📚 Science 607: Measurement and Experimental Design | 科学607：测量与实验设计
Welcome to this comprehensive revision guide for Edexcel IGCSE Science. In this article, we focus on one of the most essential skills you need to master: measurement and experimental design. These skills are tested across Biology, Chemistry, and Physics, and they form the backbone of the 'Working Scientifically' assessment objectives.
欢迎阅读爱德思IGCSE科学综合复习指南。本文将聚焦于一项你需要掌握的最关键技能：测量与实验设计。这些技能在生物、化学和物理中都会被考查，构成了“科学探究”评估目标的核心基础。
1. The Importance of Measurement | 测量的重要性
Measurement is the process of assigning a numerical value to a physical quantity. Without measurement, science would rely only on qualitative descriptions, making it impossible to compare results, identify patterns, or test theories quantitatively.
测量是为物理量赋予数值的过程。没有测量，科学将只能依赖定性的描述，从而无法定量地比较结果、识别规律或检验理论。
In Edexcel IGCSE Science, you are expected to select the appropriate measuring instrument, read values correctly, and record results with suitable accuracy and precision. This is not only a practical skill but also a key exam topic.
在爱德思IGCSE科学中，你需要选择合适的测量仪器，正确读数，并以适当的准确度和精密度记录结果。这不仅是一项实践技能，也是考试的重点内容。
2. SI Units and Prefixes | 国际单位制与词头
The International System of Units (SI) provides a universal language for scientific measurement. The base units you must know are: metre (m) for length, kilogram (kg) for mass, second (s) for time, ampere (A) for electric current, kelvin (K) for temperature, mole (mol) for amount of substance, and candela (cd) for luminous intensity.
国际单位制（SI）为科学测量提供了通用语言。你必须掌握的基本单位有：长度单位米（m）、质量单位千克（kg）、时间单位秒（s）、电流单位安培（A）、温度单位开尔文（K）、物质的量单位摩尔（mol）以及发光强度单位坎德拉（cd）。
For very large or very small quantities, we use prefixes. The table below shows the common ones you need for IGCSE:
对于非常大或非常小的量，我们使用词头。下表列出了IGCSE中需要掌握的常见词头：
| Prefix 词头 | Symbol 符号 | Factor 倍数 |
|---|---|---|
| kilo- 千 | k | 10³ |
| centi- 厘 | c | 10⁻² |
| milli- 毫 | m | 10⁻³ |
| micro- 微 | μ | 10⁻⁶ |
| nano- 纳 | n | 10⁻⁹ |
es the decimal position by a power of 10. For example, 1 cm = 10⁻² m, so 2.5 cm = 0.025 m.
进行单位换算时，记住每个词头之间的步进都对应10的幂次变化。例如，1 cm = 10⁻² m，因此2.5 cm = 0.025 m。
1 km = 1000 m = 10³ m | 1 mm = 10⁻³ m
3. Uncertainty and Errors | 不确定度与误差
ise. For example, a standard ruler with millimetre markings has an uncertainty of ±0.5 mm.
每次测量都存在一定的不确定度。除非另有说明，仪器的不确定度通常是最小刻度的一半。例如，最小刻度为毫米的标准直尺，其不确定度为±0.5 mm。
There are two types of errors: systematic errors and random errors. Systematic errors cause readings to be consistently too high or too low, often due to a faulty instrument or zero error. Random errors cause unpredictable variations in readings, often due to human reaction time or changes in environmental conditions.
误差分为两类：系统误差和随机误差。系统误差使读数持续偏高或偏低，通常由仪器故障或零位误差引起。随机误差导致读数不可预测地变化，通常由人的反应时间或环境条件变化引起。
You can reduce random errors by repeating measurements and calculating the mean. Systematic errors cannot be reduced by repetition; you must calibrate the instrument or correct the method.
你可以通过重复测量并计算平均值来减小随机误差。系统误差不能通过重复来减小；你必须校准仪器或修正方法。
Mean = (Sum of measurements) / (Number of measurements)
4. Significant Figures | 有效数字
Significant figures (s.f.) show the precision of a measured value. All non-zero digits are significant; zeros between non-zero digits are significant; leading zeros are not significant; trailing zeros after a decimal point are significant.
有效数字表示测量值的精密度。所有非零数字都是有效的；非零数字之间的零也是有效的；前导零无效；小数点后的尾随零有效。
When performing calculations, your final answer should have the same number of significant figures as the measured value with the fewest significant figures. For example, if you multiply 2.5 cm (2 s.f.) by 4.32 cm (3 s.f.), the result should be rounded to 2 s.f.
进行运算时，最终答案应与有效数字最少的测量值保持相同的有效数字位数。例如，2.5 cm（2位有效数字）乘以4.32 cm（3位有效数字），结果应保留2位有效数字。
2.5 × 4.32 = 10.8 → 11 (to 2 s.f.)
5. Common Measuring Instruments | 常用测量仪器
In Edexcel IGCSE Science, you need to know how to use a range of instruments. The most common ones are listed below.
在爱德思IGCSE科学中，你需要知道如何使用多种仪器。最常见的仪器列在下面。
Ruler or metre rule for measuring length. Read at eye level to avoid parallax error.
直尺或米尺用于测量长度。读数时视线应与刻度平齐，避免视差误差。
Measuring cylinder for liquid volume. Read the bottom of the meniscus at eye level.
量筒用于测量液体体积。读数时视线应与液面弯月面最低处平齐。
Digital balance for mass. Allow the reading to stabilise before recording.
电子天平用于测量质量。等待读数稳定后再记录。
Stopwatch for time. Practise starting and stopping consistently to reduce reaction time error.
秒表用于测量时间。练习一致地开始和停止，以减少反应时间误差。
Thermometer for temperature. Make sure the bulb is fully immersed but not touching the container walls.
温度计用于测量温度。确保感温泡完全浸入但不要接触容器壁。
Burette and pipette for precise volumes in titrations. Read the burette to ±0.05 cm³.
滴定管和移液管用于滴定中精确量取体积。滴定管读数精确到±0.05 cm³。
6. Designing a Fair Test | 设计公平实验
A fair test is an experiment in which only one independent variable is changed at a time, while all other variables are kept constant. This ensures that any observed effect is caused by the independent variable, not by a confounding factor.
公平实验是指每次只改变一个自变量，同时保持所有其他变量不变。这确保观察到的任何效应都是由自变量引起的，而不是由混杂因素引起的。
For example, when investigating the effect of temperature on the rate of a reaction, you must control the concentration, volume, pressure, and surface area of reactants. Only the temperature should change.
例如，在研究温度对反应速率的影响时，必须控制反应物的浓度、体积、压力以及固体的表面积。只有温度应该改变。
In your exam, you may be asked to describe how to make an experiment fair. Always state which variable you will change, which you will measure, and which you will control.
在考试中，你可能会被要求描述如何使实验公平。始终说明你要改变哪个变量、测量哪个变量、控制哪些变量。
7. Variables in Science | 科学变量
There are three types of variables in a scientific investigation:
科学探究中有三类变量：
The independent variable is the one you deliberately change. It is plotted on the x-axis of a graph.
自变量是你有意改变的变量。在图表中画在x轴上。
The dependent variable is the one you measure. It responds to changes in the independent variable and is plotted on the y-axis.
因变量是你测量的变量。它响应自变量的变化，画在y轴上。
Control variables are kept constant. They must be identified and controlled to make the experiment valid.
控制变量是保持不变的变量。必须确定并控制它们以保证实验有效。
Remember the phrase: "Change one, measure one, control the rest."
记住这句话：“改变一个，测量一个，控制其余。”
8. Collecting and Recording Data | 收集与记录数据
Good data collection requires planning. You should decide the range of values for the independent variable, the number of repeats, and the interval between data points. Usually, you should repeat measurements at least twice and calculate a mean to reduce random errors.
良好的数据收集需要规划。你应该决定自变量的取值范围、重复次数和数据点之间的间隔。通常，你应该至少重复测量两次，并计算平均值以减小随机误差。
When recording data, always include units and write to the correct number of decimal places. Use a table with clear headings. For example:
记录数据时，始终包含单位，并写到正确的小数位数。使用带有清晰标题的表格。例如：
| Temperature / °C | Trial 1 time / s | Trial 2 time / s | Mean time / s |
|---|---|---|---|
| 20 | 34 | 36 | 35 |
| 30 | 22 | 24 | 23 |
Notice that the mean is calculated using the raw data first, then rounded to an appropriate number of significant figures.
注意，应先使用原始数据计算平均值，然后再四舍五入到合适的有效数字位数。
9. Presenting Data: Tables and Graphs | 数据呈现：表格与图表
Graphs are essential for identifying patterns and relationships in data. For Edexcel IGCSE Science, you should be able to plot line graphs and bar charts correctly.
图表对于识别数据中的模式和关系至关重要。在爱德思IGCSE科学中，你应该能够正确绘制线图和条形图。
When plotting a line graph, follow these rules:
绘制线图时，遵循以下规则：
Choose a suitable scale so that the graph occupies at least half of the grid.
选择合适的标度，使图形至少占据网格的一半。
Label both axes with the variable name and unit.
在坐标轴上标注变量名称和单位。
Use a sharp pencil and plot points with small crosses.
用削尖的铅笔作图，用小的十字标记数据点。
Draw a best-fit line (straight line or smooth curve) that reflects the trend. Do not force the line through every point.
画出反映趋势的最佳拟合线（直线或平滑曲线）。不要强行让线穿过每个点。
Anomalous results should be circled and excluded from the best-fit line.
异常结果应圈出，并在画最佳拟合线时排除。
culated using: gradient = Δy / Δx. This is often a rate of change in a science experiment.
直线的斜率可以通过下式计算：斜率 = Δy / Δx。这通常是科学实验中的变化速率。
Gradient = (y₂ - y₁) / (x₂ - x₁)
10. Drawing Conclusions and Evaluating | 得出结论与评价
A conclusion must describe the relationship between the independent and dependent variables. Use scientific reasoning to explain why the pattern occurs. Do not simply restate the data; explain it.
结论必须描述自变量和因变量之间的关系。使用科学推理来解释为什么会出现这种模式。不要简单地复述数据，而要进行解释。
For example, if you investigated how temperature affects the dissolving time of a tablet, you might conclude: "As temperature increases, the dissolving time decreases, suggesting that higher kinetic energy causes particles to collide more frequently and with greater force."
例如，如果你研究了温度如何影响药片的溶解时间，你可以得出结论：“随着温度升高，溶解时间减少，这表明更高的动能导致粒子碰撞更频繁且作用力更大。”
Evaluation involves identifying strengths and weaknesses of the procedure, estimating the effect of errors, and suggesting improvements. You should comment on the reliability of the data, the accuracy of the instruments, and any sources of uncertainty.
评价涉及确定实验过程的优缺点，估计误差的影响，并提出改进建议。你应该评论数据的可靠性、仪器的准确性以及不确定度的来源。
11. Practical Work in Edexcel IGCSE Science | 爱德思IGCSE科学中的实践
Edexcel IGCSE Science includes a practical component that assesses your ability to carry out experiments safely and effectively. You may be examined on your practical skills through written questions that describe experimental contexts.
爱德思IGCSE科学包含实践部分，评估你安全有效地进行实验的能力。你可能通过描述实验情境的书面问题来考查实践技能。
Key practicals across the syllabus include: measuring density of solids and liquids, investigating the effect of pH on enzyme activity, testing for gases, and determining the resistance of a wire. You should revise the method, variables, and expected results for each required practical.
整个大纲中的关键实践包括：测量固体和液体的密度、研究pH对酶活性的影响、检验气体、以及测定金属丝电阻。你应该复习每个必做实验的方法、变量和预期结果。
Always remember laboratory safety: wear goggles when instructed, handle chemicals with care, and note any hazards risks.
始终记住实验室安全：按指示佩戴护目镜，小心处理化学品，并注意任何危险风险。
12. Common Exam Question Types | 常见考题类型
In the written exam, measurement and experimental design questions often appear in the following forms:
在笔试中，测量与实验设计类问题通常出现在以下形式中：
Name the equipment used to measure a given quantity.
命名用于测量给定量的仪器。
Read a scale and record the value to the correct precision.
读取刻度并记录到正确的精密度。
Identify the independent, dependent, and control variables in a scenario.
识别情境中的自变量、因变量和控制变量。
Suggest how to improve the accuracy or reliability of an experiment.
建议如何提高实验的准确度或可靠性。
Plot a graph from a table of results and use it to find a value.
根据结果表绘制图表，并利用它查找数值。
Calculate the mean, range, or gradient from given data.
从给定数据计算平均值、极差或斜率。
Practice by creating your own tables and graphs from raw data. The more comfortable you are with these routines, the higher your marks will be.
通过用原始数据创建自己的表格和图表来练习。你对这些操作越熟练，得分就会越高。
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