Name: finding rate law from initial rates
Uploaded: 2020-09-24T15:06:50.000Z
Duration: 2 min 53 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry and Physics

IPC.7

IPC.7.F

Determining Order of Reaction

في التفاعل الكيميائي،يعبر قانون معدل السرعة عن العلاقة بين درجة التفاعل وتركيز المادة المتفاعلة. القوى الأسية لتركيز المادة المتفاعلة،تؤثر في درجة التفاعل فرديًا،وتسمى درجات التفاعل. تُحدد درجة التفاعل تجريبيًا بتطبيق طريقة المعدلات الأولية،حيث يُكرر التفاعل الكيميائي عدة مرات مع القيم المختلفة لتركيز المادة المتفاعلة،وذلك لقياس معدلات سرعة التفاعل الأولية.ارتفاع تركيز المادة المتفاعلة،الذي يؤدي إلى ارتفاع خطي بنفس المعدل في معدل سرعة التفاعل،من مميزات التفاعل من الدرجة الأولى. إذا كانت مضاعفة تركيز المادة المتفاعلة،تزيد معدل السرعة الأولي بأربعة أضعاف،يكون التفاعل عندئذ من الدرجة الثانية هو الملاحظ. و مع ذلك،اذا كان التغيير في تركيز المادة المتفاعلة لم يؤثر في قيم المعدلات الأولية،يكون التفاعل من الدرجة الصفرية.عندما تعطي بيانات معدلات السرعة الأولية علاقة لا يمكن ملاحظتها،بين التغير في تركيز المادة المتفاعلة،وما يوافقه من تغير في المعدل،تُحسب النسبة حسب قانون المعدلات. في هذه الحالة،تُستخدم أي قيمتين لتركيز المادة المتفاعلة،ومعدل سرعات التفاعل المقابلة لهما،لتحديد درجة التفاعل. لكن ماذا عن التفاعلات ذات المكونات المتعددة؟أولًا،باستخدام طريقة المعدلات الأولية،تُحدد درجة تفاعل كل مادة متفاعلة على حدة.بعد ذلك،يُعبّر عن درجات التفاعل الفردية،كقوى أسية لتركيز المواد المتفاعلة،على التوالي،لصياغة قانون معدل السرعة. أخيرًا،جمع القوى الأسية الفردية من قانون المعدل،يعطي الدرجة الإجمالية للتفاعل. في حين تصف درجة التفاعل،مدى اعتماد معدل سرعة التفاعل على تركيز المادة المتفاعلة،فإن القياس المباشر لسرعة التفاعل ذات الصلة يُعبر عنه بثابت معدل السرعة.ثابت معدل السرعة هو مُعامل النسبية بين معدل سرعة التفاعل،وبين ناتج تركيز المادة المتفاعلة. تعتمد وحدة ثابت معدل السرعة على درجة التفاعل الإجمالية،ويمكن تحديدها بإعادة ترتيب قانون معدل السرعة،لإيجاد قيمة ثابت معدل السرعة. في تفاعل الدرجة الصفرية،تكون وحدة تركيب جزيئي لكل ثانية.الوحدة في تفاعل الدرجة الأولى،هي عدد واحد على الثواني،وفي تفاعل من الدرجة الثانية هي واحد على ثواني-التركيب الجزيئي ارتفاع قيمة ثابت معدل السرعة يشير إلى أن التفاعل سريع. وبالعكس،انخفاض قيمة ثابت معدل السرعة يشير إلى أن التفاعل بطيء. القيمة صفر تؤكد على غياب أي تفاعل كيميائي.

تحديد ترتيب التفاعل

تصف قوانين المعدل العلاقة بين معدل التفاعل الكيميائي وتركيز المواد المتفاعلة فيه. في قانون المعدل ، يتم تحديد ثابت المعدل k وأوامر التفاعل بشكل تجريبي من خلال ملاحظة كيفية تغير معدل التفاعل مع تغير تركيزات المواد المتفاعلة. نهج تجريبي شائع لتحديد قوانين المعدل هو طريقة المعدلات الأولية. تتضمن هذه الطريقة قياس معدلات التفاعل لتجارب تجريبية متعددة أجريت باستخدام تركيزات مختلفة من المتفاعلات الأولية. تسمح مقارنة المعدلات المقاسة لهذه التجارب بتحديد أوامر التفاعل ، وبالتالي ، ثابت المعدل ، اللذين يتم استخدامهما معًا لصياغة قانون معدل. معدل تفاعل ما، على سبيل المثال، يتضمن أكسيد النيتريك مع الأوزون [NO (g) + O3 (g) ⟶ NO2 (g) + O2 (g)] يمكن تحديده من البيانات التجريبية لطريقة المعدلات,  الأولية في المختبر. <table style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="color: black; border: 1px solid black; text-align: center;">  Trial     </td><td style="color: black; border: 1px solid black; text-align: center;"> [NO] (mol/L)</td><td style="color: black; border: 1px solid black; text-align: center;">[O3] (mol/L)</td><td style="color: black; border: 1px solid black; text-align: center;">  Δ[NO2]/Δt (mol/L·s)  </td></tr><tr><td style="color: black; border: 1px solid black; text-align: center;">1</td><td style="color: black; border: 1px solid black; text-align: center;">     1.00 × 10−6      </td><td style="color: black; border: 1px solid black; text-align: center;">   3.00 × 10−6    </td><td style="color: black; border: 1px solid black; text-align: center;">    6.60 × 10−5     </td></tr><tr><td style="color: black; border: 1px solid black; text-align: center;">2</td><td style="color: black; border: 1px solid black; text-align: center;">1.00 × 10−6</td><td style="color: black; border: 1px solid black; text-align: center;">6.00 × 10−6</td><td style="color: black; border: 1px solid black; text-align: center;">1.32 × 10−4</td></tr><tr><td style="color: black; border: 1px solid black; text-align: center;">3</td><td style="color: black; border: 1px solid black; text-align: center;">1.00 × 10−6</td><td style="color: black; border: 1px solid black; text-align: center;">9.00 × 10−6</td><td style="color: black; border: 1px solid black; text-align: center;">1.98 × 10−4</td></tr><tr><td style="color: black; border: 1px solid black; text-align: center;">4</td><td style="color: black; border: 1px solid black; text-align: center;">2.00 × 10−6</td><td style="color: black; border: 1px solid black; text-align: center;">9.00 × 10−6</td><td style="color: black; border: 1px solid black; text-align: center;">3.96 × 10−4</td></tr><tr><td style="color: black; border: 1px solid black; text-align: center;">5</td><td style="color: black; border: 1px solid black; text-align: center;">3.00 × 10−6</td><td style="color: black; border: 1px solid black; text-align: center;">9.00 × 10−6</td><td style="color: black; border: 1px solid black; text-align: center;">5.94 × 10−4</td></tr></tbody></table> من بيانات المعدّل، قانون معدل عام؛ المعدّل = k[NO]m[O3]n يمكن تشكيله. يمكن تحديد قيم أمري التفاعل m و n وثابت المعدل k من البيانات التجريبية باستخدام عملية من ثلاثة أجزاء: </ص> في الخطوة 1، يتم تحديد قيمةm من البيانات التي تتغير فيها [NO] وتكون [O3] ثابتة. في التجارب 3 و 4 و 5، تختلف [NO] بينما يظل [O3] ثابتًا. عندما تتضاعف [NO] من التجربة 3 إلى 4، يتضاعف المعدل، وعندما يتضاعف [NO] ثلاث مرات من التجربة 3 إلى 5 ، يتضاعف المعدل أيضًا ثلاث مرات. وبالتالي، فإن المعدل أيضًا يتناسب طرديًا مع [NO] ، و m في قانون المعدل يساوي 1. 
 
 في الخطوة 2، يتم تحديد قيمة n من البيانات التي يتنوع فيها [O3] ويكون [NO] ثابتًا. في التجارب 1 و 2 و 3 ، تكون [NO] ثابتة وتختلف [O3]. يتغير معدل التفاعل بالتناسب المباشر مع التغيير في [O3]. عندما يتضاعف [O3] من التجربة 1 إلى 2 ، يتضاعف المعدل؛ عندما يتضاعف [O3] ثلاث مرات من التجربة 1 إلى 3 ، يزداد المعدل أيضًا ثلاث مرات. وبالتالي ، فإن المعدل يتناسب طرديًا مع [O3]، و n يساوي 1. قانون المعدل هو: المعدّل = k [NO]1 [O3]1 = k [NO][O3] في الخطوة 3، يتم تحديد قيمة k من مجموعة واحدة من التركيزات (على سبيل المثال ، البيانات من التجربة 1) والمعدل المقابل لها. <img alt="Eq1" src="/files/ftp_upload/11376/11376_Equation 1.png" style="text-align: center; height: 145px;" /> في التفاعلات التي لا تشير فيها البيانات من طريقة المعدلات الأولية مباشرة إلى العلاقة بين التركيزات الأولية والمعدلات الأولية ، يمكن استخدام الحساب الذي يتضمن نسبة قوانين المعدل لحساب ترتيب التفاعل وثابت المعدل. على سبيل المثال ، قانون المعدل العام للتفاعل 2 NO (g) + Cl2 (g) ⟶ 2 NOCl (g) يتم التعبير عنه على النحو التالي: المعدّل = k [NO]m [Cl2]n. البيانات من طريقة المعدّلات الأولية هي: <table style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="color: black; border: 1px solid black; text-align: center;">  Trial    </td><td style="color: black; border: 1px solid black; text-align: center;">  [NO] (mol/L)  </td><td style="color: black; border: 1px solid black; text-align: center;">  [Cl2] (mol/L)  </td><td style="color: black; border: 1px solid black; text-align: center;">  Initial Rate (mol/L·s)     </td></tr><tr><td style="color: black; border: 1px solid black; text-align: center;">1</td><td style="color: black; border: 1px solid black; text-align: center;">0.10</td><td style="color: black; border: 1px solid black; text-align: center;">0.10</td><td style="color: black; border: 1px solid black; text-align: center;">0.00300</td></tr><tr><td style="color: black; border: 1px solid black; text-align: center;">2</td><td style="color: black; border: 1px solid black; text-align: center;">0.10</td><td style="color: black; border: 1px solid black; text-align: center;">0.15</td><td style="color: black; border: 1px solid black; text-align: center;">0.00450</td></tr><tr><td style="color: black; border: 1px solid black; text-align: center;">3</td><td style="color: black; border: 1px solid black; text-align: center;">0.15</td><td style="color: black; border: 1px solid black; text-align: center;">0.10</td><td style="color: black; border: 1px solid black; text-align: center;">0.00675</td></tr></tbody></table>
 يمكن تحديد قيم m و n من البيانات التجريبية باستخدام منهج جبري، وبعد ذلك يتم تحديد قيمة k . في الخطوة 1، يتم تحديد قيمة m من البيانات التي تختلف فيها [NO] وتكون [Cl2] ثابتة. يتم التعبير عن نسبة قوانين المعدّل عن طريق استبدال البيانات من تجربتين مختلفتين (على سبيل المثال، التجربة 3 والتجربة 1). <img alt="Eq2" src="/files/ftp_upload/11376/11376_Equation 2.png" style="text-align: center; height: 260px;" /> في الخطوة 2، يتم تحديد قيمة n من البيانات التي يتنوع فيها [Cl2] ويكون [NO] ثابتًا. <img alt="Eq4" src="/files/ftp_upload/11376/11376_Equation 4.png" style="text-align: center; height: 120px;" /> باستخدام القيم المحسوبة لـm و n يتم التعبير عن قانون المعدل بالصيغة: المعدّل = k [NO]2 [Cl2]. في الخطوة 3، تم تحديد القيمة العددية لثابت المعدل k بالوحدات المناسبة. وحدات معدل التفاعل هي مول/لتر. يتم الانتهاء من وحدات k عن طريق استبدال وحدات جميع المعلمات الأخرى في قانون المعدل. في هذا المثال، وحدات التركيز هي مول3/L3. يجب أن تكون وحدات k هي L L2/mol2· بحيث يكون المعدل معبّر عنه بالمول/ليتر·. يتم تحديد قيمة k بمجرد حل تعبير قانون المعدل، ببساطة عن طريق استبدال القيم من أي من التجارب التجريبية (على سبيل المثال التجربة 1). <img alt="Eq5" src="/files/ftp_upload/11376/11376_Equation 5.png" style="text-align: center; height: 70px;" /> ترتيب التفاعل والوحدات الثابتة للمعدّلات في بعض التفاعلات، تصادف أن تكون أوامر التفاعل في قانون المعدل هي نفسها المعاملات في المعادلة الكيميائية للتفاعل. هذه مجرد مصادفة وغالباً ما لا يكون الأمر كذلك. قد تعرض قوانين المعدل أوامر جزئية لبعض المواد المتفاعلة، وأحيانًا يتم ملاحظة أوامر التفاعل السلبية عندما تؤدي الزيادة في تركيز أحد المتفاعلات إلى انخفاض في معدل التفاعل. يتم تحديد قوانين المعدّل عن طريق التجربة فقط ولا يتم التنبؤ بها بشكل موثوق من خلال قياس العناصر المتفاعلة. ستختلف وحدات ثابت المعدل حسب الاقتضاء لتلائم الترتيب العام للتفاعل. وحدة معدل ثابت للتفاعل الصفري هي مول/ليتر· (أو M/s) وتلك الخاصة بالتفاعل من الدرجة الأولى هي 1/s. وحدة ثابت المعدل لتفاعل من الدرجة الثانية هي مول/ليتر· (أو 1/M·s) وتلك الخاصة بالتفاعل من الدرجة الثالثة هي L2/mol2·s. على الرغم من الإشارة إلى الوحدات المحددة للتركيز والوقت على أنها (مول/لتر) و (s)، يمكن استخدام أي وحدات صالحة أخرى لتمثيل خصائص التركيز والوقت. هذا النص مقتبس من <a href="https://openstax.org/books/chemistry-2e/pages/12-3-rate-laws#57033">Openstax, Chemistry 2e, Section 12.3: Rate Laws.</a>

تصف قوانين المعدل العلاقة بين معدل التفاعل الكيميائي وتركيز المواد المتفاعلة له. في قانون المعدل ، ثابت المعدل k و ...

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Chemical Kinetics

الحركية الكيميائية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

finding rate law from initial rates

Rate laws connect the speed of a chemical reaction to the concentration of its reactants. The rate constant, k, and the reaction orders are not taken from the chemical equation. They are found experimentally by watching how the rate changes when the reactant concentrations change.

One common way to do this is the method of initial rates. In this method, several trials are run with different starting concentrations. The measured rates are then compared to determine the reaction orders and, after that, the rate constant. These values are used to write the rate law.

For the reaction of nitric oxide with ozone, NO(g) + O3(g) → NO2(g) + O2(g), the data show how this works in the lab. When [NO] is held constant and [O3] changes, the rate changes in the same way. When [O3] doubles, the rate doubles. When [O3] triples, the rate triples. This shows that the reaction is first order in O3. A similar comparison using trials where [O3] stays constant shows that the rate is also directly proportional to [NO], so the reaction is first order in NO as well. The rate law is therefore rate = k[NO][O3].

In other reactions, the orders are found with an algebraic ratio of rate laws. For the reaction 2 NO(g) + Cl2(g) → 2 NOCl(g), the rate law is written as rate = k[NO]m[Cl2]n. Using the trial data, one step gives m = 2 and another gives n = 1. The rate law becomes rate = k[NO]2[Cl2]. The value of k is then found by using one trial and solving for the constant.

The units of the rate constant depend on the overall order of the reaction. Rate is measured in mol/L·s, and the units for k must match the rate law. For this example, the concentration terms give mol3/L3, so k must have units of L2/mol2·s. In general, a zero-order reaction has k in mol/L·s, a first-order reaction has k in 1/s, a second-order reaction has k in L/mol·s, and a third-order reaction has k in L2/mol2·s.

Reaction order does not always match the coefficients in the balanced equation. That match can happen, but it is only a coincidence. Rate laws can also include fractional orders, and some reactants can have negative orders if a higher concentration lowers the reaction rate. Because of this, rate laws are determined by experiment, not by stoichiometry. Although the examples here use mol/L and s, other valid concentration and time units can also be used.

Finding Rate Law from Initial Rates

reaction rate

Measuring Reaction Rates

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measuring reaction rates

Tracking Reaction Kinetics with Light and Pressure

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concentration and rate law

Reaction Order from Concentration

Reaction order from concentration shows how reactant amounts affect reaction rate. Rate laws, also called differential rate laws or rate equations, are mathematical expressions that connect reaction rate with the concentrations of reactants. For a generic reaction a A + b B → products, the rate law can be written using the reactant concentrations [A] and [B] and a rate constant k. In a rate law, k is the rate constant for one specific reaction at one specific temperature. The exponents m and n...

determining order of reaction

Rate laws connect the speed of a chemical reaction to the concentration of its reactants. The rate constant, k, and the reaction orders are not taken from the chemical equation. They are found experimentally by watching how the rate changes when the reactant concentrations change. One common way to do this is the method of initial rates. In this method, several trials are run with different starting concentrations. The measured rates are then compared to determine the reaction orders and,...

the integrated rate law: the dependence of concentration on time

the-integrated-rate-law-the-dependence-of-concentration-on-time

Reading Reaction Progress with Integrated Laws

Integrated rate laws connect reaction concentration to time. They help show how much reactant or product is present after a certain period. They can also help estimate how long a reaction must run to reach a given extent. A common use is finding how long radioactive material must be stored before its radioactivity drops to a safe level. These equations come from the differential rate law after it is integrated with respect to time. For a first-order reaction, where rate = k[A], the integrated...

half-life of a reaction

Reaction Half-Life in Kinetics

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temperature dependence on reaction rate

Collision Theory and Reaction Speed

Collision theory explains why reaction speed depends on how particles collide. Atoms, molecules, or ions must come close together before they can react. The theory says the reaction rate depends on the collision rate, the orientation of the colliding species, and whether the collision has enough energy for bonds to change. A gas-phase reaction between carbon monoxide and oxygen shows why orientation matters. The molecules can collide in more than one way. If the oxygen side of carbon monoxide...

arrhenius plots

Determining Activation Energy from Temperature

The Arrhenius equation links activation energy and the rate constant, k, for chemical reactions. It is written as k = Ae−Ea/RT. In this equation, R is the ideal gas constant with a value of 8.314 J/mol·K, T is the temperature on the kelvin scale, Ea is the activation energy in J/mole, e is the constant 2.7183, and A is the frequency factor. The frequency factor depends on collision frequency and the orientation of reacting molecules. Experimental kinetic data can be used to find the activation...

reaction mechanisms

Elementary Steps in Reaction Mechanisms

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Reaction Bottlenecks in Chemical Kinetics

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Catalyst Action in Reaction Rates

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enzymes

Enzyme Action and Inhibition

Enzymes are biological catalysts that speed up many reactions in living organisms. They help control cellular metabolism by lowering the activation energy needed for biochemical reactions. When activation energy drops, reaction rates can increase. Enzyme problems can also lead to serious disease. A genetic abnormality that causes G6PD, or glucose-6-phosphate dehydrogenase, deficiency can disrupt the pathway that supplies NADPH to cells. In red blood cells, this can reduce glutathione and...

key terms and concepts

Use initial-rate data to find reaction order and the rate constant. Explore examples with NO, ozone, and NOCl, plus how rate constant units change.

Finding Rate Law from Initial Rates | JoVE K12

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North Carolina K-12 Science Standard Course of Study

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Matter and its Interactions

PS.Chm.5.1

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Physical Science

Chemical Reactions

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Interactions Of Matter

Chemical reactions

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CH.7

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Matter and Its Interactions

HS-PS1-4

HS-PS1-5

Florida Department of Education

SC.912.P.12

SC.912.P.12.12

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-5.

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Ions and Ionic Charges

In ordinary chemical reactions, the nucleus &mdash; which contains the protons and neutrons of each atom and thus identifies the element &mdash; remains ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

trends-in-lattice-energy-ion-size-and-charge

Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Electronegativity

Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity.&#xA0;

Electronegativity values of ...

bond-polarity-dipole-moment-and-percent-ionic-character

Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

The absolute value of the difference in electronegativity (&Delta;EN) of two bonded atoms provides a rough measure of the polarity to be ...

lewis-structures-of-molecular-compounds-and-polyatomic-ions

Lewis Structures of Molecular Compounds and Polyatomic Ions

To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:


	Determine the ...

Bond Energies and Bond Lengths

Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break it, ...

Bonding in Metals

Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Dr&#xFC;de called the ...

Model basic atomic structure and relate an element's atomic structure to its bonding, reactivity, and placement on the Periodic Table.

IPC.7.A

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Alkali Metals

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the ...

Halogens

Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. ...

Noble Gases


The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name &ldquo;noble&rdquo; because they were ...

Use patterns within the Periodic Table to predict the relative physical and chemical properties of elements.

IPC.7.B

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

Phase Transitions

Whether solid, liquid, or gas, a substance&#39;s state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the ...

phase-transitions-vaporization-and-condensation

Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy ...

phase-transitions-sublimation-and-deposition

Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and ...

Melting Points

Melting Points in Organic Chemistry
The melting point of a compound is the temperature at which the solid phase transitions into the liquid phase at a ...

Boiling Points

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

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

Explain how physical and chemical properties of substances are related to their usage in everyday life such as in sunscreen, cookware, industrial applications, and fuels.

IPC.7.C

Emission Spectra

When solids, liquids, or condensed gases are heated sufficiently, they radiate some of the excess energy as light. Photons produced in this manner have a ...

Metal Flame Emission

Metal Flame Emission
Flame testing is an analytical technique where a sample is placed in a flame, and the characteristic flame color is used to identify ...

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

Explain how electrons can transition from a high energy level to a low energy state, emitting photons at different frequencies for different energy transitions.

IPC.7.D

The de Broglie Wavelength

In the macroscopic world, objects that are large enough to be seen by the naked eye follow the rules of classical physics. A billiard ball moving on a ...

The Uncertainty Principle

Werner Heisenberg considered the limits of how accurately one can measure properties of an electron or other microscopic particles. He determined that ...

The Quantum-Mechanical Model of an Atom

Shortly after de Broglie published his ideas that the electron in a hydrogen atom could be better thought of as being a circular standing wave instead of ...

Quantum Numbers

It is said that the energy of an electron in an atom is quantized; that is, it can be equal only to certain specific values and can jump from one energy ...

Balmer Series

The Bohr Model
Niels Bohr proposed a model for the hydrogen atom in 1913 that described discrete energy states are associated with a fixed electron orbit ...

Beer's Law

Absorbance and Fluorescence
When light hits a substance, it is either absorbed, transmitted, or reflected. Typically, a substance interacts with a range ...

The Wave Nature of Light

The nature of light has been a subject of inquiry since antiquity. In the seventeenth century, Isaac Newton performed experiments with lenses and prisms ...

Explain how atomic energy levels and emission spectra present evidence for the wave particle duality.

IPC.7.E

Science concepts. The student knows that relationships exist between the structure and properties of matter. The student is expected to:

Finding Rate Law from Initial Rates

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