Name: how temperature changes reaction rate
Uploaded: 2023-04-30T18:28:32.000Z
Duration: 2 min 24 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Matter And Its Interactions

HS-PS1-4

Predicting Reaction Outcomes

La cinétique chimique décrit la vitesse et la trajectoire par lesquelles les réactifs se déplacent d’un état à un autre dans la voie réactionnelle, tandis que la thermodynamique prend en compte les stabilités relatives des états eux-mêmes.
Les composés A et B peuvent réagir l’un avec l’autre de deux manières possibles, l’une menant aux produits C et D, et l’autre conduisant aux produits E et F.
Les produits C et D sont cinétiquement favorisés par rapport à E et F, car leur formation nécessite une énergie d’activation plus faible. De plus, ils sont thermodynamiquement plus favorables en raison de leurs énergies plus faibles.
Dans la plupart des cas, une voie de réaction est à la fois favorisée thermodynamiquement et cinétiquement, bien qu’il existe des cas où la thermodynamique et la cinétique s’opposent.
Dans ce cas, les produits C et D sont favorisés par la thermodynamique car ils ont une énergie plus faible. Cependant, les produits E et F sont préférés par la cinétique car leur formation implique une énergie d’activation plus faible.
La température joue un rôle important dans la détermination du produit principal. À basse température, les produits E et F se forment rapidement, tandis qu’à haute température, les concentrations d’équilibre sont rapidement atteintes, produisant C et D.
Si la barrière d'énergie d'activation est suffisamment élevée, les réactifs sont considérés comme « cinétiquement stables ». Cependant, l’ajout d’énergie peut surmonter cet obstacle.
Par exemple, les carburants pétroliers et l’oxygène atmosphérique ne réagissent pas spontanément à température ambiante. Cependant, dans un moteur de voiture, le carburant est enflammé par une étincelle provenant d’une source d’énergie externe, et la réaction entre le carburant et l’oxygène atmosphérique atteint l’équilibre.
La taille des particules en réaction a un impact sur leur fréquence de collision, car plusieurs particules plus petites ont une surface globale plus grande qu’une grosse particule. Plus la surface sur laquelle les collisions peuvent se produire est grande, plus la réaction est rapide.
Par exemple, casser de plus grosses bûches en petits morceaux de bois d’allumage augmente leur surface. Avec un combustible plus accessible, le feu fournit plus rapidement l’énergie nécessaire pour soutenir la réaction de combustion.

<a href="https ://chem.libretexts.org/Courses/Prince_Georges_Community_College/Chemistry_2000%3A_Chemistry_for_Engineers_(Sinex)/Unit_6%3A_Thermo_and_Electrochemistry/Chapter_16%3A_Entropy_and_Free_Energy/Chapter_16.5%3A_Comparing_Thermodynamics_and_Kinetics">Chemistry LibreTexts, Section 16.5 : Comparaison de la thermodynamique et de la cinétique</a>
<a href="https://openstax.org/books/chemistry-2e/pages/12-5-collision-theory">Openstax, Chimie 2e, Section 12.5 : Théorie des collisions.</a>

prédire les résultats des réactions

La cinétique décrit la vitesse et le chemin par lesquels une réaction se produit. En revanche, la thermodynamique traite des fonctions d’état et décrit les propriétés, le comportement et les composants d’un système. Il ne s’intéresse pas au chemin emprunté par le processus et ne peut pas aborder la vitesse à laquelle une réaction se produit. Bien qu’il fournisse des informations sur ce qui peut se produire au cours d’un processus de réaction, il ne décrit pas les étapes détaillées de ce qui apparaît au niveau atomique ou moléculaire. D’autre part, la cinétique fournit des informations au niveau atomique ou moléculaire. En bref, la thermodynamique se concentre sur l'énergétique des produits et des réactifs, tandis que la cinétique se concentre sur le cheminement des réactifs aux produits. Les processus industriels où la valeur de ΔG est négative et la valeur correspondante de K est supérieure à un sont trop lents pour être économiquement rentables. Dans de tels cas, une réaction thermodynamiquement non spontanée peut se produire spontanément en modifiant les conditions de réaction, telles que la variation de la pression ou de la température, la fourniture d'une source d'énergie externe sous forme d'électricité, etc.

Les atomes, les molécules ou les ions doivent entrer en collision avant de pouvoir réagir les uns avec les autres. Les atomes doivent être proches les uns des autres pour former des liaisons chimiques. Cette prémisse constitue la base d'une théorie qui explique de nombreuses observations concernant la cinétique chimique, y compris les facteurs affectant les vitesses de réaction. La théorie des collisions est basée sur les postulats selon lesquels (i) la vitesse de réaction est proportionnelle à la vitesse des collisions de réactifs, (ii) les espèces réactives entrent en collision dans une orientation permettant le contact entre les atomes qui se lient ensemble dans le produit, et (iii) la collision se produit avec une énergie adéquate pour permettre la pénétration mutuelle des couches de valence des espèces réactives afin que les électrons puissent se réorganiser et former de nouvelles liaisons (et de nouvelles espèces chimiques). Lorsque des espèces réactives entrent en collision avec la bonne orientation et suffisamment d’énergie d’activation, elles se combinent pour former une espèce instable appelée complexe activé ou état de transition. Ces espèces ont une durée de vie courte et sont généralement indétectables par la plupart des instruments d'analyse. Dans certains cas, des mesures spectrales sophistiquées peuvent observer des états de transition. La théorie des collisions explique pourquoi la plupart des vitesses de réaction augmentent à mesure que la température augmente ; avec une augmentation de la température, la fréquence des collisions augmente. Plus de collisions signifient une vitesse de réaction plus rapide, en supposant que l’énergie des collisions soit adéquate.

Prédire les résultats des réactions

La cinétique décrit la vitesse et la trajectoire par lesquelles une réaction se produit. En revanche, la thermodynamique traite des fonctions d’état et décrit les propriétés, ...

Education

Enseignement

JoVE Core

Organic Chemistry

Chimie organique

Unit 1

Unité 1

Thermodynamics and Chemical Kinetics

Thermodynamique et cinétique chimique

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

how temperature changes reaction rate

Reaction rate and reaction pathway are key ideas in chemical kinetics. Thermodynamics, by contrast, focuses on the state of a system. It describes the properties, behavior, and components of reactants and products. It does not describe the path of the process or the speed of the reaction. Kinetics gives information on the atomic or molecular level, while thermodynamics focuses on the energetics of the reactants and products.

Thermodynamics can show what may happen in a reaction, but it does not explain the detailed steps at the atomic level. Kinetics fills that gap by following how reactants become products. In industrial settings, some reactions have a negative ΔG and a K value greater than one, but they can still be too slow to make money. A reaction that is not spontaneous under one set of conditions can be made to happen by changing pressure or temperature or by supplying outside energy such as electricity.

Collision theory explains how reactions occur. Atoms, molecules, or ions must collide before they can react, and they must be close together to form chemical bonds. According to collision theory, the reaction rate depends on how often reactants collide, whether they collide in the right orientation, and whether the collision has enough energy for the valence shells to penetrate so electrons can rearrange and new bonds can form. When all of these conditions are met, the reactants form an unstable species called an activated complex, also called a transition state.

Transition states are very short-lived and are usually not detected by most analytical instruments. In some cases, advanced spectral measurements can observe them. Collision theory also helps explain why reaction rates usually increase when temperature rises. Higher temperature means more collisions, and more collisions can lead to a faster reaction if the collision energy is still sufficient.

How Temperature Changes Reaction Rate

chemical reactions

Stoichiometry, Rates, and Equilibrium

Stoichiometry, reaction rates, and equilibrium explain how chemical reactions are measured and predicted. A balanced chemical equation shows the chemical formulas of the reactants and products in a chemical change. It also gives the relative amounts of each substance involved. Reaction stoichiometry helps predict how much reactant is needed to make a desired amount of product. It can also show how much product forms from a given amount of reactant. The amounts shown by a balanced equation are...

enthalpy and heat of reaction

Combustion Heat and Hydrocarbon Stability

Combustion is a burning reaction that releases energy as heat, light, or sound. It happens when a substance reacts with an oxidizing agent, usually molecular oxygen. The heat of combustion is also called the enthalpy of combustion. The energy released when one mole of a substance undergoes complete combustion at constant pressure is the molar heat of combustion. Combustion reactions are exothermic, so they give off energy. For that reason, the sign of ΔH is negative. In 1772, Antoine Lavoisier...

energetics of solution formation

Why Some Solutions Form Spontaneously

Solution formation can happen spontaneously under the right conditions. A spontaneous process is one that occurs without energy from an outside source. During dissolution, solute and solvent particles separate and then attract each other in a new way. The energy change depends on the balance of intermolecular forces, which are the attractions between particles. If the solute-solute and solvent-solvent forces are about the same as the new solute-solvent forces, the solution forms with no energy...

entropy and solvation

Hydrophobic Effects in Solvation

Solvation is the process of surrounding a solute with solvent. It spreads the solute evenly through the solvent. A useful rule is that like dissolves like. A good solvent has molecular features similar to the substance being dissolved. Polar solvents dissolve polar solutes, and apolar solvents dissolve apolar solutes. A polar solvent has a high dielectric constant, with ε greater than or equal to 15. An apolar solvent has a low dielectric constant. The dielectric constant is defined by the...

gibbs free energy and thermodynamic favorability

gibbs-free-energy-and-thermodynamic-favorability

Temperature Effects on Gibbs Free Energy

Temperature changes can decide whether a process is spontaneous. This idea applies to phase changes and to some chemical reactions. The key link is Gibbs free energy, which connects free energy change with enthalpy and entropy. The sign of the Gibbs free energy change, or ΔG, depends on the signs of enthalpy change (ΔH) and entropy change (ΔS), and sometimes on the absolute temperature. Because temperature is measured in kelvin, it is always a positive value. That means there are four main...

chemical and solubility equilibria

How Solubility Depends on Free Energy

Solubility depends on free energy changes when a solute dissolves in a solvent. The free energy change for this process is called the free energy of solution, ΔGsolution. When ΔGsolution is less than zero, solution formation is favorable. When it is greater than zero, solution formation is unfavorable. For complete dissolution to happen, the Gibbs energy change must be negative. This means the balance of forces in the mixture must favor solution formation. The amount a solute dissolves in a...

rate law and reaction order

How Reactant Concentration Sets Reaction Rate

Reaction rate depends on reactant concentration, and rate laws show that relationship with a mathematical equation. A rate law, also called a differential rate law or rate equation, links the rate of a chemical reaction to the concentrations of its reactants. For a generic reaction, a A + b B  products, the rate law can be written as rate = k [A]^m [B]^n. Here, [A] and [B] are the molar concentrations of the reactants. The constant k is the rate constant, and it is specific to one reaction at...

effect of temperature change on reaction rate

effect-of-temperature-change-on-reaction-rate

Arrhenius Equation in Reaction Speed

The Arrhenius equation connects activation energy, temperature, and the rate constant, k, for many chemical reactions. It helps explain why some reactions move slowly while others happen faster. In this equation, R is the ideal gas constant, with a value of 8.314 J/mol·K. T is the temperature in kelvin, Ea is the activation energy in joules per mole, e is the constant 2.7183, and A is the frequency factor. The frequency factor, A, describes how often reacting molecules collide and how well...

multi-step reactions

Reaction Mechanisms and Rate-Determining Steps

Chemical reactions can happen in a sequence of steps. A balanced chemical equation shows the reactants and products, but it does not show how the reaction occurs at the molecular level. The reaction mechanism, or reaction path, gives that step-by-step detail. Each step in a mechanism is an elementary reaction. These elementary reactions happen in order, and together they add up to the balanced equation for the overall reaction. In a multistep mechanism, one step is often much slower than the...

bond dissociation energy and activation energy

bond-dissociation-energy-and-activation-energy

How Bond Strength Shapes Reaction Speed

Bond strength and activation energy help explain why organic reactions happen. Bond energy is the energy needed to break a bond homolytically, which means each atom takes one of the shared electrons. When a bond value is given for one specific bond, it is called bond dissociation energy. When it is given for a bond type across many compounds, it is called average bond energy. Bond dissociation energy usually follows a clear pattern. A single bond is weaker than a double bond, and a double bond...

energy diagrams, transition states, and intermediates

energy-diagrams-transition-states-and-intermediates

Reaction Coordinate Diagrams in Chemical Reactions

Reaction coordinate diagrams show how energy changes during a chemical reaction. These free-energy graphs use the horizontal axis to show reaction progress. Points near the reactants look like the reactants, while points near the products look like the products. The peaks on the diagram represent stable structures with measurable lifetimes. Other points on the curve are unstable and cannot be isolated. The high-energy, unstable peak is called the transition state, or activated complex. At the...

predicting reaction outcomes

Reaction rate and reaction pathway are key ideas in chemical kinetics. Thermodynamics, by contrast, focuses on the state of a system. It describes the properties, behavior, and components of reactants and products. It does not describe the path of the process or the speed of the reaction. Kinetics gives information on the atomic or molecular level, while thermodynamics focuses on the energetics of the reactants and products. Thermodynamics can show what may happen in a reaction, but it does...

key terms and concepts

Learn how kinetics, thermodynamics, and collision theory explain reaction speed, transition states, and why higher temperature can increase reaction rate.

How Temperature Changes Reaction Rate | JoVE K12

organic chemistry

JoVE Core Chimie Organique explique les concepts de base de la stéréochimie, des réactions et des mécanismes à l'aide de leçons vidéo animées concises et faciles à comprendre. De plus, les vidéos de scientifiques à l'action présentent l'application de ces concepts grâce à des expériences de recherche classiques et originales réalisées dans des laboratoires modernes.

HS-PS1-5

HS-PS1-6

Tennessee Academic Standards

Matter and Its Interactions

CHEM1.PS1.4

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

CHEM1.PS2.4

Virginia  Standards of Learning

HIgh School

CH.3

CH.3.f

Minnesota Academic Standards in Science

9-12

3.1.1 9C.3.1.1.1

Next Generation Science Standards

Physical Science

HS-PS1-2

HS-PS1-7

Florida Department of Education

SC.912.P.12

SC.912.P.12.12

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

C-PS1-4

C-PS1-5

C-PS1-7

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 ...

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 ...

the-periodic-table-and-organismal-elements

The Periodic Table And Organismal Elements

Atomic Structure

The Greek philosopher Democritus proposed that everything on Earth is made up of tiny particles called atomos, Greek for &#34;indivisible,&#34; from which ...

Electron Configurations

Electron configurations and orbital diagrams can be determined by applying the Aufbau principle (each added electron occupies the subshell of lowest ...

Electronic Structure of Atoms


An atom comprises protons and neutrons, which are contained inside the dense, central&#160;core called the nucleus, with electrons present around the ...

electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

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 ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

Coulomb's Law

Experiments with electric charges have shown that if two objects each have an electric charge, they exert an electric force on each other. The magnitude ...

Electric Charges

From lightning during thunderstorms to electronic devices, the phenomenon of electromagnetism is all around us. The electromagnetic force is one of the ...

sources-and-properties-of-electric-charge

Sources and Properties of Electric Charge

All objects we see around us consist of atoms, which combine to form molecules. The lightest element in the universe is hydrogen, and a hydrogen atom ...

Types of Forces

In most situations, forces can be grouped into two categories: contact forces and field forces.&#160; Contact forces occur as a result of direct physical ...

Electric Fields

Source: Yong P. Chen, PhD, Department of Physics &#38; Astronomy, College of Science, Purdue University, West Lafayette, IN
An electric field is generated ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

Van der Waals Interactions

Atoms and molecules interact with each other through intermolecular forces. These electrostatic forces arise from attractive or repulsive interactions ...

Chemical Bonds


Atoms participate in a chemical bond formation&#160;to acquire a completed valence-shell electron configuration similar to that of the noble gas nearest ...

Electron Behavior

Electrons are negatively charged subatomic particles attracted to and orbit around the positively-charged nucleus of an atom. They reside in spaces ...

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 ...

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 ...

Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level and the composition of the nucleus of atoms.  Clarification Statement: Chemistry: Examples of properties that could be predicted from patterns could include reactivity of metals, types of bonds formed, numbers of bonds formed, atomic radius, atomic mass, or reactions with oxygen. Emphasis is on main group elements and qualitative understanding of the relative trends of ionization energy and electronegativity.

HS-PS1-1

Properties of Transition Metals

Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3&#8211;12 are ...

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 ...

Chemical Reactions

A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created or ...

Chemical Equations

Chemical equations represent the identities and relative quantities of substances involved in a chemical reaction. The substances undergoing reaction are ...

Introduction to Chemical Reactions

All chemical reactions begin with a reactant, the general term for one or more substances entering the reaction. Sodium and chloride ions, for example, ...

Temperature Dependence on Reaction Rate

The Collision Theory
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. ...

stoichiometry-product-yield-and-limiting-reactants

Stoichiometry, Product Yield, and Limiting Reactants

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

	Preparation of 25% v/v Ethylenediamine in Deionized WaterExpand
	Here, we show the laboratory ...

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 ...

Dynamic Equilibrium

A reversible chemical reaction represents a chemical process that proceeds in both forward (left to right) and reverse (right to left) directions. When ...

Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.  Clarification Statement: Chemistry: Examples of chemical reactions could include the reaction of sodium and chlorine, carbon and oxygen, or carbon and hydrogen. Reaction classification aids in the prediction of products (e.g. synthesis, decomposition, single displacement, double displacement, and acid-base).

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

comparison-between-electrical-and-gravitational-forces

Comparison Between Electrical And Gravitational Forces

There are four fundamental forces in nature: the gravitational force, the electromagnetic force, the strong nuclear force, and the weak nuclear force. To ...

intermolecular-forces-and-physical-properties

Intermolecular Forces and Physical Properties



Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

electric-field-of-two-equal-and-opposite-charges

Electric Field of Two Equal and Opposite Charges

Atoms generally contain the same number of positively and negatively charged particles, protons, and electrons. Hence, they are electrically neutral. ...

Electric Field

Consider two point charges, each exerting Coulomb force on the other. It is possible to describe the Coulomb interaction via an intermediate step by ...

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 ...

Electric Dipoles and Dipole Moment

Consider two charges of equal magnitude but opposite signs. If they cannot be separated by an external electric field, the system is called a permanent ...

Plan and conduct an investigation to gather evidence to compare the structure of substances at the macroscale to infer the strength of electrical forces between particles.  Clarification Statement: Emphasis is on understanding the strengths of forces between particles, not on naming specific intermolecular forces (such as dipole-dipole). Examples of particles could include ions, atoms, molecules, and network solids (such as graphite). Examples of macro-properties of substances could include the melting point and boiling point, vapor pressure, and surface tension.

HS-PS1-3

Bond Dissociation Energy and Activation Energy

Bond energy is the energy required to break a bond homolytically. These values are usually expressed in units of kcal/mol or kJ/mol and are referred to as ...

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, ...

Coupled Reactions

Cellular processes such as building and breaking down complex molecules occur through stepwise chemical reactions. Some of these chemical reactions are ...

Energy Diagrams, Transition States, and Intermediates

Free-energy diagrams, or reaction coordinate diagrams, are graphs showing the energy changes that occur during a chemical reaction. The reaction ...

What is Metabolism?

Overview

Metabolism represents all of the chemical activity in a cell, including reactions that build molecules (anabolism) and those that break ...

types-of-chemical-reactions-anabolic-and-catabolic

Types of Chemical Reactions: Anabolic and Catabolic

The first law of thermodynamics holds that energy can neither be created nor destroyed&#8212;it can only change form. An organism&#39;s essential function ...

Non-equilibrium in the Cell

An important concept in studying metabolism and energy is that of chemical equilibrium. Most chemical reactions are reversible. They can proceed in both ...

Activation Energy

Activation energy is the minimum amount of energy necessary for a chemical reaction to move forward. The higher the activation energy, the slower the rate ...

Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.  Clarification Statement: Emphasis is on the idea that a chemical reaction is a system that affects the energy change.  Examples of models could include molecular-level drawings and diagrams of reactions, graphs showing the relative energies of reactants and products, and representations showing energy is conserved.

How Temperature Changes Reaction Rate

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