Name: combustion heat and hydrocarbon stability
Uploaded: 2025-05-22T09:05:33.000Z
Duration: 2 min 12 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry and Physics

IPC.8

IPC.8.A

Enthalpy and Heat of Reaction

약어H인 엔탈피는 내부 에너지, 약식 E 또는 U,압력 및 부피의 산물과 같습니다.
엔탈피, ΔH의변화는 제품의 엔탈피와 반응제의 차이로 표현된다. 일정한 온도와 압력에서 ΔH는 시스템과 주변 간에 교환되는 열 에너지의 양 또는 반응의 열과 동일합니다.
ΔH가 양성일 때 반응은 열을 흡수하고 동위입니다. ΔH가 음수인 경우 반응은 열을 방출하고 외형적입니다.
연소는 방출의 형태로 에너지를 방출하기 위해 대기 산소와 같은 산화제의 존재에서 물질이 타오르는 퇴외 과정의 예입니다.
방출된 열은 연소의 어금니 열로 정량화되며, 이는 물질의 두더지 한 개를 태우는 데 방출되는 열 에너지의 양입니다.
탄화수소가 연소되면 연료의 탄소와 수소가 분자 산소와 결합되어 물과 이산화탄소를 생산하며 에너지 방출이 발생합니다.
탄화수소에 대한 연소의 열의 가치는 더 많은 탄소가 연소에 사용할 수 있고 더 많은 채권이 변화를 겪고 있기 때문에 체인의 탄소 원자의 수와 함께 증가합니다.
예를 들어, 단일 탄소 화합물인 메탄의 연소는 4개의 탄소 원자를 보유한 부탄보다 더 적은 열 에너지를 생성합니다.
연소의 열은 동일한 분자 공식하지만 다른 구조를 가진 탄화수소의 상대적 안정성을 결정하는 중요한 방법입니다.
옥탄, 2-메틸헥탄, 2,2-디메틸헥산의 연소의 열을 고려하십시오.
이 화합물은 탄소 원자의 동일한 수를 가지고 있지만, 메틸 그룹은 각 분자의 다른 위치에 부착된다.
옥탄은 연소의 가장 큰 열을 가지고있다. 분기가 증가함에 따라 ΔH가 감소하여 분기가 탄화수소의 안정성을 증가시킨다는 것을 시사합니다.

엔탈피와 반응열

일반적으로 연소라고 알려진 연소는 물질이 산화제(대부분의 경우 산소 분자)와 반응하여 열, 빛 또는 소리의 형태로 에너지를 방출하는 반응입니다. 연소열은 연소엔탈피라고도 알려져 있습니다. 물질 1몰이 일정한 압력에서 완전 연소될 때 방출되는 에너지를 몰 연소열이라고 합니다. 연소 반응은 발열 반응입니다. 즉, 에너지를 방출하고 ΔH 부호 규칙은 음수입니다.

1772년 프랑스의 화학자 앙투안 라부아지에는 연소된 황의 생성물이 반응물의 초기 질량보다 더 무겁다는 것을 발견했습니다. 그는 황이 공기와 결합하여 무게가 증가한다고 가정했습니다. 나중에 조지츠 츠리스틀리가 1774년 공기의 구성 요소인 "산소"를 발견하자 라부아지에는 황이 공기 중의 산소와 결합하여 질량이 증가한다고 믿게 되었습니다. 그는 연소는 산소와 결합하는 것을 의미한다고 결론지었습니다. 즉, 유황이 연소되었습니다.

연소 반응의 예로는 천연 가스 및 석탄과 같은 탄화수소 연료의 연소가 있습니다. 탄화수소가 포함된 연소 반응의 경우 방출되는 에너지의 양은 연소되는 연료의 유형에 따라 다릅니다.

예를 들어, 천연가스인 메탄(CH4) 의 연소는 다음과 같은 반응으로 나타납니다.

<img alt="Eq2" src="/files/ftp_upload/11692/11692_Reaction%20Equation-Combustion%20of%20Methane.svg" style="text-align: center; height: 18px;">

다음 반응식에 따르면 부탄(C4H10)보다 열에너지가 적게 발생합니다.

<img alt="Eq1" src="/files/ftp_upload/11692/11692_Reaction%20Equation-Combustion%20of%20Butane.svg" style="text-align: center; height: 17.5px;">

따라서 탄화수소를 연소하는 데 필요한 산소 분자의 수와 형성된 각 생성물의 분자 수는 탄화수소 구성에 따라 달라집니다.

연소열은 동일한 분자식을 갖는 분지형 탄화수소의 상대적 안정성을 좌우합니다. 구조의 차이는 탄화수소 사슬을 따라 서로 다른 위치에 부착된 메틸 그룹으로 인해 발생합니다. 방출되는 열 에너지의 양은 분기가 증가함에 따라 감소하며, 여기서 고도로 분기된 2,2-디메틸헥산은 옥탄에 비해 낮은 에너지를 생성합니다. 따라서 가지가 없는 옥탄은 가지가 있는 옥탄보다 덜 안정적입니다.

일반적으로 연소로 알려진 연소는 물질이 대부분의 경우 분자 산소인 산화제와 반응하여 ...

Education

교육

JoVE Core

Organic Chemistry

유기 화학

Unit 1

제1단원

Thermodynamics and Chemical Kinetics

열역학과 화학 반응 속도론

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 found that burned sulfur products weighed more than the original sulfur. He suggested that sulfur combined with air. After Joseph Priestley identified oxygen in 1774, Lavoisier concluded that sulfur combined with oxygen in air. He therefore defined combustion as combining with oxygen.

Hydrocarbon fuels such as natural gas and coal also undergo combustion. The amount of energy released can change with the fuel. For example, methane (CH4) releases less heat energy than butane (C4H10). The number of oxygen molecules needed and the number of product molecules formed depend on the hydrocarbon’s composition.

The heat of combustion also helps explain the stability of branched hydrocarbons with the same molecular formula. Branching comes from methyl groups attached at different positions along the hydrocarbon chain. As branching increases, the amount of heat energy released decreases. For example, highly branched 2,2-dimethylhexane releases less energy than octane. This means unbranched octane is less stable than its branched form.

Combustion Heat and Hydrocarbon Stability

combustion-heat-and-hydrocarbon-stability

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 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

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...

key terms and concepts

Learn how combustion releases energy, why heat of combustion is negative, and how hydrocarbon structure affects stability and heat release.

Combustion Heat and Hydrocarbon Stability | JoVE K12

organic chemistry

JoVE Core Organic Chemistry explains basic concepts of stereochemistry, reactions, and mechanisms using concise and easy-to-understand animated video lessons. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Alabama Course of Study Science

9-12

Environmental Science

Earth and Human Activity

9-12.EVS.4.6

9-12.EVS.4.11.b

Chemical Reactions

A balanced chemical equation provides the information of chemical formulas of the reactants and products involved in the chemical change. A ...

Combustion, commonly known as burning, is a reaction in which a substance reacts with an oxidizing agent, which in most cases is molecular oxygen, to ...

Oxidation-Reduction Reactions

Oxidation&ndash;Reduction Reactions

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Oxidation Numbers

In redox reactions, the transfer of electrons occurs between reacting species. Electron transfer is described by a hypothetical number called the ...

Acids, Bases and Neutralization Reactions

An acid-base reaction is one in which a hydrogen ion, H+, is transferred from one chemical species to another. Such reactions are of central importance to ...

combustion-energy-a-measure-of-stability-in-alkanes-and-cycloalkanes

Combustion Energy: A Measure of Stability in Alkanes and Cycloalkanes

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Balancing Redox Equations

Electrochemistry is the science involved in the interconversion of electrical and chemical reactions. Such reactions are called reduction-oxidation, or ...

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Chemical Equilibria: Redefining Equilibrium Constant

Recall that the solubility of a sparingly soluble salt increases with the addition of an inert salt in a phenomenon known as the salt effect.
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Factors Affecting Activity Coefficient

The activity coefficient of an ion depends on the ionic strength of the solution.
As indicated by the Debye&#8211;H&#252;ckel theory, when the ionic ...

Thermochemical Equations

For a chemical reaction (the system) carried out at constant pressure &ndash; with the only work done caused by expansion or contraction &ndash; the ...

Develop and use models to balance chemical equations and support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

IPC.8.B

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

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Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

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Biological Effects of Radiation

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Research and communicate the uses, advantages, and disadvantages of nuclear reactions in current technologies.

IPC.8.C

What is Climate?

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Global Climate Change

Throughout its ~4.5 billion year history, the Earth has experienced periods of warming and cooling. However, the current drastic increase in global ...

Climate Change

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Sustainable Development

As the human population continues to grow and use resources, we must be mindful of our planet&rsquo;s natural limits. Sustainable development provides a ...

Construct and communicate an evidence-based explanation of the environmental impact of the end-products of chemical reactions such as those that may result in degradation of water, soil, air quality, and global climate change.

IPC.8.D

Science concepts. The student knows that changes in matter affect everyday life. The student is expected to:

Combustion Heat and Hydrocarbon Stability

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