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

Porque é que o metal de sódio reage com água para fazer gás de hidrogênio, mas o cloreto de sódio simplesmente se dissolve, isto pode ser explicado através do estudo da relação entre a química e a energia, chamada de termoquímica'Todas as formas de matéria estão associadas com energia, que pode ser medida como calor ou trabalho. Os dois principais tipos de energia são a energia potencial e a energia cinética. A energia potencial descreve as forças posicionais que atuam sobre o objeto.Uma rocha no topo de uma colina tem mais energia potencial do que uma rocha na base porque a rocha na parte superior está mais longe do centro de massa da Terra. A energia cinética é a energia de um objeto em movimento. Se uma pedra é empurrada para fora da colina, perde energia potencial mas ganha energia cinética à medida que se move.Isto também se aplica aos átomos ou moléculas que compõem um objeto. Um objeto em repouso ainda tem energia cinética porque os seus átomos componentes podem vibrar. Esta forma de energia cinética é chamada de energia térmica.Um objeto tem uma energia cinética mais elevada e, consequentemente uma energia térmica mais elevada quando os átomos se movem mais vigorosamente. Este objeto é visto como quente. As moléculas também têm energia potencial chamada de energia química, que está associada à posição relativa dos elétrons e núcleos.Durante uma reação, a energia química é convertida noutras formas de energia, como a luz, ou a energia que é libertada, por exemplo sob a forma de calor. A quantidade de energia transformada depende da estrutura molecular dos reagentes. Num candeeiro a gás, o acetileno torna-se dióxido de carbono e água, libertando uma grande quantidade de energia como luz.Por outro lado, a adição de hidróxido de sódio ao ácido clorídrico, liberta uma menor quantidade de energia, como calor. Para estudar as mudanças energéticas, ajuda dividir o universo num sistema'que contém o processo que está a ser observado, e o ambiente'que é tudo o resto. O sistema pode ser aberto, o que significa que tanto a energia como a massa podem ser trocadas entre o sistema e o meio envolvente.O sistema pode ser fechado, onde apenas a energia é trocada, ou o sistema pode ser isolado, onde nem a massa nem a energia são trocadas.

princípios básicos de energia

As reações químicas, tais como as que ocorrem quando se acende um fósforo, envolvem alterações na energia, bem como na matéria.

As alterações químicas e as alterações energéticas que as acompanham são partes importantes da vida quotidiana. Os macronutrientes nos alimentos sofrem reações metabólicas que fornecem a energia para manter os corpos a funcionar. Uma variedade de combustíveis (gasolina, gás natural, carvão) é queimada para produzir energia para transporte, aquecimento, e produção de eletricidade. As reações químicas industriais usam quantidades enormes de energia para produzir matérias-primas (como ferro e alumínio). A energia é então utilizada para transformar essas matérias-primas em produtos úteis, tais como carros, arranha-céus, e pontes.

Mais de 90% da energia usada pelos humanos vem originalmente do sol. Todos os dias, o sol fornece à terra quase 10.000 vezes a quantidade de energia necessária para satisfazer todas as necessidades energéticas do mundo nesse dia. O desafio continua a ser encontrar formas de converter e armazenar a energia solar recebida, para que possa ser utilizada em reações ou processos químicos que sejam simultaneamente convenientes e não poluentes. Plantas e muitas bactérias capturam energia solar através da fotossíntese. Os humanos libertam a energia armazenada em plantas ao queimar madeira, carvão, petróleo, ou outros produtos vegetais tais como o etanol. Eles também usam esta energia para alimentar os seus corpos comendo alimentos que vêm diretamente de plantas.

<h4>Termoquímica</h4>

As idéias básicas de uma área importante da ciência relativa à quantidade de calor absorvido ou libertado durante alterações químicas e físicas — são chamadas de termoquímica. Os conceitos são amplamente utilizados em quase todos os domínios científicos e técnicos. Os cientistas alimentares usam a termoquímica para determinar o índice de energia dos alimentos. Os biólogos estudam a energia dos organismos vivos, como a combustão metabólica do açúcar em dióxido de carbono e água. As indústrias de petróleo, gás, e transportes, os fornecedores de energia renovável, e muitos outros, procuram encontrar melhores métodos para produzir energia para necessidades comerciais e pessoais. Os engenheiros esforçam-se por melhorar a eficiência energética, encontrar melhores formas de aquecer e arrefecer casas, refrigerar alimentos e bebidas, e satisfazer as necessidades de energia e refrigeração de computadores e eletrónica, entre outras aplicações. Compreender os princípios termoquímicos é essencial para químicos, físicos, biólogos, geólogos, todos os tipos de engenheiros, e praticamente qualquer pessoa que estuda ou faz qualquer tipo de ciência.

<h4>Energia</h4>

A energia pode ser definida como a capacidade de fornecer calor ou fazer trabalho. Um tipo de trabalho (w) é o processo de fazer com que a matéria se mova contra uma força oposta. Por exemplo, ao encher um pneu de bicicleta — a matéria é movida (o ar na bomba) contra a força oposta do ar que já se encontra no pneu.

Como a matéria, a energia vem em tipos diferentes. Um esquema classifica a energia em dois tipos: energia potencial, a energia que um objeto tem por causa da sua posição, composição, ou condição relativa, e energia cinética, a energia que um objeto possui por causa do seu movimento.

A água no topo de uma cascata ou barragem tem energia potencial por causa da sua posição; quando flui para baixo através de geradores, tem energia cinética que pode ser usada como trabalho e para produzir eletricidade em uma central hidrelétrica. Uma bateria tem energia potencial porque os produtos químicos no seu interior podem produzir eletricidade que pode realizar trabalho.

Este texto é adaptado de <a href="https://openstax.org/books/chemistry-2e/pages/5-1-energy-basics">OpenStax Chemistry 2e, Section 5.1: Energy Basics</a>.

Princípios Básicos de Energia

Reações químicas, como as que ocorrem quando você acende um fósforo, envolvem mudanças na energia e na matéria.

Alterações químicas e suas acompanhantes...

Education

JoVE Core

Química

Thermochemistry

Termoquímica

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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 - Química dá vida a conceitos gerais de química usando vídeos de animação fáceis de entender. Além disso, nos vídeos Cientistas em ação, demonstramos experimentos de pesquisa clássicos e originais realizados atualmente por cientistas em laboratórios em todo o mundo.

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

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Classifying Matter by Composition

Matter: Pure Substances and Mixtures
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physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

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Physical Properties of Matter

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Molecular Comparison of Gases, Liquids, and Solids

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Intermolecular vs Intramolecular Forces

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Intermolecular Forces

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

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Surface Tension, Capillary Action, and Viscosity

Surface Tension
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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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