Prática de Shadowing: Chemical and Physical Changes – Quiz Edition - Aprenda a falar inglês com vídeo
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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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Vocabulário e dicas de fala para esta lição
Esta aula de conversação de nível B2 usa o vídeo “Chemical and Physical Changes – Quiz Edition”. As palavras que mais se repetem: chemical, substance, physical, transformation, dioxide. Este vídeo tem 78 frases e 879 palavras para praticar shadowing. A fala dura 10:30. O falante fala devagar, cerca de 84 palavras por minuto, o que dá tempo para imitar cada som. Apenas 73% das palavras estão entre as 3.000 mais comuns do inglês, por isso o vocabulário é exigente.
Vocabulário principal deste vídeo
As 15 palavras mais avançadas do vídeo, com pronúncia e significado:
| Palavra | Pronúncia | Significado |
|---|---|---|
| dioxide substantivo | /daɪˈɑksaɪd/ | bióxido |
| bake verbo | /beɪk/ | assar |
| transform verbo | /tɹænsˈfɔɹm/ | transformar |
| lettuce substantivo | /ˈlɛt.ɪs/ | alface |
| molecular adjetivo | /məˈlɛk.jə.ləɹ/ | molecular |
| alteration substantivo | /ɔl.tɚˈeɪ.ʃən/ | alteração |
| fireplace substantivo | /ˈfaɪɹpleɪs/ | lareira |
| vinegar substantivo | /ˈvɪnəɡɚ/ | vinagre |
| absorption substantivo | /æbˈsɔɹp.ʃn̩/ | absorção |
| rust substantivo | /ɹʌst/ | ferrugem |
| ingredient substantivo | /ɪnˈɡɹiːdi.ənt/ | ingrediente |
| glucose substantivo | /ˈɡluː.kəʊz/ | glicose, glucose |
| cube substantivo | /kjub/ | cubo |
| tomato substantivo | /təˈmeɪ.toʊ/ | tomate |
| moisture substantivo | /ˈmɔɪs.t͡ʃɚ/ | umidade, humidade |
Phrasal verbs que você vai ouvir
| Palavra | Pronúncia | Significado |
|---|---|---|
| go ahead verbo | /ˌɡoʊ əˈhɛd/ | vai em frente |
Pronúncia para ficar de olho
O falante usa 7 contrações e formas reduzidas, como I'm, don't, hasn't. Diga-as na forma curta, do jeito que você ouve.
- Os sons de “sh” e “zh”: alteration /ɔl.tɚˈeɪ.ʃən/, absorption /æbˈsɔɹp.ʃn̩/, brownish /ˈbɹaʊnɪʃ/, shatter /ˈʃætɚ/, visualize /ˈvɪʒuəˌlaɪz/
- Palavras longas — acerte a sílaba tônica: molecular /məˈlɛk.jə.ləɹ/, alteration /ɔl.tɚˈeɪ.ʃən/, ingredient /ɪnˈɡɹiːdi.ənt/, indicator /ˈɪn.dɪˌkeɪ.tə(ɹ)/, bicarbonate /baɪˈkɑɹ.bə.neɪt/
Sons difíceis para falantes de português:
- Consoante final — sem acrescentar um “i” depois: dioxide /daɪˈɑksaɪd/, bake /beɪk/, rust /ɹʌst/, ingredient /ɪnˈɡɹiːdi.ənt/, cube /kjub/
- /l/ final — a língua toca o céu da boca, não vira “u”: molecule /ˈmɑ.lɪ.kjul/, vegetable /ˈvɛd͡ʒ.tə.bəl/, bubble /ˈbʌbəl/
- s + consoante no início — sem um “i” antes: slice /slaɪs/, smash /smæʃ/
Como praticar com este vídeo
- Ouça o vídeo inteiro uma vez sem falar e anote as palavras que você não conhece.
- Faça shadowing frase por frase na velocidade normal, repetindo cada uma até o seu ritmo ficar igual ao do falante.
- Grave a sua voz e compare com o original, prestando atenção a palavras como dioxide, bake, transform.
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.