Pratique du Shadowing: Chemical and Physical Changes – Quiz Edition - Apprendre l'anglais à l'oral avec la vidéo
Création de la leçon...
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Music Take notes as you watch this video and take the short quiz at the end.
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Every day we observe a myriad of changes around us.
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A car can get crushed into a compact cube of metal at a junkyard.
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A fire can burn logs in a fireplace, turning them into ash and smoke.
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Bread bakes to a crispy golden brown loaf.
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And metal rusts when exposed to moisture and air.
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Each transformation, whether big or small, is a testament to the ever-changing nature of matter around us.
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In science, we dissect these transformations and categorize them into two primary types, physical and chemical changes.
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In a physical change, the form or state of matter changes, but the molecular structure remains the same.
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No new matter is made.
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For instance, consider the process of ice melting.
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As the temperature rises, the ice transforms from a solid state into liquid water.
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Even though the state and appearance change, the water molecules are still H2O, maintaining their original molecular structure.
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This transformation illustrates a physical change, where the state alters without changing the substance itself.
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Let's take a look at some examples of physical changes in action.
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Consider a sheet of paper.
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With a pair of scissors, the paper is cut into smaller pieces.
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The shape and size of the paper change, but chemically, it is still paper.
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Each piece retains the same properties as the original sheet.
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Another example of a physical change.
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Now think about a piece of modelling clay.
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In your hands, it can be moulded, stretched and shaped into various forms, a ball, a cube, or even a miniature animal.
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Though the shape transforms, the composition of the modelling clay remains consistent.
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The changes are physical, not chemical.
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Consider the act of making a salad.
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Crisp lettuce is torn, vegetables are sliced, and ingredients are mixed together in a bowl.
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The various components change in shape and texture as they are prepared and combined, but their chemical composition remains the same.
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The lettuce is still lettuce.
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The tomato remains a tomato.
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The salad, brimming with an assortment of colours and textures, exemplifies a physical change.
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Lastly, visualize a glass falling to the floor and smashing into pieces.
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The integrity of the glass is compromised.
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It shatters.
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However, each fragment, sharp and irregular, is still glass.
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The chemical composition hasn't altered.
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Thus, we are once again witnessing a physical change.
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Chemical changes involve a transformation at the molecular level, where the original substance turns into a different substance with new properties.
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It is characterised by the formation of new chemical substances and often involves energy changes,
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evident through the release or absorption of heat, light or sound.
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Various indicators like change in colour, production of gas or the formation of precipitate can denote a chemical change.
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When iron is exposed to oxygen and moisture, it undergoes a chemical change resulting in in the formation of a new substance, rust, iron oxide.
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This is evident by the change in color from metallic gray to brownish red, and the alteration in the material's properties like strength and appearance.
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The chemical composition of iron changes, proving that it's not just a physical alteration, but a chemical change.
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In a fireplace, wood burns and transforms into ash, heat and gases.
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This is accompanied by the release of light and heat, indicating a chemical change.
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The original wooden logs, primarily composed of cellulose and other organic compounds,
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are converted into new substances like carbon dioxide, water vapour and ash.
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The visible flames and the change in material composition underscore this transformation as a chemical change.
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When the raw ingredients like flour, eggs and sugar are baked, they transform into a cake.
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It's not just a state change.
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New compounds are formed during the baking process, changing the taste, texture and colour.
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The cake's aroma and the solidified fluffy texture are evidence of a chemical change where new substances with distinct properties are created.
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Plants convert carbon dioxide and water into glucose and oxygen using sunlight.
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This transformation is marked by the emergence of new substances, glucose and oxygen, which were not originally present.
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The absorption of light energy and the creation of food and oxygen signify a chemical change.
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When baking soda and vinegar are mixed, there is an immediate fizzing and bubbling reaction.
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This is due to the formation of carbon dioxide gas, a new substance.
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The chemical reaction occurs as acetic acid in the vinegar reacts with the bicarbonate in the baking soda to form carbonic acid,
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which quickly decomposes into water and carbon dioxide gas.
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The evolution of gas, change in temperature, and the formation of new substances like carbon dioxide,
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water and a type of salt are clear indicators of a chemical change.
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Do you think you can identify changes to matter as either physical changes or chemical changes?
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Let's put your knowledge to the test.
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Thank you.
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I'm
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going to
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go ahead and put it in the middle of the room.
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I'm
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going to go to the next video.
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Let's go.
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I'm
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going to
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go to the next video.
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I'm
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going to
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go ahead and put it in the middle of the room.
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Thanks for learning, and I'll see you next time.
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Don't forget to subscribe!
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Vocabulaire et conseils d’expression pour cette leçon
Cette leçon d’expression orale de niveau B2 s’appuie sur la vidéo « Chemical and Physical Changes – Quiz Edition ». Les mots qui reviennent le plus souvent : chemical, substance, physical, transformation, dioxide. Cette vidéo contient 78 phrases et 879 mots à répéter en shadowing. La partie parlée dure 10:30. Le locuteur parle lentement, environ 84 mots par minute, ce qui laisse le temps d’imiter chaque son. Seuls 73 % des mots font partie des 3 000 mots les plus courants en anglais, le vocabulaire est donc exigeant.
Vocabulaire clé de cette vidéo
Les 15 mots les plus avancés de la vidéo, avec leur prononciation et leur sens :
| Mot | Prononciation | Sens |
|---|---|---|
| dioxide nom | /daɪˈɑksaɪd/ | dioxyde |
| bake verbe | /beɪk/ | cuire |
| texture nom | /ˈtɛkst͡ʃə(ɹ)/ | texture |
| transform verbe | /tɹænsˈfɔɹm/ | transformer |
| lettuce nom | /ˈlɛt.ɪs/ | laitue |
| molecular adjectif | /məˈlɛk.jə.ləɹ/ | moléculaire |
| alteration nom | /ɔl.tɚˈeɪ.ʃən/ | altération, altérer |
| fireplace nom | /ˈfaɪɹpleɪs/ | âtre, foyer |
| vinegar nom | /ˈvɪnəɡɚ/ | vinaigre |
| absorption nom | /æbˈsɔɹp.ʃn̩/ | absorption |
| rust nom | /ɹʌst/ | rouille |
| ingredient nom | /ɪnˈɡɹiːdi.ənt/ | ingrédient |
| glucose nom | /ˈɡluː.kəʊz/ | glucose |
| cube nom | /kjub/ | cube |
| tomato nom | /təˈmeɪ.toʊ/ | tomate |
Les verbes à particule que vous entendrez
| Mot | Prononciation | Sens |
|---|---|---|
| go ahead verbe | /ˌɡoʊ əˈhɛd/ | vas-y, allez-y |
Prononciation à surveiller
Le locuteur utilise 7 contractions et formes réduites, comme I'm, don't, hasn't. Prononcez-les sous leur forme courte, telles que vous les entendez.
- Les sons « sh » et « zh »: alteration /ɔl.tɚˈeɪ.ʃən/, absorption /æbˈsɔɹp.ʃn̩/, brownish /ˈbɹaʊnɪʃ/, shatter /ˈʃætɚ/, visualize /ˈvɪʒuəˌlaɪz/
- Mots longs — placez bien l’accent: molecular /məˈlɛk.jə.ləɹ/, alteration /ɔl.tɚˈeɪ.ʃən/, ingredient /ɪnˈɡɹiːdi.ənt/, indicator /ˈɪn.dɪˌkeɪ.tə(ɹ)/, bicarbonate /baɪˈkɑɹ.bə.neɪt/
Les sons difficiles pour les francophones :
- /tʃ/ et /dʒ/ — à ne pas adoucir en « ch » et « j »: texture /ˈtɛkst͡ʃə(ɹ)/, moisture /ˈmɔɪs.t͡ʃɚ/, junkyard /ˈd͡ʒʌŋkˌjɑɹd/, miniature /ˈmɪn.(i)ə.tʃəɹ/, emergence /ɪˈmɝ.d͡ʒ(ə)ns/
- /r/ anglais — langue recourbée, sans frotter la gorge: texture /ˈtɛkst͡ʃə(ɹ)/, transform /tɹænsˈfɔɹm/, molecular /məˈlɛk.jə.ləɹ/, fireplace /ˈfaɪɹpleɪs/, absorption /æbˈsɔɹp.ʃn̩/
Comment s’entraîner avec cette vidéo
- Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
- Répétez phrase par phrase à vitesse normale, en reprenant chacune jusqu’à ce que votre rythme corresponde à celui du locuteur.
- Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme dioxide, bake, texture.
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.