Shadowing Practice: Lesson 7: Valency and Chemical Formulae - Learn English Speaking with Video
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11 sentences
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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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Vocabulary and speaking notes for this lesson
This speaking lesson is built on the video “Lesson 7: Valency and Chemical Formulae”. The speaker keeps coming back to these words: element, chemical, formula, valency, atom. This video has 11 sentences and 170 words to shadow. The speech runs for 1:00. The speaker talks at a natural 170 words per minute, close to everyday conversation. Only 66% of the words are among the 3,000 most common in English, so the vocabulary is demanding.
Key vocabulary in this video
15 words from the video worth learning, with pronunciation and meaning:
| Word | Pronunciation | Meaning |
|---|---|---|
| element noun | /ˈɛləmənt/ | One of the simplest or essential parts or principles of which anything consists, or upon which the constitution or fundamental powers of anything are based. |
| formula noun | /ˈfɔː.mjʊ.lə/ | Any mathematical rule expressed symbolically. |
| atom noun | /ˈætəm/ | The smallest possible amount of matter which still retains its identity as a chemical element, now known to consist of a nucleus surrounded by electrons. |
| compound noun | /ˈkɑmpaʊnd/ | Anything made by combining several things. |
| molecular adjective | /məˈlɛk.jə.ləɹ/ | Relating to, or consisting of, or produced by molecules. |
| percentage noun | /pə(ɹ)ˈsɛntɪd͡ʒ/ | The amount, number or rate of something, regarded as part of a total of 100; a part of a whole. |
| substance noun | /ˈsʌbstəns/ | Physical matter; material. |
| composition noun | /ˌkɑm.pəˈzɪʃ.ən/ | The act of putting together; assembly. |
| symbol noun | /ˈsɪmbəl/ | A character or glyph representing an idea, concept or object. |
| oxygen noun | /ˈɑksɪd͡ʒən/ | The chemical element (symbol O) with an atomic number of 8 and relative atomic mass of 15.9994. It is a colorless and odorless gas. Sometimes called elemental… |
| combine verb | /kəmˈbaɪn/ | To bring (two or more things or activities) together; to unite. |
| divide verb | /dɪˈvaɪd/ | To split or separate (something) into two or more parts. |
| atomic adjective | /əˈtɑː.mɪk/ | Of or relating to atoms; composed of atoms; monatomic. |
| calculate verb | /ˈkælkjʊleɪt/ | To determine the value of something or the solution to something by a mathematical process. |
| dioxide noun | /daɪˈɑksaɪd/ | Any oxide containing two oxygen atoms in each molecule. |
Phrasal verbs you will hear
| Word | Pronunciation | Meaning |
|---|---|---|
| make up verb | /ˌmeɪk ˈʌp/ | To constitute, to compose. |
Grammar in this video
The structures the speaker uses most, with the exact words from the video:
| Structure | In the video |
|---|---|
| Passive voice be + past participle — the focus is on what happens, not who does it | is calculated |
Pronunciation to watch
- Long words — get the stress right: molecular /məˈlɛk.jə.ləɹ/, composition /ˌkɑm.pəˈzɪʃ.ən/
How to practise with this video
- Listen to the whole video once without speaking and note the words you do not know.
- Start at 0.75× speed, shadow it sentence by sentence, then go back to normal speed once it feels easy.
- Record yourself and compare with the original, paying attention to words like element, formula, atom.
What is the Shadowing Technique?
Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.