Name: distinguishing physical and chemical changes
Uploaded: 2020-09-03T13:38:25.000Z
Duration: 2 min 57 s
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K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Chemistry

Energy

PS.Chm.7.1

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

Les caractéristiques qui nous aident à distinguer un type de matière d'une autre sont appelées propriétés. La matière présente deux types de propriétés:physiques et chimique. Les propriétés physiques de la matière peuvent être mesurées et observées sans changer la composition ou l'identité de la matière.L'Odeur, le goût, la couleur, l'apparence, la dureté, la densité, les points de fusion et d'ébullition, et la conductivité électrique, sont tous des exemples des propriétés physiques. Certaines de ces propriétés physiques peuvent être observés sans changer l'état physique de la matière. Donc, quand on dit que l'hélium est plus léger que l'air, nous parlons d'une propriété physique.De même, l'odeur de l'essence est également une propriété physique. Les autres propriétés physiques ne peuvent être observé lorsque la matière subit des changements physiques. Par exemple, l'or pur à l'état solide est composé d'atomes d'or très serrés.Mais quand il est fondu à haute température, il change son état de solide à liquide. Cependant, ce liquide est toujours composé d'atomes d'or, donc c'est un changement physique. De même, lorsque l'eau liquide gèle en glace solide, la composition chimique de l'eau et de la glace reste le même.Ainsi, les changements physiques ne modifient que l'état de la matière ou des conditions physiques, sans changer la composition chimique. Concassage, broyage, tranchage, mélange, magnétisation, ou la démagnétisation sont d'autres moyens courants à changer la condition physique de la matière. Les propriétés chimiques de la matière, d'autre part, sont des caractéristiques qui ne peuvent être mesurées et observées lorsque la substance a un changement de composition chimique.La corrosivité, l'inflammabilité, la toxicité, l'acidité, ou la réactivité chimique sont tous des exemples de propriétés chimiques de la matière. Afin d'identifier une propriété chimique, nous recherchons un changement chimique. Les changements chimiques impliquent des réactions chimiques et sont souvent observés à travers un changement de couleur ou d'odeur.Par exemple, lorsqu'un penny en cuivre est exposé à l'air et à l'eau il y a un changement chimique. Le cuivre subit une série de réactions chimiques, dont l'une est présentée ici, pour former une couche de patine bleu-vert sur un pièce de monnaie par ailleurs naturellement brune. Ainsi, les changements chimiques produisent des formes de matière entièrement nouvelles qui diffèrent de la matière présente avant le changement.Par exemple, l'inflammabilité de l'essence est une propriété chimique mise en évidence par les changements chimiques dans la composition de l'essence quand elle brûle, en tournant l'essence en substances entièrement nouvelles principalement le dioxyde de carbone et l'eau.

propriétés physiques et chimiques de la matière

Les caractéristiques qui nous permettent de distinguer une substance d'une autre sont appelées propriétés. 
 
 <h4>Propriétés physiques de la matière </h4>
 
 Une propriété physique est une caractéristique de la matière qui n'est pas associée à un changement dans sa composition chimique. Les exemples les plus connus de propriétés physiques incluent la densité, la couleur, la dureté, les points de fusion et d'ébullition et la conductivité électrique. Nous pouvons observer certaines propriétés physiques, telles que la densité et la couleur, sans changer l'état physique de la matière observée. D'autres propriétés physiques, comme la température de fusion du fer ou la température de congélation de l'eau, ne peuvent être observées que lorsque la matière subit une transformation physique.  
 
 Une transformation physique est un changement de l'état ou des propriétés de la matière qui n'est accompagné d'aucun changement de sa composition chimique (l'identité des substances contenues dans la matière). Nous observons une transformation physique lorsque, par exemple, la cire fond, le sucre se dissout dans le café et la vapeur se condense en eau liquide. D'autres exemples de transformations physiques incluent la magnétisation et la démagnétisation des métaux (comme c'est le cas avec les badges antivol courants) et le broyage des solides en poudres. Dans chacun de ces exemples, il y a un changement de l'état physique, de la forme ou des propriétés de la substance, mais aucun changement dans sa composition chimique. 
 
 <h4>Propriétés chimiques de la matière </h4>
 
 Le changement d'un type de matière en un autre (ou l'incapacité de changer) est une propriété chimique. Parmi les propriétés chimiques figurent l'inflammabilité, la toxicité, l'acidité, la réactivité (de nombreux types) et la chaleur de combustion. Le fer, par exemple, se combine à l'oxygène en présence d'eau pour former de la rouille ; le chrome ne s'oxyde pas. La nitroglycérine est très dangereuse car elle explose facilement ; le néon ne présente presque aucun danger parce qu'il est très peu réactif.  
 
 Pour identifier une propriété chimique, nous recherchons une transformation chimique. Une transformation chimique produit toujours un ou plusieurs types de matière qui diffèrent de la matière présente avant la transformation. La formation de rouille est une transformation chimique parce que la rouille est un autre genre de matière que le fer, l'oxygène et l'eau présents avant la formation de rouille. L'explosion de la nitroglycérine est une transformation chimique parce que les gaz produits sont des matières très différentes de la substance d'origine. D'autres exemples de transformations chimiques incluent les réactions qui sont réalisées dans un laboratoire (comme le cuivre réagissant avec l'acide nitrique), toutes les formes de combustion (brûlage), le mûrissement des fruits et les aliments qui sont cuits, digérés ou qui pourrissent.  
 
 Ce texte est adapté de <a href="https://openstax.org/books/chemistry-2e/pages/1-3-physical-and-chemical-properties">Openstax, Chimie 2e, Section 1.3 : Propriétés physiques et chimiques.</a>

Propriétés physiques et chimiques de la matière

Les caractéristiques qui nous permettent de distinguer une substance d’une autre sont appelées propriétés.

Propriétés physiques de la matière

Une propriété physique est ...

Education

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Introduction: Matter and Measurement

Introduction : La matière et la mesure

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

distinguishing physical and chemical changes

Matter can be identified by its properties, which are the features that help us tell one substance from another. These properties fall into two main groups: physical properties and chemical properties. Understanding the difference helps explain how matter changes.

A physical property is a feature of matter that is not linked to a change in chemical composition. Examples include density, color, hardness, melting point, boiling point, and electrical conductivity. Some physical properties can be observed without changing the state of the matter, such as density and color. Others appear only during a physical change, like the melting temperature of iron or the freezing temperature of water.

A physical change alters the state or form of matter without changing what the substance is made of. Wax melting, sugar dissolving in coffee, and steam condensing into liquid water are all physical changes. Magnetizing and demagnetizing metals, such as in anti-theft security tags, and grinding solids into powders are also physical changes. In each case, the material looks or behaves differently, but its chemical composition stays the same.

Chemical properties describe whether matter can change into a different type of matter, or resist that change. Common chemical properties include flammability, toxicity, acidity, reactivity, and heat of combustion. Iron reacts with oxygen and water to form rust, while chromium does not oxidize. Nitroglycerin explodes easily, but neon is very unreactive.

To identify a chemical property, we look for a chemical change. A chemical change produces one or more new kinds of matter that are different from the starting material. Rust formation is a chemical change because rust is not the same as iron, oxygen, or water. Nitroglycerin exploding is also a chemical change because the gases produced are different from the original substance. Other chemical changes include copper reacting with nitric acid, burning, fruit ripening, and food being cooked, digested, or rotting.

Distinguishing Physical and Chemical Changes

distinguishing-physical-and-chemical-changes

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physical and chemical properties of matter

Matter can be identified by its properties, which are the features that help us tell one substance from another. These properties fall into two main groups: physical properties and chemical properties. Understanding the difference helps explain how matter changes. A physical property is a feature of matter that is not linked to a change in chemical composition. Examples include density, color, hardness, melting point, boiling point, and electrical conductivity. Some physical properties can be...

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Distinguishing Physical and Chemical Changes

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