跟读练习: Chemical and Physical Changes – Quiz Edition - 通过视频学习英语口语
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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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本课的词汇与口语要点
这节 B2 级别的口语课以视频“Chemical and Physical Changes – Quiz Edition”为素材。 视频中反复出现的词有：chemical, substance, physical, transformation, dioxide。 这段视频共有 78 个句子、879 个单词可供跟读。 讲话部分时长为 10:30。 说话人语速较慢，每分钟约 84 个词，你有足够的时间模仿每一个音。 只有 73% 的单词属于英语最常用的 3,000 词，词汇难度较高。
视频中的重点词汇
视频中最难的 15 个单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| dioxide 名词 | /daɪˈɑksaɪd/ | 二氧化物 |
| bake 动词 | /beɪk/ | 烤, 烘 |
| texture 名词 | /ˈtɛkst͡ʃə(ɹ)/ | 質地 /质地, 材質 /材质 |
| transform 动词 | /tɹænsˈfɔɹm/ | 變換 /变换, 變形 /变形 |
| lettuce 名词 | /ˈlɛt.ɪs/ | 萵苣 /莴苣 |
| alteration 名词 | /ɔl.tɚˈeɪ.ʃən/ | 異動 /异动 |
| fireplace 名词 | /ˈfaɪɹpleɪs/ | 壁爐 /壁炉, 暖爐 /暖炉 |
| vinegar 名词 | /ˈvɪnəɡɚ/ | 醋 |
| absorption 名词 | /æbˈsɔɹp.ʃn̩/ | 吸收 |
| rust 名词 | /ɹʌst/ | 鏽 /锈, 鐵鏽 /铁锈 |
| ingredient 名词 | /ɪnˈɡɹiːdi.ənt/ | 成份, 材料 |
| cube 名词 | /kjub/ | 立方體 /立方体 |
| tomato 名词 | /təˈmeɪ.toʊ/ | 西紅柿 /西红柿, 番茄 |
| moisture 名词 | /ˈmɔɪs.t͡ʃɚ/ | 濕氣 /湿气 |
| indicator 名词 | /ˈɪn.dɪˌkeɪ.tə(ɹ)/ | 指示符 |
视频中出现的短语动词
| 单词 | 发音 | 释义 |
|---|---|---|
| go ahead 动词 | /ˌɡoʊ əˈhɛd/ | 請便 /请便 |
需要注意的发音
说话人用了 7 次缩略和弱读形式，例如 I'm, don't, hasn't。请按听到的简短形式来说。
- “sh” 和 “zh” 音: alteration /ɔl.tɚˈeɪ.ʃən/, absorption /æbˈsɔɹp.ʃn̩/, brownish /ˈbɹaʊnɪʃ/, shatter /ˈʃætɚ/, visualize /ˈvɪʒuəˌlaɪz/
- 长单词——注意重音位置: molecular /məˈlɛk.jə.ləɹ/, alteration /ɔl.tɚˈeɪ.ʃən/, ingredient /ɪnˈɡɹiːdi.ənt/, indicator /ˈɪn.dɪˌkeɪ.tə(ɹ)/, bicarbonate /baɪˈkɑɹ.bə.neɪt/
中文母语者容易读错的音：
- /v/ — 不要读成 /w/，上齿轻触下唇: vinegar /ˈvɪnəɡɚ/, evident /ˈɛv.ə.dənt/, convert /kənˈvɝt/, visualize /ˈvɪʒuəˌlaɪz/, vegetable /ˈvɛd͡ʒ.tə.bəl/
- 词尾辅音 — 要读清楚，后面不要加元音: dioxide /daɪˈɑksaɪd/, bake /beɪk/, lettuce /ˈlɛt.ɪs/, fireplace /ˈfaɪɹpleɪs/, rust /ɹʌst/
- /r/ 和 /l/ 的区别: molecular /məˈlɛk.jə.ləɹ/, fireplace /ˈfaɪɹpleɪs/, alter /ˈɔl.təɹ/, irregular /ɪˈɹɛɡ.jə.lɚ/, illustrate /ˈɪl.əˌstɹeɪt/
如何用这段视频练习
- 先完整听一遍视频，不要开口，记下不认识的单词。
- 用正常速度逐句跟读，每句重复到你的节奏与说话人一致为止。
- 录下自己的声音并与原声对比，特别注意 dioxide, bake, texture 这类单词。
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。