小分子：結合と分子間力を区別する
導入済み| English | 意味 |
|---|---|
| intermolecular force/ˌɪntəməˈlekjʊlə fɔːs/ | 分子間力 |
| small molecule/smɔːl ˈmɒlɪkjuːl/ | 小分子 |
What would explain this observation?
- Water can boil without splitting into hydrogen and oxygen. The change separates molecules while the covalent bonds within each molecule remain.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Small molecular substances usually have relatively low melting and boiling points and are often gases or liquids. Strong covalent bonds hold atoms inside each molecule, but weaker intermolecular forces 分子间作用力 act between molecules. Melting or boiling overcomes these weaker attractions, rather than breaking every covalent bond. Typical neutral molecular substances do not conduct because they have no mobile charged particles.
- intermolecular force: An attraction between separate molecules; small molecule 小分子: A discrete covalently bonded group containing relatively few atoms.
一般的な分子性液体が沸騰する際、主に克服されるものは何か？
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
沸騰は分子同士を分離させ、分子間の弱い引力のみ克服する。各分子内の共有結合は維持されるため、蒸気は依然として同じ物質である。
各専門用語を正確な意味と対応させよ。
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
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
- For comparable molecules, intermolecular forces generally increase with molecular size, so larger molecules tend to have higher melting and boiling points. Molecular shape and other interactions also matter; a size trend is not an exact universal temperature rule. A compound such as hydrogen chloride can form ions on dissolving, so the pure molecular substance and its reacting aqueous solution must be distinguished.
- Use paired molecular drawings that label strong internal bonds and weaker attractions between separate molecules. Identify what is overcome during a specified physical change and what remains intact. Compare supplied boiling-point data for a related series at the same pressure. Do not infer a substance’s identity from boiling point alone without composition and other evidence.
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。
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
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: supplied rounded boiling points for a fictional related series are −10 °C and 30 °C. The increase is 30−(−10)=40 °C. This is consistent with stronger attractions in the larger member if other relevant features are comparable, but it does not show that an internal covalent bond gained forty units of strength.
A supplied related series has boiling points −20 °C and 15 °C. Calculate the increase. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
ある系列の沸点分别是 −20 °C と 15 °C です。その上昇分を計算してください。
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
結果は 35 ℃である。既知: 沸点 -20 および 15 ℃。差 = 15 - (-20) = 35 ℃。負の値を引くことは加算となるため、後続の化合物の方が強い分子間引力を持つことを反映している。
Check the conclusion and its limits
- Low boiling point does not mean weak covalent bonds. Molecules are usually electrically neutral overall, not devoid of protons and electrons. Dissolving a molecular solute does not always create ions, while a chemical reaction with water can change which particles are present.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Boiling water necessarily breaks the O–H covalent bonds in its molecules. This claim is false: Steam is still H2O - the molecules are intact. Boiling overcomes the attractions between molecules; breaking the O-H covalent bonds would decompose water into hydrogen and oxygen, which boiling never does.
Small molecules: distinguish bonds from intermolecular forces: For comparable molecules, intermolecular forces generally increase with molecular size, so larger molecules tend to have higher melting and boiling points. Molecular shape and other interactions also matter; a size trend is not an exact universal temperature rule. A compound such as hydrogen chloride can form ions on dissolving, so the pure molecular substance and its reacting aqueous solution must be distinguished.
沸騰する水は、必ずその分子内のO–H共有結合を切断する。
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
水蒸気もなお H2O であり、分子は保持されている。沸騰は分子間の引力を克服するものであり、O-H 共有結合を切断すれば水は水素と酸素に分解するが、沸騰は決してそのようなことは行わない。
別々の分子間の引力：専門用語を記せ。
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
intermolecular force とは、別々の分子間の引力を意味する。