Topic 8: Chemical analysis
AQA · GCSE · Chemistry Topic 8 9:23 English narration · English + 中文 subtitles burned in
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A green flame suggests copper, but contamination or masking can mislead.
绿色火焰提示铜，但污染或颜色遮蔽可能误导。
Choose a test that can distinguish the possibilities and record the observation before naming the substance.
选择能够区分候选物的检验，先记录观察，再作判断。
Spectroscopy is not restricted to Higher Tier in this specification.
本大纲的光谱分析不限于高阶。
Our worked paper cases prepare you for the actual practicals; they do not replace laboratory records.
纸面例题为实际实验作准备，不能代替实验操作和原始记录。
Do not confuse the number of elements with the number of substances.
不要把元素种类与物质种类混淆。
An everyday product label does not establish chemical purity.
日常商品的纯字标签不能证明化学纯度。
Pause and compare both the position and the width of each interval.
暂停，同时比较温度位置与熔程宽度。
Decide whether matching one temperature uniquely identifies a substance.
判断一个相符的温度能否唯一鉴定物质。
A is the better-supported purity claim.
A的纯度判断有较好证据。
Boiling temperature also depends on pressure; do not invent a universal direction for every impurity effect.
沸点还受压强影响，不能声称每种杂质都让沸点朝同一方向改变。
Use the supplied product information to connect each component with its function.
根据题目资料把各组分与作用对应起来。
Simply containing several substances is not enough to show that a mixture was designed as a formulation.
仅含多种物质并不能证明混合物是按用途设计的配方。
More readily carried substances travel farther.
更容易随溶剂移动的组分走得更远。
Do not replace the distribution explanation with a rule that lighter particles always travel farther.
不能用轻粒子总是走得更远来代替两相分配的解释。
Ink can create extra spots and submerging the samples can wash them into the reservoir.
墨水可能产生额外斑点，样品浸入溶剂会被洗入液体。
Marking the front before evaporation preserves the denominator of Rf.
蒸发前标记前沿，才能保留比移值的分母。
Actual work uses the approved solvent and supervision.
实际操作使用获准溶剂并接受监督。
Read the distances in this diagram. A travels one point eight centimetres and the front travels six, so its Rf is zero point three zero.
图中A移动1.8厘米，前沿移动6.0厘米，所以比移值为0.30。
Neither distance starts at the paper edge.
两段距离都不从纸边开始。
Pause and subtract the baseline height from both measurements before dividing.
暂停，先从两次读数中减去基线高度，再相除。
Give a dimensionless answer.
答案不带单位。
Dividing four point two by nine uses the wrong origin.
直接用4.2除以9.0使用了错误起点。
The same unit cancels from numerator and denominator.
分子与分母的相同单位相消。
The unknown contains spots matching P and Q in solvent one.
未知样在溶剂1中有分别匹配P和Q的斑点。
In solvent two both components travel two point five centimetres, so they appear as one spot.
溶剂2中两者均移动2.5厘米，因此叠成一个斑点。
These references are fictional teaching data.
这些是教学用虚构参考数据。
Pause and distinguish a property of a pure compound from an inference based on limited observations.
暂停，区分纯化合物应有的性质和有限观察能支持的结论。
The second run is consistent with overlap and cannot erase the first run.
第二次实验可由斑点重叠解释，不能推翻第一次的证据。
Use another solvent or appropriate detection method if the evidence is insufficient.
证据不足时，应换合适溶剂或检测方法。
Name the reagent or splint condition together with the observation.
把试剂或木条状态与现象成对说明。
Gas handling uses approved school arrangements, with chlorine contained as required by the school.
气体操作必须按学校批准的方法进行，氯气使用规定的密闭控制。
Pause and decide what change the word relight requires you to observe.
暂停，判断复燃一词要求观察到怎样的变化。
Carbon dioxide is identified by cloudy limewater; prolonged clearing is not required.
二氧化碳的规定阳性现象是石灰水变浑浊，无需继续至澄清。
Red litmus alone is not the chlorine observation: the paper must bleach white.
石蕊变红本身不能确认氯气，关键是漂白成白色。
A missing visible colour does not prove the ion absent.
没有看到某种颜色不等于该离子不存在。
Copper gives a green flame, but its hydroxide precipitate is blue. Keep the observation types distinct.
铜的焰色是绿色，而氢氧化物沉淀是蓝色，应区分观察类型。
Read the initial colours and then the excess-reagent labels.
先看初始颜色，再看过量试剂后的变化。
Iron two gives green and iron three gives brown.
亚铁为绿，铁为棕。
A white precipitate that remains leaves calcium and magnesium unresolved.
白色沉淀不溶仍不能区分钙和镁。
Pause and retain every candidate consistent with the observations.
暂停，保留所有与观察相符的候选离子。
Do not force an identification from a test that has not distinguished the remaining candidates.
检验尚未区分剩余候选时，不要强行给出唯一结论。
Each hydroxide group contains oxygen and hydrogen.
每个氢氧根含氧和氢。
Preserve brackets and balance sodium and chloride too.
保留括号，同时配平钠和氯。
Full formation equations are both-tier here; sodium-aluminate dissolution is not required.
这里两层次均需掌握生成反应的完整方程式，不要求铝酸钠生成方程。
Pause and use aluminium three-plus with three hydroxide groups.
暂停，铝离子为三价，需要三个氢氧根。
The precipitation equation and dissolution behaviour describe different stages.
沉淀方程和过量碱中的溶解描述不同阶段。
Do not remove the solid state just because excess alkali may dissolve it later.
不能因为以后可能溶解，就省去初始沉淀的固态标记。
Hydrochloric acid introduces chloride, so it is unsuitable in the halide test.
盐酸会引入氯离子，因此不适合卤化物检验。
A white precipitate without a reagent name cannot distinguish chloride from sulfate or a white hydroxide.
只说白色沉淀而不说试剂，无法区分氯化物、硫酸盐或白色氢氧化物。
Bubbles alone only show gas evolution.
气泡只能说明有气体放出。
Use fresh portions for separate tests, preventing a previous reagent from adding an ion that creates a false result.
不同检验使用新样品，防止前一种试剂引入离子造成假阳性。
Pause and assign the flame and gas observations to different parts of the salt.
暂停，把焰色和气体观察分别对应于盐的阳离子和阴离子。
Required practical seven uses real supervised known and unknown tests.
实验7需要实际监督下的已知与未知离子检验。
Record reagent, observation and inference separately; this worked case does not certify a practical performance.
分别记录试剂、观察和推断。 本例不能证明完成了实际操作。
An instrument is useful for the stated measurement purpose, but still needs suitable references, calibration and controlled conditions.
仪器是否适用取决于测量目标，但仍需要恰当参考、校准和受控条件。
Put the sample in a flame and pass emitted light through a spectroscope.
样品置于火焰中，发出的光通过分光镜。
Compare line positions, not a general impression of flame colour.
比较谱线位置，而不是笼统的焰色印象。
These wavelengths are supplied data, not recall facts.
这些波长是题给数据，不是记忆要求。
Pause and find the fraction of the calibrated interval.
暂停，求出未知值在校准区间中的比例。
Keep the concentration unit on the answer.
最终保留浓度单位。
Do not assume all instruments are linear everywhere, or treat intensity alone as an absolute concentration.
不能假设所有仪器在任何范围都线性，也不能把强度直接当成绝对浓度。
Repeat and check suitable references before accepting a result.
接受结果前应复测并核对合适参考。
Choose evidence before naming a substance.
先选择证据，再鉴定物质。
For each calculation retain the correct origin, units and supplied model.
计算时保留正确起点、单位和题给模型。
For practicals retain actual supervised observations; for uncertain results state what remains unresolved.
实际实验应保留监督下的真实记录；证据不确定时说明仍未解决的问题。