Name: how energy changes in chemical reactions
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 27 s
Channel: JoVE

K12 Standards

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

NC K-12 Science Standard Course of Study

9-12

Chemistry

Energy

PS.Chm.7.2

Energy Basics

金属ナトリウムは水と反応して 水素ガスを作るのに 塩化ナトリウムはただ 溶けるだけなのはなぜでしょうか これは 熱化学」と呼ばれる 化学とエネルギーの関係を 研究することで説明できます 物質のすべての形態は エネルギーと関係しており 熱や仕事として 測定することができます エネルギーには位置エネルギーと 運動エネルギーがあります 位置エネルギーは 物体に作用する 位置的な力を表します 丘の頂上にある岩は 下の岩よりも高い 位置エネルギーを 持っています これは頂上の岩は地球の 質量中心からより離れているためです 運動エネルギーとは動いている 物体のエネルギーのことです 岩が丘から突き落とされた場合 岩は位置エネルギーを失いますが 落ちていくにつれて 運動エネルギーを得ます これは 物体を構成する 原子や分子にも 当てはまります 静止している物体は その構成原子が 振動することができるので 運動エネルギーを持っています この運動エネルギーは 熱エネルギーと呼ばれています 物体は 原子がより激しく動くと 運動エネルギーが高くなり その結果 熱エネルギーが高くなります この物体は熱いと感じます また 分子には 化学エネルギーと呼ばれる 位置エネルギーがあり これは電子と原子核の 相対的な位置に関連しています 反応の間 化学エネルギーは 光などの他の形の エネルギーに変換されたり 熱などの形でエネルギーが 放出されたりします 変換されるエネルギーの量は 反応物の分子構造に依存します ガスランプでは アセチレンが 燃焼して二酸化炭素と水になり 大きなエネルギーを 光として放出します 一方 塩酸に 水酸化ナトリウムを加えると 熱として放出されるエネルギーは 小さくなります エネルギーの変化を 研究するためには 宇宙を観察されているプロセスを 含む「システム」と それ以外の すべてのものを含む「周囲」に 分けるのが有効です システムは エネルギーと質量の 両方がシステムと周囲の間で 交換できるオープンな 状態にすることができます システムは閉じていてエネルギー だけが交換されている場合や 質量もエネルギーも交換されない 孤立した状態になっている 場合もあります

エネルギーの基礎

化学反応は、たとえばマッチの火を灯すときに起こるもので、エネルギーの変化だけでなく、物質の変化にも関係します。 
 
 化学変化とそれに伴うエネルギーの変化は、日常生活の中で重要な役割を果たしています。 食べ物に含まれる多量の栄養素は、代謝反応を経て、体の機能を維持するためのエネルギーとなります。 さまざまな燃料（ガソリン、天然ガス、石炭）を燃やして、輸送、暖房、発電のためのエネルギーを作り出します。 工業的な化学反応では、膨大なエネルギーを使って原料（鉄やアルミニウムなど）を生産します。 その後、エネルギーはそれらの原材料を自動車、高層ビル、橋などの有用な製品に製造するために使用されます。 
 
 人間が使用するエネルギーの 90% 以上は、もともと太陽からのものです。 日々、太陽はその日の世界のエネルギー需要を満たすために必要なエネルギー量の約 10,000 倍を地球に提供しています。 太陽エネルギーを変換して保存する方法を模索し、便利で非汚染の反応や化学プロセスで使用できるようにすることは、今でも課題です。 植物や多くのバクテリアは光合成によって太陽エネルギーを取り込んでいます。 人間は、植物に蓄えられたエネルギーを、木材、石炭、石油、あるいはエタノールなどの植物製品を燃やすことで放出します。 また、植物から直接得られた食物を食べることで、このエネルギーを体に供給しています。 
 
 <h4>熱化学 </h4>
 
 化学的・物理的変化に伴って吸収または放出される熱の量に関係する重要な科学分野の基本的な考え方を、熱化学といいます。 この概念は、ほとんどすべての科学技術分野で広く使用されています。 食品科学者は、熱化学を使用して食品のエネルギー量を測定します。 生物学者たちは、糖を燃焼させて二酸化炭素や水に変える代謝など、生物のエネルギーを研究しています。 石油、ガス、輸送業界、再生可能エネルギー事業者、その他の多くの企業は、商用および個人の需要に適したエネルギーを生成するためのより良い方法を見つけるよう努力しています。 エンジニアは、エネルギー効率の向上、家庭の暖房と冷房のためのより良い方法の発見、食品と飲料の冷蔵、コンピュータや電子機器などのエネルギーと冷却の需要への対応に努めています。 化学者、物理学者、生物学者、地質学者、あらゆるタイプのエンジニアにとって、熱化学の原理を理解することは不可欠であり、あらゆる種類の科学を研究または実行するすべての人にとって重要です。 
 
 <h4>エネルギー </h4>
 
 エネルギーは、熱を供給する能力または仕事を行う能力として定義できます。 仕事 (w) の種類の一つに、反対の力に対抗して物質を動かすというプロセスがあります。 たとえば、自転車用タイヤに空気を充填する場合、タイヤ内の空気の反対側の力に対して物質（ポンプ内の空気）が移動します。 
 
 物質と同様に、エネルギーにも様々な種類があります。ある枠組みでは、エネルギーを 2 種類に分類します。 一つは、物体の相対的な位置や組成、状態が持つエネルギーである「位置エネルギー」、もう一つは、物体が動くことによって持つエネルギーである「運動エネルギー」です。 
 
 滝やダムの上部にある水には、その位置から潜在的なエネルギーがあります。水が発電機を通して下に流れると、水力発電所での仕事や電力の生成に使用できる運動エネルギーが生じます。 電池には潜在的なエネルギーがあります。これは、電池内の化学物質が仕事可能な電力を生成できるためです。 
 
 このテキストは<a href="https://openstax.org/books/chemistry-2e/pages/5-1-energy-basics">、 OpenStax Chemistry 2e 、 Section 5.1: Energy Basics から引用</a>しています。

マッチに火をつけたときに起こるような化学反応には、物質だけでなくエネルギーの変化も伴います。

化学変化とそれに伴う...

Education

JoVE Core

化学

Thermochemistry

熱化学

KEY TERMS AND CONCEPTS

主要用語と概念

how energy changes in chemical reactions

Chemical reactions change matter and energy at the same time. A match lighting is a simple example. These energy changes are part of everyday life and appear in food, fuels, and industry.

Food provides energy through metabolic reactions. The macronutrients in food break down and help keep the body functioning. Fuels such as gasoline, natural gas, and coal are burned to produce energy for transportation, heating, and electricity generation.

Industrial chemical reactions also use large amounts of energy. That energy helps make raw materials like iron and aluminum. More energy is then needed to turn those materials into products such as cars, skyscrapers, and bridges.

Most energy used by humans comes from the sun. Every day, the sun sends Earth almost 10,000 times more energy than the world needs for that day. The challenge is to capture and store solar energy so it can drive chemical processes that are useful, convenient, and nonpolluting.

Plants and many bacteria capture solar energy through photosynthesis. Humans release stored energy by burning wood, coal, petroleum, or plant products such as ethanol. They also use this energy directly when they eat food that comes from plants.

Thermochemistry is the study of heat absorbed or released during chemical and physical changes. It is used to measure the energy content of foods and to study the energetics of living organisms, such as the breakdown of sugar into carbon dioxide and water. It also supports work in the oil, gas, transportation, and renewable energy industries, as well as in engineering.

Energy is the capacity to supply heat or do work. Work means causing matter to move against an opposing force, such as when air is pushed into a bicycle tire. Energy can be described as potential energy, which depends on position, composition, or condition, and kinetic energy, which depends on motion.

A waterfall or dam stores potential energy because of its position. When the water flows downward through generators, it has kinetic energy that can do work and produce electricity in a hydroelectric plant. A battery also stores potential energy because the chemicals inside it can produce electricity when needed.

How Energy Changes in Chemical Reactions

energy basics

Chemical reactions change matter and energy at the same time. A match lighting is a simple example. These energy changes are part of everyday life and appear in food, fuels, and industry. Food provides energy through metabolic reactions. The macronutrients in food break down and help keep the body functioning. Fuels such as gasoline, natural gas, and coal are burned to produce energy for transportation, heating, and electricity generation. Industrial chemical reactions also use large amounts...

first law of thermodynamics

Energy Conservation and Internal Energy

Energy conservation describes how energy changes form during chemical and physical changes. Energy can be converted from one form into another, but the energy present before a change still exists in some form after the change is complete. This is the law of conservation of energy. It says energy can neither be created nor destroyed. The law of conservation of matter also applies during chemical change. In most chemical reactions, the total amount of matter does not show a detectable change.

internal energy

Internal Energy, Heat, and Work

Internal energy is the total of all possible kinds of energy in a substance. It is often written as U, and sometimes as E. For a system that changes energy, the important value is the change in internal energy, or ΔU. ΔU is the difference between the final internal energy and the initial internal energy. The exact values of U final and U initial are usually not known, but the first law of thermodynamics only requires ΔU. A positive ΔU means the system gained energy from the surroundings. A...

quantifying heat

Heat Transfer and Specific Heat

Heat transfer and specific heat explain how thermal energy moves and how materials respond to it. Thermal energy is the kinetic energy linked to the random motion of atoms and molecules. Temperature is a measure of how hot or cold a substance is, and it depends on how much thermal energy those particles have. When atoms and molecules move or vibrate faster, their average kinetic energy is higher. That means the object has more thermal energy and a higher temperature. When they move more...

quantifying work

Pressure-Volume Work in Chemistry

Pressure-volume work shows how gas volume changes can transfer energy in chemistry. As a system changes, its internal energy may change too. Energy can move between the system and the surroundings through heat and work. Internal energy, heat, and work are related by an energy equation. Heat depends on a measured temperature change. Work depends on a measured change in volume called pressure-volume work. Work can be defined as a force acting through a distance. Pressure-volume work, also...

enthalpy

Enthalpy and Heat at Constant Pressure

Enthalpy describes heat changes in chemical and physical processes. Chemists use the symbol H for enthalpy. It is defined as a system’s internal energy, E, plus the product of pressure, P, and volume, V. Enthalpy is a state function, so only changes in enthalpy can be measured, not the enthalpy of a substance by itself. For many reactions, the pressure stays constant. Under those conditions, the enthalpy change, ΔH, can be written in a way that includes pressure-volume work. The term PΔV...

thermochemical equations

Heat Changes in Chemical Equations

Heat changes in chemical equations show how much energy a reaction releases or absorbs. At constant pressure, the enthalpy of reaction, or ΔHrxn, is equal to the heat exchanged with the surroundings, qp. Because this value depends on how much reactant takes part, it is an extensive property. The size and sign of ΔHrxn also depend on the reaction itself and on the physical states of the substances involved. An exothermic reaction has a negative ΔHrxn value, while an endothermic reaction has a...

constant pressure calorimetry

Coffee Cup Calorimeter Heat Changes

Coffee cup calorimetry measures heat changes in reactions and physical changes using an insulated calorimeter. The calorimeter is calibrated and designed to limit heat exchange with the outside environment. That makes it possible to measure the heat taken in or released by a substance more accurately, including the energy content of foods. In calorimetry, the system is the substance or substances undergoing change. The surroundings are everything else inside the calorimeter, including the...

constant volume calorimetry

Bomb Calorimeter Heat Measurement

Bomb calorimetry measures the heat released by reactions that produce a lot of energy, especially combustion reactions. A coffee cup calorimeter works at constant pressure and is useful for reactions in solution. A bomb calorimeter works at constant volume and is used for reactions that make large amounts of heat and gaseous products. The word "bomb" refers to the strong, explosive force some reactions can have. In a bomb calorimeter, the volume does not change, so 94V = 0. That means the...

hess's law

Calculating Reaction Heat with Hess's Law

Calculating reaction heat with Hess's law lets chemists find enthalpy changes without measuring every reaction directly. Some reactions are hard or impossible to test in the lab. Even when a reaction can be measured, it is often easier to calculate the heat change from other known enthalpy values. Hess's law says that if a process can be written as the sum of several stepwise processes, the enthalpy change for the total process equals the sum of the enthalpy changes for the steps. This works...

standard enthalpy of formation

Using Standard Enthalpy Values in Chemistry

Enthalpy changes are often listed for reactions that start and end under the same conditions. Chemists use a standard state as a reference set of conditions for comparing properties. In IUPAC terms, the standard state means 1 bar of pressure and 1 M solutions, but it does not set a temperature. Many thermochemical tables still use 1 atm as the reference pressure. Because the difference between 1 bar and 1 atm is very small, enthalpy change usually stays almost the same. A superscripted o in...

enthalpies of reaction

Calculating reaction heat with Hess's law uses standard enthalpies of formation to find the enthalpy change of a reaction. When the formation values for the reactants and products are known, the overall reaction can be broken into simpler stepwise reactions. This approach helps show how the heat change for the full reaction is built from smaller parts. First, the reactants are thought of as being decomposed into their component elements. The enthalpy change for this step is proportional to the...

key terms and concepts

Explore how chemical reactions change energy in food, fuels, photosynthesis, thermochemistry, and batteries. Built for high school science learners.

How Energy Changes in Chemical Reactions | JoVE K12

chemistry

JoVE Core 化学は、簡潔で理解しやすいアニメーションビデオレッスンを使用して、一般的な化学の概念を生き生きとしたものにします。さらに、活動する科学者のビデオでは、現在世界中の実験室で行われている古典的そして独創的な研究・実験をお見せします。

Matter and its Interactions

PS.Chm.4.1

Earth and Environmental Science

Earth's Systems

ESS.EES.3.2

Physical Science

PS.PSc.7.1

Pennsylvania State Academic Standards

3.2.9-12.O

3.2.9-12.P

3.2.9-12.Q

3.2.9-12.R

Louisiana Student Standards for Science

High School

Matter And Its Interactions

HS-PS1-4

HS-PS1-5

HS-PS3-2

HS-PS3-3

HS-PS3-4

Physics

HS-PS3-1

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Classification of matter

Energy And Waves

Thermal energy

Interactions Of Matter

Chemical reactions

Physical Geology

Earth's Resources

Energy resources

Tennessee Academic Standards

CHEM1.PS3.3

Virginia  Standards of Learning

HIgh School

CH.7

CH.7.a

Earth Science

ES.6

ES.6.d

Minnesota Academic Standards in Science

3.1.1 9C.2.2.1.1

Texas Essential Knowledge and Skills

CHEM.13

CHEM.13.A

CHEM.13.C

Alabama Course of Study Science

9-12.PS.1.1

Earth and Space Science

Earth's Place in the Universe

9-12.ESS.1.1

9-12.ESS.1.1.a

Next Generation Science Standards

Life Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

HS-LS1-7

Florida Department of Education

SC.912.E.6

SC.912.E.6.6

SC.912.P.10

SC.912.P.10.1

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

South Carolina College and Career Ready Science Standards

Matter and Its Interactions

C-PS1-4

C-PS1-5

C-PS3-4

P-PS3-1

P-PS3-2

P-PS3-3

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Energy

HS-PS3-1.

Georgia Standards of Excellence

SPS7.

Types of Energy

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 ...

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 ...

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

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

Intermolecular Forces

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

comparing-intermolecular-forces-melting-point-boiling-point

Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

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

surface-tension-capillary-action-and-viscosity

Surface Tension, Capillary Action, and Viscosity

Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded ...

States of Matter and Phase Changes

The internal energy of a substance&#8212;the total kinetic energy of all its molecules and the potential energy of their associated forces&#8212;depends ...

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 ...

Vapor Pressure

When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally ...

Clausius-Clapeyron Equation

The equilibrium between a liquid and its vapor depends on the temperature of the system; a rise in temperature causes a corresponding rise in the vapor ...

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 ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Phase Diagrams

A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. ...

Use models to explain how changes in energy affect the arrangement and movement of the particles in solids, liquids, and gases, as well as the relative strengths of their intermolecular forces.

PS.Chm.7.1

Chemical reactions, such as those that occur when you light a match, involve changes in energy as well as matter.

Chemical changes and their accompanying ...

First Law of Thermodynamics

Energy Conservation

Energy can be converted from one form into another, but all of the energy present before a change occurs always exists in some form ...

Internal Energy

The total of all possible kinds of energy present in a substance is called the internal energy (U), sometimes symbolized as E. Suppose a system with ...

Quantifying Heat

Thermal Energy&#160;

Microscopically, thermal energy is the kinetic energy associated with the random motion of atoms and molecules. Temperature is a ...

Quantifying Work

As a system undergoes a change, its internal energy can change, and energy can be transferred from the system to the surroundings, or from the ...

Enthalpy

Chemists ordinarily use a property known as enthalpy (H) to describe the thermodynamics of chemical and physical processes. Enthalpy is defined as the sum ...

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 ...

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a ...

Constant Volume Calorimetry

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant ...

Use mathematics and computational thinking to execute simple calorimetric calculations based on the Law of Conservation of Energy.

Understand the relationship among pressure, temperature, volume, and phase.

How Energy Changes in Chemical Reactions

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