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

עבור תגובה כימית, משוואת הקצב מבטאת את הקשר בין קצב התגובה וריכוז המגיב. המעריכים של ריכוזי מגיב משפיעים על קצב התגובה באופן פרטני ונקראים סדרי תגובה. סדר התגובה נקבע בניסוי באמצעות יישום שיטת הקצבים ההתחלתיים, שבהם תגובה כימית מבוצעת כמה פעמים עם ריכוזי מגיבים משתנים כדי למדוד את קצבי התגובה ההתחלתי.עלייה בריכוז המגיב, המייצרת עלייה פרופורציונלית באופן ליניארי בקצב התגובה, מאפיינת תגובה מסדר ראשון. אם הכפלה של ריכוז המגיב מכפילה פי ארבעה את הקצב ההתחלתי, אז התצפית מעידה על תגובה מסדר שני. לעומת זאת, אם השינוי בריכוזי המגיב אינו משפיע על ערכי הקצב ההתחלתי, התצפית מעידה על תגובה מסדר אפס.כשהנתונים שהתקבלו על קצבים ראשוניים אינם מציגים קשר ברור בין השינוי בריכוז המגיב לקצב המתאים, מחושב יחס על פי משוואות הקצב. כאן כל שני ערכי ריכוז של המגיב ושל קצב התגובה התואמים לו משמשים כדי לקבוע את סדר התגובה. אך מה לגבי תגובות עם כמה מגיבים?ראשית, באמצעות השיטה של קצבים התחלתיים, קצב התגובה של כל מגיב נקבע בנפרד. לאחר מכן, הקצבים הנפרדים מבוטאים כמעריכים של ריכוזי המגיבים התואמים שלהם כדי לבנות משוואת קצב. לבסוף, סכום המעריכים הנפרדים ממשוואת הקצב קובעים את סדר התגובה הכולל.בעוד שסדר התגובה מייצג את התלות של קצב התגובה בריכוז המגיב, מדד ישיר של מהירות התגובה היחסית מסומן על ידי קבוע הקצב. קבוע הקצב k הוא קבוע הפרופורציה המקשר בין קצב התגובה למכפלה של ריכוזי המגיבים. היחידה של קבוע קצב תלויה בסדר התגובה הכולל ויכולה להיקבע על ידי ארגון מחדש של משוואת הקצב כדי לפתור אותה עבור קבוע הקצב.בתגובה מסדר אפס, ל k יחידות של מולריות לשנייה. יחידת המידה לתגובה מסדר ראשון היא 1 חלקי שנייה, ולתגובה מסדר שני, 1 חלקי מולריות לשנייה. קבוע קצב גדול מעיד על תגובה מהירה.לעומת זאת, קבוע קצב נמוך יותר מעיד על תגובה איטית. ערך של אפס מעיד על היעדרה של כל תגובה כימית.

קביעת סדר התגובה

<div style="direction:rtl">

 	חוקי הקצב מתארים את הקשר בין קצב התגובה הכימית לריכוז המגיבים שלה. בחוק קצב, קבוע הקצב k וסדרי התגובה נקבעים בניסוי על ידי התבוננות כיצד קצב התגובה משתנה עם שינוי ריכוזי המגיבים. גישה ניסיונית נפוצה לקביעת חוקי הקצב היא שיטת הקצבים הראשוניים. שיטה זו כוללת מדידת קצבי תגובה עבור ניסויים מרובים המבוצעים באמצעות ריכוזי מגיבים ראשוניים שונים. השוואת הקצבים הנמדדים עבור ניסויים אלה מאפשרת קביעת סדרי התגובה ולאחר מכן, קבוע הקצב, המשמשים יחד לגיבוש חוק הקצב. 

 	ניתן לקבוע את קצב התגובה, למשל, כוללת תחמוצת חנקן עם אוזון [NO (g) + O3 (g)⟶ NO2 (g) + O2 (g)]מתוך הנתונים הניסיוניים של שיטת הקצב ההתחלתי, במעבדה.

 	<table style="margin-left: auto; margin-right: auto;"> 
 		<tbody> 

 	<tr> 

 		<td style="color: black; border: 1px solid black; text-align: center;">ניסוי </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> 

 מנתוני הקצבים, חוק קצבים גנרי; קצב = k[NO]m[O3]nמנוסח. הערכים של סדרי התגובה mו- n, וקבוע הקצב k נקבעים מנתוני הניסוי תוך שימוש בתהליך בן שלושה חלקים:

 בשלב 1, הערך של m נקבע מהנתונים שבהם [NO] משתנה, ו-[O3] קבוע. בניסויים 3, 4 ו-5, [NO] משתנה בעוד [O3] נשאר קבוע. כאשר [NO] מכפיל את עצמו מניסוי 3 ל-4, הקצב מכפיל את עצמו, וכאשר [NO] מכפיל את עצמו מניסוי 3 ל-5, הקצב גם משולש. לפיכך, הקצב גם עומד ביחס ישר ל-[NO], ו-m בחוק קצב שווה ל-1. 

 בשלב 2, הערך של n נקבע מתוך נתונים שבהם [O3] משתנה, ו-[NO] קבוע. בניסויים 1,2 ו-3, [NO] קבוע ו-[O3] משתנה. קצב התגובה משתנה ביחס ישר לשינוי ב-[O3]. כאשר [O3] מכפיל את עצמו מניסוי 1 ל-2, הקצב מוכפל; כאשר [O3] משולש מניסוי 1 ל-3, הקצב עולה גם משליש. לפיכך, הקצב עומד ביחס ישר ל-[O3], ו-n שווה ל-1. חוק השיעור הוא כך: שיעור = k [NO]1 [O3]1 = k[NO][O3] 

 בשלב 3, הערך של k נקבע מקבוצה אחת של ריכוזים (לדוגמה, הנתונים מניסוי 1) והקצב המקביל שלו. <img alt="Eq1" src="/files/ftp_upload/11376/11376_Equation 1.png" style="text-align: center; height: 145px;"> 

 בתגובות שבהן הנתונים משיטת הקצב ההתחלתי אינם מרמזים ישירות על הקשר בין הריכוזים הראשוניים לקצב ההתחלתי, ניתן להשתמש בחישוב הכולל את היחס בין חוקי הקצב כדי לחשב את סדר התגובה וקבוע הקצב. 

 לדוגמה, חוק הקצב הכללי לתגובה 2 NO(g) + Cl2 (g) ⟶ 2 NOCl (g) מבוטא כך: קצב = k [NO]m [Cl2]n.

 הנתונים משיטת הקצבים ההתחלתיים הם: 
 <table style="margin-left: auto; margin-right: auto;"> 
 	<tbody> 

	<tr> 

		<td style="color: black; border: 1px solid black; text-align: center;">ניסוי </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;">שיעור ראשוני(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> 

 ניתן לקבוע את הערכים של m ו-n מנתוני הניסוי באמצעות גישה אלגברית, שבעקבותיה נקבע הערך של k. 

 בשלב 1, הערך של m נקבע מהנתונים שבהם [NO] משתנה ו-[Cl2] קבוע. יחס של חוקי הקצב מתבטא על ידי החלפת נתונים משני ניסויים שונים (למשל ניסוי 3 וניסוי 1). 
 <img alt="Eq2" src="/files/ftp_upload/11376/11376_Equation 2.png" style="text-align: center; height: 260px;"> 

 בשלב 2, הערך של n נקבע מתוך נתונים שבהם [Cl2] משתנה, ו-[NO] קבוע. 
 <img alt="Eq4" src="/files/ftp_upload/11376/11376_Equation 4.png" style="text-align: center; height: 120px;"> 
 
 באמצעות הערכים המחושבים של m ו-n חוק הקצב מבוטא כקצב = k [NO]2 [Cl2].

 בשלב 3, הערך המספרי של קבוע הקצב k נקבע עם יחידות מתאימות. היחידות לקצב התגובה הן mol/L·s. היחידות עבור k מסתיימות בהחלפת היחידות של כל שאר הפרמטרים בחוק הקצב. בדוגמה זו, יחידות הריכוז הן mol3/L3. היחידות עבור k צריכות להיות L2/mol2·s כך שהקצב יהיה במונחים של mol/L·s. הערך של k נקבע לאחר שנפתר ביטוי חוק הקצב, פשוט על ידי החלפה של הערכים מכל אחד מהניסויים הניסיוניים (למשל ניסוי 1). 
 <img alt="Eq5" src="/files/ftp_upload/11376/11376_Equation 5.png" style="text-align: center; height: 70px;"> 

 סדר תגובה ויחידות קבועות של קצב 

 בתגובות מסוימות, סדרי התגובה בחוק הקצב זהים למקדמים במשוואה הכימית של התגובה. זה רק צירוף מקרים ולעתים קרובות מאוד לא המקרה. חוקי קצב עשויים להציג סדרים חלקיים עבור מגיבים מסוימים, ולעתים נצפים סדרי תגובה שליליים כאשר עלייה בריכוז של מגיב אחד גורמת לירידה בקצב התגובה. חוקי הקצב נקבעים על ידי ניסוי בלבד ואינם צפויים בצורה מהימנה על ידי סטוכיומטריה של התגובה. 

 היחידות עבור קבוע קצב ישתנו בהתאם לסדר התגובה הכולל. היחידה של קבוע הקצב לתגובה מסדר אפס היא mol/L·s (או M/s) וזו של תגובה מסדר ראשון היא 1/s. היחידה של קבוע הקצב לתגובה מסדר שני היא L/mol·s (או 1/M·s) וזו של תגובה מסדר שלישי היא L2/mol2·s. למרות שהיחידות הספציפיות לריכוז וזמן מסומנות כ- (mol/L) ו- (s), ניתן להשתמש בכל יחידה חוקית אחרת כדי לייצג את תכונות הריכוז והזמן.

 טקסט זה מותאם מ<a href="https://openstax.org/books/chemistry-2e/pages/12-3-rate-laws#57033">Openstax, Chemistry 2e, Section 12.3: Rate Laws.</a></div>

חוקי קצב מתארים את הקשר בין קצב התגובה הכימית לבין ריכוז המגיבים שלה. בחוק תעריף, קבוע התעריף k ו- ...

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Chemical Kinetics

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מונחים ומושגים מרכזיים

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

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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,...

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Elementary Steps in Reaction Mechanisms

Chemical reactions can happen in steps, and a balanced equation does not show the full path at the molecular level. A reaction mechanism, also called a reaction path, gives the step-by-step process that explains how reactants become products. The decomposition of ozone is one example of a reaction that can be described by a sequence of steps. Each step in a mechanism is an elementary reaction. These elementary reactions happen in order, and when they are added together, they give the balanced...

rate-determining steps

Reaction Bottlenecks in Chemical Kinetics

Reaction bottlenecks help explain rate-determining steps in multistep reaction mechanisms. In a mechanism with several elementary steps, one step is often much slower than the others. That slowest step is called the rate-limiting step, or rate-determining step. A reaction cannot move faster than its slowest step, so this step controls the overall reaction rate. The idea is like traffic on a four-lane freeway with one lane closed. Cars can only move as fast as the bottleneck allows. In the same...

catalysis

Catalyst Action in Reaction Rates

Catalysts change the rate of a chemical reaction by giving it a faster path. A catalyst increases reaction rate without being consumed during the process. Its effect is often explained with reaction mechanisms and energy diagrams. For an endothermic reaction, the reactants and products start and end at the same energies in both cases. The uncatalyzed path is a one-step mechanism with one transition state. The catalyzed path follows a different mechanism with two transition states and a lower...

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

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Matter and its Interactions

PS.Chm.5.1

Pennsylvania State Academic Standards

Physical Science

Chemical Reactions

3.2.9-12.D

3.2.9-12.E

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Chemical reactions

Virginia  Standards of Learning

HIgh School

CH.7

CH.7.e

Next Generation Science Standards

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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