元素の保存に基づいて化学反応式を係数調整すること
導入済み| English | 意味 |
|---|---|
| reactant/rɪˈæktənt/ | 反応物 |
| coefficient/ˌkəʊɪˈfɪʃənt/ | 係数 |
What would explain this observation?
- Magnesium burns in oxygen to form magnesium oxide. Writing Mg + O₂ → MgO names the substances correctly, but it does not yet account for every atom.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- A word equation gives reactant 反应物 and product names: magnesium + oxygen → magnesium oxide. A symbol equation uses correct formulae. Balance it as 2Mg + O₂ → 2MgO: both sides now contain two magnesium atoms and two oxygen atoms. Atoms are rearranged in a reaction, not created or destroyed. The numbers before formulae are coefficients 系数 describing relative particle numbers.
- coefficient: A number before a chemical formula multiplying the entire formula; reactant: A substance used up or changed in a chemical reaction.
MgとOの原子数を保存する方程式はどれか？
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2Mg + O2 -> 2MgO は、左右ともに 2 個のマグネシウム原子と 2 個の酸素原子を持つ。Mg + O2 -> MgO は酸素原子を無駄にし、MgO2 は誤った式である - マグネシウム酸化物は常に MgO である。
各専門用語を正確な意味と対応させよ。
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関連する物理量やプロセスを区別するために定義を使用せよ。
Choose evidence that can test it
- Begin with the actual substance formulae and make an element-count table. Change coefficients to equalize the count for each element. Never change MgO to MgO₂ just to balance oxygen: that would identify a different substance. For hydrogen burning, 2H₂ + O₂ → 2H₂O conserves four hydrogen atoms and two oxygen atoms. State symbols, when required, distinguish solid (s), liquid (l), gas (g) and aqueous solution (aq).
- Use coloured counters to represent atoms and construct the reactants from the stated formulae. Rearrange the same counters into product particles, then record the smallest whole-number coefficients. Confirm each element separately. Models count atoms and bonds schematically; they do not show the detailed collision mechanism or actual particle size.
この場合、調査やモデルをより妥当にする2つの習慣は何か。
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条件や仮定を明記することで他者が正確に再現でき、根拠となる証拠を記録することで結論を検証できます。相反する結果を隠すと、誤った結論を疑う証拠を失いますし、単一の測定でより広い主張を成立させることはできません。
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: aluminium reacts with oxygen to form Al₂O₃. Six oxygen atoms are supplied by 3O₂ and appear in 2Al₂O₃. Those product units contain four aluminium atoms, so 4Al + 3O₂ → 2Al₂O₃. Final count: Al 4→4 and O 6→6. The coefficients 4:3:2 are a particle ratio, not a ratio of masses in grams.
In 4Al + 3O₂ → 2Al₂O₃, how many oxygen atoms are represented on either side? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
4Al + 3O₂ → 2Al₂O₃ において、両側の酸素原子の数はそれぞれいくつですか？
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結果は 6 個の原子である。既知：4Al + 3O2 -> 2Al2O3 。左辺：3 × 2 = 6 個の酸素原子。右辺：2 × 3 = 6 個の酸素原子。方程式は釣り合っている。なぜなら、各元素の原子数が左右で一致しているからである。
Check the conclusion and its limits
- A balanced equation cannot be obtained by changing a product formula or deleting an element. A coefficient of one is normally omitted. Equal atom counts do not mean equal numbers of molecules, and a balanced equation alone does not establish that a reaction occurs under all conditions.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Balancing an equation allows the product formula to change. This claim is false: Formulae are fixed by the compounds' chemistry; balancing works only by changing coefficients - the number of particles. Changing a formula such as MgO to MgO2 invents a different substance.
Balance equations by conserving each element: Begin with the actual substance formulae and make an element-count table. Change coefficients to equalize the count for each element. Never change MgO to MgO₂ just to balance oxygen: that would identify a different substance. For hydrogen burning, 2H₂ + O₂ → 2H₂O conserves four hydrogen atoms and two oxygen atoms. State symbols, when required, distinguish solid (s), liquid (l), gas (g) and aqueous solution (aq).
方程式の係数の調整（整合化）により、生成物の化学式は変化できない。
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化学式は化合物の化学的性質によって固定されており、係数（粒子の数）を変えることでのみ方程式を釣り合わせることができる。MgO を MgO2 に変えると、別の物質が作られてしまう。
化学式の前に付く数で、全体の化学式に掛け算されるもの: 技術用語を記せ。
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係数とは、化学式の前に付いて全体の化学式に掛け算される数を指す。