跟读练习: Lesson 7: Valency and Chemical Formulae - 通过视频学习英语口语
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11 句
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1
A chemical formula shows which elements make up a substance, and the number of atoms of each element.
2
We use the symbols of chemical elements and subscripts to write chemical formulae for simple substances and compounds.
3
A subscript shows the number of atoms of an element in a chemical formula.
4
Valency describes the combining ability of an atom or a group of atoms.
5
To write a chemical formula, we use the valencies of the elements and apply the valency rule.
6
The valency rule helps us write the correct chemical formula of a compound.
7
In sulfur dioxide, the valency of sulfur is 4, and the valency of oxygen is 2.
8
So the formula is SO2.
9
The molecular mass is the sum of the atomic masses of all the atoms in a molecule.
10
The percentage by mass of an element is calculated by dividing its total mass by the molecular mass of the compound, then multiplying by 100%.
11
We can determine a chemical formula from the percentage composition of its elements and its molecular mass.
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本课的词汇与口语要点
这节口语课以视频“Lesson 7: Valency and Chemical Formulae”为素材。 视频中反复出现的词有：element, chemical, formula, valency, atom。 这段视频共有 11 个句子、170 个单词可供跟读。 讲话部分时长为 1:00。 说话人语速自然，每分钟约 170 个词，接近日常对话。 只有 66% 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 15 个值得学习的单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| element 名词 | /ˈɛləmənt/ | 要素 |
| formula 名词 | /ˈfɔː.mjʊ.lə/ | 公式 |
| atom 名词 | /ˈætəm/ | 原子 |
| compound 名词 | /ˈkɑmpaʊnd/ | 化合物 |
| percentage 名词 | /pə(ɹ)ˈsɛntɪd͡ʒ/ | 百分率, 百分比 |
| substance 名词 | /ˈsʌbstəns/ | 物質 /物质 |
| composition 名词 | /ˌkɑm.pəˈzɪʃ.ən/ | 成分 |
| symbol 名词 | /ˈsɪmbəl/ | 符號 /符号 |
| oxygen 名词 | /ˈɑksɪd͡ʒən/ | 氧 |
| combine 动词 | /kəmˈbaɪn/ | 結合 /结合, 組合 /组合 |
| divide 动词 | /dɪˈvaɪd/ | 分, 分裂 |
| atomic 形容词 | /əˈtɑː.mɪk/ | 原子 |
| calculate 动词 | /ˈkælkjʊleɪt/ | 計算 /计算, 算 |
| dioxide 名词 | /daɪˈɑksaɪd/ | 二氧化物 |
| molecule 名词 | /ˈmɑ.lɪ.kjul/ | 分子 |
视频中出现的短语动词
| 单词 | 发音 | 释义 |
|---|---|---|
| make up 动词 | /ˌmeɪk ˈʌp/ | 組成 /组成 |
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | is calculated |
需要注意的发音
- 长单词——注意重音位置: molecular /məˈlɛk.jə.ləɹ/, composition /ˌkɑm.pəˈzɪʃ.ən/
中文母语者容易读错的音：
- /v/ — 不要读成 /w/，上齿轻触下唇: divide /dɪˈvaɪd/, valency /ˈveɪ.lən.si/
- 词尾辅音 — 要读清楚，后面不要加元音: element /ˈɛləmənt/, compound /ˈkɑmpaʊnd/, percentage /pə(ɹ)ˈsɛntɪd͡ʒ/, substance /ˈsʌbstəns/, divide /dɪˈvaɪd/
- /æ/ — 嘴张大，不要读成 /e/: atom /ˈætəm/, calculate /ˈkælkjʊleɪt/
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。
- 先用 0.75 倍速逐句跟读，熟练之后再回到正常速度。
- 录下自己的声音并与原声对比，特别注意 element, formula, atom 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。