Experimental and Practical Assessment Essentials | 实验/实践考核要点

📚 Experimental and Practical Assessment Essentials | 实验/实践考核要点

In Year 7 SQA Physics, practical assessments test your ability to plan, carry out and evaluate scientific investigations. Knowing how to handle variables, collect data, plot graphs and draw valid conclusions is the key to achieving high marks. This guide walks you through every essential experimental skill, from designing a fair test to staying safe in the laboratory.

在 SQA 七年级物理中，实践考核检验你计划、实施和评估科学探究的能力。掌握如何处理变量、收集数据、绘制图表并得出有效结论是取得高分的关键。本指南将带你逐一学习从设计公平实验到实验室安全的每一项重要实验技能。

1. Understanding Variables | 理解变量

In every physics experiment, you will encounter three types of variables: the independent variable, the dependent variable and the control variables. Identifying them correctly is the first step to planning a reliable investigation.

在每个物理实验中，你都会遇到三种变量：自变量、因变量和控制变量。正确识别它们是规划可靠实验的第一步。

The independent variable is the factor you deliberately change. For example, when you investigate how the mass of a toy car affects its speed on a ramp, you alter the mass – that is your independent variable.

自变量是你故意改变的那个因素。例如，当你研究玩具小车的质量如何影响它在斜坡上的速度时，你改变的是质量——那就是你的自变量。

The dependent variable is what you measure – it depends on the change you made. In the car experiment, the speed you calculate from distance and time is the dependent variable.

因变量是你测量的量——它取决于你所做的改变。在小车实验中，由距离和时间计算出来的速度就是因变量。

Control variables are all the other quantities that could affect the results and must be kept constant. For the ramp investigation, you would keep the height of the ramp, the surface material, and the starting position the same; otherwise the test would be unfair.

控制变量是所有其他可能影响结果且必须保持不变的量。在斜坡实验中，你需要保持斜坡高度、表面材质和起始位置相同；否则测试就不公平。

Variable Type	Meaning	Car-Ramp Example
Independent	What you change	Mass added to the car
Dependent	What you measure	Average speed
Control	What stays the same	Ramp height, surface, release point

Getting the variables right at the planning stage makes it much easier to write a clear hypothesis and design a valid experiment.

在计划阶段把变量弄清楚，可以使撰写清晰的假设和设计有效的实验变得更加容易。

2. Writing Hypotheses and Predictions | 撰写假设和预测

A hypothesis is a testable statement that predicts how the independent variable will affect the dependent variable. It often uses an ‘If … then … because …’ structure.

假设是一个可检验的陈述，预测自变量将如何影响因变量。它通常使用“如果……那么……因为……”的结构。

For instance: ‘If I increase the current flowing through a wire, then the strength of the electromagnet will increase, because more current produces a stronger magnetic field.’ This gives a clear cause-and-effect relationship that you can check with data.

例如：“如果 I 增大流过导线的电流，那么电磁铁的磁性会增强，因为更大的电流会产生更强的磁场。”这给出了一个清晰的因果关系，你可以用数据来检验。

Predictions are more specific – they state exactly what you expect to observe, often with numbers. ‘When the pendulum length is doubled, the time for ten swings will increase by about 1.4 times.’ This shows you have thought about the outcome before the experiment.

预测则更具体——它准确说明你期望观察到的现象，通常带有数字。“当摆长加倍时，十次摆动的时间将增加约1.4倍。”这表明你在实验前就已经思考过结果。

Always base your hypothesis on scientific reasoning, not just a guess. Refer to concepts you have learned, such as forces, energy or electric circuits.

始终要以科学推理为基础提出假设，而不是仅凭猜测。引用你学过的概念，如力、能量或电路。

3. Designing a Fair Test | 设计公平实验

A fair test is one where only the independent variable is changed while all control variables are kept the same. This ensures any difference in the dependent variable is truly caused by the thing you changed.

公平实验是指只改变自变量，而所有控制变量保持不变。这样可以确保因变量的任何差异确实是由你改变的那个因素造成的。

Imagine you are testing how the type of surface affects the force needed to pull a block. You must use the same block, the same pulling speed, and measure force with the same newton meter. If you changed the block’s mass or used different surfaces in different places, you could not compare results reliably.

假设你正在测试表面类型如何影响拉动木块所需的力。你必须使用同一木块、同样的拉动速度，并用同一弹簧秤测量力。如果你改变了木块的质量或在不同的地点使用不同的表面，你就无法可靠地比较结果。

A good experimental design also includes a clear method written in numbered steps, a list of equipment with sizes and ranges, and a risk assessment to keep everyone safe.

一个好的实验设计还包括用编号步骤写清楚的方法、带有规格和量程的设备清单，以及确保所有人安全的风险评估。

4. Measurements and Units | 测量与单位

Using standard units is vital in physics. Length is measured in metres (m), centimetres (cm) or millimetres (mm); mass in grams (g) or kilograms (kg); time in seconds (s); and volume in cubic centimetres (cm³) or litres (L).

使用标准单位在物理中至关重要。长度以米 (m)、厘米 (cm) 或毫米 (mm) 为单位；质量以克 (g) 或千克 (kg) 为单位；时间以秒 (s) 为单位；体积以立方厘米 (cm³) 或升 (L) 为单位。

When taking readings, you should record to the nearest small division on the measuring instrument and estimate one extra digit where possible. For a ruler marked in millimetres, a length might be recorded as 5.3 cm (53 mm) if you can judge halfway between marks.

读取数值时，你应当记录到测量仪器上最小刻度，并尽可能多估计一位数字。对于以毫米为刻度的直尺，如果你能判断到刻度之间的一半，长度可以记录为5.3厘米（53毫米）。

Always write the unit next to the number in a results table, e.g., ‘Length (cm)’, ‘Time for 10 swings (s)’. Never leave a measurement without its unit.

在结果表格中始终在数字旁写上单位，例如“长度 (cm)”、“10次摆动时间 (s)”。绝不要让测量值没有单位。

v = d ÷ t

The formula for speed connects distance (d) and time (t). When you calculate speed, you must use matching units – if distance is in metres and time in seconds, speed will be in metres per second (m/s).

速度公式将距离 (d) 和时间 (t) 联系起来。当你计算速度时，必须使用匹配的单位——如果距离的单位是米，时间的单位是秒，那么速度的单位就是米每秒 (m/s)。

5. Using Basic Laboratory Equipment | 使用基本实验设备

Year 7 practicals involve simple but important apparatus. You need to use a stopwatch accurately: press start exactly as the event begins and stop without delay. Repeating the timing and taking an average reduces human reaction-time errors.

七年级的实验会用到简单但重要的仪器。你需要准确使用秒表：在事件开始的瞬间按下开始，并不延误地停止。重复计时并取平均值可以减少人的反应时间误差。

Newton meters (force meters) must be zeroed before use and read at eye level to avoid parallax error. Thermometers should be read while still in the liquid, with the bulb fully immersed but not touching the container walls.

弹簧秤（测力计）在使用前必须调零，并在眼睛平视时读数以避免视差。温度计应在仍处于液体中时读取，感温泡完全浸没但不接触容器壁。

When building electrical circuits, always connect components in the correct order and check that the switch is open before making adjustments. A simple series circuit with a battery, bulb and switch is a common starting point.

搭建电路时，始终以正确顺序连接元件，并在调整前确认开关是断开的。由电池、灯泡和开关组成的简单串联电路是常见的起点。

6. Recording Data in Tables | 数据记录与表格

A well-organised results table makes your experiment easier to analyse. Draw the table before you start and include clear headings with units. The independent variable usually goes in the first column and the dependent variable in the next columns.

一个组织良好的结果表格能让你的实验更容易分析。在开始前画好表格，并包含带单位的清晰表头。自变量通常放在第一列，因变量放在后续列。

For a pendulum experiment, you might have columns: ‘Length (cm)’, ‘Time for 10 swings – Trial 1 (s)’, ‘Trial 2 (s)’, ‘Trial 3 (s)’, ‘Average time for 10 swings (s)’, ‘Period (s)’. The period equals the average time divided by 10.

对于摆的实验，你可能有以下几列：“长度 (cm)”“10次摆动时间 – 试验1 (s)”“试验2 (s)”“试验3 (s)”“10次摆动的平均时间 (s)”“周期 (s)”。周期等于平均时间除以10。

Always carry out at least three repeats and calculate the arithmetic mean. Discard anomalous results that clearly do not fit the pattern, but always make a note of why you are removing them.

始终至少进行三次重复并计算算术平均值。舍弃明显不符合规律的异常结果，但总要记录下移除它们的原因。

A tidy table allows you to spot trends quickly and provides the numbers you need for accurate graph plotting.

整洁的表格使你能够快速发现趋势，并为你提供绘制精确图表所需的数字。

7. Drawing Graphs | 绘制图表

Graphs turn numerical data into a visual story. Plot the independent variable on the horizontal (x) axis and the dependent variable on the vertical (y) axis. Label each axis with the quantity and unit, e.g., ‘Length (cm)’ and ‘Average time (s)’.

图表将数字数据转化为直观的故事。将自变量标在水平 (x) 轴上，因变量标在垂直 (y) 轴上。给每个轴标注量和单位，例如“长度 (cm)”和“平均时间 (s)”。

Use sensible scales that spread your data across more than half the grid. Mark each data point with a small ‘x’. If the points suggest a straight line, draw a single best-fit straight line with a ruler – not just dot-to-dot.

使用合理的刻度，使数据分布在网格的一半以上。用一个小“x”标记每个数据点。如果数据点暗示一条直线，用直尺画一条最佳拟合的直线——而不是简单的点对点连线。

If the graph is a curve, draw a smooth curve through the points. Sometimes you can recognise direct proportion – a straight line passing through the origin (0,0). For a pendulum, a graph of average time squared (T²) against length gives a straight line, showing T² is proportional to L.

如果图形是曲线，就画一条穿过各点的平滑曲线。有时你可以识别出正比例关系——一条通过原点 (0,0) 的直线。对于摆，将平均时间的平方 (T²) 对长度作图会得到一条直线，表明 T² 与 L 成正比。

T² ∝ L

Understanding what the graph shape tells you about the relationship between variables is an assessed skill. Learn to describe it using phrases like ‘as length increases, the period also increases’.

理解图形形状所揭示的变量之间的关系是一项需要评估的技能。学会用诸如“随着长度增加，周期也增加”之类的短语来描述它。

8. Analysing Results and Drawing Conclusions | 分析结果与得出结论

After constructing your graph, examine the pattern. Does the dependent variable increase, decrease or stay the same when the independent variable changes? Decide if the relationship is linear, curved or shows a peak.

完成图形绘制后，检查其规律。随着自变量改变，因变量是增加、减少还是保持不变？判断关系是线性的、弯曲的还是有峰值。

Your conclusion must directly answer the original question and refer back to the hypothesis. For example: ‘The results support the hypothesis that a longer pendulum has a longer period. The data show that doubling the length increased the average time for 10 swings from 8.2 s to 11.6 s.’

你的结论必须直接回答最初的问题，并回扣假设。例如：“结果支持了假设，即更长的摆有更长的周期。数据显示，将长度加倍使10次摆动的平均时间从8.2秒增加到11.6秒。”

If the data do not agree with the prediction, say so honestly and suggest a scientific reason why. This is not a failure – it is how real science works.

如果数据与预测不一致，请如实说明，并提出一个科学上的原因。这不是失败——真正的科学就是这样进行的。

9. Evaluating Experiments and Identifying Errors | 评估实验与识别误差

No experiment is perfect. Random errors occur when readings are slightly different each time due to human reaction or small environmental changes. You can reduce their effect by taking many readings, calculating averages and using more sensitive instruments.

没有实验是完美的。由于人的反应或微小的环境变化，每次读数都可能略有不同，这叫做随机误差。你可以通过多次读数、取平均值和使用更灵敏的仪器来减少它们的影响。

Systematic errors are consistent biases – for example, a stopwatch that starts 0.2 s late every time, or a ruler with a worn zero mark. These shift all results by the same amount and cannot be fixed by averaging. You must spot them and, if possible, recalibrate the equipment.

系统误差是一致性的偏差——例如，秒表每次启动都晚0.2秒，或者直尺的零刻度磨损了。这些会让所有结果偏移相同的量，无法通过取平均值来修正。你必须发现它们，并在可能时重新校准设备。

An evaluation also considers whether the method could be improved. Could you use a light gate instead of a stopwatch? Would clamping the ruler prevent movement? Suggest at least two realistic improvements for high marks.

评估还要考虑方法是否可以改进。你能用光门代替秒表吗？夹紧直尺能防止移动吗？想获得高分，至少要提出两条切实可行的改进建议。

10. Interpreting Data and Spotting Anomalies | 解读数据与发现异常值

An anomalous result is one that does not fit the overall pattern. On a graph it sits well away from the line of best fit. You must be able to identify anomalies and decide whether to repeat the measurement or exclude it with justification.

异常结果是不符合整体规律的结果。在图形上，它远离最佳拟合线。你必须能够识别异常值，并决定是重测还是在给出理由后将其排除。

For example, if one time-of-swing reading is much higher than the others and you remember the bob hit the table, you can label that trial as anomalous, exclude it, and recalculate the average from the remaining trials.

例如，如果某次摆动时间读数远高于其他值，并且你记得当时摆锤碰到了桌子，你就可以把那次试验标记为异常，予以排除，并用其余试验重新计算平均值。

Interpreting data also means using numerical evidence to back up your statements. Instead of saying ‘the period got bigger’, say ‘the period increased from 1.2 s to 1.7 s when the length rose from 20 cm to 40 cm’.

解读数据还意味着用数字证据来支持你的陈述。不要说“周期变大了”，而要说“当长度从20厘米增加到40厘米时，周期从1.2秒增加到1.7秒”。

11. Safety in the Lab | 实验室安全

Safety is the most important practical skill. Before any experiment, read the method and identify potential hazards – hot objects, sharp edges, electrical risks or spilled water near sockets.

安全是最重要的实践技能。在任何实验之前，都要阅读方法并识别潜在的危险——高温物体、锋利边缘、电风险或插座附近的水渍。

Always wear safety goggles when heating, using chemicals or stretching springs. Tie back long hair and tuck in loose clothing. Keep your workspace tidy and never run or play in the lab.

加热、使用化学品或拉伸弹簧时，务必佩戴护目镜。将长发束起，扎好宽松的衣物。保持工作区整洁，绝不在实验室奔跑打闹。

If a beaker of hot water tips over, do not touch it; tell the teacher immediately. Know where the first-aid kit, fire extinguisher and emergency exits are located.

如果烧杯中的热水被打翻，不要触碰；立即报告老师。要清楚急救箱、灭火器和紧急出口的位置。

Only carry out the investigation as instructed, and never change the circuit or add extra weights without permission. A careful scientist is a safe scientist.

只按指示进行实验，未经允许绝不改动电路或增加额外负重。细心的科学家才是安全的科学家。

Published by TutorHao | Physics Revision Series | aleveler.com

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Experimental and Practical Assessment Essentials | 实验/实践考核要点