Topic 6: The rate and extent of chemical change
AQA · GCSE · Chemistry Topic 6 9:43 English narration · English + 中文 subtitles burned in
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A fast reaction does not necessarily give a large amount of product.
反应快不一定意味着产物多。
We will measure changes over time, explain them by collisions and then distinguish reaction speed from an equilibrium mixture.
先测量随时间的变化，用碰撞解释速率，再区分反应速度与平衡组成。
Subtract both readings.
两个读数都要相减。
Dividing thirty-six by thirty gives the mean since time zero, not the requested interval.
三十六除以三十是从零时刻起的平均值，不是指定区间。
A measured quantity used up gives a positive consumption rate when we subtract final from initial.
反应物消耗量用初始量减末量，再除以时间。
Pause and identify the mass lost and elapsed time separately. Do not divide the remaining mass by the clock reading.
暂停，分别找出损失质量与经过时间，不要把剩余质量除以时钟读数。
The consumption or loss rate is reported as a positive magnitude.
损失或消耗速率用正值表示。
The negative change in mass tells us the direction; it does not make the reaction run backwards.
质量变化为负说明质量减少，不表示反应逆向进行。
These illustrative curves use matched conditions and the same limiting amount.
示意曲线对应相同限量反应物与匹配条件。
A reaches the same final collected gas volume sooner.
A更早达到相同终体积。
A lower observed plateau in a real experiment could instead result from a leak or a different limiting amount.
真实实验中较低平台也可能来自漏气或限量物质不同，不能单独证明速率更低。
Both tiers draw and interpret tangents. Numerical tangent gradients are Higher Tier here.
两层次都画和解读切线；本节数值切线斜率属于高阶。
Choose widely separated points on the tangent, not two arbitrary points on the curved line.
选切线上相距较远的点，不要任取曲线上两点。
The tangent gives the rate at one instant.
切线给出某一时刻的速率。
Use moles only when amount data are supplied.
给出物质的量数据时才用摩尔计算。
Do not substitute concentration or gas volume into this calculation without a justified conversion.
没有合理换算，不能直接代入浓度或气体体积。
The numerator and unit must describe the same measured quantity.
分子中的量必须与单位一致。
Do not merely say more particles. Specify more particles in the same volume.
不要只说粒子更多，应说相同体积内反应粒子更多。
Compression of a reacting gas has the analogous effect at fixed temperature. It does not increase the average kinetic energy when temperature is unchanged.
恒温压缩反应气体有类似作用；温度不变时平均动能不增加。
The surface-area-to-volume ratio doubles for this geometry. That does not prove an exact doubling of reaction rate: the experiment has not established a rate law.
这种几何切法使表面积体积比加倍，但不能据此断言速率精确加倍，实验没有建立速率定律。
Compare equal masses under matched conditions.
比较时质量相同，其他条件匹配。
Keep collision frequency separate from the proportion with enough energy.
分别说明碰撞频率和具有足够能量的比例。
Do not claim that every collision succeeds at a higher temperature or that the activation energy itself has increased.
不能说升温后每次碰撞都成功，也不能说活化能因此增大。
The orange pathway has a smaller barrier than the blue pathway.
橙色路径的能垒低于蓝色路径，总能量变化不变。
The overall energy change is unchanged. A catalyst is not used up overall, does not appear in the overall equation and may be unsuitable for another reaction.
催化剂总体不被消耗，不出现在总反应方程中，也不一定适合另一反应。
Enzymes are biological catalysts.
酶是生物催化剂。
Pause to combine the rate result with the mass and equation evidence.
暂停，把速率结果与质量、方程证据结合。
Decide whether this one trial establishes catalytic action in every reaction.
判断一次实验能否证明对所有反应都具有催化作用。
Mass alone does not establish unchanged chemical identity.
质量相同不能单独证明化学性质未变。
The observations together are consistent with a catalyst.
这些观察共同支持催化解释。
Rate and final product amount remain different measurements.
速率与最终产量仍是不同测量。
The adopted practical uses fifty cubic centimetres of acid and equal cleaned three-centimetre magnesium strips.
采用的操作使用五十立方厘米酸和清洁的三厘米镁条。
Fit the bung and begin timing consistently and promptly.
迅速且一致地装塞计时，定时记录气体，比较初始斜率。
Keep the outlet unobstructed; do not seal a reacting system without a gas outlet.
气体出口必须畅通，不能无出口密封反应体系。
A delayed bung or a leak lowers collected volume. Different limiting amounts can also change the plateau.
延迟装塞或漏气会使收集体积偏低，限量物质不同也会改变平台。
These faults cannot be diagnosed as slower chemistry from the final volume alone.
仅凭终体积不能判定反应更慢。
A supervised practical remains necessary; a written plan is not its completion.
仍需完成有监督的实际实验，书面方案不能代替操作。
Vary thiosulfate concentration while controlling acid volume and concentration, total mixture volume, temperature and viewing conditions.
改变硫代硫酸盐浓度，控制酸的浓度和体积、混合物总体积、温度与观察条件。
The sulfur suspension scatters light.
硫悬浮物使液体浑浊。
The endpoint is a chosen visibility threshold, not complete reaction.
终点是指定可见度阈值，不是反应完成。
Pause to distinguish the fifty cubic centimetres before acid addition from the final sixty cubic centimetres.
暂停，区分加酸前五十立方厘米和加酸后六十立方厘米。
Use the same endpoint for the two reciprocal-time comparisons.
倒数时间的比较必须使用相同可见度终点。
Reciprocal time is a relative-rate proxy, not a mass or volume rate.
时间倒数是相对速率指标，不是质量或体积速率。
Sulfur dioxide can aggravate breathing difficulties: use teacher-controlled quantities and suitable ventilation, and do not inhale fumes.
二氧化硫会加重呼吸不适，应采用教师控制的用量、适当通风，避免吸入。
Repeating does not remove a systematic viewing difference.
重复实验不能消除观察方式的系统差异。
Products can react to form the original substance again.
产物可以反应重新生成原物质。
Use the named ammonium chloride example to distinguish reversal from merely slowing the forward reaction. Chemical substances change in both directions.
用氯化铵例子区分逆反应与仅仅降低正反应速率，两方向都有化学变化。
One direction is endothermic and the reverse is exothermic.
一个方向吸热，逆方向放热。
The transferred energy has equal magnitude for the same corresponding quantity of material, not for any arbitrary masses.
对应相同物质量时，转移能量大小相等；不是任意质量都释放相同能量。
This is an illustrative rate diagram, not an experimental rate law.
这是速率示意图，不是实验速率定律。
A closed system prevents reactants and products from escaping.
封闭体系防止反应物和产物逸出。
Equal rates do not require equal concentrations or equal amounts of the substances.
速率相等不要求各物质浓度或物质的量相等。
Pause to compare rates rather than amounts.
暂停，比较速率而不是物质的量。
Recorded times may not locate the precise onset of equilibrium between measurements.
记录时刻不能精确确定两次测量之间何时首次达到平衡。
Dynamic means ongoing opposing reactions.
动态表示相反方向的反应持续进行。
The amount comparison is not an equilibrium criterion. The sealed vessel supplies the closed-system condition.
物质的量比较不是平衡判据，密封容器提供封闭体系条件。
Le Chatelier principle predicts a response that opposes the change. It does not say that C must return exactly to its old concentration.
勒夏特列原理预测抵消改变的响应，不要求C恰好回到原浓度。
Keep the instantaneous addition separate from subsequent chemical adjustment.
应区分瞬间加入物质与随后的化学调整。
Removing reactant favours the direction that makes it.
移走反应物有利于生成该反应物的方向。
Adding a reactant or removing a product favours product formation.
加入反应物或移走产物有利于生成产物。
State the direction relative to the displayed equation and explain the opposing response.
根据所写方程明确方向，并解释抵消作用。
Name which direction is endothermic before predicting the shift.
先确认哪一方向吸热，再预测移动。
A temperature increase can increase rate while lowering the equilibrium yield of an exothermic product. These statements answer different questions.
升温可以提高速率，同时降低放热正反应的平衡产率，两句话回答不同问题。
Count gaseous coefficients, not different chemical formulae.
数气态物质的系数，不数不同化学式种类。
A pressure change from changing volume favours fewer gas molecules when pressure rises and more when it falls.
改变体积导致增压时有利于气体分子少的一侧，降压则相反。
Equal gas counts give no position change.
气体数相等时平衡位置不移动。
Pause to exclude the solid from the gas count.
暂停，气体计数不包括固体。
Pressure information alone does not specify which direction absorbs heat.
压力信息不能确定哪一方向吸热。
Do not transfer the pressure rule to temperature.
不能把压力规则用于温度。
Le Chatelier principle uses the particular disturbance: gas count for volume compression, energy-transfer direction for temperature.
勒夏特列原理针对具体扰动：压缩看气体数，温度看能量转移方向。
Pause to check both inequalities.
暂停，检查两个最低要求。
A high equilibrium yield is not useful if production is too slow for the stated target.
若生产过慢，平衡产率高也不能满足目标。
Cost needs separate evidence.
成本需要单独证据。
The choice is justified by the supplied targets, not by a universal best temperature.
选择依据是给定目标，不是普遍最佳温度。
At a fixed temperature a catalyst speeds both directions and reaches the same equilibrium sooner; it does not increase equilibrium yield.
温度固定时，催化剂加快正逆反应，使同一平衡更快达到，不提高平衡产率。
Use the same starting amounts and closed-system conditions when comparing the catalyst trials.
比较催化试验时采用相同起始量和封闭体系条件。
Explain the data rather than repeating a slogan.
根据数据解释，不要只背口号。
Revisit both required-practical methods; a written answer does not certify practical performance.
复习两种必做实验方法，书面答案不能认证实际操作。