質量保存則：完全な系を数え上げよ
導入済み| English | 意味 |
|---|---|
| conservation of mass/ˌkɒnsəˈveɪʃn ɒv mæs/ | 質量保存の法則 |
| system boundary/ˈsɪstəm ˈbaʊndəri/ | 系境界 |
What would explain this observation?
- A sealed reaction vessel weighs the same before and after a chemical reaction even when a gas appears. The atoms have been rearranged inside the weighed system.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- The law of conservation of mass 质量守恒 states that atoms are neither made nor lost in a chemical reaction. The total mass of products equals the total mass of reactants when every substance is included. A balanced symbol equation has the same number of atoms of each element on both sides. It does not require the same number of separate molecules on each side.
- conservation of mass: The total mass of all reactants equals the total mass of all products in a chemical reaction; system boundary 系统边界: The defined limit separating the material being considered from its surroundings.
バランス方程式におけるH₂Oの前の2は何を意味するか？
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係数 2 は水分子の個数を表します：2つの H2O です。式内の添字 2 は水の固有の性質の一部であり、H2O2 は過酸化水素であり、別の物質です。
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 2H₂ + O₂ → 2H₂O, the coefficient 2 multiplies an entire formula. The subscript 2 belongs to the preceding element, so one water molecule contains two H atoms and one O atom. Both sides contain four H atoms and two O atoms. Using supplied relative atomic masses H=1 and O=16 gives reactant totals 2×2 + 32 =36 and product total 2×18=36. The coefficients 2:1:2 are not gram ratios.
- Make an atom-count table before doing a mass calculation. Identify the physical boundary of the weighed system: vessel, liquid, solid and any contained gas. For an actual supervised demonstration, use an approved arrangement that accommodates any pressure change; do not improvise a heated sealed vessel. Compare readings only after correcting for anything added or removed from the balance.
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: an enclosed model reaction starts with 4.0 g A and 7.0 g B, and has no other reactants. The combined products weigh 11.0 g. If one product weighs 8.5 g, the other weighs 11.0−8.5=2.5 g. This mass accounting uses the complete stated system and does not identify either substance chemically.
A closed model reaction starts with 6 g and 9 g of reactants. One product weighs 11 g. Find the other product mass. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
密閉系での反応に 6 g と 9 g の反応物を使用し、生成物の一つが 11 g でした。他の生成物の質量を求めよ。
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結果は 4 g です。既知：閉じた系における反応物の総量は 6 + 9 = 15 g です。生成物の一つが 11 g であるため、保存則により、他の生成物 = 15 - 11 = 4 g となります。反応中、質量は生成も消滅もしません。
Check the conclusion and its limits
- Conservation does not mean that every individual substance keeps its own mass. Reactants are converted into products. Altering a subscript to balance an equation changes the substance, whereas changing a coefficient changes the number of particles. Include material crossing the system boundary before calling a result a failure of conservation.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Balanced coefficients always give the ratio of masses in grams. This claim is false: Coefficients count PARTICLES (or moles of them). Because each substance has a different molar mass, a 2:1 particle ratio is not a 2:1 mass ratio - convert through moles before comparing masses.
Conservation of mass: count the complete system: For 2H₂ + O₂ → 2H₂O, the coefficient 2 multiplies an entire formula. The subscript 2 belongs to the preceding element, so one water molecule contains two H atoms and one O atom. Both sides contain four H atoms and two O atoms. Using supplied relative atomic masses H=1 and O=16 gives reactant totals 2×2 + 32 =36 and product total 2×18=36. The coefficients 2:1:2 are not gram ratios.
平衡係数は常にグラム単位の質量比を示す。
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係数は粒子（またはそのモル数）の個数を表します。各物質のモル質量が異なるため、粒子比 2:1 が質量比 2:1 と等しくなるわけではありません。質量を比較する前にモル変換を行う必要があります。
化学反応において、全反応物の総質量は全生成物の総質量に等しい：技術用語を記せ。
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
質量保存則とは、化学反応において全反応物の総質量は全生成物の総質量に等しいことを意味する。