Name: matter: elements, compounds, and mixtures
Uploaded: 2020-09-03T13:38:25.000Z
Duration: 3 min 35 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Energy

PS.Chm.7.1

Classifying Matter by Composition

A matéria é feita de átomos as mais pequenas unidades básicas da matéria e moléculas que são formadas pela combinação de dois ou mais átomos juntos. Com base na sua composição, a matéria pode ser dividida em dois grupos substâncias puras e misturas. Por definição, diz-se que uma matéria é pura se for constituída por apenas um componente, com uma composição uniforme durante todo o processo.Por exemplo, o hidrogênio. O hidrogênio é composto apenas por átomos de hidrogênio. Da mesma forma, a água é composta por moléculas de água.Estas composições não variam de amostra para amostra. As substâncias puras podem ser divididas em dois tipos elementos e compostos, dependendo se podem ou não serem decompostos. Os elementos são substâncias puras que não podem ser decompostas em substâncias mais simples por meios químicos.Por exemplo, o hidrogênio é um elemento. Os compostos, pelo contrário, são substâncias que podem ser separados nos seus constituintes apenas por meios químicos. Por exemplo, a água, também uma substância pura, podem ser quimicamente decompostas em duas substâncias mais simples hidrogênio e oxigênio o que significa que é um composto.Na Terra, os compostos são mais comuns do que os elementos puros porque a maior parte dos elementos prontamente se combinam com outros elementos. Por exemplo, o giz utilizado para escrever no quadro é feito de cálcio, carbono e oxigênio;o açúcar é feito de carbono, hidrogênio e oxigênio. As misturas, ao contrário das substâncias puras, são constituídas por um ou mais componentes.A sua proporção também pode variar de amostra para amostra. Por exemplo, a limonada é uma mistura de três componentes sumo de limão, açúcar e água E as suas proporções podem ser variadas de forma a tornar a bebida mais ou menos doce. As próprias misturas podem ser divididas em dois tipos-homogêneas e heterogêneas, dependendo do grau de uniformidade da mistura das substâncias que as compõem.Uma mistura homogênea apresenta uma composição uniforme e visualmente parece durante todo o processo. É frequentemente referida como uma solução. Por exemplo, uma colher cheia de sal dissolvido em água dá uma mistura homogênea uma vez que cada gota da mistura tem a mesma composição.Do mesmo modo, a limonada é também uma mistura homogênea. Numa mistura heterogênea, os componentes não estão distribuídos uniformemente e, portanto, a composição varia de um ponto para o outro. Por exemplo, areia misturada com limalhas de ferro aqui, as diferentes partes desta mistura terão provavelmente diferentes quantidades de limalhas de ferro e areia.Independentemente disto, qualquer mistura, seja ela homogênea ou heterogênea, pode ser separada nos seus componentes puros por meios físicos sem alterar as identidades dos componentes. Por exemplo, o sal pode ser recuperado da solução de água, aquecendo a mistura até que seque. Da mesma forma, as limalhas de ferro podem ser separadas da areia utilizando um imã.

classificação da matéria por composição

<h4>Matéria: Substâncias Puras e Misturas </h4>

De acordo com a sua composição, a matéria pode ser classificada em duas grandes categorias: Substâncias puras e misturas. 

Uma substância pura é um tipo de matéria que tem uma composição constante em toda a parte com propriedades uniformes. Por exemplo, qualquer amostra de sacarose tem a mesma composição e as mesmas propriedades físicas, tais como o ponto de fusão, a cor, e a doçura, independentemente da fonte a partir da qual é isolada. 

Uma mistura é composta por dois ou mais tipos de matéria que podem estar presentes em quantidades variáveis e podem ser separadas por alterações físicas, tais como a evaporação. Os componentes em uma mistura retêm as suas identidades distintas. 

<h4>Substâncias Puras: Elementos e Compostos </h4>

As substâncias puras podem ser divididas em duas classes: elementos e compostos. As substâncias puras que não podem ser separadas em substâncias mais simples por alterações químicas são designadas por elementos. Ferro, prata, ouro, alumínio, enxofre, oxigénio, e cobre são elementos.

As substâncias puras que podem ser separadas por alterações químicas são chamadas compostos. Esta separação pode produzir elementos ou outros compostos, ou ambos. O óxido de mercúrio (II), um sólido cristalino laranja, pode ser separado por calor nos elementos mercúrio e oxigénio. Quando aquecido na ausência de ar, o composto sacarose é separado no elemento carbono e no composto água. O cloreto de prata (I) é um sólido branco que pode ser separado nos seus elementos, prata e cloro, por absorção de luz. 

As propriedades dos elementos combinados são diferentes das suas propriedades no estado livre ou não combinado. Por exemplo, o açúcar branco cristalino (sacarose) é um composto resultante da combinação química do elemento carbono, que é um sólido preto em uma das suas formas não combinadas, e dos dois elementos hidrogénio e oxigénio, que são gases incolores quando não combinados. O sódio livre, um elemento que é um sólido macio, brilhante, metálico, e o cloro livre, um elemento que é um gás amarelo-verde, combinam-se para formar cloreto de sódio (sal de mesa), um composto que é um sólido cristalino branco.

<h4>Misturas: Homogéneas e Heterogéneas  </h4>

Uma mistura homogénea, também designada por solução, apresenta uma composição uniforme e parece visualmente igual em toda a parte. Um exemplo de solução é uma bebida desportiva, constituída por água, açúcar, corantes, aromatizantes, e eletrólitos uniformemente misturados. Cada gota de uma bebida desportiva tem o mesmo sabor porque cada gota contém as mesmas quantidades de água, açúcar e outros componentes. Tenha em atenção que a composição de uma bebida desportiva pode variar, podendo ser feita com um pouco mais ou menos de açúcar, aroma, ou outros componentes, e ainda ser uma bebida desportiva. Outros exemplos de misturas homogéneas incluem ar, xarope de ácer, gasolina, e uma solução de sal em água. 

Uma mistura com uma composição que varia de ponto a ponto é chamada uma mistura heterogénea. O molho Italiano é um exemplo de uma mistura heterogénea. A sua composição pode variar porque pode ser preparada com quantidades variadas de óleo, vinagre, e ervas. Não é igual de ponto a ponto por toda a mistura—uma gota pode ser maioritariamente vinagre, enquanto que uma gota diferente pode ser principalmente óleo ou ervas porque o óleo e o vinagre separam-se e as ervas assentam. Outros exemplos de misturas heterogéneas são bolachas com pepitas de chocolate (podemos ver as pepitas de chocolate, nozes, e massa de biscoito separados) e granito (podemos ver o quartzo, mica, feldspato, e mais). 

Qualquer mistura, homogénea ou heterogénea, pode ser separada em componentes puros por meios físicos sem alterar as identidades dos componentes. Embora haja pouco mais de 100 elementos, dezenas de milhões de compostos químicos resultam de diferentes combinações desses elementos. Cada composto tem uma composição específica e possui propriedades químicas e físicas definidas que o distinguem de todos os outros compostos. E, naturalmente, há formas inumeráveis de combinar elementos e compostos para formar diferentes misturas. 

Este texto é adaptado de <a href="https://openstax.org/books/chemistry-2e/pages/1-2-phases-and-classification-of-matter">Openstax, Chemistry 2e, Section 1.2: Phases and Classification of Matter. </a>

Classificação da Matéria por Composição

Matéria: Substâncias e Misturas Puras
De acordo com sua composição, a matéria pode ser classificada em duas grandes categorias - substâncias puras e ...

Education

JoVE Core

Química

Introduction: Matter and Measurement

Introdução: Matéria e Medida

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

matter: elements, compounds, and mixtures

Matter can be grouped by composition into pure substances and mixtures. A pure substance has a constant composition throughout and uniform properties. For example, any sample of sucrose has the same composition and the same physical properties, such as melting point, color, and sweetness, no matter where it is isolated from.

A mixture contains two or more kinds of matter in varying amounts. Its parts can be separated by physical changes, such as evaporation. The components keep their own identities, so the mixture is not a new substance in the same way a compound is.

Pure substances are divided into elements and compounds. Elements cannot be broken down into simpler substances by chemical changes. Iron, silver, gold, aluminum, sulfur, oxygen, and copper are examples of elements.

Compounds are pure substances that can be broken down by chemical changes. This breakdown may produce elements, other compounds, or both. Mercury(II) oxide can be heated to form mercury and oxygen, sucrose can break down into carbon and water when heated without air, and silver(I) chloride can be broken down by light into silver and chlorine.

The properties of combined elements are different from the properties of the elements in their free state. White crystalline sugar comes from carbon, hydrogen, and oxygen, but those elements look very different when uncombined. Free sodium is a soft, shiny metal, and free chlorine is a yellow-green gas, yet together they form sodium chloride, a white crystalline solid.

Mixtures can be homogeneous or heterogeneous. A homogeneous mixture, also called a solution, has a uniform composition and looks the same throughout. Sports drink is one example. It contains water, sugar, coloring, flavoring, and electrolytes mixed evenly, so each drop tastes the same. Its exact composition can still vary and remain a sports drink. Air, maple syrup, gasoline, and salt water are other homogeneous mixtures.

A heterogeneous mixture has a composition that varies from point to point. Italian dressing is one example, since the amounts of oil, vinegar, and herbs can differ and the parts may separate or settle. Chocolate chip cookies and granite are also heterogeneous mixtures because their different parts can be seen.

Any mixture, whether homogeneous or heterogeneous, can be separated into pure components by physical means without changing what the components are. There are just over 100 elements, but they combine in many ways to form tens of millions of compounds. Each compound has a specific composition and its own chemical and physical properties. Elements, compounds, and mixtures can combine in countless ways to make matter.

Matter: Elements, Compounds, and Mixtures

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classifying matter by composition

Matter can be grouped by composition into pure substances and mixtures. A pure substance has a constant composition throughout and uniform properties. For example, any sample of sucrose has the same composition and the same physical properties, such as melting point, color, and sweetness, no matter where it is isolated from. A mixture contains two or more kinds of matter in varying amounts. Its parts can be separated by physical changes, such as evaporation. The components keep their own...

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PS.PSc.1.3

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Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Classification of matter

Physical Geology

Minerals

Crystallinity (crystal structure)

Virginia  Standards of Learning

HIgh School

CH.7

CH.7.a

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ES.4

ES.4.a

PS.3

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Arizona Science Standards

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Earth and Space Science

HS.E1

HS.E1U1.12

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Earth's Place in the Universe

HS-ESS1-2

Texas Essential Knowledge and Skills

CHEM.2

CHEM.2.A

Alabama Course of Study Science

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9-12.PS.3.5

9-12.PS.3.5.a

Next Generation Science Standards

HS-PS1-5

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Matter: Elements, Compounds, and Mixtures

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