، لا يمكن تكرار أو إعادة إنتاج تجربة أجريت في المختبر. لذلك ، فإن الاحتفاظ بدفتر ملاحظات دقيق ومحدث أمر ضروري لتحقيق قابلية التكرار في العلوم. يعد دفتر المختبر أداة قوية في كل من البيئات الأكاديمية والصناعية. يصبح من المهم بشكل خاص عندما يتم تسجيل براءة اختراع الاكتشاف وتسويقه. في هذه الحالة ، يعد دفتر المختبر مستندا قانونيا يثبت ملكية فكرة أو عملية أو مادة أو تقنية. 
تتضمن المعلومات الهامة في دفتر ملاحظات المختبر الخطوات التي تم إجراؤها وجميع الملاحظات. يجب أن يكون الهدف التجريبي واضحا ومكتوبا جيدا بحيث يسهل فهمه. لكل تجربة ، يتم تسجيل العديد من الأقسام الأساسية في دفتر المختبر. يتكون تقرير المختبر من بروتوكول ما قبل المختبر ، وبروتوكول المختبر ، والملاحظات والنتائج ، وما بعد المختبر. 
يفضل استخدام دفتر ملاحظات مختبر بدون صفحات فضفاضة. يجب ألا يكون من الممكن تمزيق الصفحات بسهولة، لأن هذا يضر بصلاحية السجلات الموجودة في دفتر الملاحظات. بالنسبة لفصول المختبر التي سيتم تصنيفك فيها ، يجب استخدام دفتر ملاحظات يحتوي على أوراق ذاتية التكرار. يتيح لك ولمعلمك الحصول على نسخة من صفحات دفتر ملاحظات المختبر الخاص بك. 
أكمل كل حفظ السجلات بالقلم. أي أداة كتابة يمكن مسحها بسهولة غير مقبولة. يجب أن تكون جميع الملاحظات دائمة لأن هذا يضمن صحة السجلات الموجودة في دفتر الملاحظات. يجب كتابة جميع الملاحظات والملاحظات والتغييرات التي تطرأ على الإجراء والبيانات التي تم جمعها مباشرة في دفتر المختبر. لا تكتب أبدا ملاحظات على ورق سائب أو خربشة السجلات في دفتر ملاحظات المختبر الخاص بك. إذا كان هناك خطأ أو تم إجراء تغيير على سجل في دفتر الملاحظات ، فقم بشطب الخطأ بدقة بسطر واحد واكتب التصحيح بجانبه. تؤدي الملاحظات المكتوبة أو الصفحات الممزقة إلى إبطال حفظ السجلات الخاص بك وتتصدى للغرض الأساسي من حفظ السجلات بدقة. عند اكتمال جميع عمليات حفظ السجلات، يجب شطب الجزء الفارغ من الصفحة المتبقية. يجب أن تكون جميع الصفحات المستخدمة موقعة ومؤرخة. 
<h4>ما قبل المختبر</h4>
يجب إكمال ما قبل المختبر قبل التجربة. لكتابة ما قبل المختبر ، اقرأ الإجراء جيدا ، وابحث في خلفية التجربة ، وقم بتسمية التجربة بعبارة وصفية. على سبيل المثال ، "توليف 1،3-بنتانيديول" هو عنوان أفضل من "التجربة 1". قم بتضمين تاريخ إجراء الإجراء التجريبي واسمك واسم شريكك في المختبر إذا لزم الأمر. يجب أن تتضمن أيضا هدف التجربة ، الذي يسرد الأهداف. بعد ذلك ، اكتب جميع التفاعلات الكيميائية المتوازنة التي ستحدث في التجربة. ضع قائمة بأي خصائص ذات صلة بالمواد الكيميائية المستخدمة أو المنتجة أثناء التجربة في شكل جدولي ، مثل نقاط الانصهار والأوزان الجزيئية والكثافة. قم بإجراء أي حسابات ضرورية قبل التجربة الفعلية. 
بالإضافة إلى ذلك ، حدد مخاطر سلامة جميع الكواشف. يتم تضمينها في أوراق بيانات سلامة المواد (MSDS) ، والتي توفرها الشركة المصنعة. من المهم أيضا حساب العائد النظري للمنتج. سيساعدك هذا على فهم ما إذا كانت تجربتك تسير بشكل صحيح. أخيرا ، اكتب الإجراء خطوة بخطوة في دفتر ملاحظاتك. يجب كتابة هذا بمعلومات وصفية كافية حتى يتمكن شخص آخر من إعادة إنتاج تجربتك. على هذا النحو ، لا ينبغي أن تكون هذه نسخة كلمة بكلمة من إجراء من مصدر مختلف. يجب أن تكون مكتوبة بكلماتك الخاصة. 
<h4>ملاحظات المختبر</h4>
يحتوي هذا القسم على جميع الملاحظات والنتائج من الإجراء التجريبي ، لذلك يجب تعبئتها بالتزامن مع التجربة. هنا ، ستسجل أي ملاحظات ذات صلة ، مثل درجة حرارة التفاعل وأي تغييرات في اللون أو الأس الهيدروجيني مع استمرار التجربة. هذا هو المكان الذي يتم فيه تسجيل الكتلة الدقيقة للمواد المتفاعلة والمنتجات. تأكد أيضا من تدوين أسماء أي ملفات كمبيوتر تم إنشاؤها أثناء التجربة. 
<h4>ما بعد المختبر</h4>
يقدم تقرير ما بعد المختبر البيانات والتحليل النهائي. يتضمن ما بعد المختبر فرضيتك أو توقعاتك مقارنة بالنتائج التجريبية. إذا اختلفت التوقعات عن الملاحظات ، فيجب مناقشة ذلك ، بما في ذلك التفسيرات المحتملة لسبب الاختلافات. يجب مناقشة قيود هذه التقنية ، وكذلك أي تحسينات يمكن إجراؤها للحصول على نتائج أفضل. أخيرا ، يجب أن يلخص تقرير ما بعد المختبر البيانات التجريبية ويقدم استنتاجا واضحا مع شرح لأي أخطاء. 
<h4>المراجع</h4>
<ol>
	<li style="font-size:17px">هاريس ، العاصمة (2015). التحليل الكيميائي الكمي. نيويورك ، نيويورك: دبليو إتش فريمان وشركاه . </li>
</ol>

حفظ دفتر المختبر العضوي
يعد حفظ السجلات مهارة حيوية في مختبرات العلوم والكيمياء العضوية. بدون ملاحظات أو أوصاف أو كميات أو ...

Education

JoVE Lab Manual

Chemistry

الكيمياء

recording a reproducible lab experiment

Accurate lab notebook records are essential in science and organic chemistry labs. Without clear notes, descriptions, quantities, and observations, an experiment cannot be repeated or checked. Good record keeping supports reproducibility, which means other people can follow the same work and get similar results.

A laboratory notebook is useful in school labs, research settings, and industry. It can also become a legal record when an idea, process, substance, or technique is patented and commercialized. For that reason, the notebook must clearly show what was done and what was observed during the experiment.

A strong lab notebook entry includes several parts. The full lab report usually contains a pre-lab, lab protocol, observations and results, and a post-lab. A bound notebook with no loose pages is preferred, and pages should not tear out easily. In graded lab classes, self-duplicating sheets are useful because both the student and the instructor can keep a copy.

All records should be written in pen. Erasable writing tools are not acceptable because the notes must stay permanent. Notes, observations, procedure changes, and data should go directly into the notebook. Do not use loose paper, and do not scribble out or remove records. If a mistake happens, cross it out neatly with one line and write the correction beside it. When the page is finished, cross out any blank space. Every used page should also be signed and dated.

The pre-lab is completed before the experiment begins. It starts with careful reading of the procedure and research on the experiment background. The title should be descriptive, such as a specific synthesis name instead of a label like Experiment 1. The pre-lab should also include the date, the student name, and the lab partner name if needed, along with the objective of the experiment.

The pre-lab also includes the balanced chemical reactions that will occur. Relevant properties of the chemicals, such as melting point, molecular weight, and density, are listed in a table. Any needed calculations should be done before the lab starts. Safety risks for each reagent must also be identified using the material safety data sheets, or MSDS, provided by the manufacturer. It is also important to calculate the theoretical yield of the product so you can judge whether the experiment is progressing as expected. Finally, the procedure should be written in the notebook in clear, step-by-step form and in your own words so someone else could repeat the work.

The lab observations section is filled out during the experiment. This is where you record temperature changes, color changes, pH changes, and other relevant observations as they happen. You also record the exact mass of reactants and products. If the experiment creates computer files, write down the file names as part of the record.

The post-lab report comes after the experiment and presents the data and final analysis. It compares the hypothesis or expectations with the actual results. If the results were different, the reasons should be discussed. The post-lab should also cover limits of the technique and possible improvements for better results. It ends with a clear summary of the data, a conclusion, and an explanation of any errors.

Recording a Reproducible Lab Experiment

lab techniques

Measuring with Accuracy in the Lab

Measuring with accuracy in the lab starts with careful records, the right tools, and correct reading of data. Scientists use lab notebooks to record how an experiment was done. These notes include the amounts of materials used and each step of the procedure. Without that record, an experiment cannot be repeated in the same way. Balances and glassware are used to measure solids and liquids for experiments. The precision of a measurement depends on the equipment used. Digital balances show the...

scientific measurement and lab skills

Graphs, Curve Fit, and Standard Deviation

Two-dimensional graphs help students compare an independent variable with a dependent variable in science data. In a chemistry example, temperature is the independent variable and volume is the dependent variable. After data are collected, the relationship between the two measurements must be quantified so it can be evaluated and compared with other relationships. A graph can also show when no relationship exists between the two variables. To make a two-dimensional graph, each data point needs...

stoichiometry, product yield, and limiting reactants

stoichiometry-product-yield-and-limiting-reactants

Balancing Equations and Reactant Limits

Chemical equations show how reactants change into products during a reaction. Stoichiometry is the study of the relative amounts of reactants and products. It is based on the Law of Conservation of Mass, which says matter is neither created nor destroyed. Because atoms are only rearranged, the number and identity of atoms must match on both sides of a reaction. That is why a chemical equation must be balanced. A balanced equation has the same number of atoms for each element in the reactants...

redox reactions

Oxidation States in Redox Reactions

Oxidation states help identify redox reactions. In a redox reaction, oxidation is the loss of one or more electrons, and reduction is the gain of one or more electrons. These reactions are often tracked by changes in oxidation state, also called oxidation number. Each atom in a molecule has an oxidation state. This number shows how oxidized an atom is compared with its free elemental form. It is written as the charge an atom would have if every bond were purely ionic. In that model, bonding...

ideal gas law

Gas Laws Behind the Ideal Gas Equation

The ideal gas equation brings together the main gas laws used in chemistry. Gases have molecules that are far apart, so their behavior is described with four measurable variables: pressure, volume, number of moles, and temperature. The ideal gas law links these variables with the gas constant, R, which equals 8.314 J·K−1 mol−1. Boyle’s law describes the link between pressure and volume. When temperature and the number of moles stay constant, pressure and volume change in opposite directions.

acid and base concentrations

Acids, Bases, and pH in Titration

Acids, bases, and pH explain how acidic or basic a solution is. An Arrhenius acid releases hydrogen ions when it dissolves in water, while an Arrhenius base releases hydroxide ions. These reactions also create conjugate partners: an acid forms a conjugate base after losing hydrogen, and a base forms a conjugate acid after losing hydroxyl. Every acid has a conjugate base, and every base has a conjugate acid. pH measures the amount of hydrogen ions in a solution. The pH scale runs from 0 to 14...

buffers

Buffer pH and the Common Ion Effect

Buffer solutions help keep pH steady when acids or bases are added. In water, an Arrhenius acid (HA) dissociates into hydrogen ions, H+, and a conjugate base, A-. More hydrogen ions make a solution more acidic and lower its pH. An Arrhenius base (BOH) dissociates into a conjugate acid, B+, and hydroxide ions, OH-. Strong acids and strong bases usually change pH a lot because they react completely in water and raise the amount of H+ or OH-. Buffers reduce those pH changes. A buffer usually...

enthalpy of reaction

Reaction Heat, Hess’s Law, and Calorimetry

Reaction heat is explained through enthalpy, Hess’s law, and calorimetry. These ideas show how heat moves during chemical reactions and how scientists measure it. Thermodynamics is the study of heat energy and other forms of energy, such as work. Its laws are used across science, from biology to physics. The first law says energy is conserved in an isolated system. Energy can change form, such as thermal energy becoming work, but it cannot be created or destroyed. The second law of...

solubility

Solubility in Water and Other Solvents

Solubility describes how much of a solute can dissolve in a specific solvent. It is usually reported as solute mass per solvent volume or as solute mass per solvent mass. For example, sodium chloride has a solubility of 36 g per 100 mL of water at room temperature. If solubility is given by solvent mass, that mass must be converted to volume for later calculations. Temperature changes solubility. Sodium carbonate dissolves at about 7 g per 100 mL of water at 0 °C, 22 g per 100 mL at room...

metal flame emission

Flame Test Metal Color Clues

Flame testing uses a metal sample and a flame to identify a substance by its color. Each element gives off a characteristic light emission in the flame, so the color can help distinguish one element from another. This same idea appears in fireworks, where different metal components create different colors. The color comes from energy absorbed by the metallic component. When a species absorbs energy, that energy can go into translation, vibration, rotation, or electron excitement. Electron...

balmer series

Hydrogen Emission Lines

Hydrogen emission lines show how electrons move between fixed energy levels in the Bohr model. Niels Bohr proposed this model for the hydrogen atom in 1913. In this model, an electron can only occupy certain orbits, and it cannot exist between them. These energy states are labeled with the quantum number n. The ground state is n = 1. Higher values, such as n = 2, 3, 4, and so on, are excited states. An electron changes state only by absorbing or emitting energy equal to the difference between...

beer's law

Absorbance Spectra and Beer-Lambert Analysis

Absorbance spectra and the Beer-Lambert Law show how light can be used to study molecules in solution. When light hits a substance, it may be absorbed, transmitted, or reflected. A substance often interacts with a range of wavelengths, and each wavelength can affect the molecules or atoms in a different way. When a molecule absorbs light, that energy can be used for translation, vibration, rotation, or electron excitement. Electron excitement is especially important in spectroscopy because it...

concentration dependence

Reaction Order and Rate Constants

Chemical kinetics describes the speed of a chemical reaction. The rate depends on the reaction mechanism, the complexity of the reaction, and the number of reactants involved. Reactant concentration also affects how fast a reaction happens. The rate law is the experimental relationship that connects these factors to reaction rate. In the rate law, each reactant contributes through a reaction order. The general form is r = k[A]^m[B]^n for aA + bB + ... → cC. Here, r is the reaction rate, k is...

temperature dependence

Reaction Rate, Arrhenius, and Catalysts

Chemical kinetics explains how fast a reaction happens and why that speed changes. The reaction rate is the speed of a chemical reaction. It is defined as the change in concentration of a reactant or product over time. Reaction speed depends on several factors, including the concentration of the reactants and the temperature of the reaction. Each reactant affects the rate in a specific way. That relationship is described by the rate law. The rate law is an equation that connects the...

galvanic cells

Battery Power from Redox Reactions

Electrochemistry studies how chemical change and electrical energy are linked. In this branch of chemistry, electrons move from one species to another. That movement can either produce current or be driven by an applied current. The main reaction in electrochemistry is the oxidation-reduction, or redox, reaction. A redox reaction has two half-reactions. Oxidation is the loss of electrons, and reduction is the gain of electrons. These changes also shift the oxidation state of each substance. The...

electrolytic cells

Electroplating with Electrolytic Cells

Electrochemistry links electrical energy with chemical change, and electrolytic cells show how electricity can drive a nonspontaneous reaction. In these reactions, electrons move from one species to another. The key chemistry is a redox reaction, or oxidation-reduction reaction, which happens in two half-reactions. Oxidation is the loss of electrons, and reduction is the gain of electrons. The substance that loses electrons is the reducing agent, and the substance that gains electrons is the...

proper lab notebook keeping

Accurate lab notebook records are essential in science and organic chemistry labs. Without clear notes, descriptions, quantities, and observations, an experiment cannot be repeated or checked. Good record keeping supports reproducibility, which means other people can follow the same work and get similar results. A laboratory notebook is useful in school labs, research settings, and industry. It can also become a legal record when an idea, process, substance, or technique is patented and...

basic organic chemistry techniques

Organic Lab Glassware and Safe Handling

Organic chemistry labs use specific glassware, careful weighing steps, and controlled heating to keep reactions safe and accurate. Beakers and Erlenmeyer flasks are often used for mixing or holding solvents, but they are not meant for measuring volume unless only an approximate amount is needed. Volumetric glassware is used when a precise volume matters. This group includes graduated cylinders, volumetric pipettes, and volumetric flasks. A graduated cylinder is commonly used in the organic lab...

melting points

How Impurities Change Melting Points

Melting point helps identify an organic compound by showing the temperature where a solid turns into a liquid at 1 atmosphere of pressure. It is a physical property, like solubility, density, color, and electronegativity. Because the exact start of melting is hard to measure, the result is reported as a range. The lower end is when the first drops of liquid appear. The upper end is when the last solid has melted. Scientists compare this range with literature values to help identify a compound. <br...

boiling points

Boiling Point and Vapor Pressure

Boiling point and vapor pressure are key physical properties of a liquid. For a pure compound, the boiling point can help identify the substance. In experiments, the boiling point is usually recorded as a range because exact values are hard to measure and may differ by a few degrees from the literature value. Vapor pressure explains why a liquid boils. In a sealed container, some molecules at the liquid surface gain enough energy to escape into the gas phase. At the same time, some gas...

recrystallization

Purifying Crystals by Solubility

Purifying crystals by solubility is a key organic chemistry technique. Recrystallization uses differences in solubility to separate a desired solid product from starting materials, solvent, and impurities. It is one of the three standard purification methods, along with distillation and extraction. Solubility is the maximum amount of a substance that can dissolve in a fixed volume of solvent at a given temperature. Different solutes dissolve in different solvents, and their behavior can vary...

extraction

Separating Mixtures with Solvent Extraction

Solvent extraction is a common way to separate and isolate a target compound in organic chemistry. In this process, a solute moves from one phase to another so it can be separated from unreacted starting materials or impurities. Extraction is also useful when a product is dissolved in a reaction solvent that is hard to remove by evaporation, such as a solvent with a high boiling point. There are three main types of extraction. In solid-liquid extraction, the solute moves from a solid phase...

simple distillation

Separating Liquids by Boiling Point

Separating liquids by boiling point is the goal of distillation. A miscible mixture contains liquids that mix evenly, and it can be heated so that the more volatile liquid evaporates first. Volatility is a liquid’s tendency to vaporize, and boiling begins when bubbles form in the liquid phase. In a closed container, liquid and vapor can reach equilibrium, which means the rate of vaporization equals the rate of condensation. The pressure from the vapor above the liquid is called vapor pressure.

steam distillation

Steam Distillation and Low-Boiling Separation

Steam distillation is a separation method for temperature-sensitive organic compounds. It works best when the organic compound is immiscible in water, meaning the two liquids do not mix. The method helps remove the organic molecule from a non-volatile contaminant without using the higher temperatures needed for many other separations. In steam distillation, the immiscible mixture is heated until both water and the volatile organic compound distill together. The vapor rises to a condenser,...

thin-layer chromatography

TLC Separation by Polarity

Thin-layer chromatography (TLC) separates compounds in a mixture by polarity. It uses the same basic parts as other chromatography methods: a stationary phase, a mobile phase, and the solute. In TLC, the stationary phase is a thin coating on a plate instead of material packed into a column. The stationary phase in most TLC systems is polar silica gel, a form of silicon dioxide. Its surface has OH groups that can form hydrogen bonds. The sample is first spotted on a pencil start line with a...

column chromatography

Separating Mixtures by Polarity

Column chromatography separates compounds in an organic chemistry lab by using differences in physical properties. It is especially useful for microscale separations when less than 10 grams of material is available for analysis. The method can separate a mixture based on solubility, polarity, hydrophobicity, size, and charge. Any chromatography system has three main parts: the stationary phase, the mobile phase, and the sample mixture. In column chromatography, the stationary phase is usually...

hydrolysis of an ester

Soap Formation from Triglycerides

Triglycerides are lipids made of a glycerol backbone linked to three fatty acids. They are common in vegetable oils and animal fats. Plant lipids are the basis of vegetable oils, while animal lipids are used as lard or general sources of fats. A fatty acid has a long carbon chain, usually between 12 and 20 carbons, with a weak organic acid at one end. Some fatty acids contain double bonds. These are unsaturated fats. The double bond usually gives the chain a bent, cis shape. As a result,...

synthesis of luminol

Luminol Chemiluminescence in Forensics

Luminol chemiluminescence shows how a chemical reaction can produce light and help with blood detection. Chemical reactions may be endothermic or exothermic, depending on whether they absorb or release heat as reactants become products. The enthalpy of a reaction is the energy difference between reactants and products, or ΔH. A positive ΔH means the reaction is endothermic. A negative ΔH means it is exothermic. Many reactions do not happen in a single step. They can pass through intermediates...

esterification

Ester Formation and Everyday Fragrances

Esters are organic compounds with a carbonyl group attached to an oxygen that connects to another alkyl or aryl group. Their general formula is RCOOR'. They are often made by reacting a carboxylic acid with an alcohol in an esterification reaction. In this process, the hydroxyl group of the acid is replaced by an alkyl or aryl group. Many simple esters have familiar fruit and flower smells because their structures are small and less complex. Formic acid and methanol can combine to form methyl...

identification of unknown aldehydes and ketones

identification-of-unknown-aldehydes-and-ketones

Carbonyl Tests for Aldehydes and Ketones

Aldehydes and ketones are carbonyl compounds, which means they contain a C=O functional group. A ketone has two alkyl or aryl groups attached to the carbonyl carbon. Acetone is the simplest ketone, with two methyl groups. An aldehyde is similar, but it has at least one hydrogen attached to the carbonyl carbon. Formaldehyde is the simplest aldehyde, and acetaldehyde has one hydrogen and one methyl group. The carbonyl carbon in both aldehydes and ketones is electrophilic because the oxygen atom...

uv-vis spectroscopy of dyes

How Dyes Absorb Visible Light

Dyes absorb visible light because their molecular structure lets them interact with specific wavelengths. When light hits a substance, some light is absorbed and the rest is reflected or transmitted. The color we see depends on the wavelength that is reflected. A blue substance reflects blue light, around 430 to 480 nm, and absorbs the complementary orange region, around 590 to 630 nm. Compounds that do not absorb in the visible range appear colorless to the human eye. Light also has energy and...

identifying alcohols

Alcohol Tests for Primary, Secondary, and Tertiary

Alcohol tests can help sort alcohols by structure and reactivity. Alcohols are organic molecules with a hydroxyl group attached to an alkyl or aryl group, written as ROH. If the carbon with the hydroxyl group has one R group, the alcohol is primary. If it has two R groups, it is secondary. If it has three R groups, it is tertiary. Alcohols can also be aromatic when they contain a benzene ring. Phenol is the simplest aromatic alcohol. To identify an alcohol, chemists can use its chemical...

chemistry

Comprehensive, curriculum-focused videos for both instructors and students in introductory chemistry lab courses.

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Learn how to keep a clear lab notebook with pre-lab, observations, and post-lab sections, plus proper recording, corrections, and results.

Recording a Reproducible Lab Experiment | JoVE K12

CHEM.1

CHEM.1.D

استعد لتدريس حفظ دفتر المختبر المناسب من خلال هذا الدليل الإرشادي للمدرسين لمدة 3 دقيقة. يغطي خطوات التحضير الأساسية لمختبر Chemistry على JoVE Lab Manual.

تحضير المدرّس لـ حفظ دفتر المختبر المناسب في Chemistry - أكثر من 3.8K مشاهدة | JoVE Lab Manual

اتبع إجراءات حفظ دفتر المختبر المناسب خطوة بخطوة في فيديو بروتوكول الطالب هذا لمدة 10 دقيقة. جزء من مجموعة Chemistry على JoVE Lab Manual.

بروتوكول الطالب لـ حفظ دفتر المختبر المناسب في Chemistry - أكثر من 28K مشاهدة | JoVE Lab Manual

The Scientific Method

The scientific method is a detailed, empirical problem-solving process used by biologists and other scientists. This iterative approach involves ...

Inductive Reasoning

Inductive reasoning is a form of logical thinking that uses related observations to arrive at a general conclusion. It is uncertain and operates in ...

Deductive Reasoning

Deductive reasoning, or deduction, is the type of logic used in hypothesis-based science. In deductive reasoning, the pattern of thinking moves in the ...

Correlation and Causation

Correlation and CausationStatistical tests can calculate whether there is a relationship, or correlation, between independent and dependent variables. A ...

Ask questions and define problems related to specialized topics of study based on observations or information from text, phenomena, models, or investigations;

112.51.c.1.A.

Scientific Method

The scientific method is used to solve problems and explain phenomena. The development of the scientific method coincided with changes in philosophy ...

Demonstrating the Scientific Method with Tree Branches
ExpandObtain branches containing a few dozen typical leaves from five different local tree species. ...

Observation and Background Research
ExpandNOTE: The first two steps in the scientific process involve studying and observing natural phenomena of ...

Problem-Solving

A problem-solving strategy is a plan of action used to find a solution. It involves trial and error, algorithms, heuristics, and insights. Effective ...

Problem Definition

Problem definition is the initial and the most essential step in research.
The researcher identifies and explains the specific issue or gap to be ...

Apply science practices related to specialized topics of study to plan and conduct investigations or use engineering practices to design solutions to problems;

112.51.c.1.B.

Proper Personal Protective Equipment

Robert M. Rioux &#38; William A Elliott, Pennsylvania State University, University Park, PA
Hazards are many and varied in the laboratory, but the right ...

Emergency Eyewash and Shower Stations

Robert M. Rioux, Pennsylvania State University, University Park, PA
The Occupational Safety and Health Administration (OSHA) mandates that an emergency ...

Electrical Safety

Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Among the many hazards present in the laboratory, electrical ...

Working with Centrifuges

Source: Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Earth's gravitational force is capable of separating ...

Working with Hot and Cold Sources

Source: Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Working with extreme temperatures, both high and low, ...

guidelines-in-case-of-a-laboratory-emergency

Guidelines in Case of a Laboratory Emergency

Robert M. Rioux &amp; Zhifeng Chen, Pennsylvania State University, University Park, PA
The most common laboratory emergencies include chemical spills, ...

chemical-storage-categories-hazards-and-compatibilities

Chemical Storage: Categories, Hazards And Compatibilities

Source: Robert M. Rioux &amp; Taslima A. Zaman, Pennsylvania State University, University Park, PA
While the use of various chemicals in experimental ...

Safe Handling of Mineral Acids

Source: Robert M. Rioux &#38; Taslima A. Zaman, Pennsylvania State University, University Park, PA
A mineral acid (or inorganic acid) is defined as a ...

Handling Chemical Spills

Source: Robert M. Rioux &#38; Taslima Zaman, Pennsylvania State University, University Park, PA
Since chemicals are commonly used for laboratory research ...

Proper Use of Autoclaves

Robert M. Rioux &amp; Zhifeng Chen, Pennsylvania State University, University Park, PA
Autoclaving is one of the most commonly used methods in the ...

Fume Hoods and Laminar Flow Cabinets

Robert M. Rioux &amp; William A. Elliott, Pennsylvania State University, University Park, PA
Fume hoods and laminar flow cabinets are engineering controls ...

Decontamination for Laboratory Biosafety

Robert M. Rioux and Zhifeng Chen, Pennsylvania State University, University Park, PA
Decontamination is essential for laboratory biosafety, as the ...

Proper Waste Disposal

Robert M. Rioux and Taslima A. Zaman, Pennsylvania State University, Pennsylvania, PA

Users are responsible for the proper disposal of the waste ...

Use appropriate safety equipment and practices during laboratory, classroom, and field investigations as outlined in Texas Education Agency-approved safety standards;

112.51.c.1.C.

Common Lab Glassware and Uses

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
Glassware is a regular appearance in the professional ...

Lab Techniques

Measurement Accuracy
The ability to repeat an experiment and get the same results, or reproducibility, is essential in scientific research. However, ...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Preparation of LaboratoryExpand
	Here we show the laboratory preparation for 10 students ...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Determining the Density of an EggExpand
	Density is a measure of how compact a substance or ...

Organic Lab Notebook Keeping
Record keeping is a vital skill in science and organic chemistry labs. Without proper notes, descriptions, quantities, or ...

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

	Preparation of the LaboratoryExpand
	Here, we show the laboratory preparation ...

Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	Nitration of Methyl BenzoateExpand
	From this lab onward, ...

Use tools appropriate to the specialized topic of study;

SI Units: 2019 Redefinition

Measurement is integral to analytical chemistry. Each record comprises a number &#8211; denoting the magnitude&#160; &#8211; and the unit &#8211; a ...

International System of Units

The International System of Units, known as the SI system, is a universally accepted measurement system recognized and used worldwide. The SI system is ...

Measurement: Standard Units

Every measurement provides three kinds of information: the size or magnitude of the measurement (a number), a standard of comparison for the measurement ...

Measurement: Derived Units

The International System of Units or SI system, by international agreement, has fixed measurement units for seven fundamental properties: length, mass, ...

Collect quantitative data using the International System of Units (SI) or qualitative data as evidence as appropriate to the specialized topic of study;

112.51.c.1.E.

Review and Preview

Data are individual items of information obtained from a population or sample. Data may be classified as qualitative (categorical), quantitative ...

What is a Frequency Distribution

A frequency is the number of times a value of the data occurs. The sum of all the frequency values represents the total number of students included in the ...

Cumulative Frequency Distribution

A cumulative frequency distribution is another type of frequency distribution. Instead of reporting how many data values fall in some classes, it reports ...

Organize quantitative or qualitative data using representations appropriate to the specialized topic of study such as scatter plots, line graphs, bar graphs, charts, data tables, diagrams, scientific drawings, and student-prepared models;

112.51.c.1.F.

Scientific and engineering practices. The student, for at least 40% of instructional time, asks questions, identifies problems, and plans and safely conducts classroom, laboratory, and field investigations to explain phenomena or design solutions using appropriate tools and models. The student is expected to:

Recording a Reproducible Lab Experiment

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