📚 Year 7 WJEC Science: Key Points for Practical Assessments | 七年级 WJEC 科学：实验/实践考核要点
In Year 7 WJEC Science, practical assessments are just as important as written tests. They give you a chance to show your skills in planning experiments, handling equipment safely, collecting data and drawing conclusions. This guide walks you through every key point you need to master, from lab safety to evaluating your results, so you can feel confident and well-prepared for any practical task.
在七年级 WJEC 科学课程中，实践考核与书面测试同等重要。它让你有机会展示设计实验、安全操作仪器、收集数据并得出结论的能力。本指南将带你梳理每一个需要掌握的关键点，从实验室安全到结果评估，帮助你在任何实践任务中自信应对、充分准备。
1. Lab Safety Rules | 实验室安全规则
Before you even touch any equipment, you must know how to keep yourself and others safe. Always follow your teacher's instructions and never run or play in the lab.
在你接触任何仪器之前，必须知道如何保护自己和他人。始终听从老师的指导，绝不在实验室里奔跑或嬉戏。
Wear safety goggles whenever you are heating substances, mixing chemicals or working with glassware. Even a tiny splash can damage your eyes.
在加热物质、混合化学品或使用玻璃器皿时，始终佩戴护目镜。即使是一丁点飞溅也可能伤害你的眼睛。
Tie back long hair and tuck in loose clothing or scarves. These can easily catch fire or dip into chemicals without you noticing.
将长发束起，并将宽松衣物或围巾塞好。它们很容易在你没察觉时着火或浸入化学品中。
Never taste any chemical or put anything in your mouth during a practical. If you need to smell a gas, use the wafting technique – gently fan the vapour towards your nose.
切勿品尝任何化学药品，也不要在实验过程中把任何东西放进嘴里。如果需要闻气体，请使用扇闻法——轻轻地用手将蒸气扇向鼻子。
Report all breakages, spills and accidents to your teacher straight away. Do not try to clean up broken glass with your hands; use a dustpan and brush.
所有破损、泄漏和意外都立即向老师报告。不要用手清理碎玻璃，应使用簸箕和刷子。
Wash your hands thoroughly at the end of every practical session, even if you wore gloves. This simple habit removes any chemical residues and reduces the risk of contamination.
每次实验结束后彻底洗手，即便戴了手套也要洗。这个简单的习惯能去除化学残留，降低污染风险。
2. Understanding Variables | 理解变量
In any investigation, there are three types of variables you must identify: the independent variable, the dependent variable and the control variables. Getting these right is the foundation of a good experiment.
在任何探究活动中，你必须识别三种变量：自变量、因变量和控制变量。正确区分它们是做好实验的基础。
The independent variable is the factor you deliberately change or choose different values for. For example, if you are testing how light intensity affects plant growth, the independent variable is light intensity.
自变量是你刻意改变或选取不同数值的因素。例如，如果测试光照强度对植物生长的影响，自变量就是光照强度。
The dependent variable is what you measure or observe. It depends on the independent variable. In the plant example, the dependent variable could be the height of the seedlings after two weeks.
因变量是你测量或观察的内容。它随着自变量的变化而变化。在上面的植物例子中，因变量可以是两周后幼苗的高度。
Control variables are all the other factors you must keep the same to make the test fair. For the plant investigation, these might include the type of seed, amount of water, temperature and type of soil.
控制变量是你必须保持不变的所有其他因素，以确保测试公平。对于植物探究，控制变量可能包括种子类型、浇水量、温度和土壤种类。
The table below shows another common example – investigating how the length of a pendulum affects its swing time.
下表展示了另一个常见例子——探究摆长如何影响摆动时间。
| Variable Type | 变量类型 | Example | 示例 |
|---|---|
| Independent | 自变量 | Length of pendulum (cm) | 摆长（厘米） |
| Dependent | 因变量 | Time for 10 swings (s) | 10 次摆动的时间（秒） |
| Control | 控制变量 | Mass of bob, angle of release, same stopwatch | 摆锤质量、释放角度、同一秒表 |
3. Forming a Hypothesis | 形成假设
A hypothesis is a prediction that you can test. It is not just a guess – it is based on some scientific knowledge or a pattern you have noticed. In Year 7, you are expected to write a clear hypothesis that links the independent and dependent variables.
假设是一种你可以检验的预测。它不仅仅是猜测——而是基于一些科学知识或你注意到的规律。七年级要求你能写出一个清晰的假设，将自变量与因变量联系起来。
A good hypothesis often follows the 'If … then … because …' structure. The 'if' part states how you will change the independent variable, the 'then' part predicts what will happen to the dependent variable, and the 'because' part gives a simple scientific reason.
一个好的假设通常遵循“如果……那么……因为……”结构。“如果”部分说明你将如何改变自变量，“那么”部分预测因变量会发生什么变化，“因为”部分给出一个简单的科学理由。
For example: 'If the temperature of water is increased, then the time taken for sugar to dissolve will decrease, because particles move faster and collide more often at higher temperatures.' This statement is testable and uses correct variables.
例如：“如果水温升高，那么糖溶解所需的时间就会减少，因为温度更高时粒子运动更快、碰撞更频繁。” 这个陈述可检验，且使用了正确的变量。
Always make sure your hypothesis is specific. Instead of saying 'water temperature affects dissolving,' give a direction: 'as temperature increases, dissolving time decreases.' This helps you later when comparing your results to your prediction.
始终确保假设具体明确。不要说“水温影响溶解”，而应给出方向：“随着温度升高，溶解时间缩短。” 这有助于后续将结果与预测进行对比。
4. Designing a Fair Test | 设计公平测试
A fair test is one where you change only the independent variable and keep all control variables the same. If you change more than one thing at a time, you won't know which factor caused the result – your experiment becomes unreliable.
公平测试就是只改变自变量，而保持所有控制变量不变。如果一次改变多个因素，就无法知道是哪个因素引起了结果——实验变得不可靠。
Start by listing all the variables in your investigation. Decide which one you will change (independent), which you will measure (dependent) and which must stay constant (control). Write these down in your plan.
首先要列出探究中的所有变量。决定哪个是你要改变的（自变量）、哪个是需要测量的（因变量），以及哪些必须保持不变（控制变量）。把这些写进你的计划里。
When you write a method, use numbered steps and be precise. For instance, 'Measure exactly 25 cm³ of water using a measuring cylinder' is better than 'Add some water.' Repeating each measurement several times and calculating a mean also makes your test more reliable.
写方法时，要用带编号的步骤并且表达精确。例如，“用量筒准确量取 25 cm³ 水” 比 “加一些水” 更好。对每次测量重复多次并计算平均值也会使测试更可靠。
Think about the equipment you will need. If you are measuring temperature, do you need a thermometer or a data logger? If you are timing, will you use a stopwatch or a phone timer? Choosing the right tool is part of designing a fair test.
想一想你需要哪些仪器。如果要测量温度，是需要温度计还是数据记录仪？如果要计时，会使用秒表还是手机定时器？选择合适的工具也是设计公平测试的一部分。
5. Using Apparatus and Taking Measurements | 使用仪器和测量
Accurate measurements are the heart of any practical. You need to know how to read scales correctly, use the right units and record readings with the correct precision.
精确的测量是任何实践的核心。你需要知道如何正确读取刻度、使用正确单位，并以适当精度记录读数。
When reading a liquid volume in a measuring cylinder, always read the bottom of the meniscus at eye level. For a thermometer, make sure the bulb is fully immersed but not touching the container walls.
读取量筒中的液体体积时，始终在视线水平处读取液面凹液面的底部。使用温度计时，确保感温泡完全浸入但不接触容器壁。
Common units you will use include metres (m), centimetres (cm), grams (g), kilograms (kg), seconds (s), degrees Celsius (°C) and Newtons (N). Always write the unit next to every measurement in your table.
你将使用的常见单位包括米（m）、厘米（cm）、克（g）、千克（kg）、秒（s）、摄氏度（°C）和牛顿（N）。始终在表格中的每个测量值旁边写出单位。
Repeating measurements helps identify odd results. For each trial, record the value carefully. Then calculate the mean by adding up the repeated values and dividing by the number of trials. Do not include obvious anomalies in your mean calculation.
重复测量有助于发现异常结果。每次试验仔细记录数值。然后通过把重复值相加再除以试验次数来计算平均值。不要将明显异常值纳入平均值计算。
The resolution of an instrument is the smallest division it can show. For example, a ruler marked in millimetres has a resolution of 1 mm. Using instruments with higher resolution can make your data more precise, but you must still be careful about human reaction time in stopwatch measurements.
仪器的分度值是它能显示的最小刻度。例如，一把以毫米为刻度的尺子，其分度值为 1 mm。使用分辨率更高的仪器能让数据更精确，但在使用秒表测量时仍需注意人的反应时间。
6. Recording and Presenting Data | 记录和呈现数据
Good results tables make your data easy to understand and analyse. Always draw your table before you start the experiment, using a ruler and a pencil.
好的结果表格能让你的数据易于理解和分析。务必在实验开始前用尺子和铅笔画好表格。
The first column usually lists the independent variable or the trial number, and the second (and further) columns list the dependent variable readings. Each column heading must include the name of the quantity and its unit, like 'Length of spring (cm)' – the unit goes in brackets.
第一列通常列出自变量或试验编号，第二列（及后续列）列出因变量的读数。每个列标题必须包含物理量的名称和单位，例如“弹簧长度 (cm)”——单位写在括号里。
Record data as you collect it, not later from memory. Write numbers neatly and to the same number of decimal places if possible. Avoid rubbing out and overwriting; if you make a mistake, put a single line through it and write the correct value nearby.
边收集数据边记录，不要事后凭记忆补写。数字书写要工整，尽可能保持一致的小数位数。避免擦除和改写；如果写错了，就用单线划掉，在旁边写上正确的数值。
Here is a simple example of a results table for an investigation into how the number of bulbs in a circuit affects the brightness of a lamp, measured subjectively on a 1–5 scale:
下面是一个简单的结果表示例，用于探究电路中灯泡数量如何影响某一灯泡的亮度，用 1–5 等级主观评定：
| Number of bulbs in series | 串联灯泡数量 | Brightness rating (1–5) Trial 1 | 亮度评级 (1–5) 第1次 | Brightness rating Trial 2 | 亮度评级 第2次 | Brightness rating Trial 3 | 亮度评级 第3次 | Mean brightness | 平均亮度 |
|---|---|---|---|---|
| 1 | 5 | 5 | 5 | 5.0 |
| 2 | 3 | 4 | 3 | 3.3 |
7. Drawing Graphs and Charts | 绘制图表
Graphs turn rows of numbers into a visual story. In Year 7, you will mainly use bar charts when the independent variable is categorical (like colours or types) and line graphs when both variables are continuous numbers.
图表将一行行数字转化为视觉故事。在七年级，当自变量为类别变量（如颜色或种类）时主要使用条形图；当两个变量都是连续数值时使用折线图。
For a line graph, plot the independent variable on the horizontal x-axis and the dependent variable on the vertical y-axis. Both axes need labels with units, and the graph needs a clear title such as 'A graph to show how temperature affects the volume of a gas'.
对于折线图，将自变量标在水平 x 轴上，因变量标在垂直 y 轴上。两条轴都要有带单位的标签，图表需要一个清晰的标题，例如“显示温度如何影响气体体积的图”。
Choose a scale that uses more than half of the graph paper. The scale must go up in equal steps (e.g. 0, 2, 4, 6) – never use uneven jumps like 0, 1, 3, 7. Plot each point with a small cross (x), then draw a line of best fit, which could be straight or curved depending on the pattern.
选择的尺度要能占据坐标纸一半以上的范围。刻度必须以等间距增加（如 0、2、4、6）——绝不要使用 0、1、3、7 这样不均匀的间隔。用小小的十字 (x) 标出每个数据点，然后画一条最佳拟合线，可以是直线也可以是曲线，取决于数据模式。
If you spot a point that lies far away from the line, circle it and label it as an anomaly. Do not force your best-fit line to pass through anomalies. In a bar chart, bars should be equal in width and should not touch unless the categories are continuous ranges.
如果发现一个点远离线条，圈出它并标为异常值。不要让最佳拟合线强行穿过异常点。在条形图中，条柱应等宽，并且除非类别是连续范围，否则条柱之间不应接触。
8. Analysing Results and Drawing Conclusions | 分析结果和得出结论
Once you have your graph or table, look for patterns. Does the dependent variable increase, decrease or stay the same as the independent variable changes? Use phrases like 'as the independent variable increases, the dependent variable...' to describe the trend.
有了图表或表格之后，寻找规律。因变量是随着自变量的改变而增加、减少还是保持不变？使用“随着自变量的增加，因变量…”这样的短语来描述趋势。
Compare your results to your original hypothesis. Was your prediction correct? If the data matches the hypothesis, you can say the evidence supports it. If not, you say the evidence does not support it – and that is still valuable science.
将结果与最初的假设进行比较。你的预测正确吗？如果数据与假设一致，你可以说证据支持假设。如果不一致，就说证据不支持假设——这仍然是有价值的科学发现。
Your conclusion should link directly to the data, not just repeat your hypothesis. For example: 'From the graph, as the mass added to the spring increased, the extension of the spring increased proportionally. This supports the hypothesis that a greater force causes a greater extension.'
结论应直接与数据关联，而不仅仅是重复假设。例如：“从图表可以看出，随着加在弹簧上的质量增大，弹簧的伸长量成比例增加。这支持了‘更大的力导致更大的伸长量’这一假设。”
Mentioning numbers makes your conclusion stronger. You could say 'The temperature rose by an average of 8°C over ten minutes.' Try to use quantitative statements whenever possible.
引用具体数字能让结论更有说服力。可以说“温度在十分钟内平均上升了 8°C。” 尽可能使用定量描述。
9. Evaluating the Experiment and Identifying Errors | 评估实验和识别误差
Evaluation is about looking back at your method and results to judge how reliable and valid they are. Two main types of error can affect your data: random errors and systematic errors.
评估就是回顾方法和结果，判断它们的可靠性和有效性。两类主要误差会影响数据：随机误差和系统误差。
Random errors cause readings to be spread out on either side of the true value. They often come from human reaction time when using a stopwatch or from reading a scale slightly differently each time. Repeating measurements and calculating a mean helps reduce random errors.
随机误差导致读数在真实值两侧分散。它们常来源于使用秒表时人的反应时间，或每次读取刻度时的细微差异。重复测量并计算平均值有助于减少随机误差。
Systematic errors push all readings in one direction. For example, if a thermometer always reads 2°C too high, all your temperature measurements will be wrong by the same amount. Using properly calibrated equipment helps avoid systematic errors.
系统误差会使所有读数朝一个方向偏离。例如，如果一支温度计始终偏高 2°C，那么所有温度测量值都会以相同的量出错。使用经过正确校准的仪器有助于避免系统误差。
Identify any anomalies and suggest reasons for them. An anomaly might be a point that does not fit the trend because you misread the thermometer or recorded a time incorrectly. In your evaluation, say how you could improve the method to prevent such mistakes next time.
识别任何异常值并解释其原因。异常可能是某个不符合趋势的点，因为你误读了温度计或记错了时间。在评估中，说明下次可以如何改进方法以避免此类错误。
Good improvement suggestions are realistic, such as 'use a data logger to record temperature every second instead of reading a thermometer by eye,' or 'clamp the ruler vertically so it does not slip when measuring length.' Always link improvements to the weaknesses you found.
好的改进建议要切实可行，比如“使用数据记录仪每秒记录温度，而不是肉眼读取温度计”，或“将直尺垂直夹紧，以免测量长度时滑动”。始终将改进建议与你发现的弱点联系起来。
10. WJEC Practical Assessment Criteria | WJEC 实践考核标准
In a WJEC practical assessment, your teacher will look at several skill areas. Understanding what these are helps you to focus on doing your best in each part.
在 WJEC 实践考核中，老师会观察多个技能领域。了解这些内容有助于你在每个环节中做到最好。
Planning: You need to write a clear aim, identify variables and produce a logical method. Shows you can design a fair test and anticipate what equipment you will need.
计划：你需要写出清晰的目标，识别变量并制定合乎逻辑的方法。这展示你能否设计公平测试并预见到所需的器材。
Obtaining evidence: You collect data safely and accurately, using apparatus correctly and repeating measurements where appropriate. Your results table should be neat, with units in the headings.
获取证据：你安全、准确地收集数据，正确使用仪器，并在适当时重复测量。结果表格应整洁，并在标题中注明单位。
Analysing: You can present data in a graph or chart, describe patterns and use numbers to support your description. You can also calculate means and spot anomalous results.
分析：你能用图表展示数据，描述规律并用数字支持描述。你还能计算平均值并发现异常结果。
Evaluating: You comment on how reliable your results are, suggest improvements to the method and explain how errors might have occurred. You show that you understand science is about testing ideas and learning from what happened.
评估：你评论结果的可靠性，对方法提出改进建议，并解释可能产生误差的原因。你展现出你理解科学就是检验想法并从结果中学习的过程。
Your teacher may use a checklist similar to this when marking your work. Always ask yourself: Have I made my test fair? Am I recording data neatly? Can I explain what my graph shows? Could I do anything better next time?
老师评分时可能会使用类似的检查表。始终问自己：我是否让测试公平了？我是否整洁地记录了数据？我能否解释图表所显示的内容？下次我能否做得更好？
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