📚 Key Points for Practical Assessments in Year 7 WJEC Chemistry | 威尔士联合教育委员会7年级化学：实验考核要点
Practical work is at the heart of Year 7 chemistry. In WJEC science, you are assessed not only on what you know but also on how you work safely, use equipment correctly, record data and draw conclusions. This article covers the key points you need to master for your practical assessments, from safety rules to evaluating your experiments.
实验操作是7年级化学学习的核心。在WJEC科学课程中，考核的不仅仅是你的知识掌握程度，更看重你是否能安全操作、正确使用仪器、记录数据并得出结论。本文涵盖了你必须掌握的各项实验考核要点，从安全守则到实验评估，帮助你从容应对每一次动手实践。
1. Lab Safety Rules | 实验室安全规则
Safety is the most important part of any practical lesson. Before starting any experiment, you must tie back long hair, tuck in ties or scarves, and wear safety goggles. Always listen carefully to your teacher's instructions and never run or play in the lab.
安全是一切实验课的头等大事。开始任何实验前，你必须束起长发、塞好领带或围巾，并佩戴护目镜。务必认真听老师的讲解，绝对不要在实验室里奔跑或嬉戏。
Never taste any chemical and do not touch substances unless told to. If you smell a gas, use the 'wafting' technique — gently wave the vapour towards your nose with your hand. Always point the open end of a test tube away from yourself and others when heating.
切勿品尝任何化学品，未经允许不要触碰药品。闻气体时要使用“扇闻法”——用手轻轻将蒸气扇向鼻子。加热试管时，试管口必须背对自己和他人。
If a spill occurs, report it to your teacher immediately. Wash your hands after handling chemicals, even if you think they are harmless. Know the location of the fire extinguisher, fire blanket and eye wash station.
若发生泼溅事故，立即报告老师。即使感觉无害，接触过化学药品后也要洗手。清楚灭火器、灭火毯和洗眼站的位置。
2. Common Laboratory Apparatus | 常用实验仪器
Being able to name and use common equipment is a basic skill WJEC assessments look for. You should recognise a beaker for holding or heating liquids, a conical flask for swirling without spilling, and a test tube for small-scale reactions.
能说出并正确使用常用仪器是WJEC考核的基础技能。你应该能认出烧杯用于盛放或加热液体，锥形瓶方便摇匀而不溅出，试管则用于小规模反应。
When measuring volumes, you will usually use a measuring cylinder. For more precise work, a pipette or burette is used, though in Year 7 you will mainly work with cylinders. Always read the bottom of the meniscus at eye level when measuring liquids.
测量体积时通常用量筒。更精密的实验会用到移液管或滴定管，不过7年级主要使用量筒。测量液面时，视线必须与凹液面的最低处保持水平。
Learn to use a Bunsen burner safely: the air hole controls the flame type — a closed air hole gives a yellow safety flame (luminous), while an open hole produces a blue roaring flame (non‑luminous) for heating. Use a tripod and gauze to support apparatus over the flame.
学会安全使用本生灯：气孔打开程度决定火焰类型——气孔关闭时产生黄色安全焰（发光焰），气孔打开则产生蓝色强热焰（无光焰）用于加热。使用三脚架和石棉网支撑器皿放在火焰上方。
3. Key Skills in Measurement: Mass and Volume | 测量的关键技能：质量与体积
In WJEC practical tasks, you will often be asked to measure the mass of a solid or the volume of a liquid. Always use a top‑pan balance for mass, placing a weighing boat or paper on it first and pressing tare to zero the balance before adding your substance.
在WJEC实验任务中，经常会要求你测量固体的质量或液体的体积。测量质量要使用电子天平，首先放上称量舟或称量纸，按去皮键归零后再加入药品。
For volume, choose the correct measuring cylinder size to get an accurate reading — it is better to use a 100 cm³ cylinder to measure 80 cm³ of water than a 250 cm³ cylinder. Record your measurements using sensible units, such as grams (g) and cubic centimetres (cm³).
测量体积时要选择恰当的量筒规格，以获得准确读数——测量80 cm³水用100 cm³量筒比250 cm³量筒更合适。记录数据要使用合适的单位，如克（g）和立方厘米（cm³）。
Always repeat measurements if possible to reduce random errors. If you obtain a set of three values, calculate the mean by adding them up and dividing by three. This improves the reliability of your data.
尽量重复测量以减少偶然误差。如果得到三个数值，相加后除以三求出平均值。这能提高数据的可靠性。
4. Heating Substances: Methods and Precautions | 加热物质的方法与注意事项
Different solids and liquids behave differently when heated. Use test tubes in a water bath for gentle, even heating of liquids. For direct heating with a Bunsen burner, make sure the test tube is one‑third full and held at an angle, moving continuously to prevent boiling over or bumping.
不同的固体和液体受热表现不同。温和且均匀地加热液体可使用水浴加热试管。若用本生灯直接加热，确保试管内液量不超过三分之一，倾斜试管并持续移动，防止暴沸或样品溅出。
When heating a solid in a boiling tube, often a delivery tube is attached to collect gas. Always remove the delivery tube from the water before stopping heating, otherwise ‘suck‑back’ can cause cold water to rush into the hot tube and crack it.
加热大试管中的固体时，常连接导管收集气体。停止加热前，务必先将导管从水中移出，否则会发生“倒吸”，冷水冲入热试管导致试管炸裂。
For evaporating a solution, use an evaporating basin on a tripod over a beaker of boiling water (steam bath) or directly on a gentle blue flame. Avoid strong, direct heating that might cause spitting.
蒸发溶液时，可用蒸发皿置于三脚架上的沸水烧杯上（蒸汽浴）或用小火直接加热。避免剧烈直接加热导致液体飞溅。
5. Observing and Recording Data | 观察与记录数据
Good chemists make detailed observations. WJEC practical assessment marks are often awarded for recording what you actually see, smell (only when instructed) or measure. Write down colour changes, bubbling, temperature rises, or new solids forming (precipitates).
优秀的化学家会进行细致的观察。WJEC实验考核往往根据你实际看到、闻到（仅在允许时）或测量到的现象给分。记下颜色变化、气泡产生、温度升高或新固体生成（沉淀）。
Results should be written clearly in a table with headings, including units. For example:
结果要清晰地记录在带表头的表格中，并注明单位。例如：
| Time (s) | Temperature (°C) |
|---|---|
| 0 | 22 |
| 30 | 35 |
| 60 | 46 |
Never change data to match what you think should happen — record it honestly. Anomalous results (ones that do not fit the pattern) should be circled and may be mentioned later in your evaluation.
切勿为迎合预期而篡改数据——诚实记录。异常结果（不合规律的数据点）应当圈出，并可在后续评估中提及。
6. Drawing Graphs and Charts of Results | 绘制结果图表
ales that use most of the graph paper. Plot points with small crosses (×) and draw a smooth line of best fit, either straight or curved.
针对连续数据（如温度随时间变化）应绘制折线图。用尖细铅笔作图，两条坐标轴均标出物理量与单位，选择合适的刻度以使图形占满格子纸。用小小的叉号（×）标出数据点，再画一条平滑的拟合线，直线或曲线皆可。
For category data (like counting different gases released), use a bar chart. Ensure bars are of equal width, drawn with a ruler, and separated by a gap. The chart must have a title that describes what it shows.
对于分类数据（如统计生成的不同气体），使用柱状图。柱宽相等，用尺子画，柱间留空隙。图表必须写有标题，说明展示的是什么。
WJEC markers will check if your graph is correctly scaled, labelled and has a suitable line. Never join the dots one‑by‑one with a ruler — always draw a line of best fit to show the overall trend.
WJEC评分员会检查你的图表刻度是否得当、标注是否正确、拟合线是否合理。永远不要用直尺逐点连线——一定要画一条能反映整体趋势的拟合线。
7. Analysing Results and Drawing Conclusions | 分析结果与得出结论
Analysing means looking at your data to find patterns. In your lab report, describe the relationship shown: for example, 'as the temperature increased, the amount of gas produced per minute also increased' or 'the mass decreased over time as gas escaped'.
分析意味着审视数据以找出规律。在实验报告中，描述数据呈现的关系：例如“温度升高，每分钟产生的气体量也增加”或“由于气体逸出，质量随时间减少”。
Link your conclusion directly to your data — use phrases like 'the results show that...' Do not talk about things you did not measure. Mention specific numbers from your table or graph to support your statement.
结论要直接从数据出发——使用“结果表明……”之类的表述。不要谈那些你未测量的事情。用表格或图表中的具体数值来支持你的论断。
Your conclusion should also answer the original aim of the experiment. If the aim was to find out which metal reacts fastest with acid, state which one and give a reason based on evidence.
结论还应回应实验的最初目标。如果目标是探究哪种金属与酸反应最快，就要明确指出来，并依据数据给出理由。
8. Evaluating Experiments and Improving Methods | 评估实验与改进方法
Evaluation is about reflecting on your method. Identify any problems you faced: was the measuring cylinder difficult to read? Did the temperature drop quickly when you took the reading? Mention any anomalous results and suggest why they occurred.
评估是对实验方法的反思。找出你遇到的问题：量筒读数是否困难？记录温度时温度值是否下降很快？提及异常结果，并推测其产生原因。
Always suggest at least one improvement. For example, 'We could use a polystyrene cup with a lid instead of a beaker to reduce heat loss', or 'Repeat the experiment three times to calculate a mean and improve reliability'. Improvements must be specific and realistic.
务必提出至少一项改进建议。例如，“我们可以用带盖的聚苯乙烯杯代替烧杯以减少散热”，或“重复实验三次求平均值以提高可靠性”。改进措施必须具体且可行。
In WJEC assessments, you may be asked to comment on precision, repeatability and the range of data. Saying 'use a more precise balance' or 'collect data over a longer time' often scores marks.
在WJEC考核中，可能要求你评价精密度、数据可重复性和数据范围。说出“使用精度更高的天平”或“延长数据采集时间”这类话通常能得分。
9. Understanding WJEC Command Words for Practical Tasks | 理解 WJEC 实验题中的指令词
WJEC practical assignments and questions use specific command words that tell you exactly what to do. Understanding these is vital for scoring full marks.
WJEC的实验作业和问题会使用特定的指令词，准确告诉你需要做什么。理解这些词汇是获得满分的关键。
| Command Word | Meaning |
|---|---|
| Describe | Say what happens or what you see, without explaining why. |
| Explain | Give reasons using scientific ideas. |
| State | Give a short, clear answer, often a word or phrase. |
| Suggest | Use your knowledge to offer a possible reason or improvement, even if not taught directly. |
| Evaluate | Give both good and bad points of a method or data, then make a judgement. |
When told to 'describe', write only observations. If asked to 'explain', include the science — often linking to particle theory or energy changes. Practise answering past paper questions underlining the command word.
看见“描述”就只写观察结果。若要求“解释”，则要包含科学原理——通常涉及粒子理论或能量变化。多做往年真题练习，划出指令词再作答。
10. Example Practical: Filtration | 典型实验范例：过滤
Filtration is commonly used to separate an insoluble solid from a liquid, such as sand from a salt‑sand‑water mixture. Fold a filter paper into a cone and place it in a filter funnel. Pour the mixture carefully; the sand stays in the paper as residue, and the salt water passes through as filtrate.
过滤常用于分离不溶性固体与液体，比如从沙子和盐的水溶液中分离出沙子。将滤纸折成圆锥形放入漏斗中。小心倒入混合物：沙子作为残渣留在滤纸上，盐水则透过滤纸成为滤液。
In your practical assessment, you must describe how to hold the funnel over the beaker correctly, using a glass rod to direct the liquid to the centre of the filter paper. Ensure the tip of the funnel touches the side of the receiving beaker to avoid splashing.
在实验考核中，你需要描述如何正确地将漏斗架在烧杯上，并用玻璃棒将液体引流至滤纸中央。确保漏斗颈尖端紧贴承接烧杯内壁，防止飞溅。
A common improvement is to wash the residue with a small amount of distilled water to remove any remaining soluble salt. Do not use too much water, or the filtration will become slow.
常见的改进方法是用少量蒸馏水清洗残渣，以除去残留的可溶性盐。但不要用太多水，否则过滤会变得很慢。
11. Example Practical: Evaporation | 典型实验范例：蒸发
Evaporation is used to obtain a soluble solid from a solution, like salt from salt water. Pour the salt solution into an evaporating basin and heat it gently over a Bunsen burner or steam bath. As the water boils off, white salt crystals will begin to appear.
蒸发用来从溶液中回收可溶性固体，例如从盐水中获得食盐。将盐水倒入蒸发皿，放在本生灯或蒸汽浴上缓缓加热。水分蒸发后，白色食盐晶体便会显现。
Stop heating when only a small amount of liquid remains, or the solid may start spitting. Turn off the Bunsen burner and let the remaining heat finish the evaporation. This is called ‘heating to dryness’ and requires care.
当只剩少量液体时就应停止加热，否则固体可能飞溅。关闭本生灯，让余热完成最后的蒸发。这就是“加热至干”，操作需要十分小心。
Never touch the evaporating basin with bare hands immediately after heating — use tongs and allow it to cool. Record the appearance of the crystals and compare the mass obtained with the expected yield.
加热后切勿马上徒手触碰蒸发皿——要使用坩埚钳，并让其冷却。记录晶体的外观，比较实际所得质量与理论产率。
12. Example Practical: Measuring pH with Indicators | 典型实验范例：使用指示剂测量pH
To test whether a solution is acidic or alkaline, you can use universal indicator or litmus paper. Add a few drops of universal indicator to the solution and match the colour to a pH chart. The pH scale runs from 0 (strongly acidic) to 14 (strongly alkaline), with 7 being neutral.
要检测溶液是酸性还是碱性，可使用通用指示剂或石蕊试纸。向溶液中滴加几滴通用指示剂，将变色情况与pH比色卡对照。pH标度从0（强酸性）到14（强碱性），7为中性。
A new key concept in Year 7 is the idea of neutralisation: when an acid reacts with an alkali, they cancel each other out, producing water and a salt. You can test this by adding the acid drop by drop to an alkali containing indicator until the colour changes to green (pH 7).
7年级引入的一个重要概念是中和：酸与碱反应，彼此抵消，生成水和盐。你可以通过向含指示剂的碱液中逐滴加酸来测试这一过程，直到溶液颜色变为绿色（pH 7）。
WJEC practicals often ask you to record the colour change accurately and compare the effectiveness of different indicators, such as red cabbage juice, which turns reddish‑pink in acids and greenish‑yellow in alkalis. Remember to wear goggles — even mild acids can irritate.
WJEC实验常常要求准确记录颜色变化，并比较不同指示剂的效果，比如红甘蓝汁：在酸性溶液中变为红粉色，在碱性溶液中变为绿黄色。别忘了戴护目镜——即使弱酸也可能刺激皮肤。
Published by TutorHao | Chemistry Revision Series | aleveler.com
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